💾 Archived View for gmi.noulin.net › rfc › rfc7897.gmi captured on 2022-04-29 at 02:55:55. Gemini links have been rewritten to link to archived content
⬅️ Previous capture (2022-01-08)
-=-=-=-=-=-=-
Keywords: PCEP, PCE, domain, subobjects
Internet Engineering Task Force (IETF) D. Dhody
Request for Comments: 7897 U. Palle
Category: Experimental Huawei Technologies
ISSN: 2070-1721 R. Casellas
CTTC
June 2016
Domain Subobjects
for the Path Computation Element Communication Protocol (PCEP)
Abstract
The ability to compute shortest constrained Traffic Engineering Label
Switched Paths (TE LSPs) in Multiprotocol Label Switching (MPLS) and
Generalized MPLS (GMPLS) networks across multiple domains has been
identified as a key requirement. In this context, a domain is a
collection of network elements within a common sphere of address
management or path computational responsibility such as an Interior
Gateway Protocol (IGP) area or an Autonomous System (AS). This
document specifies a representation and encoding of a domain
sequence, which is defined as an ordered sequence of domains
traversed to reach the destination domain to be used by Path
Computation Elements (PCEs) to compute inter-domain constrained
shortest paths across a predetermined sequence of domains. This
document also defines new subobjects to be used to encode domain
identifiers.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.
This document defines an Experimental Protocol for the Internet
community. 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). Not
all documents approved by the IESG are a candidate 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
http://www.rfc-editor.org/info/rfc7897.
Dhody, et al. Experimental [Page 1]
RFC 7897 Domain Subobjects for PCEP June 2016
Copyright Notice
Copyright (c) 2016 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
(http://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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Detail Description . . . . . . . . . . . . . . . . . . . . . 6
3.1. Domains . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Domain Sequence . . . . . . . . . . . . . . . . . . . . . 6
3.3. Domain Sequence Representation . . . . . . . . . . . . . 7
3.4. Include Route Object (IRO) . . . . . . . . . . . . . . . 8
3.4.1. Subobjects . . . . . . . . . . . . . . . . . . . . . 8
3.4.1.1. Autonomous System . . . . . . . . . . . . . . . . 8
3.4.1.2. IGP Area . . . . . . . . . . . . . . . . . . . . 9
3.4.2. Update in IRO Specification . . . . . . . . . . . . . 10
3.4.3. IRO for Domain Sequence . . . . . . . . . . . . . . . 11
3.4.3.1. PCC Procedures . . . . . . . . . . . . . . . . . 11
3.4.3.2. PCE Procedures . . . . . . . . . . . . . . . . . 11
3.5. Exclude Route Object (XRO) . . . . . . . . . . . . . . . 13
3.5.1. Subobjects . . . . . . . . . . . . . . . . . . . . . 13
3.5.1.1. Autonomous System . . . . . . . . . . . . . . . . 14
3.5.1.2. IGP Area . . . . . . . . . . . . . . . . . . . . 14
3.6. Explicit Exclusion Route Subobject (EXRS) . . . . . . . . 16
3.7. Explicit Route Object (ERO) . . . . . . . . . . . . . . . 16
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1. Inter-Area Path Computation . . . . . . . . . . . . . . . 17
4.2. Inter-AS Path Computation . . . . . . . . . . . . . . . . 19
4.2.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . 20
4.2.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . 22
4.3. Boundary Node and Inter-AS Link . . . . . . . . . . . . . 25
4.4. PCE Serving Multiple Domains . . . . . . . . . . . . . . 25
4.5. P2MP . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.6. Hierarchical PCE . . . . . . . . . . . . . . . . . . . . 27
Dhody, et al. Experimental [Page 2]
RFC 7897 Domain Subobjects for PCEP June 2016
5. Other Considerations . . . . . . . . . . . . . . . . . . . . 27
5.1. Relationship to PCE Sequence . . . . . . . . . . . . . . 27
5.2. Relationship to RSVP-TE . . . . . . . . . . . . . . . . . 27
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
6.1. New Subobjects . . . . . . . . . . . . . . . . . . . . . 28
7. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8. Manageability Considerations . . . . . . . . . . . . . . . . 29
8.1. Control of Function and Policy . . . . . . . . . . . . . 29
8.2. Information and Data Models . . . . . . . . . . . . . . . 29
8.3. Liveness Detection and Monitoring . . . . . . . . . . . . 30
8.4. Verify Correct Operations . . . . . . . . . . . . . . . . 30
8.5. Requirements on Other Protocols . . . . . . . . . . . . . 30
8.6. Impact on Network Operations . . . . . . . . . . . . . . 30
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.1. Normative References . . . . . . . . . . . . . . . . . . 31
9.2. Informative References . . . . . . . . . . . . . . . . . 32
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35
1. Introduction
A Path Computation Element (PCE) may be used to compute end-to-end
paths across multi-domain environments using a per-domain path
computation technique [RFC5152]. The Backward-Recursive PCE-Based
Computation (BRPC) mechanism [RFC5441] also defines a PCE-based path
computation procedure to compute an inter-domain constrained path for
(G)MPLS TE LSPs. However, both per-domain and BRPC techniques assume
that the sequence of domains to be crossed from source to destination
is known and is either fixed by the network operator or obtained by
other means. Also, for inter-domain point-to-multipoint (P2MP) tree
computation, it is assumed per [RFC7334] that the domain tree is
known a priori.
The list of domains (domain sequence) in point-to-point (P2P) or a
domain tree in P2MP is usually a constraint in inter-domain path
computation procedure.
The domain sequence (the set of domains traversed to reach the
destination domain) is either administratively predetermined or
discovered by some means like Hierarchical PCE (H-PCE).
[RFC5440] defines the Include Route Object (IRO) and the Explicit
Route Object (ERO). [RFC5521] defines the Exclude Route Object (XRO)
and the Explicit Exclusion Route subobject (EXRS). The use of an
Autonomous System (albeit with a 2-byte AS number) as an abstract
node representing a domain is defined in [RFC3209]. In the current
document, we specify new subobjects to include or exclude domains
including an IGP area or an AS (4 bytes as per [RFC6793]).
Dhody, et al. Experimental [Page 3]
RFC 7897 Domain Subobjects for PCEP June 2016
Further, the domain identifier may simply act as a delimiter to
specify where the domain boundary starts and ends in some cases.
This is a companion document to Resource Reservation Protocol -
Traffic Engineering (RSVP-TE) extensions for the domain identifiers
[RFC7898].
