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Internet Engineering Task Force (IETF) M. Boucadair, Ed.
Request for Comments: 8512 Orange
Category: Standards Track S. Sivakumar
ISSN: 2070-1721 Cisco Systems
C. Jacquenet
Orange
S. Vinapamula
Juniper Networks
Q. Wu
Huawei
January 2019
A YANG Module for
Network Address Translation (NAT) and Network Prefix Translation (NPT)
Abstract
This document defines a YANG module for the Network Address
Translation (NAT) function.
Network Address Translation from IPv4 to IPv4 (NAT44), Network
Address and Protocol Translation from IPv6 Clients to IPv4 Servers
(NAT64), customer-side translator (CLAT), Stateless IP/ICMP
Translation (SIIT), Explicit Address Mappings (EAM) for SIIT,
IPv6-to-IPv6 Network Prefix Translation (NPTv6), and Destination NAT
are covered in this document.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8512.
Boucadair, et al. Standards Track [Page 1]
RFC 8512 YANG Module for NAT and NPT January 2019
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Boucadair, et al. Standards Track [Page 2]
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Overview of the NAT YANG Data Model . . . . . . . . . . . . . 6
2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2. Various Translation Flavors . . . . . . . . . . . . . . . 7
2.3. TCP/UDP/ICMP NAT Behavioral Requirements . . . . . . . . 8
2.4. Other Transport Protocols . . . . . . . . . . . . . . . . 8
2.5. IP Addresses Used for Translation . . . . . . . . . . . . 9
2.6. Port-Set Assignment . . . . . . . . . . . . . . . . . . . 9
2.7. Port-Restricted IP Addresses . . . . . . . . . . . . . . 9
2.8. NAT Mapping Entries . . . . . . . . . . . . . . . . . . . 10
2.9. Resource Limits . . . . . . . . . . . . . . . . . . . . . 13
2.10. Binding the NAT Function to an External Interface . . . . 16
2.11. Relationship to NATV2-MIB . . . . . . . . . . . . . . . . 16
2.12. Tree Structure . . . . . . . . . . . . . . . . . . . . . 17
3. NAT YANG Module . . . . . . . . . . . . . . . . . . . . . . . 24
4. Security Considerations . . . . . . . . . . . . . . . . . . . 68
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 70
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 70
6.1. Normative References . . . . . . . . . . . . . . . . . . 70
6.2. Informative References . . . . . . . . . . . . . . . . . 73
Appendix A. Some Examples . . . . . . . . . . . . . . . . . . . 75
A.1. Traditional NAT44 . . . . . . . . . . . . . . . . . . . . 75
A.2. Carrier Grade NAT (CGN) . . . . . . . . . . . . . . . . . 76
A.3. CGN Pass-Through . . . . . . . . . . . . . . . . . . . . 80
A.4. NAT64 . . . . . . . . . . . . . . . . . . . . . . . . . . 80
A.5. Stateless IP/ICMP Translation (SIIT) . . . . . . . . . . 81
A.6. Explicit Address Mappings (EAM) for Stateless IP/ICMP
Translation (SIIT) . . . . . . . . . . . . . . . . . . . 82
A.7. Static Mappings with Port Ranges . . . . . . . . . . . . 85
A.8. Static Mappings with IP Prefixes . . . . . . . . . . . . 86
A.9. Destination NAT . . . . . . . . . . . . . . . . . . . . . 86
A.10. Customer-Side Translator (CLAT) . . . . . . . . . . . . . 89
A.11. IPv6 Network Prefix Translation (NPTv6) . . . . . . . . . 90
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 93
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 94
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1. Introduction
This document defines a data model for Network Address Translation
(NAT) and Network Prefix Translation (NPT) capabilities using the
YANG data modeling language [RFC7950].
Traditional NAT is defined in [RFC2663], while Carrier Grade NAT
(CGN) is defined in [RFC6888]. Unlike traditional NAT, the CGN is
used to optimize the usage of global IP address space at the scale of
a domain: a CGN is not managed by end users but by service providers
instead. This document covers both traditional NATs and CGNs.
This document also covers NAT64 [RFC6146], customer-side translator
(CLAT) [RFC6877], Stateless IP/ICMP Translation (SIIT) [RFC7915],
Explicit Address Mappings (EAM) for SIIT [RFC7757], IPv6 Network
Prefix Translation (NPTv6) [RFC6296], and Destination NAT. The full
set of translation schemes that are in scope is included in
Section 2.2.
Some examples are provided in Appendix A. These examples are not
intended to be exhaustive.
1.1. Terminology
This document makes use of the following terms:
o Basic Network Address Translation from IPv4 to IPv4 (NAT44):
translation is limited to IP addresses alone (Section 2.1 of
[RFC3022]).
o Network Address Port Translator (NAPT): translation in NAPT is
extended to include IP addresses and transport identifiers (such
as a TCP/UDP port or ICMP query ID); refer to Section 2.2 of
[RFC3022]. A NAPT may use an extra identifier, in addition to the
five transport tuples, to disambiguate bindings [RFC6619].
o Destination NAT: is a translation that acts on the destination IP
address and/or destination port number. This flavor is usually
deployed in load balancers or at devices in front of public
servers.
o Port-restricted IPv4 address: an IPv4 address with a restricted
port set. Multiple hosts may share the same IPv4 address;
however, their port sets must not overlap [RFC7596].
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o Restricted port set: a non-overlapping range of allowed external
ports to use for NAT operation. Source ports of IPv4 packets
translated by a NAT must belong to the assigned port set. The
port set is used for all port-aware IP protocols [RFC7596].
o Internal host: a host that may need to use a translation
capability to send to and receive traffic from the Internet.
o Internal address/prefix: the IP address/prefix of an internal
host.
o External address: the IP address/prefix assigned by a translator
to an internal host; this is the address that will be seen by a
remote host on the Internet.
o Mapping: denotes a state at the translator that is necessary for
network address and/or port translation.
o Dynamic implicit mapping: is created implicitly as a side effect
of processing a packet (e.g., an initial TCP SYN packet) that
requires a new mapping. A validity lifetime is associated with
this mapping.
o Dynamic explicit mapping: is created as a result of an explicit
request, e.g., a Port Control Protocol (PCP) message [RFC6887]. A
validity lifetime is associated with this mapping.
o Static explicit mapping: is created using, e.g., a command-line
interface (CLI). This mapping is likely to be maintained by the
NAT function till an explicit action is executed to remove it.
The usage of the term NAT in this document refers to any translation
flavor (NAT44, NAT64, etc.) indifferently.
This document uses the term "session" as defined in [RFC2663] and
[RFC6146] for NAT64.
This document follows the guidelines of [RFC8407], uses the common
YANG types defined in [RFC6991], and adopts the Network Management
Datastore Architecture (NMDA). The meaning of the symbols in tree
diagrams is defined in [RFC8340].
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2. Overview of the NAT YANG Data Model
2.1. Overview
The NAT YANG module is designed to cover dynamic implicit mappings
and static explicit mappings. The required functionality to instruct
dynamic explicit mappings is defined in separate documents such as
[YANG-PCP]. Considerations about instructing by explicit dynamic
means (e.g., [RFC6887], [RFC6736], or [RFC8045]) are out of scope.
As a reminder, REQ-9 of [RFC6888] requires that a CGN must implement
a protocol giving subscribers explicit control over NAT mappings;
that protocol should be the Port Control Protocol [RFC6887].
A single NAT device can have multiple NAT instances; each of these
instances can be provided with its own policies (e.g., be responsible
for serving a group of hosts). This document does not make any
assumption about how internal hosts or flows are associated with a
given NAT instance.
The NAT YANG module assumes that each NAT instance can be enabled/
disabled, be provisioned with a specific set of configuration data,
and maintain its own mapping tables.
The NAT YANG module allows for a NAT instance to be provided with
multiple NAT policies (/nat/instances/instance/policy). The document
does not make any assumption about how flows are associated with a
given NAT policy of a given NAT instance. Classification filters are
out of scope.
Defining multiple NAT instances or configuring multiple NAT policies
within one single NAT instance is implementation and deployment
specific.
This YANG module does not provide any method to instruct a NAT
function to enable the logging feature or to specify the information
to be logged for administrative or regulatory reasons (Section 2.3 of
[RFC6908] and REQ-12 of [RFC6888]). Those considerations are out of
the scope of this document.
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2.2. Various Translation Flavors
The following translation modes are supported:
o Basic NAT44
o NAPT
o Destination NAT
o Port-restricted NAT
o Stateful NAT64 (including with destination-based Pref64::/n
[RFC7050])
o SIIT
o CLAT
o EAM
o NPTv6
o Combination of Basic NAT/NAPT and Destination NAT
o Combination of port-restricted and Destination NAT
o Combination of NAT64 and EAM
o Stateful and Stateless NAT64
[RFC8513] specifies an extension to the NAT YANG module to support
Dual-Stack Lite (DS-Lite).
The YANG "feature" statement is used to indicate which of the
different translation modes is relevant for a specific data node.
Table 1 lists defined features:
+---------------------------------+--------------+
| Translation Mode | YANG Feature |
+---------------------------------+--------------+
| Basic NAT44 | basic-nat44 |
| NAPT | napt44 |
| Destination NAT | dst-nat |
| Stateful NAT64 | nat64 |
| Stateless IPv4/IPv6 Translation | siit |
| CLAT | clat |
| EAM | eam |
| NPTv6 | nptv6 |
+---------------------------------+--------------+
Table 1: NAT YANG Features
The following translation modes do not require that dedicated
features be defined:
o Port-restricted NAT: This mode corresponds to supplying port-
restriction policies to a NAPT or NAT64 (port-set-restrict).
o Combination of Basic NAT/NAPT and Destination NAT: This mode
corresponds to setting 'dst-nat-enable' for Basic NAT44 or NAPT.
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o Combination of port-restricted and Destination NAT: This mode can
be achieved by configuring a NAPT with port restriction policies
(port-set-restrict) together with a destination IP address pool
(dst-ip-address-pool).
o Combination of NAT64 and EAM: This mode corresponds to configuring
static mappings for NAT64.
o Stateful and stateless NAT64: A NAT64 implementation can be
instructed to behave in the stateless mode for a given prefix by
setting the parameter (nat64-prefixes/stateless-enable). A NAT64
implementation may behave in both stateful and stateless modes if,
in addition to appropriately setting the parameter
(nat64-prefixes/stateless-enable), an external IPv4 address pool
is configured.
The NAT YANG module provides a method to retrieve the capabilities of
a NAT instance (including a list of supported translation modes, a
list of supported protocols, the supported NAT mapping types, the
supported NAT filtering types, the behavior for handling fragments
(all, out-of-order, in-order), and the support statuses for the
following: port restriction, port range allocation, port parity
preservation, and port preservation).
2.3. TCP/UDP/ICMP NAT Behavioral Requirements
This document assumes NAT behavioral recommendations for UDP
[RFC4787], TCP [RFC5382], and ICMP [RFC5508] are enabled by default.
Furthermore, the NAT YANG module relies upon the recommendations
detailed in [RFC6888] and [RFC7857].
2.4. Other Transport Protocols
The module is structured to support protocols other than UDP, TCP,
and ICMP. Concretely, the module allows the operator to enable
translation for other transport protocols when required
(/nat/instances/instance/policy/transport-protocols). Moreover, the
mapping table is designed so that it can indicate any transport
protocol. For example, this module may be used to manage a NAT
capable of the Datagram Congestion Control Protocol (DCCP) that
adheres to [RFC5597].
Future extensions may be needed to cover NAT-related considerations
that are specific to other transport protocols such as the Stream
Control Transmission Protocol (SCTP) [NAT-SUPP]. Typically, the
mapping entry can be extended to record two optional SCTP-specific
parameters: the Internal Verification Tag (Int-VTag) and External
Verification Tag (Ext-VTag).
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This document only specifies transport-protocol-specific timers for
UDP, TCP, and ICMP. While some timers could potentially be
generalized for other connection-oriented protocols, this document
does not follow such an approach because there is no standard
document specifying such generic behavior. Future documents may be
edited to clarify how to reuse TCP-specific timers when needed.
2.5. IP Addresses Used for Translation
The NAT YANG module assumes that blocks of IP external addresses
(external-ip-address-pool) can be provisioned to the NAT function.
These blocks may be contiguous or not.
This behavior is aligned with [RFC6888], which specifies that a NAT
function should not have any limitations on the size or the
contiguity of the external address pool. In particular, the NAT
function must be configurable with contiguous or non-contiguous
external IPv4 address ranges. To accommodate traditional NAT, the
module allows for a single IP address to be configured for external-
ip-address-pool.
Likewise, one or multiple IP address pools may be configured for
Destination NAT (dst-ip-address-pool).
2.6. Port-Set Assignment
Port numbers can be assigned by a NAT individually (that is, a single
port is assigned on a per-session basis), but this port allocation
scheme may not be optimal for logging purposes (Section 12 of
[RFC6269]). A NAT function should be able to assign port sets (e.g.,
[RFC7753]) to optimize the volume of the logging data (REQ-14 of
[RFC6888]). Both allocation schemes are supported in the NAT YANG
module.
When port-set assignment is activated (i.e., port-allocation-
type==port-range-allocation), the NAT can be provided with the size
of the port set to be assigned (port-set-size).
2.7. Port-Restricted IP Addresses
Some NATs restrict the source port numbers (e.g., Lightweight 4over6
[RFC7596] and Mapping of Address and Port with Encapsulation (MAP-E)
[RFC7597]). Two schemes of port-set assignments (port-set-restrict)
are supported in this document:
o Simple port range: is defined by two port values, the start and
the end of the port range [RFC8045].
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o Algorithmic: an algorithm is defined in [RFC7597] to characterize
the set of ports that can be used.
2.8. NAT Mapping Entries
A TCP/UDP mapping entry maintains an association between the
following information:
(internal-src-address, internal-src-port) (internal-dst-address,
internal-dst-port) <=> (external-src-address, external-src-port)
(external-dst-address, external-dst-port)
An ICMP mapping entry maintains an association between the following
information:
(internal-src-address, internal-dst-address, internal ICMP/ICMPv6
identifier) <=> (external-src-address, external-dst-address,
external ICMP/ICMPv6 identifier)
As a reminder, all the ICMP Query messages contain an 'Identifier'
field, which is referred to in this document as the 'ICMP
Identifier'.
To cover TCP, UDP, and ICMP, the NAT YANG module assumes the
following structure of a mapping entry:
type: Indicates how the mapping was instantiated. For example, it
may indicate whether a mapping is dynamically instantiated by a
packet or statically configured.
transport-protocol: Indicates the transport protocol (e.g., UDP,
TCP, and ICMP) of a given mapping.
internal-src-address: Indicates the source IP address/prefix as used
by an internal host.
internal-src-port: Indicates the source port number (or ICMP
identifier) as used by an internal host.
external-src-address: Indicates the source IP address/prefix as
assigned by the NAT.
external-src-port: Indicates the source port number (or ICMP
identifier) as assigned by the NAT.
internal-dst-address: Indicates the destination IP address/prefix as
used by an internal host when sending a packet to a remote host.
