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Independent Submission D. Liu
Request for Comments: 9296 J. Halpern
Category: Informational C. Zhang
ISSN: 2070-1721 Ericsson
August 2022
ifStackTable for the Point-to-Point (P2P) Interface over a LAN Type:
Definition and Examples
Abstract
RFC 5309 defines the Point-to-Point (P2P) circuit type, one of the
two circuit types used in the link-state routing protocols, and
highlights that it is important to identify the correct circuit type
when forming adjacencies, flooding link-state database packets, and
monitoring the link state.
This document provides advice about the ifStack for the P2P interface
over a LAN Type to facilitate operational control, maintenance, and
statistics.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This is a contribution to the RFC Series, independently of any other
RFC stream. The RFC Editor has chosen to publish this document at
its discretion and makes no statement about its value for
implementation or deployment. Documents approved for publication by
the RFC Editor are not candidates for any level of Internet Standard;
see 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/rfc9296.
Copyright Notice
Copyright (c) 2022 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.
Table of Contents
1. Introduction
2. Requirements Language
3. Interface Stack Table for P2P Interface Type
3.1. P2P Interface: higher-layer-if and lower-layer-if
3.2. P2P Interface Statistics
3.3. P2P Interface Administrative State
4. Security Considerations
5. IANA Considerations
6. References
6.1. Normative References
6.2. Informative References
Appendix A. Examples
Acknowledgements
Authors' Addresses
1. Introduction
[RFC5309] defines the Point-to-Point (P2P) circuit type and
highlights that it is important to identify the correct circuit type
when forming adjacencies, flooding link-state database packets, and
monitoring the link state.
To simplify configuration and operational control, it is helpful to
represent the fact that an interface is to be considered a P2P
interface over a LAN type explicitly in the interface stack. This
enables, for example, routing protocols to automatically inherit the
correct operating mode from the interface stack without further
configuration (i.e., there is no need to explicitly configure the P2P
interface in routing protocols).
It is helpful to map the P2P interface over a LAN type in the
interface management stack table. If no entry specifies the lower
layer of the P2P interface, then management tools lose the ability to
retrieve and measure properties specific to lower layers.
In standard network management protocols that make use of
ifStackTables, the P2P interface over a LAN type is intended to be
used solely as a means to signal that the upper-layer interface of
link-data layer is a P2P interface. Thus, the upper and lower layers
of P2P over a LAN type are expected to apply appropriate semantics.
In general, the higher layer of a P2P over a LAN type SHOULD be
"ipForward" (value 142 in [Assignment]), and the lower layer of P2P
over a LAN type SHOULD be any appropriate link-data layer of
"ipForward".
The assignment of 303 as the value for the p2pOverLan ifType was made
by Expert Review (see [Assignment] and [RFC8126]). The purpose of
this document is to serve as a reference for ifType 303 by suggesting
how the ifStackTable for the P2P interface over a LAN type is to be
used and providing examples.
It should be noted that this document reflects the operating model
used on some routers. Other routers that use different models may
not represent a P2P as a separate interface.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Interface Stack Table for P2P Interface Type
3.1. P2P Interface: higher-layer-if and lower-layer-if
If a device implements the IF-MIB [RFC2863], then each entry in the
"/interfaces/interface" list (see "A YANG Data Model for Interface
Management" [RFC8343]) in the operational state is typically mapped
to one ifEntry as required in [RFC8343]. Therefore, the P2P
interface over a LAN type should also be fully mapped to one ifEntry
by defining the "ifStackTable" ("higher-layer-if" and "lower-layer-
if", defined in [RFC8343]).
In the ifStackTable, the higher layer of the P2P interface over a LAN
type SHALL be network layer "ipForward" to enable IP routing, and the
lower layer of the P2P interface over a LAN type SHOULD be any link-
data layer that can be bound to "ipForward", including
"ethernetCsmacd", "ieee8023adLag", "l2vlan", and so on (defined in
the iana-if-type YANG module [IANA-ifTYPE]).
The P2P interface over the LAN type ifStackTable can be defined along
the lines of the following example, which complies with [RFC8343] and
[RFC6991]. In the example, "lower-layer-if" takes "ethernetCsmacd",
but, in fact, "lower-layer-if" can be any other available link-data
layer. See Appendix A for more examples.
<CODE BEGINS>
<interface>
<name>isis_int</name>
<type>ianaift:ipForward</type>
</interface>
<interface>
<name>eth1</name>
<type>ianaift:ethernetCsmacd</type>
</interface>
<interface>
<name>p2p</name>
<type>ianaift:p2pOverLan</type>
<higher-layer-if>isis_int</higher-layer-if>
<lower-layer-if>eth1</lower-layer-if>
<enabled>false</enabled>
<admin-status>down</admin-status>
<oper-status>down</oper-status>
<statistics>
<discontinuity-time>
2021-04-01T03:00:00+00:00
</discontinuity-time>
<!-- counters now shown here -->
</statistics>
</interface>
<CODE ENDS>
Figure 1
3.2. P2P Interface Statistics
Because multiple IP interfaces can be bound to one physical port, the
statistics on the physical port SHOULD be a complete set that
includes statistics of all upper-layer interfaces. Therefore, each
P2P interface collects and displays traffic that has been sent to it
via higher layers or received from it via lower layers.
3.3. P2P Interface Administrative State
The P2P interface can be shut down independently of the underlying
interface.