1.1. Scope
The procedures described in this document are experimental. The
experiment is intended to enable research for the usage of the domain
sequence at the PCEs for inter-domain paths. For this purpose, this
document specifies new domain subobjects as well as how they
incorporate with existing subobjects to represent a domain sequence.
The experiment will end two years after the RFC is published. At
that point, the RFC authors will attempt to determine how widely this
has been implemented and deployed.
This document does not change the procedures for handling existing
subobjects in the PCE Communication Protocol (PCEP).
The new subobjects introduced by this document will not be understood
by legacy implementations. If a legacy implementation receives one
of the subobjects that it does not understand in a PCEP object, the
legacy implementation will behave according to the rules for a
malformed object as per [RFC5440]. Therefore, it is assumed that
this experiment will be conducted only when both the PCE and the Path
Computation Client (PCC) form part of the experiment. It is possible
that a PCC or PCE can operate with peers, some of which form part of
the experiment and some that do not. In this case, since no
capabilities exchange is used to identify which nodes can use these
extensions, manual configuration should be used to determine which
peerings form part of the experiment.
When the results of implementation and deployment are available, this
document will be updated and refined, and then it could be moved from
Experimental to Standards Track.
1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Dhody, et al. Experimental [Page 4]
RFC 7897 Domain Subobjects for PCEP June 2016
2. Terminology
The following terminology is used in this document.
ABR: Area Border Router. Routers used to connect two IGP areas
(Open Shortest Path First (OSPF) or Intermediate System to
Intermediate System (IS-IS).
AS: Autonomous System
ASBR: Autonomous System Border Router
BN: Boundary node; can be an ABR or ASBR.
BRPC: Backward-Recursive PCE-Based Computation
Domain: As per [RFC4655], any collection of network elements within
a common sphere of address management or path computational
responsibility. Examples of domains include IGP area and AS.
Domain Sequence: An ordered sequence of domains traversed to reach
the destination domain.
ERO: Explicit Route Object
H-PCE: Hierarchical PCE
IGP: Interior Gateway Protocol. Either of the two routing
protocols: OSPF or IS-IS.
IRO: Include Route Object
IS-IS: Intermediate System to Intermediate System
OSPF: Open Shortest Path First
PCC: Path Computation Client. Any client application requesting a
path computation to be performed by a Path Computation Element.
PCE: Path Computation Element. An entity (component, application,
or network node) that is capable of computing a network path or
route based on a network graph and applying computational
constraints.
P2MP: Point-to-Multipoint
P2P: Point-to-Point
Dhody, et al. Experimental [Page 5]
RFC 7897 Domain Subobjects for PCEP June 2016
RSVP: Resource Reservation Protocol
TE LSP: Traffic Engineering Label Switched Path
XRO: Exclude Route Object
3. Detail Description
3.1. Domains
[RFC4726] and [RFC4655] define a domain as a separate administrative
or geographic environment within the network. A domain could be
further defined as a zone of routing or computational ability. Under
these definitions, a domain might be categorized as an AS or an IGP
area. Each AS can be made of several IGP areas. In order to encode
a domain sequence, it is required to uniquely identify a domain in
the domain sequence. A domain can be uniquely identified by an
area-id, AS number, or both.
3.2. Domain Sequence
A domain sequence is an ordered sequence of domains traversed to
reach the destination domain.
A domain sequence can be applied as a constraint and carried in a
path computation request to a PCE(s). A domain sequence can also be
the result of a path computation. For example, in the case of H-PCE
[RFC6805], a parent PCE could send the domain sequence as a result in
a path computation reply.
In a P2P path, the domains listed appear in the order that they are
crossed. In a P2MP path, the domain tree is represented as a list of
domain sequences.
A domain sequence enables a PCE to select the next domain and the PCE
serving that domain to forward the path computation request based on
the domain information.
A domain sequence can include boundary nodes (ABR or ASBR) or border
links (inter-AS links) to be traversed as an additional constraint.
Dhody, et al. Experimental [Page 6]
RFC 7897 Domain Subobjects for PCEP June 2016
Thus, a domain sequence can be made up of one or more of the
following:
o AS Number
o Area ID
o Boundary Node ID
o Inter-AS Link Address
These are encoded in the new subobjects defined in this document as
well as in the existing subobjects that represent a domain sequence.
Consequently, a domain sequence can be used by:
1. a PCE in order to discover or select the next PCE in a
collaborative path computation, such as in BRPC [RFC5441];
2. the parent PCE to return the domain sequence when unknown; this
can then be an input to the BRPC procedure [RFC6805];
3. a PCC or a PCE to constrain the domains used in inter-domain path
computation, explicitly specifying which domains to be expanded
or excluded; and
4. a PCE in the per-domain path computation model [RFC5152] to
identify the next domain.
3.3. Domain Sequence Representation
A domain sequence appears in PCEP messages, notably in:
o Include Route Object (IRO): As per [RFC5440], IRO can be used to
specify a set of network elements to be traversed to reach the
destination, which includes subobjects used to specify the domain
sequence.
o Exclude Route Object (XRO): As per [RFC5521], XRO can be used to
specify certain abstract nodes, to be excluded from the whole
path, which include subobjects used to specify the domain
sequence.
o Explicit Exclusion Route Subobject (EXRS): As per [RFC5521], EXRS
can be used to specify exclusion of certain abstract nodes
(including domains) between a specific pair of nodes. EXRS is a
subobject inside the IRO.
Dhody, et al. Experimental [Page 7]
RFC 7897 Domain Subobjects for PCEP June 2016
o Explicit Route Object (ERO): As per [RFC5440], ERO can be used to
specify a computed path in the network. For example, in the case
of H-PCE [RFC6805], a parent PCE can send the domain sequence as a
result in a path computation reply using ERO.
3.4. Include Route Object (IRO)
As per [RFC5440], IRO can be used to specify that the computed path
needs to traverse a set of specified network elements or abstract
nodes.
3.4.1. Subobjects
Some subobjects are defined in [RFC3209], [RFC3473], [RFC3477], and
[RFC4874], but new subobjects related to domain sequence are needed.
This document extends the support for 4-byte AS numbers and IGP
areas.
Value Description
----- ----------------
5 4-byte AS number
6 OSPF Area ID
7 IS-IS Area ID
Note: Identical subobjects are carried in RSVP-TE messages as defined
in [RFC7898].
3.4.1.1. Autonomous System
[RFC3209] already defines 2-byte AS numbers.