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internal-dst-port: Indicates the destination port number as used by
an internal host when sending a packet to a remote host.
external-dst-address: Indicates the destination IP address/prefix
used by a NAT when processing a packet issued by an internal host
towards a remote host.
external-dst-port: Indicates the destination port number used by a
NAT when processing a packet issued by an internal host towards a
remote host.
In order to cover both NAT64 and NAT44 flavors, the NAT mapping
structure allows for the inclusion of an IPv4 or an IPv6 address as
an internal IP address. Remaining fields are common to both NAT
schemes.
For example, the mapping that will be created by a NAT64 upon receipt
of a TCP SYN from source address 2001:db8:aaaa::1 and source port
number 25636 to destination IP address 2001:db8:1234::198.51.100.1
and destination port number 8080 is shown in Table 2. This example
assumes Endpoint-Dependent Mapping (EDM).
+-----------------------+-------------------------------------------+
| Mapping Entry | Value |
| Attribute | |
+-----------------------+-------------------------------------------+
| type | dynamic implicit mapping |
| transport-protocol | 6 (TCP) |
| internal-src-address | 2001:db8:aaaa::1 |
| internal-src-port | 25636 |
| external-src-address | T (an IPv4 address configured on the |
| | NAT64) |
| external-src-port | t (a port number that is chosen by the |
| | NAT64) |
| internal-dst-address | 2001:db8:1234::198.51.100.1 |
| internal-dst-port | 8080 |
| external-dst-address | 198.51.100.1 |
| external-dst-port | 8080 |
+-----------------------+-------------------------------------------+
Table 2: Example of an EDM NAT64 Mapping
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The mappings that will be created by a NAT44 upon receipt of an ICMP
request from source address 198.51.100.1 and ICMP identifier (ID1) to
destination IP address 198.51.100.11 is depicted in Table 3. This
example assumes Endpoint-Independent Mapping (EIM).
+----------------------+--------------------------------------------+
| Mapping-Entry | Value |
| Attribute | |
+----------------------+--------------------------------------------+
| type | dynamic implicit mapping |
| transport-protocol | 1 (ICMP) |
| internal-src-address | 198.51.100.1 |
| internal-src-port | ID1 |
| external-src-address | T (an IPv4 address configured on the |
| | NAT44) |
| external-src-port | ID2 (an ICMP identifier that is chosen by |
| | the NAT44) |
+----------------------+--------------------------------------------+
Table 3: Example of an EIM NAT44 Mapping Entry
The mapping that will be created by a NAT64 (EIM mode) upon receipt
of an ICMP request from source address 2001:db8:aaaa::1 and ICMP
identifier (ID1) to destination IP address
2001:db8:1234::198.51.100.1 is shown in Table 4.
+----------------------+--------------------------------------------+
| Mapping-Entry | Value |
| Attribute | |
+----------------------+--------------------------------------------+
| type | dynamic implicit mapping |
| transport-protocol | 58 (ICMPv6) |
| internal-src-address | 2001:db8:aaaa::1 |
| internal-src-port | ID1 |
| external-src-address | T (an IPv4 address configured on the |
| | NAT64) |
| external-src-port | ID2 (an ICMP identifier that is chosen by |
| | the NAT64) |
+----------------------+--------------------------------------------+
Table 4: Example of an EIM NAT64 Mapping Entry
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Note that a mapping table is maintained only for stateful NAT
functions. Particularly:
o No mapping table is maintained for NPTv6 given that it is
stateless and transport-agnostic.
o The double translations are stateless in CLAT if a dedicated IPv6
prefix is provided for CLAT. If not, a stateful NAT44 will be
required.
o No per-flow mapping is maintained for EAM [RFC7757].
o No mapping table is maintained for Stateless IPv4/IPv6
translation. As a reminder, in such deployments, internal IPv6
nodes are addressed using IPv4-translatable IPv6 addresses, which
enable them to be accessed by IPv4 nodes [RFC6052].
2.9. Resource Limits
In order to comply with CGN deployments in particular, the NAT YANG
module allows limiting the number of external ports per subscriber
(port-quota) and the amount of state memory allocated per mapping and
per subscriber (mapping-limits and connection-limits). According to
[RFC6888], the module is designed to allow for the following:
o Per-subscriber limits are configurable by the NAT administrator.
o Per-subscriber limits are configurable independently per the
transport protocol.
o Administrator-adjustable thresholds to prevent a single subscriber
from consuming excessive CPU resources from the NAT (e.g., rate-
limit the subscriber's creation of new mappings) can be
configured.
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Table 5 lists the various limits that can be set using the NAT YANG
module. Once a limit is reached, packets that would normally trigger
new port mappings or be translated because they match existing
mappings, are dropped by the translator.
+-------------------+-----------------------------------------------+
| Limit | Description |
+-------------------+-----------------------------------------------+
| port-quota | Specifies a port quota to be assigned per |
| | subscriber. It corresponds to the maximum |
| | number of ports to be used by a subscriber. |
| | The port quota can be configured to apply to |
| | all protocols or to a specific protocol. |
| | Distinct port quota may be configured per |
| | protocol. |
+-------------------+-----------------------------------------------+
| fragments-limit | In order to prevent denial-of-service (DoS) |
| | attacks that can be caused by fragments, this |
| | parameter is used to limit the number of out- |
| | of-order fragments that can be handled by a |
| | translator. |
+-------------------+-----------------------------------------------+
| mapping-limits | This parameter can be used to control the |
| | maximum number of subscribers that can be |
| | serviced by a NAT instance (limit-subscriber) |
| | and the maximum number of address and/or port |
| | mappings that can be maintained by a NAT |
| | instance (limit-address-mappings and limit- |
| | port-mappings). Also, limits specific to |
| | protocols (e.g., TCP, UDP, ICMP) can also be |
| | specified (limit-per-protocol). |
+-------------------+-----------------------------------------------+
| connection-limits | In order to prevent exhausting the resources |
| | of a NAT implementation and to ensure |
| | fairness usage among subscribers, various |
| | rate limits can be specified. Rate-limiting |
| | can be enforced per subscriber (limit- |
| | subscriber), per NAT instance (limit-per- |
| | instance), and/or be specified for each |
| | supported protocol (limit-per-protocol). |
+-------------------+-----------------------------------------------+
Table 5: NAT Limits
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Table 6 describes limits that, once exceeded, will trigger
notifications to be generated:
+--------------------------+----------------------------------------+
| Notification Threshold | Description |
+--------------------------+----------------------------------------+
| high-threshold | Used to notify high address |
| | utilization of a given pool. When |
| | exceeded, a nat-pool-event |
| | notification will be generated. |
+--------------------------+----------------------------------------+
| low-threshold | Used to notify low address utilization |
| | of a given pool. An administrator is |
| | supposed to configure low-threshold so |
| | that it can reflect an abnormal usage |
| | of NAT resources. When exceeded, a |
| | nat-pool-event notification will be |
| | generated. |
+--------------------------+----------------------------------------+
| notify-addresses-usage | Used to notify high address |
| | utilization of all pools configured to |
| | a NAT instance. When exceeded, a nat- |
| | instance-event will be generated. |
+--------------------------+----------------------------------------+
| notify-ports-usage | Used to notify high port allocation |
| | taking into account all pools |
| | configured to a NAT instance. When |
| | exceeded, a nat-instance-event |
| | notification will be generated. |
+--------------------------+----------------------------------------+
| notify-subscribers-limit | Used to notify a high number of active |
| | subscribers that are serviced by a NAT |
| | instance. When exceeded, a nat- |
| | instance-event notification will be |
| | generated. |
+--------------------------+----------------------------------------+
Table 6: Notification Thresholds
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In order to prevent a NAT implementation from generating frequent
notifications, the NAT YANG module supports the following limits
(Table 7) used to control how frequent notifications can be
generated. That is, notifications are subject to rate-limiting
imposed by these intervals.
+-------------------------------------+-----------------------------+
| Interval | Description |
+-------------------------------------+-----------------------------+
| notify-pool-usage/notify-interval | Indicates the minimum |
| | number of seconds between |
| | successive notifications |
| | for a given address pool. |
+-------------------------------------+-----------------------------+
| notification-limits/notify-interval | Indicates the minimum |
| | number of seconds between |
| | successive notifications |
| | for a NAT instance. |
+-------------------------------------+-----------------------------+
Table 7: Notification Intervals
2.10. Binding the NAT Function to an External Interface
The module is designed to specify an external realm on which the NAT
function must be applied (external-realm). The module supports
indicating an interface as an external realm [RFC8343], but the
module is extensible so that other choices can be indicated in the
future (e.g., Virtual Routing and Forwarding (VRF) instance).
Distinct external realms can be provided as a function of the NAT
policy (see, for example, Section 4 of [RFC7289]).
If no external realm is provided, this assumes that the system is
able to determine the external interface (VRF instance, etc.) on
which the NAT will be applied. Typically, the WAN and LAN interfaces
of Customer Premises Equipment (CPE) are determined by the CPE.
2.11. Relationship to NATV2-MIB
Section of 5.1 of [RFC7659] indicates that the NATV2-MIB assumes that
the following information is configured on the NAT by some means,
which is not specified in [RFC7659]:
o The set of address realms to which the device connects.
Boucadair, et al. Standards Track [Page 16]
RFC 8512 YANG Module for NAT and NPT January 2019
o For the CGN case, per-subscriber information including the
subscriber index, address realm, assigned prefix or address, and
(possibly) policies regarding address pool selection in the
various possible address realms to which the subscriber may
connect.
o The set of NAT instances running on the device, identified by NAT
instance index and name.
o The port mapping, filtering, pooling, and fragment behaviors for
each NAT instance.
o The set of protocols supported by each NAT instance.
o Address pools for each NAT instance, including for each pool the
pool index, address realm, and minimum and maximum port numbers.
o Static address and port mapping entries.
All the above parameters can be configured by means of the NAT YANG
module.
Unlike the NATV2-MIB, the NAT YANG module allows the configuration of
multiple policies per NAT instance.
2.12. Tree Structure
The tree structure of the NAT YANG module is provided below:
module: ietf-nat
+--rw nat
+--rw instances
+--rw instance* [id]
+--rw id uint32
+--rw name? string
+--rw enable? boolean
+--ro capabilities
| +--ro nat-flavor*
| | identityref
| +--ro per-interface-binding*
| | enumeration
| +--ro transport-protocols* [protocol-id]
| | +--ro protocol-id uint8
| | +--ro protocol-name? string
| +--ro restricted-port-support?
| | boolean
| +--ro static-mapping-support?
| | boolean
Boucadair, et al. Standards Track [Page 17]
RFC 8512 YANG Module for NAT and NPT January 2019
| +--ro port-randomization-support?
| | boolean
| +--ro port-range-allocation-support?
| | boolean
| +--ro port-preservation-suport?
| | boolean
| +--ro port-parity-preservation-support?
| | boolean
| +--ro address-roundrobin-support?
| | boolean
| +--ro paired-address-pooling-support?
| | boolean
| +--ro endpoint-independent-mapping-support?
| | boolean
| +--ro address-dependent-mapping-support?
| | boolean
| +--ro address-and-port-dependent-mapping-support?
| | boolean
| +--ro endpoint-independent-filtering-support?
| | boolean
| +--ro address-dependent-filtering?
| | boolean
| +--ro address-and-port-dependent-filtering?
| | boolean
| +--ro fragment-behavior?
| enumeration
+--rw type? identityref
+--rw per-interface-binding? enumeration
+--rw nat-pass-through* [id]
| {basic-nat44 or napt44 or dst-nat}?
| +--rw id uint32
| +--rw prefix inet:ip-prefix
| +--rw port? inet:port-number
+--rw policy* [id]
| +--rw id uint32
| +--rw clat-parameters {clat}?
| | +--rw clat-ipv6-prefixes* [ipv6-prefix]
| | | +--rw ipv6-prefix inet:ipv6-prefix
| | +--rw ipv4-prefixes* [ipv4-prefix]
| | +--rw ipv4-prefix inet:ipv4-prefix
| +--rw nptv6-prefixes* [internal-ipv6-prefix] {nptv6}?
| | +--rw internal-ipv6-prefix inet:ipv6-prefix
| | +--rw external-ipv6-prefix inet:ipv6-prefix
| +--rw eam* [ipv4-prefix] {eam}?
| | +--rw ipv4-prefix inet:ipv4-prefix
| | +--rw ipv6-prefix inet:ipv6-prefix
Boucadair, et al. Standards Track [Page 18]
RFC 8512 YANG Module for NAT and NPT January 2019
| +--rw nat64-prefixes* [nat64-prefix]
| | {siit or nat64 or clat}?
| | +--rw nat64-prefix inet:ipv6-prefix
| | +--rw destination-ipv4-prefix* [ipv4-prefix]
| | | +--rw ipv4-prefix inet:ipv4-prefix
| | +--rw stateless-enable? boolean
| +--rw external-ip-address-pool* [pool-id]
| | {basic-nat44 or napt44 or nat64}?
| | +--rw pool-id uint32
| | +--rw external-ip-pool inet:ipv4-prefix
| +--rw port-set-restrict {napt44 or nat64}?
| | +--rw (port-type)?
| | +--:(port-range)
| | | +--rw start-port-number? inet:port-number
| | | +--rw end-port-number? inet:port-number
| | +--:(port-set-algo)
| | +--rw psid-offset? uint8
| | +--rw psid-len uint8
| | +--rw psid uint16
| +--rw dst-nat-enable? boolean
| | {basic-nat44 or napt44}?
| +--rw dst-ip-address-pool* [pool-id] {dst-nat}?
| | +--rw pool-id uint32
| | +--rw dst-in-ip-pool? inet:ip-prefix
| | +--rw dst-out-ip-pool inet:ip-prefix
| +--rw transport-protocols* [protocol-id]
| | {napt44 or nat64 or dst-nat}?
| | +--rw protocol-id uint8
| | +--rw protocol-name? string
| +--rw subscriber-mask-v6? uint8
| +--rw subscriber-match* [match-id]
| | {basic-nat44 or napt44 or dst-nat}?
| | +--rw match-id uint32
| | +--rw subnet inet:ip-prefix
| +--rw address-allocation-type? enumeration
| +--rw port-allocation-type? enumeration
| | {napt44 or nat64}?
| +--rw mapping-type? enumeration
| | {napt44 or nat64}?
| +--rw filtering-type? enumeration
| | {napt44 or nat64}?