If the P2P interface is administratively up, then the "oper-status"
(defined in [RFC8343]) of that interface SHALL fully reflect the
state of the underlying interface; if the P2P interface is
administratively down, then the "oper-status" of that interface SHALL
be down. Examples can be found in Appendix A.
4. Security Considerations
The writable attribute "admin-status" of the p2povervlan ifType is
inherited from [RFC8343]. Other objects associated with the
p2povervlan ifType are read-only. With this in mind, the
considerations discussed in Section 7 of [RFC8343] otherwise apply to
the p2povervlan ifType.
5. IANA Considerations
In the "Interface Types (ifType)" registry, value 303 is assigned to
p2pOverLan [Assignment]. As this document explains how the
p2pOverLan (303) ifType is to be used, IANA has amended the reference
for p2pOverLan (303) to point to this document (instead of [RFC5309])
and made a similar amendment in the YANG iana-if-type module
[IANA-ifTYPE] (originally specified in [RFC7224]).
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group
MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000,
<https://www.rfc-editor.org/info/rfc2863>.
[RFC5309] Shen, N., Ed. and A. Zinin, Ed., "Point-to-Point Operation
over LAN in Link State Routing Protocols", RFC 5309,
DOI 10.17487/RFC5309, October 2008,
<https://www.rfc-editor.org/info/rfc5309>.
[RFC7224] Bjorklund, M., "IANA Interface Type YANG Module",
RFC 7224, DOI 10.17487/RFC7224, May 2014,
<https://www.rfc-editor.org/info/rfc7224>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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>.
6.2. Informative References
[Assignment]
IANA, "Interface Types (ifType)",
<https://www.iana.org/assignments/smi-numbers>.
[IANA-ifTYPE]
IANA, "YANG Module Names",
<https://www.iana.org/assignments/yang-parameters>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
Appendix A. Examples
If the underlying interface is a VLAN sub-interface, the
ifStackTable should be defined as:
<CODE BEGINS>
<interface>
<name>isis_int</name>
<type>ianaift:ipForward</type>
</interface>
<interface>
<name>eth1_valn1</name>
<type>ianaift:l2vlan</type>
</interface>
<interface>
<name>p2p</name>
<type>ianaift:p2pOverLan</type>
<higher-layer-if>isis_int</higher-layer-if>
<lower-layer-if>eth1_valn1</lower-layer-if>
<enabled>false</enabled>
<admin-status>down</admin-status>
<oper-status>down</oper-status>
<statistics>
<discontinuity-time>
2021-04-01T03:00:00+00:00
</discontinuity-time>
<!-- counters now shown here -->
</statistics>
</interface>
<CODE ENDS>
Figure 2
If the underlying interface is Link Aggregation Group (LAG), the
ifStackTable should be defined as:
<CODE BEGINS>
<interface>
<name>isis_int</name>
<type>ianaift:ipForward</type>
</interface>
<interface>
<name>eth1_lag1</name>
<type>ianaift:ieee8023adLag</type>
</interface>
<interface>
<name>p2p</name>
<type>ianaift:p2pOverLan</type>
<higher-layer-if>isis_int</higher-layer-if>
<lower-layer-if>eth1_lag1</lower-layer-if>
<enabled>false</enabled>
<admin-status>down</admin-status>
<oper-status>down</oper-status>
<statistics>
<discontinuity-time>
2021-04-01T03:00:00+00:00
</discontinuity-time>
<!-- counters now shown here -->
</statistics>
</interface>
<CODE ENDS>
Figure 3
If the P2P interface and underlying interface are both
administratively up and the underlying interface operational status
is up:
<CODE BEGINS>
<interface>
<name>p2p</name>
<type>ianaift:p2pOverLan</type>
<higher-layer-if>isis_int</higher-layer-if>
<lower-layer-if>eth1</lower-layer-if>
<admin-status>up</admin-status>
<oper-status>up</oper-status>
</interface>
<CODE ENDS>
Figure 4
If the P2P interface and underlying interface are administratively up
but the underlying interface operational status is down:
<CODE BEGINS>
<interface>
<name>p2p</name>
<type>ianaift:p2pOverLan</type>
<higher-layer-if>isis_int</higher-layer-if>
<lower-layer-if>eth1</lower-layer-if>
<admin-status>up</admin-status>
<oper-status>down</oper-status>
</interface>
<CODE ENDS>
Figure 5
If the P2P interface is administratively down:
<CODE BEGINS>
<interface>
<name>p2p</name>
<type>ianaift:p2pOverLan</type>
<higher-layer-if>isis_int</higher-layer-if>
<lower-layer-if>eth1</lower-layer-if>
<admin-status>down</admin-status>
<oper-status>down</oper-status>
</interface>
<CODE ENDS>
Figure 6
If the P2P interface is administratively up but the underlying
interface is administratively down:
<CODE BEGINS>
<interface>
<name>p2p</name>
<type>ianaift:p2pOverLan</type>
<higher-layer-if>isis_int</higher-layer-if>
<lower-layer-if>eth1</lower-layer-if>
<admin-status>up</admin-status>
<oper-status>down</oper-status>
</interface>
<CODE ENDS>
Figure 7
Acknowledgements
The authors would like to thank Rob Wilton for his reviews and
valuable comments and suggestions.
Authors' Addresses
Daiying Liu
Ericsson
No.5 Lize East Street
Beijing
100102
China
Email: harold.liu@ericsson.com
Joel Halpern
Ericsson
Email: joel.halpern@ericsson.com
Congjie Zhang
Ericsson
Email: congjie.zhang@ericsson.com