To support 4-byte AS numbers as per [RFC6793], the following
subobject is defined:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS Number (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L: The L bit is an attribute of the subobject as defined in
[RFC3209], and its usage in the IRO subobject is defined in
[RFC7896].
Type: 5 (indicating a 4-byte AS number).
Dhody, et al. Experimental [Page 8]
RFC 7897 Domain Subobjects for PCEP June 2016
Length: 8 (total length of the subobject in bytes).
Reserved: Zero at transmission; ignored at receipt.
AS Number: The 4-byte AS number. Note that if 2-byte AS numbers are
in use, the low-order bits (16 through 31) MUST be used, and the
high-order bits (0 through 15) MUST be set to zero.
3.4.1.2. IGP Area
Since the length and format of Area ID is different for OSPF and
IS-IS, the following two subobjects are defined below:
For OSPF, the Area ID is a 32-bit number. The subobject is encoded
as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OSPF Area ID (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L: The L bit is an attribute of the subobject as defined in
[RFC3209], and its usage in the IRO subobject is defined in
[RFC7896].
Type: 6 (indicating a 4-byte OSPF Area ID).
Length: 8 (total length of the subobject in bytes).
Reserved: Zero at transmission; ignored at receipt.
OSPF Area ID: The 4-byte OSPF Area ID.
Dhody, et al. Experimental [Page 9]
RFC 7897 Domain Subobjects for PCEP June 2016
For IS-IS, the Area ID is of variable length; thus, the length of the
subobject is variable. The Area ID is as described in IS-IS by the
ISO standard [ISO10589]. The subobject is encoded as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Area-Len | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// IS-IS Area ID //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L: The L bit is an attribute of the subobject as defined in
[RFC3209], and its usage in the IRO subobject is defined in
[RFC7896].
Type: 7 (indicating the IS-IS Area ID).
Length: Variable. The length MUST be at least 8 and MUST be a
multiple of 4.
Area-Len: Variable (length of the actual (non-padded) IS-IS area
identifier in octets; valid values are from 1 to 13, inclusive).
Reserved: Zero at transmission; ignored at receipt.
IS-IS Area ID: The variable-length IS-IS area identifier. Padded
with trailing zeroes to a 4-byte boundary.
3.4.2. Update in IRO Specification
[RFC5440] describes IRO as an optional object used to specify network
elements to be traversed by the computed path. It further states
that the L bit of such subobject has no meaning within an IRO. It
also does not mention if IRO is an ordered or unordered list of
subobjects.
An update to the IRO specification [RFC7896] makes IRO as an ordered
list and includes support for the L bit.
The use of IRO for the domain sequence assumes the updated
specification is being used for IRO, as per [RFC7896].
Dhody, et al. Experimental [Page 10]
RFC 7897 Domain Subobjects for PCEP June 2016
3.4.3. IRO for Domain Sequence
The subobject type for IPv4, IPv6, and unnumbered Interface IDs can
be used to specify boundary nodes (ABR/ASBR) and inter-AS links. The
subobject type for the AS Number (2 or 4 bytes) and the IGP area are
used to specify the domain identifiers in the domain sequence.
The IRO can incorporate the new domain subobjects with the existing
subobjects in a sequence of traversal.
Thus, an IRO, comprising subobjects, that represents a domain
sequence defines the domains involved in an inter-domain path
computation, typically involving two or more collaborative PCEs.
A domain sequence can have varying degrees of granularity. It is
possible to have a domain sequence composed of, uniquely, AS
identifiers. It is also possible to list the involved IGP areas for
a given AS.
In any case, the mapping between domains and responsible PCEs is not
defined in this document. It is assumed that a PCE that needs to
obtain a "next PCE" from a domain sequence is able to do so (e.g.,
via administrative configuration or discovery).
3.4.3.1. PCC Procedures
A PCC builds an IRO to encode the domain sequence, so that the
cooperating PCEs could compute an inter-domain shortest constrained
path across the specified sequence of domains.
A PCC may intersperse area and AS subobjects with other subobjects
without change to the previously specified processing of those
subobjects in the IRO.
3.4.3.2. PCE Procedures
If a PCE receives an IRO in a Path Computation Request (PCReq)
message that contains the subobjects defined in this document that it
does not recognize, it will respond according to the rules for a
malformed object as per [RFC5440]. The PCE MAY also include the IRO
in the PCEP Error (PCErr) message as per [RFC5440].
The interpretation of the L bit is as per Section 4.3.3.1 of
[RFC3209] (as per [RFC7896]).
Dhody, et al. Experimental [Page 11]
RFC 7897 Domain Subobjects for PCEP June 2016
In a Path Computation Reply (PCRep), PCE MAY also supply IRO (with
domain sequence information) with the NO-PATH object indicating that
the set of elements (domains) of the request's IRO prevented the PCEs
from finding a path.
The following processing rules apply for a domain sequence in IRO:
o When a PCE parses an IRO, it interprets each subobject according
to the AS number associated with the preceding subobject. We call
this the "current AS". Certain subobjects modify the current AS,
as follows.
* The current AS is initialized to the AS number of the PCC.
* If the PCE encounters an AS subobject, then it updates the
current AS to this new AS number.
* If the PCE encounters an area subobject, then it assumes that
the area belongs to the current AS.
* If the PCE encounters an IP address that is globally routable,
then it updates the current AS to the AS that owns this IP
address. This document does not define how the PCE learns
which AS owns the IP address.
* If the PCE encounters an IP address that is not globally
routable, then it assumes that it belongs to the current AS.
* If the PCE encounters an unnumbered link, then it assumes that
it belongs to the current AS.
o When a PCE parses an IRO, it interprets each subobject according
to the Area ID associated with the preceding subobject. We call
this the "current area". Certain subobjects modify the current
area, as follows.
* The current area is initialized to the Area ID of the PCC.
* If the current AS is changed, the current area is reset and
needs to be determined again by a current or subsequent
subobject.
* If the PCE encounters an area subobject, then it updates the
current area to this new Area ID.
Dhody, et al. Experimental [Page 12]
RFC 7897 Domain Subobjects for PCEP June 2016
* If the PCE encounters an IP address that belongs to a different
area, then it updates the current area to the area that has
this IP address. This document does not define how the PCE
learns which area has the IP address.
* If the PCE encounters an unnumbered link that belongs to a
different area, then it updates the current Area to the area
that has this link.
* Otherwise, it assumes that the subobject belongs to the current
area.
o In case the current PCE is not responsible for the path
computation in the current AS or area, then the PCE selects the
"next PCE" in the domain sequence based on the current AS and
area.