| +--rw fragment-behavior? enumeration
| | {napt44 or nat64}?
| +--rw port-quota* [quota-type] {napt44 or nat64}?
| | +--rw port-limit? uint16
| | +--rw quota-type uint8
Boucadair, et al. Standards Track [Page 19]
RFC 8512 YANG Module for NAT and NPT January 2019
| +--rw port-set {napt44 or nat64}?
| | +--rw port-set-size uint16
| | +--rw port-set-timeout? uint32
| +--rw timers {napt44 or nat64}?
| | +--rw udp-timeout? uint32
| | +--rw tcp-idle-timeout? uint32
| | +--rw tcp-trans-open-timeout? uint32
| | +--rw tcp-trans-close-timeout? uint32
| | +--rw tcp-in-syn-timeout? uint32
| | +--rw fragment-min-timeout? uint32
| | +--rw icmp-timeout? uint32
| | +--rw per-port-timeout* [port-number]
| | | +--rw port-number inet:port-number
| | | +--rw protocol? uint32
| | | +--rw timeout uint32
| | +--rw hold-down-timeout? uint32
| | +--rw hold-down-max? uint32
| +--rw fragments-limit? uint32
| +--rw algs* [name]
| | +--rw name string
| | +--rw transport-protocol? uint32
| | +--rw dst-transport-port
| | | +--rw start-port-number? inet:port-number
| | | +--rw end-port-number? inet:port-number
| | +--rw src-transport-port
| | | +--rw start-port-number? inet:port-number
| | | +--rw end-port-number? inet:port-number
| | +--rw status? boolean
| +--rw all-algs-enable? boolean
| +--rw notify-pool-usage
| | {basic-nat44 or napt44 or nat64}?
| | +--rw pool-id? uint32
| | +--rw low-threshold? percent
| | +--rw high-threshold? percent
| | +--rw notify-interval? uint32
| +--rw external-realm
| +--rw (realm-type)?
| +--:(interface)
| +--rw external-interface? if:interface-ref
+--rw mapping-limits {napt44 or nat64}?
| +--rw limit-subscribers? uint32
| +--rw limit-address-mappings? uint32
| +--rw limit-port-mappings? uint32
| +--rw limit-per-protocol* [protocol-id]
| {napt44 or nat64 or dst-nat}?
| +--rw protocol-id uint8
| +--rw limit? uint32
Boucadair, et al. Standards Track [Page 20]
RFC 8512 YANG Module for NAT and NPT January 2019
+--rw connection-limits
| {basic-nat44 or napt44 or nat64}?
| +--rw limit-per-subscriber? uint32
| +--rw limit-per-instance? uint32
| +--rw limit-per-protocol* [protocol-id]
| {napt44 or nat64}?
| +--rw protocol-id uint8
| +--rw limit? uint32
+--rw notification-limits
| +--rw notify-interval? uint32
| | {basic-nat44 or napt44 or nat64}?
| +--rw notify-addresses-usage? percent
| | {basic-nat44 or napt44 or nat64}?
| +--rw notify-ports-usage? percent
| | {napt44 or nat64}?
| +--rw notify-subscribers-limit? uint32
| {basic-nat44 or napt44 or nat64}?
+--rw mapping-table
| |{basic-nat44 or napt44 or nat64 or clat or dst-nat}?
| +--rw mapping-entry* [index]
| +--rw index uint32
| +--rw type? enumeration
| +--rw transport-protocol? uint8
| +--rw internal-src-address? inet:ip-prefix
| +--rw internal-src-port
| | +--rw start-port-number? inet:port-number
| | +--rw end-port-number? inet:port-number
| +--rw external-src-address? inet:ip-prefix
| +--rw external-src-port
| | +--rw start-port-number? inet:port-number
| | +--rw end-port-number? inet:port-number
| +--rw internal-dst-address? inet:ip-prefix
| +--rw internal-dst-port
| | +--rw start-port-number? inet:port-number
| | +--rw end-port-number? inet:port-number
| +--rw external-dst-address? inet:ip-prefix
| +--rw external-dst-port
| | +--rw start-port-number? inet:port-number
| | +--rw end-port-number? inet:port-number
| +--rw lifetime? uint32
+--ro statistics
+--ro discontinuity-time yang:date-and-time
+--ro traffic-statistics
| +--ro sent-packets?
| | yang:zero-based-counter64
| +--ro sent-bytes?
| | yang:zero-based-counter64
Boucadair, et al. Standards Track [Page 21]
RFC 8512 YANG Module for NAT and NPT January 2019
| +--ro rcvd-packets?
| | yang:zero-based-counter64
| +--ro rcvd-bytes?
| | yang:zero-based-counter64
| +--ro dropped-packets?
| | yang:zero-based-counter64
| +--ro dropped-bytes?
| | yang:zero-based-counter64
| +--ro dropped-fragments?
| | yang:zero-based-counter64
| | {napt44 or nat64}?
| +--ro dropped-address-limit-packets?
| | yang:zero-based-counter64
| | {basic-nat44 or napt44 or nat64}?
| +--ro dropped-address-limit-bytes?
| | yang:zero-based-counter64
| | {basic-nat44 or napt44 or nat64}?
| +--ro dropped-address-packets?
| | yang:zero-based-counter64
| | {basic-nat44 or napt44 or nat64}?
| +--ro dropped-address-bytes?
| | yang:zero-based-counter64
| | {basic-nat44 or napt44 or nat64}?
| +--ro dropped-port-limit-packets?
| | yang:zero-based-counter64
| | {napt44 or nat64}?
| +--ro dropped-port-limit-bytes?
| | yang:zero-based-counter64
| | {napt44 or nat64}?
| +--ro dropped-port-packets?
| | yang:zero-based-counter64
| | {napt44 or nat64}?
| +--ro dropped-port-bytes?
| | yang:zero-based-counter64
| | {napt44 or nat64}?
| +--ro dropped-subscriber-limit-packets?
| | yang:zero-based-counter64
| | {basic-nat44 or napt44 or nat64}?
| +--ro dropped-subscriber-limit-bytes?
| yang:zero-based-counter64
| {basic-nat44 or napt44 or nat64}?
+--ro mappings-statistics
| +--ro total-active-subscribers? yang:gauge32
| | {basic-nat44 or napt44 or nat64}?
| +--ro total-address-mappings? yang:gauge32
| |{basic-nat44 or napt44 or nat64 or clat or dst-nat}?
| +--ro total-port-mappings? yang:gauge32
| | {napt44 or nat64}?
Boucadair, et al. Standards Track [Page 22]
RFC 8512 YANG Module for NAT and NPT January 2019
| +--ro total-per-protocol* [protocol-id]
| {napt44 or nat64}?
| +--ro protocol-id uint8
| +--ro total? yang:gauge32
+--ro pools-stats {basic-nat44 or napt44 or nat64}?
+--ro addresses-allocated? yang:gauge32
+--ro addresses-free? yang:gauge32
+--ro ports-stats {napt44 or nat64}?
| +--ro ports-allocated? yang:gauge32
| +--ro ports-free? yang:gauge32
+--ro per-pool-stats* [pool-id]
| {basic-nat44 or napt44 or nat64}?
+--ro pool-id uint32
+--ro discontinuity-time yang:date-and-time
+--ro pool-stats
| +--ro addresses-allocated? yang:gauge32
| +--ro addresses-free? yang:gauge32
+--ro port-stats {napt44 or nat64}?
+--ro ports-allocated? yang:gauge32
+--ro ports-free? yang:gauge32
notifications:
+---n nat-pool-event {basic-nat44 or napt44 or nat64}?
| +--ro id -> /nat/instances/instance/id
| +--ro policy-id?
| | -> /nat/instances/instance/policy/id
| +--ro pool-id
| | -> /nat/instances/instance/policy/
| | external-ip-address-pool/pool-id
| +--ro notify-pool-threshold percent
+---n nat-instance-event {basic-nat44 or napt44 or nat64}?
+--ro id
| -> /nat/instances/instance/id
+--ro notify-subscribers-threshold? uint32
+--ro notify-addresses-threshold? percent
+--ro notify-ports-threshold? percent
Boucadair, et al. Standards Track [Page 23]
RFC 8512 YANG Module for NAT and NPT January 2019
3. NAT YANG Module
<CODE BEGINS> file "ietf-nat@2019-01-10.yang"
module ietf-nat {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-nat";
prefix nat;
import ietf-inet-types {
prefix inet;
reference
"Section 4 of RFC 6991";
}
import ietf-yang-types {
prefix yang;
reference
"Section 3 of RFC 6991";
}
import ietf-interfaces {
prefix if;
reference
"RFC 8343: A YANG Data Model for Interface Management";
}
organization
"IETF OPSAWG (Operations and Management Area Working Group)";
contact
"WG Web: <https://datatracker.ietf.org/wg/opsawg/>
WG List: <mailto:opsawg@ietf.org>
Editor: Mohamed Boucadair
<mailto:mohamed.boucadair@orange.com>
Author: Senthil Sivakumar
<mailto:ssenthil@cisco.com>
Author: Christian Jacquenet
<mailto:christian.jacquenet@orange.com>
Author: Suresh Vinapamula
<mailto:sureshk@juniper.net>
Author: Qin Wu
<mailto:bill.wu@huawei.com>";
description
"This module is a YANG module for NAT implementations.
Boucadair, et al. Standards Track [Page 24]
RFC 8512 YANG Module for NAT and NPT January 2019
NAT44, Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers (NAT64), customer-side translator
(CLAT), Stateless IP/ICMP Translation (SIIT), Explicit
Address Mappings (EAM) for SIIT, IPv6 Network Prefix
Translation (NPTv6), and Destination NAT are covered.
Copyright (c) 2018 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 8512; see
the RFC itself for full legal notices.";
revision 2019-01-10 {
description
"Initial revision.";
reference
"RFC 8512: A YANG Module for Network Address Translation
(NAT) and Network Prefix Translation (NPT)";
}
/*
* Definitions
*/
typedef percent {
type uint8 {
range "0 .. 100";
}
description
"Percentage";
}
/*
* Features
*/
feature basic-nat44 {
description
"Basic NAT44 translation is limited to IP addresses alone.";
reference
"RFC 3022: Traditional IP Network Address Translator
Boucadair, et al. Standards Track [Page 25]
RFC 8512 YANG Module for NAT and NPT January 2019
(Traditional NAT)";
}
feature napt44 {
description
"Network Address Port Translator (NAPT): translation is
extended to include IP addresses and transport identifiers
(such as a TCP/UDP port or ICMP query ID).
If the internal IP address is not sufficient to uniquely
disambiguate NAPT44 mappings, an additional attribute is
required. For example, that additional attribute may
be an IPv6 address (a.k.a., DS-Lite) or
a Layer 2 identifier (a.k.a., Per-Interface NAT)";
reference
"RFC 3022: Traditional IP Network Address Translator
(Traditional NAT)";
}
feature dst-nat {
description
"Destination NAT is a translation that acts on the destination
IP address and/or destination port number. This flavor is
usually deployed in load balancers or at devices
in front of public servers.";
}
feature nat64 {
description
"NAT64 translation allows IPv6-only clients to contact IPv4
servers using, e.g., UDP, TCP, or ICMP. One or more
public IPv4 addresses assigned to a NAT64 translator are
shared among several IPv6-only clients.";
reference
"RFC 6146: Stateful NAT64: Network Address and Protocol
Translation from IPv6 Clients to IPv4 Servers";
}
feature siit {
description
"The Stateless IP/ICMP Translation Algorithm (SIIT), which
translates between IPv4 and IPv6 packet headers (including
ICMP headers).
In the stateless mode, an IP/ICMP translator converts IPv4
addresses to IPv6, and vice versa, solely based on the
configuration of the stateless IP/ICMP translator and
information contained within the packet being translated.
Boucadair, et al. Standards Track [Page 26]
RFC 8512 YANG Module for NAT and NPT January 2019
The translator must support the stateless address mapping
algorithm defined in RFC 6052, which is the default behavior.";
reference
"RFC 7915: IP/ICMP Translation Algorithm";
}
feature clat {
description
"CLAT is customer-side translator that algorithmically
translates 1:1 private IPv4 addresses to global IPv6
addresses, and vice versa.
When a dedicated /64 prefix is not available for translation
from DHCPv6-PD, the CLAT may perform NAT44 for all IPv4 LAN
packets so that all the LAN-originated IPv4 packets appear
from a single IPv4 address and are then statelessly translated
to one interface IPv6 address that is claimed by the CLAT via
the Neighbor Discovery Protocol (NDP) and defended with
Duplicate Address Detection.";
reference
"RFC 6877: 464XLAT: Combination of Stateful and
Stateless Translation";
}
feature eam {
description
"Explicit Address Mapping (EAM) is a bidirectional coupling
between an IPv4 prefix and an IPv6 prefix.";
reference
"RFC 7757: Explicit Address Mappings for Stateless IP/ICMP
Translation";
}
feature nptv6 {
description
"NPTv6 is a stateless transport-agnostic IPv6-to-IPv6
prefix translation.";
reference
"RFC 6296: IPv6-to-IPv6 Network Prefix Translation";
}
/*
* Identities
*/
identity nat-type {
description
"Base identity for nat type.";
Boucadair, et al. Standards Track [Page 27]
RFC 8512 YANG Module for NAT and NPT January 2019
}
identity basic-nat44 {
base nat:nat-type;
description
"Identity for Basic NAT support.";
reference
"RFC 3022: Traditional IP Network Address Translator
(Traditional NAT)";
}
identity napt44 {
base nat:nat-type;
description
"Identity for NAPT support.";
reference
"RFC 3022: Traditional IP Network Address Translator
(Traditional NAT)";
}
identity dst-nat {
base nat:nat-type;
description
"Identity for Destination NAT support.";
}
identity nat64 {
base nat:nat-type;
description
"Identity for NAT64 support.";
reference
"RFC 6146: Stateful NAT64: Network Address and Protocol
Translation from IPv6 Clients to IPv4 Servers";
}
identity siit {
base nat:nat-type;
description
"Identity for SIIT support.";
reference
"RFC 7915: IP/ICMP Translation Algorithm";
}
identity clat {
base nat:nat-type;
description
"Identity for CLAT support.";
reference
Boucadair, et al. Standards Track [Page 28]
RFC 8512 YANG Module for NAT and NPT January 2019
"RFC 6877: 464XLAT: Combination of Stateful and Stateless
Translation";
}
identity eam {
base nat:nat-type;
description
"Identity for EAM support.";
reference
"RFC 7757: Explicit Address Mappings for Stateless IP/ICMP
Translation";
}
identity nptv6 {
base nat:nat-type;
description
"Identity for NPTv6 support.";
reference
"RFC 6296: IPv6-to-IPv6 Network Prefix Translation";
}
/*
* Grouping
*/
grouping port-number {
description
"An individual port number or a range of ports.
When only start-port-number is present,
it represents a single port number.";
leaf start-port-number {
type inet:port-number;
description
"Beginning of the port range.";
reference
"Section 3.2.9 of RFC 8045";
}
leaf end-port-number {
type inet:port-number;
must '. >= ../start-port-number' {
error-message
"The end-port-number must be greater than or
equal to start-port-number.";
}
description
"End of the port range.";
reference
"Section 3.2.10 of RFC 8045";
Boucadair, et al. Standards Track [Page 29]
RFC 8512 YANG Module for NAT and NPT January 2019
}
}
grouping port-set {
description
"Indicates a set of port numbers.
It may be a simple port range, or use the Port Set
Identifier (PSID) algorithm to represent a range of
transport-layer port numbers that will be used by a
NAPT.";
choice port-type {
default "port-range";
description
"Port type: port-range or port-set-algo.";
case port-range {
uses port-number;
}
case port-set-algo {
leaf psid-offset {
type uint8 {
range "0..15";
}
description
"The number of offset bits (a.k.a., 'a' bits).
Specifies the numeric value for the excluded port
range/offset bits.
Allowed values are between 0 and 15.";
reference
"Section 5.1 of RFC 7597";
}
leaf psid-len {
type uint8 {
range "0..15";
}
mandatory true;
description
"The length of PSID, representing the sharing
ratio for an IPv4 address.
(also known as 'k').
The address-sharing ratio would be 2^k.";
reference
"Section 5.1 of RFC 7597";
}
leaf psid {
Boucadair, et al. Standards Track [Page 30]
RFC 8512 YANG Module for NAT and NPT January 2019
type uint16;
mandatory true;
description
"PSID value, which identifies a set
of ports algorithmically.";
reference
"Section 5.1 of RFC 7597";
}
}
reference
"RFC 7597: Mapping of Address and Port with
Encapsulation (MAP-E)";
}
}
grouping mapping-entry {
description
"NAT mapping entry.
If an attribute is not stored in the mapping/session table,
it means the corresponding field of a packet that
matches this entry is not rewritten by the NAT or this
information is not required for NAT filtering purposes.";
leaf index {
type uint32;
description
"A unique identifier of a mapping entry. This identifier
can be automatically assigned by the NAT instance or be
explicitly configured.";
}
leaf type {
type enumeration {
enum static {
description
"The mapping entry is explicitly configured
(e.g., via a command-line interface).";
}
enum dynamic-implicit {
description
"This mapping is created implicitly as a side effect
of processing a packet that requires a new mapping.";
}
enum dynamic-explicit {
description
"This mapping is created as a result of an explicit
request, e.g., a PCP message.";
}
}
Boucadair, et al. Standards Track [Page 31]
RFC 8512 YANG Module for NAT and NPT January 2019
description
"Indicates the type of a mapping entry. For example,
a mapping can be: static, implicit dynamic,
or explicit dynamic.";
}
leaf transport-protocol {
type uint8;
description
"The upper-layer protocol associated with this mapping.
Values are taken from the IANA Protocol Numbers registry:
<https://www.iana.org/assignments/protocol-numbers/>.
For example, this field contains 6 for TCP,
17 for UDP, 33 for DCCP, or 132 for SCTP.
If this leaf is not instantiated, then the mapping
applies to any protocol.";
}
leaf internal-src-address {
type inet:ip-prefix;
description
"Corresponds to the source IPv4/IPv6 address/prefix
of the packet received on an internal interface.";
}
container internal-src-port {
description
"Corresponds to the source port of the packet received
on an internal interface.
It is also used to indicate the internal source ICMP
identifier.
As a reminder, all the ICMP Query messages contain
an 'Identifier' field, which is referred to in this
document as the 'ICMP Identifier'.";
uses port-number;
}
leaf external-src-address {
type inet:ip-prefix;
description
"Source IP address/prefix of the packet sent on an
external interface of the NAT.";
}
container external-src-port {
description
"Source port of the packet sent on an external
interface of the NAT.
Boucadair, et al. Standards Track [Page 32]
RFC 8512 YANG Module for NAT and NPT January 2019
It is also used to indicate the external source ICMP
identifier.";
uses port-number;
}
leaf internal-dst-address {
type inet:ip-prefix;
description
"Corresponds to the destination IP address/prefix
of the packet received on an internal interface
of the NAT.
For example, some NAT implementations support
the translation of both source and destination
addresses and port numbers, sometimes referred to
as 'Twice NAT'.";
}
container internal-dst-port {
description
"Corresponds to the destination port of the
IP packet received on the internal interface.
It is also used to include the internal
destination ICMP identifier.";
uses port-number;
}
leaf external-dst-address {
type inet:ip-prefix;
description
"Corresponds to the destination IP address/prefix
of the packet sent on an external interface
of the NAT.";
}
container external-dst-port {
description
"Corresponds to the destination port number of
the packet sent on the external interface
of the NAT.
It is also used to include the external
destination ICMP identifier.";
uses port-number;
}
leaf lifetime {
type uint32;
units "seconds";
description
"When specified, it is used to track the connection that is
fully formed (e.g., once the three-way handshake
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TCP is completed) or the duration for maintaining
an explicit mapping alive. The mapping entry will be
removed by the NAT instance once this lifetime is expired.
When reported in a get operation, the lifetime indicates
the remaining validity lifetime.
Static mappings may not be associated with a
lifetime. If no lifetime is associated with a
static mapping, an explicit action is required to
remove that mapping.";
}
}
/*
* NAT Module
*/
container nat {
description
"NAT module";
container instances {
description
"NAT instances";
list instance {
key "id";
description
"A NAT instance. This identifier can be automatically
assigned or explicitly configured.";
leaf id {
type uint32;
must '. >= 1';
description
"NAT instance identifier.
The identifier must be greater than zero.";
reference
"RFC 7659: Definitions of Managed Objects for Network
Address Translators (NATs)";
}
leaf name {
type string;
description
"A name associated with the NAT instance.";
reference
"RFC 7659: Definitions of Managed Objects for Network
Address Translators (NATs)";
}
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leaf enable {
type boolean;
description
"Status of the NAT instance.";
}
container capabilities {
config false;
description
"NAT capabilities.";
leaf-list nat-flavor {
type identityref {
base nat-type;
}
description
"Supported translation type(s).";
}
leaf-list per-interface-binding {
type enumeration {
enum unsupported {
description
"No capability to associate a NAT binding with
an extra identifier.";
}
enum layer-2 {
description
"The NAT instance is able to associate a mapping with
a Layer 2 identifier.";
}
enum dslite {
description
"The NAT instance is able to associate a mapping with
an IPv6 address (a.k.a., DS-Lite).";
}
}
description
"Indicates the capability of a NAT to associate a
particular NAT session not only with the five
tuples used for the transport connection on both
sides of the NAT but also with the internal
interface on which the user device is
connected to the NAT.";
reference
"Section 4 of RFC 6619";
}
list transport-protocols {
key "protocol-id";
description
"List of supported protocols.";
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leaf protocol-id {
type uint8;
mandatory true;
description
"The upper-layer protocol associated with a mapping.
Values are taken from the IANA Protocol Numbers
registry.
For example, this field contains 6 for TCP,
17 for UDP, 33 for DCCP, or 132 for SCTP.";
}
leaf protocol-name {
type string;
description
"The name of the upper-layer protocol associated
with this mapping.
For example, TCP, UDP, DCCP, and SCTP.";
}
}
leaf restricted-port-support {
type boolean;
description
"Indicates source port NAT restriction support.";
reference
"RFC 7596: Lightweight 4over6: An Extension to
the Dual-Stack Lite Architecture";
}
leaf static-mapping-support {
type boolean;
description
"Indicates whether static mappings are supported.";
}
leaf port-randomization-support {
type boolean;
description
"Indicates whether port randomization is supported.";
reference
"Section 4.2.1 of RFC 4787";
}
leaf port-range-allocation-support {
type boolean;
description
"Indicates whether port range allocation is supported.";
reference
"Section 1.1 of RFC 7753";
}
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leaf port-preservation-suport {
type boolean;
description
"Indicates whether port preservation is supported.";
reference
"Section 4.2.1 of RFC 4787";
}
leaf port-parity-preservation-support {
type boolean;
description
"Indicates whether port parity preservation is
supported.";
reference
"Section 8 of RFC 7857";
}
leaf address-roundrobin-support {
type boolean;
description
"Indicates whether address allocation round robin is
supported.";
}
leaf paired-address-pooling-support {
type boolean;
description
"Indicates whether paired-address-pooling is
supported";
reference
"REQ-2 of RFC 4787";
}
leaf endpoint-independent-mapping-support {
type boolean;
description
"Indicates whether endpoint-independent-
mapping is supported.";
reference
"Section 4 of RFC 4787";
}
leaf address-dependent-mapping-support {
type boolean;
description
"Indicates whether address-dependent-mapping is
supported.";
reference
"Section 4 of RFC 4787";
}
leaf address-and-port-dependent-mapping-support {
type boolean;
description
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"Indicates whether address-and-port-dependent-mapping is
supported.";
reference
"Section 4 of RFC 4787";
}
leaf endpoint-independent-filtering-support {
type boolean;
description
"Indicates whether endpoint-independent-filtering is
supported.";
reference
"Section 5 of RFC 4787";
}
leaf address-dependent-filtering {
type boolean;
description
"Indicates whether address-dependent-filtering is
supported.";
reference
"Section 5 of RFC 4787";
}
leaf address-and-port-dependent-filtering {
type boolean;
description
"Indicates whether address-and-port-dependent is
supported.";
reference
"Section 5 of RFC 4787";
}
leaf fragment-behavior {
type enumeration {
enum unsupported {
description
"No capability to translate incoming fragments.
All received fragments are dropped.";
}
enum in-order {
description
"The NAT instance is able to translate fragments
only if they are received in order. That is, in
particular the header is in the first packet.
Fragments received out of order are dropped. ";
}
enum out-of-order {
description
"The NAT instance is able to translate a fragment even
if it is received out of order.
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This behavior is recommended.";
reference
"REQ-14 of RFC 4787";
}
}
description
"The fragment behavior is the NAT instance's capability to
translate fragments received on the external interface of
the NAT.";
}
}
leaf type {
type identityref {
base nat-type;
}
description
"Specify the translation type. Particularly useful when
multiple translation flavors are supported.
If one type is supported by a NAT, this parameter is by
default set to that type.";
}
leaf per-interface-binding {
type enumeration {
enum disabled {
description
"Disable the capability to associate an extra identifier
with NAT mappings.";
}
enum layer-2 {
description
"The NAT instance is able to associate a mapping with
a Layer 2 identifier.";
}
enum dslite {
description
"The NAT instance is able to associate a mapping with
an IPv6 address (a.k.a., DS-Lite).";
}
}
description
"A NAT that associates a particular NAT session not
only with the five tuples used for the transport
connection on both sides of the NAT but also with
the internal interface on which the user device is
connected to the NAT.
If supported, this mode of operation should be
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configurable, and it should be disabled by default in
general-purpose NAT devices.
If one single per-interface binding behavior is
supported by a NAT, this parameter is by default set to
that behavior.";
reference
"Section 4 of RFC 6619";
}
list nat-pass-through {
if-feature "basic-nat44 or napt44 or dst-nat";
key "id";
description
"IP prefix NAT pass-through.";
leaf id {
type uint32;
description
"An identifier of the IP prefix pass-through.";
}
leaf prefix {
type inet:ip-prefix;
mandatory true;
description
"The IP addresses that match should not be translated.
It must be possible to administratively turn
off translation for specific destination addresses
and/or ports.";
reference
"REQ-6 of RFC 6888";
}
leaf port {
type inet:port-number;
description
"It must be possible to administratively turn off
translation for specific destination addresses
and/or ports.
If no prefix is defined, the NAT pass-through bound
to a given port applies for any destination address.";
reference
"REQ-6 of RFC 6888";
}
}
list policy {
key "id";
description
"NAT parameters for a given instance";
leaf id {
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type uint32;
description
"An identifier of the NAT policy. It must be unique
within the NAT instance.";
}
container clat-parameters {
if-feature "clat";
description
"CLAT parameters.";
list clat-ipv6-prefixes {
key "ipv6-prefix";
description
"464XLAT double-translation treatment is stateless
when a dedicated /64 is available for translation
on the CLAT. Otherwise, the CLAT will have both
stateful and stateless translation since it requires
NAT44 from the LAN to a single IPv4 address and then
stateless translation to a single IPv6 address.";
reference
"RFC 6877: 464XLAT: Combination of Stateful and
Stateless Translation";
leaf ipv6-prefix {
type inet:ipv6-prefix;
description
"An IPv6 prefix used for CLAT.";
}
}
list ipv4-prefixes {
key "ipv4-prefix";
description
"Pool of IPv4 addresses used for CLAT.
192.0.0.0/29 is the IPv4 service continuity prefix.";
reference
"RFC 7335: IPv4 Service Continuity Prefix";
leaf ipv4-prefix {
type inet:ipv4-prefix;
description
"464XLAT double-translation treatment is
stateless when a dedicated /64 is available
for translation on the CLAT. Otherwise, the
CLAT will have both stateful and stateless
translation since it requires NAT44 from the
LAN to a single IPv4 address and then stateless
translation to a single IPv6 address.
The CLAT performs NAT44 for all IPv4 LAN
packets so that all the LAN-originated IPv4
packets appear from a single IPv4 address
and are then statelessly translated to one
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interface IPv6 address that is claimed by
the CLAT.
An IPv4 address from this pool is also
provided to an application that makes
use of literals.";
reference
"RFC 6877: 464XLAT: Combination of Stateful and
Stateless Translation";
}
}
}
list nptv6-prefixes {
if-feature "nptv6";
key "internal-ipv6-prefix";
description
"Provides one or a list of (internal IPv6 prefix,
external IPv6 prefix) required for NPTv6.
In its simplest form, NPTv6 interconnects two
network links: one is an 'internal' network
link attached to a leaf network within a single
administrative domain, and the other is an
'external' network with connectivity to the
global Internet.";
reference
"RFC 6296: IPv6-to-IPv6 Network Prefix Translation";
leaf internal-ipv6-prefix {
type inet:ipv6-prefix;
mandatory true;
description
"An IPv6 prefix used by an internal interface of
NPTv6.";
reference
"RFC 6296: IPv6-to-IPv6 Network Prefix Translation";
}
leaf external-ipv6-prefix {
type inet:ipv6-prefix;
mandatory true;
description
"An IPv6 prefix used by the external interface of
NPTv6.";
reference
"RFC 6296: IPv6-to-IPv6 Network Prefix Translation";
}
}
list eam {
if-feature "eam";
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key "ipv4-prefix";
description
"The Explicit Address Mapping Table is a conceptual
table in which each row represents an EAM.