Note that it is advised that PCC should use AS and area subobjects
while building the domain sequence in IRO and avoid using other
mechanisms to change the "current AS" and "current area" as described
above.
3.5. Exclude Route Object (XRO)
XRO [RFC5521] is an optional object used to specify exclusion of
certain abstract nodes or resources from the whole path.
3.5.1. Subobjects
Some subobjects are to be used in XRO as defined in [RFC3209],
[RFC3477], [RFC4874], and [RFC5520], but new subobjects related to
domain sequence are needed.
This document extends the support for 4-byte AS numbers and IGP
areas.
Value Description
----- ----------------
5 4-byte AS number
6 OSPF Area ID
7 IS-IS Area ID
Note: Identical subobjects are carried in RSVP-TE messages as defined
in [RFC7898].
Dhody, et al. Experimental [Page 13]
RFC 7897 Domain Subobjects for PCEP June 2016
3.5.1.1. Autonomous System
The new subobjects to support 4-byte AS numbers and the IGP
(OSPF/IS-IS) area MAY also be used in the XRO to specify exclusion of
certain domains in the path computation procedure.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS Number (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The X-bit indicates whether the exclusion is mandatory or desired.
0: indicates that the AS specified MUST be excluded from the path
computed by the PCE(s).
1: indicates that the AS specified SHOULD be avoided from the inter-
domain path computed by the PCE(s), but it MAY be included subject
to PCE policy and the absence of a viable path that meets the
other constraints.
All other fields are consistent with the definition in Section 3.4.
3.5.1.2. IGP Area
Since the length and format of the Area ID is different for OSPF and
IS-IS, the following two subobjects are defined:
For OSPF, the Area ID is a 32-bit number. The subobject is encoded
as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OSPF Area ID (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The X-bit indicates whether the exclusion is mandatory or desired.
0: indicates that the OSPF area specified MUST be excluded from the
path computed by the PCE(s).
Dhody, et al. Experimental [Page 14]
RFC 7897 Domain Subobjects for PCEP June 2016
1: indicates that the OSPF area specified SHOULD be avoided from the
inter-domain path computed by the PCE(s), but it MAY be included
subject to PCE policy and the absence of a viable path that meets
the other constraints.
All other fields are consistent with the definition in Section 3.4.
For IS-IS, the Area ID is of variable length; thus, the length of the
subobject is variable. The Area ID is as described in IS-IS by the
ISO standard [ISO10589]. The subobject is encoded as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type | Length | Area-Len | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// IS-IS Area ID //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The X-bit indicates whether the exclusion is mandatory or desired.
0: indicates that the IS-IS area specified MUST be excluded from the
path computed by the PCE(s).
1: indicates that the IS-IS area specified SHOULD be avoided from the
inter-domain path computed by the PCE(s), but it MAY be included
subject to PCE policy and the absence of a viable path that meets
the other constraints.
All other fields are consistent with the definition in Section 3.4.
All the processing rules are as per [RFC5521].
Note that if a PCE receives an XRO in a PCReq message that contains
subobjects defined in this document that it does not recognize, it
will respond according to the rules for a malformed object as per
[RFC5440].
IGP area subobjects in the XRO are local to the current AS. In case
multi-AS path computation excludes an IGP area in a different AS, the
IGP area subobject should be part of EXRS in the IRO to specify the
AS in which the IGP area is to be excluded. Further, policy may be
applied to prune/ignore area subobjects in XRO after a "current AS"
change during path computation.
Dhody, et al. Experimental [Page 15]
RFC 7897 Domain Subobjects for PCEP June 2016
3.6. Explicit Exclusion Route Subobject (EXRS)
The EXRS [RFC5521] is used to specify exclusion of certain abstract
nodes between a specific pair of nodes.
The EXRS can carry any of the subobjects defined for inclusion in the
XRO; thus, the new subobjects to support 4-byte AS numbers and the
IGP (OSPF / IS-IS) area can also be used in the EXRS. The meanings
of the fields of the new XRO subobjects are unchanged when the
subobjects are included in an EXRS, except that the scope of the
exclusion is limited to the single hop between the previous and
subsequent elements in the IRO.
The EXRS should be interpreted in the context of the current AS and
current area of the preceding subobject in the IRO. The EXRS does
not change the current AS or current area. All other processing
rules are as per [RFC5521].
Note that if a PCE that supports the EXRS in an IRO parses an IRO,
and encounters an EXRS that contains subobjects defined in this
document that it does not recognize, it will act according to the
setting of the X-bit in the subobject as per [RFC5521].
3.7. Explicit Route Object (ERO)
ERO [RFC5440] is used to specify a computed path in the network.
PCEP ERO subobject types correspond to RSVP-TE ERO subobject types as
defined in [RFC3209], [RFC3473], [RFC3477], [RFC4873], [RFC4874], and
[RFC5520]. The subobjects related to the domain sequence are further
defined in [RFC7898].
The new subobjects to support 4-byte AS numbers and the IGP
(OSPF/IS-IS) area can also be used in the ERO to specify an abstract
node (a group of nodes whose internal topology is opaque to the
ingress node of the LSP). Using this concept of abstraction, an
explicitly routed LSP can be specified as a sequence of domains.
In case of H-PCE [RFC6805], a parent PCE can be requested to find the
domain sequence. Refer to the example in Section 4.6 of this
document. The ERO in reply from the parent PCE can then be used in
per-domain path computation or BRPC.
If a PCC receives an ERO in a PCRep message that contains a subobject
defined in this document that it does not recognize, it will respond
according to the rules for a malformed object as per [RFC5440].
Dhody, et al. Experimental [Page 16]
RFC 7897 Domain Subobjects for PCEP June 2016
4. Examples
The examples in this section are for illustration purposes only to
highlight how the new subobjects could be encoded. They are not
meant to be an exhaustive list of all possible use cases and
combinations.
4.1. Inter-Area Path Computation
In an inter-area path computation where the ingress and the egress
nodes belong to different IGP areas within the same AS, the domain
sequence could be represented using an ordered list of area
subobjects.