Each EAM describes a mapping between IPv4 and IPv6
prefixes/addresses.";
reference
"Section 3.1 of RFC 7757";
leaf ipv4-prefix {
type inet:ipv4-prefix;
mandatory true;
description
"The IPv4 prefix of an EAM.";
reference
"Section 3.2 of RFC 7757";
}
leaf ipv6-prefix {
type inet:ipv6-prefix;
mandatory true;
description
"The IPv6 prefix of an EAM.";
reference
"Section 3.2 of RFC 7757";
}
}
list nat64-prefixes {
if-feature "siit or nat64 or clat";
key "nat64-prefix";
description
"Provides one or a list of NAT64 prefixes
with or without a list of destination IPv4 prefixes.
It allows mapping IPv4 address ranges to IPv6 prefixes.
For example:
192.0.2.0/24 is mapped to 2001:db8:122:300::/56.
198.51.100.0/24 is mapped to 2001:db8:122::/48.";
reference
"Section 5.1 of RFC 7050";
leaf nat64-prefix {
type inet:ipv6-prefix;
mandatory true;
description
"A NAT64 prefix. Can be a Network-Specific Prefix (NSP)
or a Well-Known Prefix (WKP).
Organizations deploying stateless IPv4/IPv6 translation
should assign an NSP to their IPv4/IPv6 translation
service.
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For stateless NAT64, IPv4-translatable IPv6 addresses
must use the selected NSP.
Both IPv4-translatable IPv6 addresses and
IPv4-converted IPv6 addresses should use
the same prefix.";
reference
"Sections 3.3 and 3.4 of RFC 6052";
}
list destination-ipv4-prefix {
key "ipv4-prefix";
description
"An IPv4 prefix/address.";
leaf ipv4-prefix {
type inet:ipv4-prefix;
description
"An IPv4 address/prefix.";
}
}
leaf stateless-enable {
type boolean;
default "false";
description
"Enable explicitly stateless NAT64.";
}
}
list external-ip-address-pool {
if-feature "basic-nat44 or napt44 or nat64";
key "pool-id";
description
"Pool of external IP addresses used to service internal
hosts.
A pool is a set of IP prefixes.";
leaf pool-id {
type uint32;
must '. >= 1';
description
"An identifier that uniquely identifies the address pool
within a NAT instance.
The identifier must be greater than zero.";
reference
"RFC 7659: Definitions of Managed Objects for
Network Address Translators (NATs)";
}
leaf external-ip-pool {
type inet:ipv4-prefix;
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mandatory true;
description
"An IPv4 prefix used for NAT purposes.";
}
}
container port-set-restrict {
if-feature "napt44 or nat64";
description
"Configures contiguous and non-contiguous port ranges.
The port set is used to restrict the external source
port numbers used by the translator.";
uses port-set;
}
leaf dst-nat-enable {
if-feature "basic-nat44 or napt44";
type boolean;
default "false";
description
"Enable/disable Destination NAT.
A NAT44 may be configured to enable Destination
NAT, too.";
}
list dst-ip-address-pool {
if-feature "dst-nat";
key "pool-id";
description
"Pool of IP addresses used for Destination NAT.";
leaf pool-id {
type uint32;
description
"An identifier of the address pool.";
}
leaf dst-in-ip-pool {
type inet:ip-prefix;
description
"Is used to identify an internal destination
IP prefix/address to be translated.";
}
leaf dst-out-ip-pool {
type inet:ip-prefix;
mandatory true;
description
"IP address/prefix used for Destination NAT.";
}
}
list transport-protocols {
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if-feature "napt44 or nat64 or dst-nat";
key "protocol-id";
description
"Configure the transport protocols to be handled by
the translator.
TCP and UDP are supported by default.";
leaf protocol-id {
type uint8;
mandatory true;
description
"The upper-layer protocol associated with this
mapping.
Values are taken from the IANA Protocol Numbers
registry.
For example, this field contains 6 for TCP,
17 for UDP, 33 for DCCP, or 132 for SCTP.";
}
leaf protocol-name {
type string;
description
"The name of the upper-layer protocol associated
with this mapping.
For example, TCP, UDP, DCCP, and SCTP.";
}
}
leaf subscriber-mask-v6 {
type uint8 {
range "0 .. 128";
}
description
"The subscriber mask is an integer that indicates
the length of significant bits to be applied on
the source IPv6 address (internal side) to
unambiguously identify a user device (e.g., CPE).
Subscriber mask is a system-wide configuration
parameter that is used to enforce generic
per-subscriber policies (e.g., port-quota).
The enforcement of these generic policies does not
require the configuration of every subscriber's
prefix.
Example: suppose the 2001:db8:100:100::/56 prefix
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is assigned to a NAT64-serviced CPE. Suppose also
that 2001:db8:100:100::1 is the IPv6 address used
by the client that resides in that CPE. When the
NAT64 receives a packet from this client,
it applies the subscriber-mask-v6 (e.g., 56) on
the source IPv6 address to compute the associated
prefix for this client (2001:db8:100:100::/56).
Then, the NAT64 enforces policies based on that
prefix (2001:db8:100:100::/56), not on the exact
source IPv6 address.";
}
list subscriber-match {
if-feature "basic-nat44 or napt44 or dst-nat";
key "match-id";
description
"IP prefix match.
A subscriber is identified by a subnet.";
leaf match-id {
type uint32;
description
"An identifier of the subscriber match.";
}
leaf subnet {
type inet:ip-prefix;
mandatory true;
description
"The IP address subnets that match
should be translated. For example, all addresses
that belong to the 192.0.2.0/24 prefix must
be processed by the NAT.";
}
}
leaf address-allocation-type {
type enumeration {
enum arbitrary {
if-feature "basic-nat44 or napt44 or nat64";
description
"Arbitrary pooling behavior means that the NAT
instance may create the new port mapping using any
address in the pool that has a free port for the
protocol concerned.";
}
enum roundrobin {
if-feature "basic-nat44 or napt44 or nat64";
description
"Round-robin allocation.";
}
enum paired {
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if-feature "napt44 or nat64";
description
"Paired address pooling informs the NAT
that all the flows from an internal IP
address must be assigned the same external
address. This is the recommended behavior
for NAPT/NAT64.";
reference
"RFC 4787: Network Address Translation (NAT)
Behavioral Requirements for Unicast UDP";
}
}
description
"Specifies how external IP addresses are allocated.";
}
leaf port-allocation-type {
if-feature "napt44 or nat64";
type enumeration {
enum random {
description
"Port randomization is enabled. A NAT port allocation
scheme should make it hard for attackers to guess
port numbers";
reference
"REQ-15 of RFC 6888";
}
enum port-preservation {
description
"Indicates whether the NAT should preserve the
internal port number.";
}
enum port-parity-preservation {
description
"Indicates whether the NAT should preserve the port
parity of the internal port number.";
}
enum port-range-allocation {
description
"Indicates whether the NAT assigns a range of ports
for an internal host. This scheme allows the
minimizing of the log volume.";
reference
"REQ-14 of RFC 6888";
}
}
description
"Indicates the type of port allocation.";
}
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leaf mapping-type {
if-feature "napt44 or nat64";
type enumeration {
enum eim {
description
"endpoint-independent-mapping.";
reference
"Section 4 of RFC 4787";
}
enum adm {
description
"address-dependent-mapping.";
reference
"Section 4 of RFC 4787";
}
enum edm {
description
"address-and-port-dependent-mapping.";
reference
"Section 4 of RFC 4787";
}
}
description
"Indicates the type of NAT mapping.";
}
leaf filtering-type {
if-feature "napt44 or nat64";
type enumeration {
enum eif {
description
"endpoint-independent-filtering.";
reference
"Section 5 of RFC 4787";
}
enum adf {
description
"address-dependent-filtering.";
reference
"Section 5 of RFC 4787";
}
enum edf {
description
"address-and-port-dependent-filtering";
reference
"Section 5 of RFC 4787";
}
}
description
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"Indicates the type of NAT filtering.";
}
leaf fragment-behavior {
if-feature "napt44 or nat64";
type enumeration {
enum drop-all {
description
"All received fragments are dropped.";
}
enum in-order {
description
"Translate fragments only if they are received
in order.";
}
enum out-of-order {
description
"Translate a fragment even if it is received out
of order.
This behavior is recommended.";
reference
"REQ-14 of RFC 4787";
}
}
description
"The fragment behavior instructs the NAT about the
behavior to follow to translate fragments received
on the external interface of the NAT.";
}
list port-quota {
if-feature "napt44 or nat64";
key "quota-type";
description
"Configures a port quota to be assigned per subscriber.
It corresponds to the maximum number of ports to be
used by a subscriber.";
leaf port-limit {
type uint16;
description
"Configures a port quota to be assigned per subscriber.
It corresponds to the maximum number of ports to be
used by a subscriber.";
reference
"REQ-4 of RFC 6888";
}
leaf quota-type {
type uint8;
description
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"Indicates whether the port quota applies to
all protocols (0) or to a specific protocol.";
}
}
container port-set {
when "../port-allocation-type = 'port-range-allocation'";
if-feature "napt44 or nat64";
description
"Manages port-set assignments.";
leaf port-set-size {
type uint16;
mandatory true;
description
"Indicates the size of assigned port sets.";
}
leaf port-set-timeout {
type uint32;
units "seconds";
description
"inactivity timeout for port sets.";
}
}
container timers {
if-feature "napt44 or nat64";
description
"Configure values of various timeouts.";
leaf udp-timeout {
type uint32;
units "seconds";
default "300";
description
"UDP inactivity timeout. That is the time a mapping
will stay active without packets traversing the NAT.";
reference
"RFC 4787: Network Address Translation (NAT)
Behavioral Requirements for Unicast UDP";
}
leaf tcp-idle-timeout {
type uint32;
units "seconds";
default "7440";
description
"TCP idle timeout should be 2 hours and 4 minutes.";
reference
"RFC 5382: NAT Behavioral Requirements for TCP";
}
leaf tcp-trans-open-timeout {
type uint32;
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units "seconds";
default "240";
description
"The value of the transitory open connection
idle-timeout.
A NAT should provide different configurable
parameters for configuring the open and
closing idle timeouts.
To accommodate deployments that consider
a partially open timeout of 4 minutes as being
excessive from a security standpoint, a NAT may
allow the configured timeout to be less than
4 minutes.
However, a minimum default transitory connection
idle-timeout of 4 minutes is recommended.";
reference
"Section 2.1 of RFC 7857";
}
leaf tcp-trans-close-timeout {
type uint32;
units "seconds";
default "240";
description
"The value of the transitory close connection
idle-timeout.
A NAT should provide different configurable
parameters for configuring the open and
closing idle timeouts.";
reference
"Section 2.1 of RFC 7857";
}
leaf tcp-in-syn-timeout {
type uint32;
units "seconds";
default "6";
description
"A NAT must not respond to an unsolicited
inbound SYN packet for at least 6 seconds
after the packet is received. If during
this interval the NAT receives and translates
an outbound SYN for the connection the NAT
must silently drop the original unsolicited
inbound SYN packet.";
reference
Boucadair, et al. Standards Track [Page 52]
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"RFC 5382 NAT Behavioral Requirements for TCP";
}
leaf fragment-min-timeout {
when "../../fragment-behavior='out-of-order'";
type uint32;
units "seconds";
default "2";
description
"As long as the NAT has available resources,
the NAT allows the fragments to arrive
over the fragment-min-timeout interval.
The default value is inspired from RFC 6146.";
}
leaf icmp-timeout {
type uint32;
units "seconds";
default "60";
description
"An ICMP Query session timer must not expire
in less than 60 seconds. It is recommended
that the ICMP Query session timer be made
configurable";
reference
"RFC 5508: NAT Behavioral Requirements for ICMP";
}
list per-port-timeout {
key "port-number";
description
"Some NATs are configurable with short timeouts
for some ports, e.g., as 10 seconds on
port 53 (DNS) and 123 (NTP), and longer timeouts
on other ports.";
leaf port-number {
type inet:port-number;
description
"A port number.";
}
leaf protocol {
type uint8;
description
"The upper-layer protocol associated with this port.
Values are taken from the IANA Protocol Numbers
registry.
If no protocol is indicated, it means 'any
protocol'.";
}
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leaf timeout {
type uint32;
units "seconds";
mandatory true;
description
"Timeout for this port number";
}
}
leaf hold-down-timeout {
type uint32;
units "seconds";
default "120";
description
"Hold-down timer.
Ports in the hold-down pool are not reassigned until
hold-down-timeout expires.
The length of time and the maximum number of ports in
this state must be configurable by the administrator.
This is necessary in order to prevent collisions
between old and new mappings and sessions. It ensures
that all established sessions are broken instead of
redirected to a different peer.";
reference
"REQ-8 of RFC 6888";
}
leaf hold-down-max {
type uint32;
description
"Maximum ports in the hold-down port pool.";
reference
"REQ-8 of RFC 6888";
}
}
leaf fragments-limit {
when "../fragment-behavior='out-of-order'";
type uint32;
description
"Limits the number of out-of-order fragments that can
be handled.";
reference
"Section 11 of RFC 4787";
}
list algs {
key "name";
description
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"Features related to the Application Layer
Gateway (ALG).";
leaf name {
type string;
description
"The name of the ALG.";
}
leaf transport-protocol {
type uint32;
description
"The transport protocol used by the ALG
(e.g., TCP and UDP).";
}
container dst-transport-port {
uses port-number;
description
"The destination port number(s) used by the ALG.
For example,
- 21 for the FTP ALG
- 53 for the DNS ALG.";
}
container src-transport-port {
uses port-number;
description
"The source port number(s) used by the ALG.";
}
leaf status {
type boolean;
description
"Enable/disable the ALG.";
}
}
leaf all-algs-enable {
type boolean;
description
"Disable/enable all ALGs.
When specified, this parameter overrides the one
that may be indicated, eventually, by the 'status'
of an individual ALG.";
}
container notify-pool-usage {
if-feature "basic-nat44 or napt44 or nat64";
description
"Notification of pool usage when certain criteria
are met.";
leaf pool-id {
type uint32;
Boucadair, et al. Standards Track [Page 55]
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description
"Pool-ID for which the notification criteria
is defined";
}
leaf low-threshold {
type percent;
description
"Notification must be generated when the defined low
threshold is reached.
For example, if a notification is required when the
pool utilization reaches below 10%, this
configuration parameter must be set to 10.
0% indicates that low-threshold notification is
disabled.";
}
leaf high-threshold {
type percent;
must '. >= ../low-threshold' {
error-message
"The high threshold must be greater than or equal
to the low threshold.";
}
description
"Notification must be generated when the defined high
threshold is reached.