Dhody, et al. Experimental [Page 17]
RFC 7897 Domain Subobjects for PCEP June 2016
----------------- -----------------
| | | |
| +--+ | | +--+ |
| +--+ | | | | | | |
| | | +--+ | | +--+ +--+ |
| +--+ | | | | |
| | | +--+ |
| +--+ | | |
| | | | | +--+ |
| +--+ | | | | |
| | -------------------------- | +--+ |
| +--+ +--+ |
| | | +--+ | | |
|Area 2 +--+ | | +--+ Area 4 |
----------------- | +--+ | -----------------
| |
| +--+ |
| +--+ | | |
| | | +--+ |
| +--+ |
| |
| |
| |
| |
| +--+ |
| | | |
| +--+ |
----------------- | | ------------------
| +--+ +--+ |
| | | | | |
| +--+ Area 0 +--+ |
| | -------------------------- | +--+ |
| +--+ | | | | |
| | | | | +--+ |
| +--+ +--+ | | |
| | | | | +--+ |
| +--+ | | | | |
| | | +--+ |
| +--+ | | |
| | | | | +--+ |
| +--+ | | | | |
| | | +--+ |
| | | |
| Area 1 | | Area 5 |
----------------- ------------------
Figure 1: Inter-Area Path Computation
Dhody, et al. Experimental [Page 18]
RFC 7897 Domain Subobjects for PCEP June 2016
The AS Number is 100.
If the ingress is in area 2, the egress is in area 4, and transit is
through area 0, here are some possible ways a PCC can encode the IRO:
+---------+ +---------+ +---------+
|IRO | |Sub- | |Sub- |
|Object | |object | |object |
|Header | |Area 0 | |Area 4 |
| | | | | |
| | | | | |
+---------+ +---------+ +---------+
or
+---------+ +---------+ +---------+ +---------+
|IRO | |Sub- | |Sub- | |Sub- |
|Object | |object | |object | |object |
|Header | |Area 2 | |Area 0 | |Area 4 |
| | | | | | | |
| | | | | | | |
+---------+ +---------+ +---------+ +---------+
or
+---------+ +---------+ +---------+ +---------+ +---------+
|IRO | |Sub- | |Sub- | |Sub- | |Sub- |
|Object | |object AS| |object | |object | |object |
|Header | |100 | |Area 2 | |Area 0 | |Area 4 |
| | | | | | | | | |
| | | | | | | | | |
+---------+ +---------+ +---------+ +---------+ +---------+
The domain sequence can further include encompassing AS information
in the AS subobject.
4.2. Inter-AS Path Computation
In inter-AS path computation, where the ingress and egress belong to
different ASes, the domain sequence could be represented using an
ordered list of AS subobjects. The domain sequence can further
include decomposed area information in the area subobject.
Dhody, et al. Experimental [Page 19]
RFC 7897 Domain Subobjects for PCEP June 2016
4.2.1. Example 1
As shown in Figure 2, where AS has a single area, the AS subobject in
the domain sequence can uniquely identify the next domain and PCE.
AS A AS E AS C
<-------------> <----------> <------------->
A4----------E1---E2---E3---------C4
/ / \
/ / \
/ / AS B \
/ / <----------> \
Ingress------A1---A2------B1---B2---B3------C1---C2------Egress
\ / /
\ / /
\ / /
\ / /
A3----------D1---D2---D3---------C3
<---------->
AS D
* All ASes have one area (area 0)
Figure 2: Inter-AS Path Computation
Dhody, et al. Experimental [Page 20]
RFC 7897 Domain Subobjects for PCEP June 2016
If the ingress is in AS A, the egress is in AS C, and transit is
through AS B, here are some possible ways a PCC can encode the IRO:
+-------+ +-------+ +-------+
|IRO | |Sub- | |Sub- |
|Object | |object | |object |
|Header | |AS B | |AS C |
| | | | | |
+-------+ +-------+ +-------+
or
+-------+ +-------+ +-------+ +-------+
|IRO | |Sub- | |Sub- | |Sub- |
|Object | |object | |object | |object |
|Header | |AS A | |AS B | |AS C |
| | | | | | | |
+-------+ +-------+ +-------+ +-------+
or
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+ +-------+
|IRO | |Sub- | |Sub- | |Sub- | |Sub- | |Sub- | |Sub- |
|Object | |object | |object | |object | |object | |object | |object |
|Header | |AS A | |Area 0 | |AS B | |Area 0 | |AS C | |Area 0 |
| | | | | | | | | | | | | |
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+ +-------+
Note that to get a domain disjoint path, the ingress could also
request the backup path with:
+-------+ +-------+
|XRO | |Sub |
|Object | |Object |
|Header | |AS B |
| | | |
+-------+ +-------+
Dhody, et al. Experimental [Page 21]
RFC 7897 Domain Subobjects for PCEP June 2016
As described in Section 3.4.3, a domain subobject in IRO changes the
domain information associated with the next set of subobjects till
you encounter a subobject that changes the domain too. Consider the
following IRO:
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+
|IRO | |Sub- | |Sub- | |Sub- | |Sub- | |Sub- |
|Object | |object | |object | |object | |object | |object |
|Header | |AS B | |IP | |IP | |AS C | |IP |
| | | | |B1 | |B3 | | | |C1 |
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+
On processing subobject "AS B", it changes the AS of the subsequent
subobjects till we encounter another subobject "AS C" that changes
the AS for its subsequent subobjects.
Consider another IRO:
+-------+ +-------+ +-------+ +-------+ +-------+
|IRO | |Sub- | |Sub- | |Sub- | |Sub- |
|Object | |object | |object | |object | |object |
|Header | |AS D | |IP | |IP | |IP |
| | | | |D1 | |D3 | |C3 |
+-------+ +-------+ +-------+ +-------+ +-------+
Here as well, on processing "AS D", it changes the AS of the
subsequent subobjects till you encounter another subobject "C3" that
belongs in another AS and changes the AS for its subsequent
subobjects.
Further description for the boundary node and inter-AS link can be
found in Section 4.3.
4.2.2. Example 2
In Figure 3, AS 200 is made up of multiple areas.