For example, if a notification is required when the
pool utilization reaches 90%, this configuration
parameter must be set to 90.
Setting the same value as low-threshold is equivalent
to disabling high-threshold notification.";
}
leaf notify-interval {
type uint32 {
range "1 .. 3600";
}
units "seconds";
default "20";
description
"Minimum number of seconds between successive
notifications for this pool.";
reference
"RFC 7659: Definitions of Managed Objects for
Network Address Translators (NATs)";
}
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}
container external-realm {
description
"Identifies the external realm of the NAT instance.";
choice realm-type {
description
"Can be an interface, VRF instance, etc.";
case interface {
description
"External interface.";
leaf external-interface {
type if:interface-ref;
description
"Name of the external interface.";
}
}
}
}
}
container mapping-limits {
if-feature "napt44 or nat64";
description
"Information about the configuration parameters that
limits the mappings based upon various criteria.";
leaf limit-subscribers {
type uint32;
description
"Maximum number of subscribers that can be serviced
by a NAT instance.
A subscriber is identified by a given prefix.";
reference
"RFC 7659: Definitions of Managed Objects for
Network Address Translators (NATs)";
}
leaf limit-address-mappings {
type uint32;
description
"Maximum number of address mappings that can be
handled by a NAT instance.
When this limit is reached, packets that would
normally trigger translation will be dropped.";
reference
"RFC 7659: Definitions of Managed Objects for
Network Address Translators (NATs)";
}
leaf limit-port-mappings {
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type uint32;
description
"Maximum number of port mappings that can be handled
by a NAT instance.
When this limit is reached, packets that would
normally trigger translation will be dropped.";
reference
"RFC 7659: Definitions of Managed Objects for
Network Address Translators (NATs)";
}
list limit-per-protocol {
if-feature "napt44 or nat64 or dst-nat";
key "protocol-id";
description
"Configure limits per transport protocol";
leaf protocol-id {
type uint8;
mandatory true;
description
"The upper-layer protocol.
Values are taken from the IANA Protocol Numbers
registry.
For example, this field contains 6 for TCP,
17 for UDP, 33 for DCCP, or 132 for SCTP.";
}
leaf limit {
type uint32;
description
"Maximum number of protocol-specific NAT mappings
per instance.";
}
}
}
container connection-limits {
if-feature "basic-nat44 or napt44 or nat64";
description
"Information about the configuration parameters that
rate-limit the translation based upon various criteria.";
leaf limit-per-subscriber {
type uint32;
units "bits/second";
description
"Rate-limit the number of new mappings and sessions
per subscriber.";
}
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leaf limit-per-instance {
type uint32;
units "bits/second";
description
"Rate-limit the number of new mappings and sessions
per instance.";
}
list limit-per-protocol {
if-feature "napt44 or nat64";
key "protocol-id";
description
"Configure limits per transport protocol";
leaf protocol-id {
type uint8;
mandatory true;
description
"The upper-layer protocol.
Values are taken from the IANA Protocol Numbers
registry.
For example, this field contains 6 for TCP,
17 for UDP, 33 for DCCP, or 132 for SCTP.";
}
leaf limit {
type uint32;
description
"Limit the number of protocol-specific mappings
and sessions per instance.";
}
}
}
container notification-limits {
description
"Sets notification limits.";
leaf notify-interval {
if-feature "basic-nat44 or napt44 or nat64";
type uint32 {
range "1 .. 3600";
}
units "seconds";
default "10";
description
"Minimum number of seconds between successive
notifications for this NAT instance.";
reference
"RFC 7659: Definitions of Managed Objects for
Network Address Translators (NATs)";
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}
leaf notify-addresses-usage {
if-feature "basic-nat44 or napt44 or nat64";
type percent;
description
"Notification of address mappings usage over
the whole NAT instance.
Notification must be generated when the defined
threshold is reached.
For example, if a notification is required when
the address mappings utilization reaches 90%,
this configuration parameter must be set
to 90.";
}
leaf notify-ports-usage {
if-feature "napt44 or nat64";
type percent;
description
"Notification of port mappings usage over the
whole NAT instance.
Notification must be generated when the defined
threshold is reached.
For example, if a notification is required when
the port mappings utilization reaches 90%, this
configuration parameter must be set to 90.";
}
leaf notify-subscribers-limit {
if-feature "basic-nat44 or napt44 or nat64";
type uint32;
description
"Notification of active subscribers per NAT
instance.
Notification must be generated when the defined
threshold is reached.";
}
}
container mapping-table {
if-feature "basic-nat44 or napt44 or nat64 "
+ "or clat or dst-nat";
description
"NAT mapping table. Applicable for functions that maintain
static and/or dynamic mappings, such as NAT44, Destination
NAT, NAT64, or CLAT.";
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list mapping-entry {
key "index";
description
"NAT mapping entry.";
uses mapping-entry;
}
}
container statistics {
config false;
description
"Statistics related to the NAT instance.";
leaf discontinuity-time {
type yang:date-and-time;
mandatory true;
description
"The time on the most recent occasion at which the NAT
instance suffered a discontinuity. This must be
initialized when the NAT instance is configured
or rebooted.";
}
container traffic-statistics {
description
"Generic traffic statistics.";
leaf sent-packets {
type yang:zero-based-counter64;
description
"Number of packets sent.";
}
leaf sent-bytes {
type yang:zero-based-counter64;
units "bytes";
description
"Counter for sent traffic in bytes.";
}
leaf rcvd-packets {
type yang:zero-based-counter64;
description
"Number of received packets.";
}
leaf rcvd-bytes {
type yang:zero-based-counter64;
units "bytes";
description
"Counter for received traffic in bytes.";
}
leaf dropped-packets {
type yang:zero-based-counter64;
description
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"Number of dropped packets.";
}
leaf dropped-bytes {
type yang:zero-based-counter64;
units "bytes";
description
"Counter for dropped traffic in bytes.";
}
leaf dropped-fragments {
if-feature "napt44 or nat64";
type yang:zero-based-counter64;
description
"Number of dropped fragments on the external realm.";
}
leaf dropped-address-limit-packets {
if-feature "basic-nat44 or napt44 or nat64";
type yang:zero-based-counter64;
description
"Number of dropped packets because an address limit
is reached.";
}
leaf dropped-address-limit-bytes {
if-feature "basic-nat44 or napt44 or nat64";
type yang:zero-based-counter64;
units "bytes";
description
"Counter of dropped packets because an address limit
is reached, in bytes.";
}
leaf dropped-address-packets {
if-feature "basic-nat44 or napt44 or nat64";
type yang:zero-based-counter64;
description
"Number of dropped packets because no address is
available for allocation.";
}
leaf dropped-address-bytes {
if-feature "basic-nat44 or napt44 or nat64";
type yang:zero-based-counter64;
units "bytes";
description
"Counter of dropped packets because no address is
available for allocation, in bytes.";
}
leaf dropped-port-limit-packets {
if-feature "napt44 or nat64";
type yang:zero-based-counter64;
description
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"Number of dropped packets because a port limit
is reached.";
}
leaf dropped-port-limit-bytes {
if-feature "napt44 or nat64";
type yang:zero-based-counter64;
units "bytes";
description
"Counter of dropped packets because a port limit
is reached, in bytes.";
}
leaf dropped-port-packets {
if-feature "napt44 or nat64";
type yang:zero-based-counter64;
description
"Number of dropped packets because no port is
available for allocation.";
}
leaf dropped-port-bytes {
if-feature "napt44 or nat64";
type yang:zero-based-counter64;
units "bytes";
description
"Counter of dropped packets because no port is
available for allocation, in bytes.";
}
leaf dropped-subscriber-limit-packets {
if-feature "basic-nat44 or napt44 or nat64";
type yang:zero-based-counter64;
description
"Number of dropped packets because the subscriber
limit per instance is reached.";
}
leaf dropped-subscriber-limit-bytes {
if-feature "basic-nat44 or napt44 or nat64";
type yang:zero-based-counter64;
units "bytes";
description
"Counter of dropped packets because the subscriber
limit per instance is reached, in bytes.";
}
}
container mappings-statistics {
description
"Mappings statistics.";
leaf total-active-subscribers {
if-feature "basic-nat44 or napt44 or nat64";
type yang:gauge32;
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description
"Total number of active subscribers (that is,
subscribers for which the NAT maintains active
mappings).
A subscriber is identified by a subnet,
subscriber-mask, etc.";
}
leaf total-address-mappings {
if-feature "basic-nat44 or napt44 or nat64 "
+ "or clat or dst-nat";
type yang:gauge32;
description
"Total number of address mappings present at a given
time. It includes both static and dynamic mappings.";
reference
"Section 3.3.8 of RFC 7659";
}
leaf total-port-mappings {
if-feature "napt44 or nat64";
type yang:gauge32;
description
"Total number of NAT port mappings present at
a given time. It includes both static and dynamic
mappings.";
reference
"Section 3.3.9 of RFC 7659";
}
list total-per-protocol {
if-feature "napt44 or nat64";
key "protocol-id";
description
"Total mappings for each enabled/supported protocol.";
leaf protocol-id {
type uint8;
mandatory true;
description
"The upper-layer protocol.
For example, this field contains 6 for TCP,
17 for UDP, 33 for DCCP, or 132 for SCTP.";
}
leaf total {
type yang:gauge32;
description
"Total number of a protocol-specific mappings present
at a given time. The protocol is identified by
protocol-id.";
}
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}
}
container pools-stats {
if-feature "basic-nat44 or napt44 or nat64";
description
"Statistics related to address/prefix pools
usage";
leaf addresses-allocated {
type yang:gauge32;
description
"Number of all allocated addresses.";
}
leaf addresses-free {
type yang:gauge32;
description
"Number of unallocated addresses of all pools at
a given time. The sum of unallocated and allocated
addresses is the total number of addresses of
the pools.";
}
container ports-stats {
if-feature "napt44 or nat64";
description
"Statistics related to port numbers usage.";
leaf ports-allocated {
type yang:gauge32;
description
"Number of allocated ports from all pools.";
}
leaf ports-free {
type yang:gauge32;
description
"Number of unallocated addresses from all pools.";
}
}
list per-pool-stats {
if-feature "basic-nat44 or napt44 or nat64";
key "pool-id";
description
"Statistics related to address/prefix pool usage";
leaf pool-id {
type uint32;
description
"Unique identifier that represents a pool of
addresses/prefixes.";
}
leaf discontinuity-time {
type yang:date-and-time;
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mandatory true;
description
"The time on the most recent occasion at which this
pool counter suffered a discontinuity. This must
be initialized when the address pool is
configured.";
}
container pool-stats {
description
"Statistics related to address/prefix pool usage";
leaf addresses-allocated {
type yang:gauge32;
description
"Number of allocated addresses from this pool.";
}
leaf addresses-free {
type yang:gauge32;
description
"Number of unallocated addresses in this pool.";
}
}
container port-stats {
if-feature "napt44 or nat64";
description
"Statistics related to port numbers usage.";
leaf ports-allocated {
type yang:gauge32;
description
"Number of allocated ports from this pool.";
}
leaf ports-free {
type yang:gauge32;
description
"Number of unallocated addresses from this pool.";
}
}
}
}
}
}
}
}
/*
* Notifications
*/
notification nat-pool-event {
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if-feature "basic-nat44 or napt44 or nat64";
description
"Notifications must be generated when the defined high/low
threshold is reached. Related configuration parameters
must be provided to trigger the notifications.";
leaf id {
type leafref {
path "/nat/instances/instance/id";
}
mandatory true;
description
"NAT instance identifier.";
}
leaf policy-id {
type leafref {
path "/nat/instances/instance/policy/id";
}
description
"Policy identifier.";
}
leaf pool-id {
type leafref {
path "/nat/instances/instance/policy"
+ "/external-ip-address-pool/pool-id";
}
mandatory true;
description
"Pool Identifier.";
}
leaf notify-pool-threshold {
type percent;
mandatory true;
description
"A threshold (high threshold or low threshold) has
been fired.";
}
}
notification nat-instance-event {
if-feature "basic-nat44 or napt44 or nat64";
description
"Notifications must be generated when notify-addresses-usage
and/or notify-ports-usage thresholds are reached.";
leaf id {
type leafref {
path "/nat/instances/instance/id";
}
mandatory true;
Boucadair, et al. Standards Track [Page 67]
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description
"NAT instance identifier.";
}
leaf notify-subscribers-threshold {
type uint32;
description
"The notify-subscribers-limit threshold has been fired.";
}
leaf notify-addresses-threshold {
type percent;
description
"The notify-addresses-usage threshold has been fired.";
}
leaf notify-ports-threshold {
type percent;
description
"The notify-ports-usage threshold has been fired.";
}
}
}
<CODE ENDS>
4. Security Considerations
Security considerations related to address and prefix translation are
discussed in [RFC6888], [RFC6146], [RFC6877], [RFC6296], and
[RFC7757].
The YANG module specified in this document defines a schema for data
that is designed to be accessed via network management protocols such
as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer
is the secure transport layer, and the mandatory-to-implement secure
transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer
is HTTPS, and the mandatory-to-implement secure transport is TLS
[RFC8446].
The Network Configuration Access Control Model (NACM) [RFC8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content.
All data nodes defined in the YANG module that can be created,
modified, and deleted (i.e., config true, which is the default) are
considered sensitive. Write operations (e.g., edit-config) applied
to these data nodes without proper protection can negatively affect
network operations. The NAT YANG module provides a method to set
parameters to prevent a user from aggressively using NAT resources
Boucadair, et al. Standards Track [Page 68]
RFC 8512 YANG Module for NAT and NPT January 2019
(port-quota), rate-limit connections as a guard against DoS, or to
enable notifications so that appropriate measures are enforced to
anticipate traffic drops. Nevertheless, an attacker who is able to
access the NAT can undertake various attacks, such as:
o Set a high or low resource limit to cause a DoS attack:
* /nat/instances/instance/policy/port-quota
* /nat/instances/instance/policy/fragments-limit
* /nat/instances/instance/mapping-limits
* /nat/instances/instance/connection-limits
o Set a low notification threshold to cause useless notifications to
be generated:
* /nat/instances/instance/policy/notify-pool-usage/high-threshold
* /nat/instances/instance/notification-limits/notify-addresses-
usage
* /nat/instances/instance/notification-limits/notify-ports-usage
* /nat/instances/instance/notification-limits/notify-subscribers-
limit
o Set an arbitrarily high threshold, which may lead to the
deactivation of notifications:
* /nat/instances/instance/policy/notify-pool-usage/high-threshold
* /nat/instances/instance/notification-limits/notify-addresses-
usage
* /nat/instances/instance/notification-limits/notify-ports-usage
* /nat/instances/instance/notification-limits/notify-subscribers-
limit
o Set a low notification interval and a low notification threshold
to induce useless notifications to be generated:
* /nat/instances/instance/policy/notify-pool-usage/notify-
interval
Boucadair, et al. Standards Track [Page 69]
RFC 8512 YANG Module for NAT and NPT January 2019
* /nat/instances/instance/notification-limits/notify-interval
o Access to privacy data maintained in the mapping table. Such data
can be misused to track the activity of a host:
* /nat/instances/instance/mapping-table
5. IANA Considerations
IANA has registered the following URI in the "ns" subregistry within
the "IETF XML Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-nat
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
IANA has registered the following YANG module in the "YANG Module
Names" subregistry [RFC7950] within the "YANG Parameters" registry.
name: ietf-nat
namespace: urn:ietf:params:xml:ns:yang:ietf-nat
prefix: nat
reference: RFC 8512
6. References
6.1. Normative References
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC4787] Audet, F., Ed. and C. Jennings, "Network Address
Translation (NAT) Behavioral Requirements for Unicast
UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
2007, <https://www.rfc-editor.org/info/rfc4787>.
[RFC5382] Guha, S., Ed., Biswas, K., Ford, B., Sivakumar, S., and
P. Srisuresh, "NAT Behavioral Requirements for TCP",
BCP 142, RFC 5382, DOI 10.17487/RFC5382, October 2008,
<https://www.rfc-editor.org/info/rfc5382>.
[RFC5508] Srisuresh, P., Ford, B., Sivakumar, S., and S. Guha, "NAT
Behavioral Requirements for ICMP", BCP 148, RFC 5508,
DOI 10.17487/RFC5508, April 2009,
<https://www.rfc-editor.org/info/rfc5508>.
Boucadair, et al. Standards Track [Page 70]
RFC 8512 YANG Module for NAT and NPT January 2019
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and
X. Li, "IPv6 Addressing of IPv4/IPv6 Translators",
RFC 6052, DOI 10.17487/RFC6052, October 2010,
<https://www.rfc-editor.org/info/rfc6052>.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
April 2011, <https://www.rfc-editor.org/info/rfc6146>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC6296] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
Translation", RFC 6296, DOI 10.17487/RFC6296, June 2011,
<https://www.rfc-editor.org/info/rfc6296>.
[RFC6619] Arkko, J., Eggert, L., and M. Townsley, "Scalable
Operation of Address Translators with Per-Interface
Bindings", RFC 6619, DOI 10.17487/RFC6619, June 2012,
<https://www.rfc-editor.org/info/rfc6619>.
[RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
Combination of Stateful and Stateless Translation",
RFC 6877, DOI 10.17487/RFC6877, April 2013,
<https://www.rfc-editor.org/info/rfc6877>.
[RFC6888] Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa,
A., and H. Ashida, "Common Requirements for Carrier-Grade
NATs (CGNs)", BCP 127, RFC 6888, DOI 10.17487/RFC6888,
April 2013, <https://www.rfc-editor.org/info/rfc6888>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[RFC7596] Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and
I. Farrer, "Lightweight 4over6: An Extension to the Dual-
Stack Lite Architecture", RFC 7596, DOI 10.17487/RFC7596,
July 2015, <https://www.rfc-editor.org/info/rfc7596>.
Boucadair, et al. Standards Track [Page 71]
RFC 8512 YANG Module for NAT and NPT January 2019
[RFC7597] Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S.,
Murakami, T., and T. Taylor, Ed., "Mapping of Address and
Port with Encapsulation (MAP-E)", RFC 7597,
DOI 10.17487/RFC7597, July 2015,
<https://www.rfc-editor.org/info/rfc7597>.
[RFC7757] Anderson, T. and A. Leiva Popper, "Explicit Address
Mappings for Stateless IP/ICMP Translation", RFC 7757,
DOI 10.17487/RFC7757, February 2016,
<https://www.rfc-editor.org/info/rfc7757>.
[RFC7857] Penno, R., Perreault, S., Boucadair, M., Ed., Sivakumar,
S., and K. Naito, "Updates to Network Address Translation
(NAT) Behavioral Requirements", BCP 127, RFC 7857,
DOI 10.17487/RFC7857, April 2016,
<https://www.rfc-editor.org/info/rfc7857>.
[RFC7915] Bao, C., Li, X., Baker, F., Anderson, T., and F. Gont,
"IP/ICMP Translation Algorithm", RFC 7915,
DOI 10.17487/RFC7915, June 2016,
<https://www.rfc-editor.org/info/rfc7915>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.
[RFC8343] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
<https://www.rfc-editor.org/info/rfc8343>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
Boucadair, et al. Standards Track [Page 72]
RFC 8512 YANG Module for NAT and NPT January 2019
6.2. Informative References
[NAT-SUPP]
Stewart, R., Tuexen, M., and I. Ruengeler, "Stream Control
Transmission Protocol (SCTP) Network Address Translation
Support", Work in Progress, draft-ietf-tsvwg-natsupp-12,
July 2018.
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations",
RFC 2663, DOI 10.17487/RFC2663, August 1999,
<https://www.rfc-editor.org/info/rfc2663>.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022,
DOI 10.17487/RFC3022, January 2001,
<https://www.rfc-editor.org/info/rfc3022>.
[RFC5597] Denis-Courmont, R., "Network Address Translation (NAT)
Behavioral Requirements for the Datagram Congestion
Control Protocol", BCP 150, RFC 5597,
DOI 10.17487/RFC5597, September 2009,
<https://www.rfc-editor.org/info/rfc5597>.
[RFC6269] Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and
P. Roberts, "Issues with IP Address Sharing", RFC 6269,
DOI 10.17487/RFC6269, June 2011,
<https://www.rfc-editor.org/info/rfc6269>.
[RFC6736] Brockners, F., Bhandari, S., Singh, V., and V. Fajardo,
"Diameter Network Address and Port Translation Control
Application", RFC 6736, DOI 10.17487/RFC6736, October
2012, <https://www.rfc-editor.org/info/rfc6736>.
[RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
DOI 10.17487/RFC6887, April 2013,
<https://www.rfc-editor.org/info/rfc6887>.
[RFC6908] Lee, Y., Maglione, R., Williams, C., Jacquenet, C., and
M. Boucadair, "Deployment Considerations for Dual-Stack
Lite", RFC 6908, DOI 10.17487/RFC6908, March 2013,
<https://www.rfc-editor.org/info/rfc6908>.
[RFC7050] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
the IPv6 Prefix Used for IPv6 Address Synthesis",
RFC 7050, DOI 10.17487/RFC7050, November 2013,
<https://www.rfc-editor.org/info/rfc7050>.
Boucadair, et al. Standards Track [Page 73]
RFC 8512 YANG Module for NAT and NPT January 2019
[RFC7289] Kuarsingh, V., Ed. and J. Cianfarani, "Carrier-Grade NAT
(CGN) Deployment with BGP/MPLS IP VPNs", RFC 7289,
DOI 10.17487/RFC7289, June 2014,
<https://www.rfc-editor.org/info/rfc7289>.
[RFC7335] Byrne, C., "IPv4 Service Continuity Prefix", RFC 7335,
DOI 10.17487/RFC7335, August 2014,
<https://www.rfc-editor.org/info/rfc7335>.
[RFC7659] Perreault, S., Tsou, T., Sivakumar, S., and T. Taylor,
"Definitions of Managed Objects for Network Address
Translators (NATs)", RFC 7659, DOI 10.17487/RFC7659,
October 2015, <https://www.rfc-editor.org/info/rfc7659>.
[RFC7753] Sun, Q., Boucadair, M., Sivakumar, S., Zhou, C., Tsou, T.,
and S. Perreault, "Port Control Protocol (PCP) Extension
for Port-Set Allocation", RFC 7753, DOI 10.17487/RFC7753,
February 2016, <https://www.rfc-editor.org/info/rfc7753>.
[RFC8045] Cheng, D., Korhonen, J., Boucadair, M., and S. Sivakumar,
"RADIUS Extensions for IP Port Configuration and
Reporting", RFC 8045, DOI 10.17487/RFC8045, January 2017,
<https://www.rfc-editor.org/info/rfc8045>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of
Documents Containing YANG Data Models", BCP 216, RFC 8407,
DOI 10.17487/RFC8407, October 2018,
<https://www.rfc-editor.org/info/rfc8407>.
[RFC8513] Boucadair, M., Jacquenet, C., and S. Sivakumar, "A YANG
Data Model for Dual-Stack Lite (DS-Lite)", RFC 8513,
DOI 10.17487/RFC8513, January 2019,
<https://www.rfc-editor.org/info/rfc8513>.
[YANG-PCP] Boucadair, M., Jacquenet, C., Sivakumar, S., and
S. Vinapamula, "YANG Modules for the Port Control Protocol
(PCP)", Work in Progress, draft-boucadair-pcp-yang-05,
October 2017.
Boucadair, et al. Standards Track [Page 74]
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Appendix A. Some Examples
This section provides a non-exhaustive set of examples to illustrate
the use of the NAT YANG module.
A.1. Traditional NAT44
Traditional NAT44 is a Basic NAT44 or NAPT that is used to share the
same IPv4 address among hosts that are owned by the same subscriber.
This is typically the NAT that is embedded in CPE devices.
This NAT is usually provided with one single external IPv4 address;
disambiguating connections is achieved by rewriting the source port
number. The XML snippet to configure the external IPv4 address in
such case together with a mapping entry is depicted below:
<instances>
<instance>
<id>1</id>
<name>NAT_Subscriber_A</name>
....
<external-ip-address-pool>
<pool-id>1</pool-id>
<external-ip-pool>
198.51.100.1/32
</external-ip-pool>
</external-ip-address-pool>
....
<mapping-table>
....
<external-src-address>
198.51.100.1/32
</external-src-address>
....
</mapping-table>
</instance>
</instances>
Boucadair, et al. Standards Track [Page 75]
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The following shows the XML excerpt depicting a dynamic UDP mapping
entry maintained by a traditional NAPT44. In reference to this
example, the UDP packet received with a source IPv4 address
(192.0.2.1) and source port number (1568) is translated into a UDP
packet having a source IPv4 address (198.51.100.1) and source port
(15000). The remaining lifetime of this mapping is 300 seconds.
<mapping-entry>
<index>15</index>
<type>
dynamic-explicit
</type>
<transport-protocol>
17
</transport-protocol>
<internal-src-address>
192.0.2.1/32
</internal-src-address>
<internal-src-port>
<start-port-number>
1568
</start-port-number>
</internal-src-port>
<external-src-address>
198.51.100.1/32
</external-src-address>
<external-src-port>
<start-port-number>
15000
</start-port-number>
</external-src-port>
<lifetime>
300
</lifetime>
</mapping-entry>
A.2. Carrier Grade NAT (CGN)
The following XML snippet shows the example of the capabilities
supported by a CGN as retrieved using NETCONF.
<capabilities>
<nat-flavor>napt44</nat-flavor>
<transport-protocols>
<protocol-id>1</protocol-id>
</transport-protocols>
<transport-protocols>
<protocol-id>6</protocol-id>
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</transport-protocols>
<transport-protocols>
<protocol-id>17</protocol-id>
</transport-protocols>
<restricted-port-support>
false
</restricted-port-support>
<static-mapping-support>
true
</static-mapping-support>
<port-randomization-support>
true
</port-randomization-support>
<port-range-allocation-support>
true
</port-range-allocation-support>
<port-preservation-suport>
true
</port-preservation-suport>
<port-parity-preservation-support>
false
</port-parity-preservation-support>
<address-roundrobin-support>
true
</address-roundrobin-support>
<paired-address-pooling-support>
true
</paired-address-pooling-support>
<endpoint-independent-mapping-support>
true
</endpoint-independent-mapping-support>
<address-dependent-mapping-support>
true
</address-dependent-mapping-support>
<address-and-port-dependent-mapping-support>
true
</address-and-port-dependent-mapping-support>
<endpoint-independent-filtering-support>
true
</endpoint-independent-filtering-support>
<address-dependent-filtering>
true
</address-dependent-filtering>
<address-and-port-dependent-filtering>
true
</address-and-port-dependent-filtering>
</capabilities>
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The following XML snippet shows the example of a CGN that is
provisioned with one contiguous pool of external IPv4 addresses
(198.51.100.0/24). Further, the CGN is instructed to limit the
number of allocated ports per subscriber to 1024. Ports can be
allocated by the CGN by assigning ranges of 256 ports (that is, a
subscriber can be allocated up to four port ranges of 256 ports
each).
<instances>
<instance>
<id>1</id>
<name>myCGN</name>
....
<external-ip-address-pool>
<pool-id>1</pool-id>
<external-ip-pool>
198.51.100.0/24
</external-ip-pool>
</external-ip-address-pool>
<port-quota>
<port-limit>
1024
</port-limit>
<quota-type >
all
</quota-type >
</port-quota>
<port-allocation-type>
port-range-allocation
</port-allocation-type>
<port-set>
<port-set-size>
256
</port-set-size>
</port-set>
....
</instance>
</instances>
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An administrator may decide to allocate one single port range per
subscriber (e.g., a port range of 1024 ports) as shown below:
<instances>
<instance>
<id>1</id>
<name>myCGN</name>
....
<external-ip-address-pool>
<pool-id>1</pool-id>
<external-ip-pool>
198.51.100.0/24
</external-ip-pool>
</external-ip-address-pool>
<port-quota>
<port-limit>
1024
</port-limit>
<quota-type >
all
</quota-type >
</port-quota>
<port-allocation-type>
port-range-allocation
</port-allocation-type>
<port-set>
<port-set-size>
1024
</port-set-size>
</port-set>
....
</instance>
</instances>
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A.3. CGN Pass-Through
Figure 1 illustrates an example of the CGN pass-through feature.
X1:x1 X1':x1' X2:x2
+---+from X1:x1 +---+from X1:x1 +---+
| C | to X2:x2 | | to X2:x2 | S |
| l |>>>>>>>>>>>>| C |>>>>>>>>>>>>>>| e |
| i | | G | | r |
| e |<<<<<<<<<<<<| N |<<<<<<<<<<<<<<| v |
| n |from X2:x2 | |from X2:x2 | e |
| t | to X1:x1 | | to X1:x1 | r |
+---+ +---+ +---+
Figure 1: CGN Pass-Through
For example, in order to disable NAT for communications issued by the
client (192.0.2.1), the following configuration parameter must be
set:
<nat-pass-through>
...
<prefix>192.0.2.1/32</prefix>
...
</nat-pass-through>
A.4. NAT64
Let's consider the example of a NAT64 that should use
2001:db8:122:300::/56 to perform IPv6 address synthesis [RFC6052].