Dhody, et al. Experimental [Page 22]
RFC 7897 Domain Subobjects for PCEP June 2016
|
| +-------------+ +----------------+
| |Area 2 | |Area 4 |
| | +--+| | +--+ |
| | | || | | B| |
| | +--+ +--+| | +--+ +--+ |
| | | | | | | | |
| | +--+ | | +--+ |
| | +--+ | | +--+ |
| | | | | | | | |
| | +--+ | | +--+ +--+ |
| | +--+ |+--------------+| | | |
| | | | +--+ +--+ +--+ |
+-------------+| | +--+ | | | | |
| || | +--+ +--+ |
| +--+|| +-------------+| |+----------------+
| | ||| | +--+ |
| +--+|| | | | |
| +--+ || | +--+ |
| | | +---+ +--+ |
| +--+ | |----------------| | |
| +---+ Inter-AS +--+ +--+ |
|+--+ || Links | | | |
||A | +---+ +--+ +--+ |
|+--+ | |----------------| | |
| +---+ +--+ +--+ |
| +--+ || +------------+ | | | |+----------------+
| | | || |Area 3 +--+ +--+ +--+ Area 5 |
| +--+ || | | | | | |
| || | +--+ +--+ |
| +--+|| | +--+ | | Area 0 || +--+ |
| | ||| | | | | +--------------+| | | |
| +--+|| | +--+ | | +--+ |
| || | | | +--+ |
|Area 0 || | +--+ | | +--+ | | |
+-------------+| | | | | | | | +--+ |
| | +--+ +--+ | +--+ |
| | | | | |
| | +--+ | +--+ |
| | +--+ | | | C| |
| | | | | | +--+ |
| | +--+ | | |
| | | | |
| +------------+ +----------------+
|
AS 100 | AS 200
|
Figure 3: Inter-AS Path Computation
Dhody, et al. Experimental [Page 23]
RFC 7897 Domain Subobjects for PCEP June 2016
For LSP (A-B), where ingress A is in (AS 100, area 0), egress B is in
(AS 200, area 4), and transit is through (AS 200, area 0), here are
some possible ways a PCC can encode the IRO:
+-------+ +-------+ +-------+ +-------+
|IRO | |Sub- | |Sub- | |Sub- |
|Object | |object | |object | |object |
|Header | |AS 200 | |Area 0 | |Area 4 |
| | | | | | | |
+-------+ +-------+ +-------+ +-------+
or
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+
|IRO | |Sub- | |Sub- | |Sub- | |Sub- | |Sub- |
|Object | |object | |object | |object | |object | |object |
|Header | |AS 100 | |Area 0 | |AS 200 | |Area 0 | |Area 4 |
| | | | | | | | | | | |
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+
For LSP (A-C), where ingress A is in (AS 100, area 0), egress C is in
(AS 200, area 5), and transit is through (AS 200, area 0), here are
some possible ways a PCC can encode the IRO:
+-------+ +-------+ +-------+ +-------+
|IRO | |Sub- | |Sub- | |Sub- |
|Object | |object | |object | |object |
|Header | |AS 200 | |Area 0 | |Area 5 |
| | | | | | | |
+-------+ +-------+ +-------+ +-------+
or
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+
|IRO | |Sub- | |Sub- | |Sub- | |Sub- | |Sub- |
|Object | |object | |object | |object | |object | |object |
|Header | |AS 100 | |Area 0 | |AS 200 | |Area 0 | |Area 5 |
| | | | | | | | | | | |
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+
Dhody, et al. Experimental [Page 24]
RFC 7897 Domain Subobjects for PCEP June 2016
4.3. Boundary Node and Inter-AS Link
A PCC or PCE can include additional constraints covering which
boundary nodes (ABR or ASBR) or border links (inter-AS link) to be
traversed while defining a domain sequence. In which case, the
boundary node or link can be encoded as a part of the domain
sequence.
Boundary nodes (ABR/ASBR) can be encoded using the IPv4 or IPv6
prefix subobjects, usually with a loopback address of 32 and a prefix
length of 128, respectively. An inter-AS link can be encoded using
the IPv4 or IPv6 prefix subobjects or unnumbered interface
subobjects.
For Figure 1, an ABR (say, 203.0.113.1) to be traversed can be
specified in IRO as:
+---------+ +---------+ +---------++---------+ +---------+
|IRO | |Sub- | |Sub- ||Sub- | |Sub- |
|Object | |object | |object ||object | |object |
|Header | |Area 2 | |IPv4 ||Area 0 | |Area 4 |
| | | | |203.0. || | | |
| | | | |112.1 || | | |
+---------+ +---------+ +---------++---------+ +---------+
For Figure 3, an inter-AS link (say, 198.51.100.1 - 198.51.100.2) to
be traversed can be specified as:
+---------+ +---------+ +---------+ +---------+
|IRO | |Sub- | |Sub- | |Sub- |
|Object | |object AS| |object | |object AS|
|Header | |100 | |IPv4 | |200 |
| | | | |198.51. | | |
| | | | |100.2 | | |
+---------+ +---------+ +---------+ +---------+
4.4. PCE Serving Multiple Domains
A single PCE can be responsible for multiple domains; for example,
PCE function deployed on an ABR could be responsible for multiple
areas. A PCE that can support adjacent domains can internally handle
those domains in the domain sequence without any impact on the other
domains in the domain sequence.
Dhody, et al. Experimental [Page 25]
RFC 7897 Domain Subobjects for PCEP June 2016
4.5. P2MP
[RFC7334] describes an experimental inter-domain P2MP path
computation mechanism where the path domain tree is described as a
series of domain sequences; an example is shown in the figure below:
+----------------+
| |Domain D1
| R |
| |
| A |
| |
+-B------------C-+
/ \
/ \
/ \
Domain D2 / \ Domain D3
+-------------D--+ +-----E----------+
| | | |
| F | | |
| G | | H |
| | | |
| | | |
+-I--------------+ +-J------------K-+
/\ / \
/ \ / \
/ \ / \
/ \ / \
/ \ / \
/ \ / \
/ Domain D4 \ Domain D5 / Domain D6 \
+-L-------------W+ +------P---------+ +-----------T----+
| | | | | |
| | | Q | | U |
| M O | | S | | |
| | | | | V |
| N | | R | | |
+----------------+ +----------------+ +----------------+
Figure 4: Domain Tree Example
The domain tree can be represented as a series of domain sequences:
o Domain D1, Domain D3, Domain D6
o Domain D1, Domain D3, Domain D5
o Domain D1, Domain D2, Domain D4
Dhody, et al. Experimental [Page 26]
RFC 7897 Domain Subobjects for PCEP June 2016
The domain sequence handling described in this document could be
applied to the P2MP path domain tree.
4.6. Hierarchical PCE
In case of H-PCE [RFC6805], the parent PCE can be requested to
determine the domain sequence and return it in the path computation
reply, using the ERO. For the example in Section 4.6 of [RFC6805],
the domain sequence can possibly appear as:
+---------+ +---------+ +---------+ +---------+
|ERO | |Sub- | |Sub- | |Sub- |
|Object | |object | |object | |object |
|Header | |Domain 1 | |Domain 2 | |Domain 3 |
| | | | | | | |
| | | | | | | |
+---------+ +---------+ +---------+ +---------+
or
+---------+ +---------+ +---------+
|ERO | |Sub- | |Sub- |
|Object | |object | |object |
|Header | |BN 21 | |Domain 3 |
| | | | | |
| | | | | |
+---------+ +---------+ +---------+
5. Other Considerations
5.1. Relationship to PCE Sequence
Instead of a domain sequence, a sequence of PCEs MAY be enforced by
policy on the PCC, and this constraint can be carried in the PCReq
message (as defined in [RFC5886]).
Note that PCE Sequence can be used along with domain sequence, in
which case PCE Sequence MUST have higher precedence in selecting the
next PCE in the inter-domain path computation procedures.
5.2. Relationship to RSVP-TE
[RFC3209] already describes the notion of abstract nodes, where an
abstract node is a group of nodes whose internal topology is opaque
to the ingress node of the LSP. It further defines a subobject for
AS but with a 2-byte AS number.
Dhody, et al. Experimental [Page 27]
RFC 7897 Domain Subobjects for PCEP June 2016
[RFC7898] extends the notion of abstract nodes by adding new
subobjects for IGP areas and 4-byte AS numbers. These subobjects can
be included in ERO, XRO, or EXRS in RSVP-TE.
In any case, subobject types defined in RSVP-TE are identical to the
subobject types defined in the related documents in PCEP.
6. IANA Considerations
6.1. New Subobjects
IANA maintains the "Path Computation Element Protocol (PCEP) Numbers"
registry at <http://www.iana.org/assignments/pcep>. Within this
registry, IANA maintains two sub-registries:
o IRO Subobjects
o XRO Subobjects
IANA has made identical additions to those registries as follows:
Value Description Reference
----- ---------------- -------------------
5 4-byte AS number RFC 7897, [RFC7898]
6 OSPF Area ID RFC 7897, [RFC7898]
7 IS-IS Area ID RFC 7897, [RFC7898]
Further, IANA has added a reference to this document to the new RSVP
numbers that are registered by [RFC7898], as shown on
<http://www.iana.org/assignments/rsvp-parameters>.
7. Security Considerations
The protocol extensions defined in this document do not substantially
change the nature of PCEP. Therefore, the security considerations
set out in [RFC5440] apply unchanged. Note that further security
considerations for the use of PCEP over TCP are presented in
[RFC6952].
This document specifies a representation of the domain sequence and
new subobjects, which could be used in inter-domain PCE scenarios as
explained in [RFC5152], [RFC5441], [RFC6805], [RFC7334], etc. The
security considerations set out in each of these mechanisms remain
unchanged by the new subobjects and domain sequence representation in
this document.
Dhody, et al. Experimental [Page 28]
RFC 7897 Domain Subobjects for PCEP June 2016
But the new subobjects do allow finer and more specific control of
the path computed by a cooperating PCE(s). Such control increases
the risk if a PCEP message is intercepted, modified, or spoofed
because it allows the attacker to exert control over the path that
the PCE will compute or to make the path computation impossible.
Consequently, it is important that implementations conform to the
relevant security requirements of [RFC5440]. These mechanisms
include:
o Securing the PCEP session messages using TCP security techniques
(Section 10.2 of [RFC5440]). PCEP implementations SHOULD also
consider the additional security provided by the TCP
Authentication Option (TCP-AO) [RFC5925] or Transport Layer
Security (TLS) [PCEPS].
o Authenticating the PCEP messages to ensure the messages are intact
and sent from an authorized node (Section 10.3 of [RFC5440]).
o PCEP operates over TCP, so it is also important to secure the PCE
and PCC against TCP denial-of-service attacks. Section 10.7.1 of
[RFC5440] outlines a number of mechanisms for minimizing the risk
of TCP-based denial-of-service attacks against PCEs and PCCs.
o In inter-AS scenarios, attacks may be particularly significant
with commercial- as well as service-level implications.
Note, however, that the domain sequence mechanisms also provide the
operator with the ability to route around vulnerable parts of the
network and may be used to increase overall network security.
8. Manageability Considerations
8.1. Control of Function and Policy
The exact behavior with regards to desired inclusion and exclusion of
domains MUST be available for examination by an operator and MAY be
configurable. Manual configurations are needed to identify which
PCEP peers understand the new domain subobjects defined in this
document.
8.2. Information and Data Models
A MIB module for management of the PCEP is being specified in a
separate document [RFC7420]. This document does not imply any new
extension to the current MIB module.
Dhody, et al. Experimental [Page 29]
RFC 7897 Domain Subobjects for PCEP June 2016
8.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements aside from those already listed
in [RFC5440].
8.4. Verify Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements aside from those already listed in
[RFC5440].
8.5. Requirements on Other Protocols
In case of per-domain path computation [RFC5152], where the full path
of an inter-domain TE LSP cannot be determined (or is not determined)
at the ingress node, a signaling message can use the domain
identifiers. The subobjects defined in this document SHOULD be
supported by RSVP-TE. [RFC7898] extends the notion of abstract nodes
by adding new subobjects for IGP areas and 4-byte AS numbers.
Apart from this, mechanisms defined in this document do not imply any
requirements on other protocols aside from those already listed in
[RFC5440].
8.6. Impact on Network Operations
The mechanisms described in this document can provide the operator
with the ability to exert finer and more specific control of the path
computation by inclusion or exclusion of domain subobjects. There
may be some scaling benefit when a single domain subobject may
substitute for many subobjects and can reduce the overall message
size and processing.
Backward compatibility issues associated with the new subobjects
arise when a PCE does not recognize them, in which case PCE responds
according to the rules for a malformed object as per [RFC5440]. For
successful operations, the PCEs in the network would need to be
upgraded.
Dhody, et al. Experimental [Page 30]
RFC 7897 Domain Subobjects for PCEP June 2016
9. References
9.1. Normative References
[ISO10589] International Organization for Standardization,
"Information technology -- Telecommunications and
information exchange between systems -- Intermediate
System to Intermediate System intra-domain routeing
information exchange protocol for use in conjunction with
the protocol for providing the connectionless-mode network
service (ISO 8473)", ISO/IEC 10589:2002, Second Edition,
2002.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<http://www.rfc-editor.org/info/rfc3209>.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
DOI 10.17487/RFC3473, January 2003,
<http://www.rfc-editor.org/info/rfc3473>.
[RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links
in Resource ReSerVation Protocol - Traffic Engineering
(RSVP-TE)", RFC 3477, DOI 10.17487/RFC3477, January 2003,
<http://www.rfc-editor.org/info/rfc3477>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<http://www.rfc-editor.org/info/rfc5440>.
[RFC5441] Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux,
"A Backward-Recursive PCE-Based Computation (BRPC)
Procedure to Compute Shortest Constrained Inter-Domain
Traffic Engineering Label Switched Paths", RFC 5441,
DOI 10.17487/RFC5441, April 2009,
<http://www.rfc-editor.org/info/rfc5441>.
Dhody, et al. Experimental [Page 31]
RFC 7897 Domain Subobjects for PCEP June 2016
[RFC5521] Oki, E., Takeda, T., and A. Farrel, "Extensions to the
Path Computation Element Communication Protocol (PCEP) for
Route Exclusions", RFC 5521, DOI 10.17487/RFC5521, April
2009, <http://www.rfc-editor.org/info/rfc5521>.
[RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the
Path Computation Element Architecture to the Determination
of a Sequence of Domains in MPLS and GMPLS", RFC 6805,
DOI 10.17487/RFC6805, November 2012,
<http://www.rfc-editor.org/info/rfc6805>.
[RFC7896] Dhody, D., "Update to the Include Route Object (IRO)
Specification in the Path Computation Element
Communication Protocol (PCEP)", RFC 7896,
DOI 10.17487/RFC7896, June 2016,
<http://www.rfc-editor.org/info/rfc7896>.
[RFC7898] Dhody, D., Palle, U., Kondreddy, V., and R. Casellas,
"Domain Subobjects for Resource Reservation Protocol -
Traffic Engineering (RSVP-TE)", RFC 7898,
DOI 10.17487/RFC7898, June 2016,
<http://www.rfc-editor.org/info/rfc7898>.
9.2. Informative References
[PCEPS] Lopez, D., Dios, O., Wu, W., and D. Dhody, "Secure
Transport for PCEP", Work in Progress,
draft-ietf-pce-pceps-09, November 2015.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<http://www.rfc-editor.org/info/rfc4655>.
[RFC4726] Farrel, A., Vasseur, J., and A. Ayyangar, "A Framework for
Inter-Domain Multiprotocol Label Switching Traffic
Engineering", RFC 4726, DOI 10.17487/RFC4726, November
2006, <http://www.rfc-editor.org/info/rfc4726>.
[RFC4873] Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
"GMPLS Segment Recovery", RFC 4873, DOI 10.17487/RFC4873,
May 2007, <http://www.rfc-editor.org/info/rfc4873>.
[RFC4874] Lee, CY., Farrel, A., and S. De Cnodder, "Exclude Routes -
Extension to Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE)", RFC 4874, DOI 10.17487/RFC4874,
April 2007, <http://www.rfc-editor.org/info/rfc4874>.
Dhody, et al. Experimental [Page 32]
RFC 7897 Domain Subobjects for PCEP June 2016
[RFC5152] Vasseur, JP., Ed., Ayyangar, A., Ed., and R. Zhang, "A
Per-Domain Path Computation Method for Establishing Inter-
Domain Traffic Engineering (TE) Label Switched Paths
(LSPs)", RFC 5152, DOI 10.17487/RFC5152, February 2008,
<http://www.rfc-editor.org/info/rfc5152>.
[RFC5520] Bradford, R., Ed., Vasseur, JP., and A. Farrel,
"Preserving Topology Confidentiality in Inter-Domain Path
Computation Using a Path-Key-Based Mechanism", RFC 5520,
DOI 10.17487/RFC5520, April 2009,
<http://www.rfc-editor.org/info/rfc5520>.
[RFC5886] Vasseur, JP., Ed., Le Roux, JL., and Y. Ikejiri, "A Set of
Monitoring Tools for Path Computation Element (PCE)-Based
Architecture", RFC 5886, DOI 10.17487/RFC5886, June 2010,
<http://www.rfc-editor.org/info/rfc5886>.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <http://www.rfc-editor.org/info/rfc5925>.
[RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet
Autonomous System (AS) Number Space", RFC 6793,
DOI 10.17487/RFC6793, December 2012,
<http://www.rfc-editor.org/info/rfc6793>.
[RFC6952] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
BGP, LDP, PCEP, and MSDP Issues According to the Keying
and Authentication for Routing Protocols (KARP) Design
Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,
<http://www.rfc-editor.org/info/rfc6952>.
[RFC7334] Zhao, Q., Dhody, D., King, D., Ali, Z., and R. Casellas,
"PCE-Based Computation Procedure to Compute Shortest
Constrained Point-to-Multipoint (P2MP) Inter-Domain
Traffic Engineering Label Switched Paths", RFC 7334,
DOI 10.17487/RFC7334, August 2014,
<http://www.rfc-editor.org/info/rfc7334>.
[RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
Hardwick, "Path Computation Element Communication Protocol
(PCEP) Management Information Base (MIB) Module",
RFC 7420, DOI 10.17487/RFC7420, December 2014,
<http://www.rfc-editor.org/info/rfc7420>.
Dhody, et al. Experimental [Page 33]
RFC 7897 Domain Subobjects for PCEP June 2016
Acknowledgments
The authors would like to especially thank Adrian Farrel for his
detailed reviews as well as providing text to be included in the
document.
Further, we would like to thank Pradeep Shastry, Suresh Babu, Quintin
Zhao, Fatai Zhang, Daniel King, Oscar Gonzalez, Chen Huaimo,
Venugopal Reddy, Reeja Paul, Sandeep Boina, Avantika Sergio Belotti,
and Jonathan Hardwick for their useful comments and suggestions.
Thanks to Jonathan Hardwick for shepherding this document.
Thanks to Deborah Brungard for being the responsible AD.
Thanks to Amanda Baber for the IANA review.
Thanks to Joel Halpern for the Gen-ART review.
Thanks to Klaas Wierenga for the SecDir review.
Thanks to Spencer Dawkins and Barry Leiba for comments during the
IESG review.
Dhody, et al. Experimental [Page 34]
RFC 7897 Domain Subobjects for PCEP June 2016
Authors' Addresses
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: dhruv.ietf@gmail.com
Udayasree Palle
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: udayasree.palle@huawei.com
Ramon Casellas
CTTC
Av. Carl Friedrich Gauss n7
Castelldefels, Barcelona 08860
Spain
Email: ramon.casellas@cttc.es
Dhody, et al. Experimental [Page 35]