The XML snippet to configure the NAT64 prefix in such case is
depicted below:
<nat64-prefixes>
<nat64-prefix>
2001:db8:122:300::/56
</nat64-prefix>
</nat64-prefixes>
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Let's now consider the example of a NAT64 that should use
2001:db8:122::/48 to perform IPv6 address synthesis [RFC6052] only if
the destination address matches 198.51.100.0/24. The XML snippet to
configure the NAT64 prefix in such case is shown below:
<nat64-prefixes>
<nat64-prefix>
2001:db8:122::/48
</nat64-prefix>
<destination-ipv4-prefix>
<ipv4-prefix>
198.51.100.0/24
</ipv4-prefix>
</destination-ipv4-prefix>
</nat64-prefixes>
A.5. Stateless IP/ICMP Translation (SIIT)
Let's consider the example of a stateless translator that is
configured with 2001:db8:100::/40 to perform IPv6 address synthesis
[RFC6052]. Similar to the NAT64 case, the XML snippet to configure
the NAT64 prefix in such case is depicted below:
<nat64-prefixes>
<nat64-prefix>
2001:db8:100::/40
</nat64-prefix>
</nat64-prefixes>
When the translator receives an IPv6 packet, for example, with a
source address (2001:db8:1c0:2:21::) and destination address
(2001:db8:1c6:3364:2::), it extracts embedded IPv4 addresses
following rules per RFC 6052 with 2001:db8:100::/40 as the NSP:
o 192.0.2.33 is extracted from 2001:db8:1c0:2:21::
o 198.51.100.2 is extracted from 2001:db8:1c6:3364:2::
The translator transforms the IPv6 header into an IPv4 header using
the IP/ICMP Translation Algorithm [RFC7915]. The IPv4 packets will
include 192.0.2.33 as the source address and 198.51.100.2 as the
destination address.
Also, a NAT64 can be instructed to behave in the stateless mode by
providing the following configuration. The same NAT64 prefix is used
for constructing both IPv4-translatable IPv6 addresses and
IPv4-converted IPv6 addresses (see Section 3.3 of [RFC6052]).
Boucadair, et al. Standards Track [Page 81]
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<nat64-prefixes>
<nat64-prefix>
2001:db8:122:300::/56
</nat64-prefix>
<stateless-enable>
true
</stateless-enable>
</nat64-prefixes>
A.6. Explicit Address Mappings (EAM) for Stateless IP/ICMP Translation
(SIIT)
As specified in [RFC7757], an EAM consists of an IPv4 prefix and an
IPv6 prefix. Let's consider the set of EAM examples in Table 8.
+----------------+----------------------+
| IPv4 Prefix | IPv6 Prefix |
+----------------+----------------------+
| 192.0.2.1 | 2001:db8:aaaa:: |
| 192.0.2.2/32 | 2001:db8:bbbb::b/128 |
| 192.0.2.16/28 | 2001:db8:cccc::/124 |
| 192.0.2.128/26 | 2001:db8:dddd::/64 |
| 192.0.2.192/29 | 2001:db8:eeee:8::/62 |
| 192.0.2.224/31 | 64:ff9b::/127 |
+----------------+----------------------+
Table 8: EAM Examples (RFC 7757)
The following XML excerpt illustrates how these EAMs can be
configured using the NAT YANG module:
<eam>
<ipv4-prefix>
192.0.2.1/32
</ipv4-prefix>
<ipv6-prefix>
2001:db8:aaaa::/128
</ipv6-prefix>
</eam>
<eam>
<ipv4-prefix>
192.0.2.2/32
</ipv4-prefix>
<ipv6-prefix>
2001:db8:bbbb::b/128
</ipv6-prefix>
</eam>
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<eam>
<ipv4-prefix>
192.0.2.16/28
</ipv4-prefix>
<ipv6-prefix>
2001:db8:cccc::/124
</ipv6-prefix>
</eam>
<eam>
<ipv4-prefix>
192.0.2.128/26
</ipv4-prefix>
<ipv6-prefix>
2001:db8:dddd::/64
</ipv6-prefix>
</eam>
<eam>
<ipv4-prefix>
192.0.2.192/29
</ipv4-prefix>
<ipv6-prefix>
2001:db8:eeee:8::/62
</ipv6-prefix>
</eam>
<eam>
<ipv4-prefix>
192.0.2.224/31
</ipv4-prefix>
<ipv6-prefix>
64:ff9b::/127
</ipv6-prefix>
</eam>
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EAMs may be enabled jointly with stateful NAT64. This example shows
a NAT64 function that supports static mappings:
<capabilities>
<nat-flavor>
nat64
</nat-flavor>
<static-mapping-support>
true
</static-mapping-support>
<port-randomization-support>
true
</port-randomization-support>
<port-range-allocation-support>
true
</port-range-allocation-support>
<port-preservation-suport>
true
</port-preservation-suport>
<address-roundrobin-support>
true
</address-roundrobin-support>
<paired-address-pooling-support>
true
</paired-address-pooling-support>
<endpoint-independent-mapping-support>
true
</endpoint-independent-mapping-support>
<endpoint-independent-filtering-support>
true
</endpoint-independent-filtering-support>
</capabilities>
Boucadair, et al. Standards Track [Page 84]
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A.7. Static Mappings with Port Ranges
The following example shows a static mapping that instructs a NAT to
translate packets issued from 192.0.2.1 and with source ports in the
100-500 range to 198.51.100.1:1100-1500.
<mapping-entry>
<index>1</index>
<type>
static
</type>
<transport-protocol>
6
</transport-protocol>
<internal-src-address>
192.0.2.1/32
</internal-src-address>
<internal-src-port>
<start-port-number>
100
</start-port-number>
<end-port-number>
500
</end-port-number>
</internal-src-port>
<external-src-address>
198.51.100.1/32
</external-src-address>
<external-src-port>
<start-port-number>
1100
</start-port-number>
<end-port-number>
1500
</end-port-number>
</external-src-port>
...
</mapping-entry>
Boucadair, et al. Standards Track [Page 85]
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A.8. Static Mappings with IP Prefixes
The following example shows a static mapping that instructs a NAT to
translate TCP packets issued from 192.0.2.0/24 to 198.51.100.0/24.
<mapping-entry>
<index>1</index>
<type>
static
</type>
<transport-protocol>
6
</transport-protocol>
<internal-src-address>
192.0.2.0/24
</internal-src-address>
<external-src-address>
198.51.100.0/24
</external-src-address>
...
</mapping-entry>
A.9. Destination NAT
The following XML snippet shows an example of a Destination NAT that
is instructed to translate all packets having 192.0.2.1 as a
destination IP address to 198.51.100.1.
<dst-ip-address-pool>
<pool-id>1</pool-id>
<dst-in-ip-pool>
192.0.2.1/32
</dst-in-ip-pool>
<dst-out-ip-pool>
198.51.100.1/32
</dst-out-ip-pool>
</dst-ip-address-pool>
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In order to instruct a NAT to translate TCP packets destined to
'192.0.2.1:80' to '198.51.100.1:8080', the following XML snippet
shows the static mapping configured on the NAT:
<mapping-entry>
<index>1568</index>
<type>
static
</type>
<transport-protocol>
6
</transport-protocol>
<internal-dst-address>
192.0.2.1/32
</internal-dst-address>
<internal-dst-port>
<start-port-number>
80
</start-port-number>
</internal-dst-port>
<external-dst-address>
198.51.100.1/32
</external-dst-address>
<external-dst-port>
<start-port-number>
8080
</start-port-number>
</external-dst-port>
</mapping-entry>
Boucadair, et al. Standards Track [Page 87]
RFC 8512 YANG Module for NAT and NPT January 2019
In order to instruct a NAT to translate TCP packets destined to
'192.0.2.1:80' (HTTP traffic) to 198.51.100.1 and '192.0.2.1:22' (SSH
traffic) to 198.51.100.2, the following XML snippet shows the static
mappings configured on the NAT:
<mapping-entry>
<index>123</index>
<type>
static
</type>
<transport-protocol>
6
</transport-protocol>
<internal-dst-address>
192.0.2.1/32
</internal-dst-address>
<internal-dst-port>
<start-port-number>
80
</start-port-number>
</internal-dst-port>
<external-dst-address>
198.51.100.1/32
</external-dst-address>
...
</mapping-entry>
<mapping-entry>
<index>1236</index>
<type>
static
</type>
<transport-protocol>
6
</transport-protocol>
<internal-dst-address>
192.0.2.1/32
</internal-dst-address>
<internal-dst-port>
<start-port-number>
22
</start-port-number>
</internal-dst-port>
<external-dst-address>
198.51.100.2/32
</external-dst-address>
...
</mapping-entry>
Boucadair, et al. Standards Track [Page 88]
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The NAT may also be instructed to proceed with both source and
Destination NAT. To do so, in addition to the above example to
configure Destination NAT, the NAT may be provided, for example with
a pool of external IP addresses (198.51.100.0/24) to use for source
address translation. An example of the corresponding XML snippet is
provided hereafter:
<external-ip-address-pool>
<pool-id>1</pool-id>
<external-ip-pool>
198.51.100.0/24
</external-ip-pool>
</external-ip-address-pool>
Instead of providing an external IP address to share, the NAT may be
configured with static mapping entries that modify the internal IP
address and/or port number.
A.10. Customer-Side Translator (CLAT)
The following XML snippet shows the example of a CLAT that is
configured with 2001:db8:1234::/96 as a PLAT-side IPv6 prefix and
2001:db8:aaaa::/96 as a CLAT-side IPv6 prefix. The CLAT is also
provided with 192.0.0.1/32 (which is selected from the IPv4 service
continuity prefix defined in [RFC7335]).
<clat-ipv6-prefixes>
<ipv6-prefix>
2001:db8:aaaa::/96
</ipv6-prefix>
</clat-ipv6-prefixes>
<clat-ipv4-prefixes>
<ipv4-prefix>
192.0.0.1/32
</ipv4-prefix>
</clat-ipv4-prefixes>
<nat64-prefixes>
<nat64-prefix>
2001:db8:1234::/96
</nat64-prefix>
</nat64-prefixes>
Boucadair, et al. Standards Track [Page 89]
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A.11. IPv6 Network Prefix Translation (NPTv6)
Let's consider the example of an NPTv6 translator that should rewrite
packets with the source prefix (fd03:c03a:ecab::/48) with the
external prefix (2001:db8:1::/48). The internal interface is "eth0"
while the external interface is "eth1" (Figure 2).
External Network: Prefix = 2001:db8:1::/48
--------------------------------------
|
|eth1
+-------------+
eth4| NPTv6 |eth2
...-----| |------...
+-------------+
|eth0
|
--------------------------------------
Internal Network: Prefix = fd03:c03a:ecab::/48
Figure 2: Example of NPTv6
The XML snippet to configure NPTv6 prefixes in such case is depicted
below:
<nptv6-prefixes>
<internal-ipv6-prefix>
fd03:c03a:ecab::/48
</internal-ipv6-prefix>
<external-ipv6-prefix>
2001:db8:1::/48
</external-ipv6-prefix>
</nptv6-prefixes>
...
<external-realm>
<external-interface>
eth1
</external-interface>
</external-realm>
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RFC 8512 YANG Module for NAT and NPT January 2019
Figure 3 shows an example of an NPTv6 translator that interconnects
two internal networks (fd03:c03a:ecab::/48 and fda8:d5cb:14f3::/48);
each is translated using a dedicated prefix (2001:db8:1::/48 and
2001:db8:6666::/48, respectively).
Internal Prefix = fda8:d5cb:14f3::/48
--------------------------------------
V | External Prefix
V |eth1 2001:db8:1::/48
V +---------+ ^
V | NPTv6 | ^
V | | ^
V +---------+ ^
External Prefix |eth0 ^
2001:db8:6666::/48 | ^
--------------------------------------
Internal Prefix = fd03:c03a:ecab::/48
Figure 3: Connecting Two Peer Networks
Boucadair, et al. Standards Track [Page 91]
RFC 8512 YANG Module for NAT and NPT January 2019
To that aim, the following configuration is provided to the NPTv6
translator:
<policy>
<id>1</id>
<nptv6-prefixes>
<internal-ipv6-prefix>
fd03:c03a:ecab::/48
</internal-ipv6-prefix>
<external-ipv6-prefix>
2001:db8:1::/48
</external-ipv6-prefix>
</nptv6-prefixes>
<external-realm>
<external-interface>
eth1
</external-interface>
</external-realm>
</policy>
<policy>
<id>2</id>
<nptv6-prefixes>
<internal-ipv6-prefix>
fda8:d5cb:14f3::/48
</internal-ipv6-prefix>
<external-ipv6-prefix>
2001:db8:6666::/48
</external-ipv6-prefix>
</nptv6-prefixes>
<external-realm>
<external-interface>
eth0
</external-interface>
</external-realm>
</policy>
Boucadair, et al. Standards Track [Page 92]
RFC 8512 YANG Module for NAT and NPT January 2019
Acknowledgements
Many thanks to Dan Wing, Tianran Zhou, Tom Petch, Warren Kumari, and
Benjamin Kaduk for their review.
Thanks to Juergen Schoenwaelder for the comments on the YANG
structure and the suggestion to use NMDA. Mahesh Jethanandani
provided useful comments.
Thanks to Lee Howard and Jordi Palet for the CLAT comments, Fred
Baker for the NPTv6 comments, Tore Anderson for the EAM SIIT review,
and Kristian Poscic for the CGN review.
Special thanks to Maros Marsalek and Marek Gradzki for sharing their
comments based on the FD.io implementation of this module
(https://git.fd.io/hc2vpp/tree/nat/nat-api/src/main/yang).
Rajiv Asati suggested clarifying how the module applies for both
stateless and stateful NAT64.
Juergen Schoenwaelder provided an early YANG Doctors review. Many
thanks to him.
Thanks to Roni Even, Mach(Guoyi) Chen, Tim Chown, and Stephen Farrell
for the directorates review. Igor Ryzhov identified a nit in one
example.
Mirja Kuehlewind made a comment about the reuse of some TCP timers
for any connection-oriented protocol.
Boucadair, et al. Standards Track [Page 93]
RFC 8512 YANG Module for NAT and NPT January 2019
Authors' Addresses
Mohamed Boucadair (editor)
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Senthil Sivakumar
Cisco Systems
7100-8 Kit Creek Road
Research Triangle Park, North Carolina 27709
United States of America
Phone: +1 919 392 5158
Email: ssenthil@cisco.com
Christian Jacquenet
Orange
Rennes 35000
France
Email: christian.jacquenet@orange.com
Suresh Vinapamula
Juniper Networks
1133 Innovation Way
Sunnyvale 94089
United States of America
Email: sureshk@juniper.net
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: bill.wu@huawei.com
Boucadair, et al. Standards Track [Page 94]