PCE Working Group
Internet Engineering Task Force (IETF) M. Koldychev
Internet-Draft
Request for Comments: 9862 S. Sivabalan
Updates: 8231 (if approved) Ciena Corporation
Intended status:
Category: Standards Track S. Sidor
Expires: 6 October 2025
ISSN: 2070-1721 Cisco Systems, Inc.
C. Barth
Juniper Networks, Inc.
S. Peng
Huawei Technologies
H. Bidgoli
Nokia
4 April
September 2025
Path Computation Element Communication Protocol (PCEP) Extensions for
Segment Routing (SR) Policy Candidate Paths
draft-ietf-pce-segment-routing-policy-cp-27
Abstract
A Segment Routing (SR) Policy is an ordered list of instructions, instructions
called "segments" that represent a source-routed policy. Packet
flows are steered into an SR Policy on a node where it is
instantiated. An SR Policy is made of one or more candidate paths.
This document specifies the Path Computation Element Communication
Protocol (PCEP) extension to signal candidate paths of an SR Policy.
Additionally, this document updates RFC 8231 to allow delegation and
setup of an SR Label Switched Path (LSP), (LSP) without using the path
computation request and reply messages. This document is applicable
to both Segment Routing over MPLS (SR-MPLS) and Segment Routing over
IPv6 (SRv6).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for a maximum publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of six months RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 6 October 2025.
https://www.rfc-editor.org/info/rfc9862.
Copyright Notice
Copyright (c) 2025 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. SR Policy Association (SRPA) . . . . . . . . . . . . . . . . 6
4.1. SR Policy Identifier . . . . . . . . . . . . . . . . . . 7
4.2. SR Policy Candidate Path Identifier . . . . . . . . . . . 7
4.3. SR Policy Candidate Path Attributes . . . . . . . . . . . 7
4.4. Association Parameters . . . . . . . . . . . . . . . . . 8
4.5. Association Information . . . . . . . . . . . . . . . . . 9
4.5.1. SR Policy Name SRPOLICY-POL-NAME TLV . . . . . . . . . . . . . . . . . 10
4.5.2. SR Policy Candidate Path Identifier SRPOLICY-CPATH-ID TLV . . . . . . . 10
4.5.3. SR Policy Candidate Path Name SRPOLICY-CPATH-NAME TLV . . . . . . . . . . 12
4.5.4. SR Policy Candidate Path Preference SRPOLICY-CPATH-PREFERENCE TLV . . . . . . . 12
5. SR Policy Signaling Extensions . . . . . . . . . . . . . . . 13
5.1. SR Policy Capability SRPOLICY-CAPABILITY TLV . . . . . . . . . . . . . . . . 13
5.2. LSP Object TLVs . . . . . . . . . . . . . . . . . . . . . 15
5.2.1. Computation Priority COMPUTATION-PRIORITY TLV . . . . . . . . . . . . . . 15
5.2.2. Explicit Null Label Policy (ENLP) TLV . . . . . . . . 15
5.2.3. Invalidation INVALIDATION TLV . . . . . . . . . . . . . . . . . . 16
5.2.3.1. Drop-upon-invalid applies Drop-Upon-Invalid Applies to SR Policy . . . . . 18
5.3. Update Updates to RFC 8231 . . . . . . . . . . . . . . . . . . . 18
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
6.1. Association Type . . . . . . . . . . . . . . . . . . . . 19
6.2. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 19
6.3. PCEP Errors . . . . . . . . . . . . . . . . . . . . . . . 20
6.4. TE-PATH-BINDING TLV Flag field . . . . . . . . . . . . . 21 Field
6.5. SR Policy Invalidation Operational State . . . . . . . . 21
6.6. SR Policy Invalidation Configuration State . . . . . . . 22
6.7. SR Policy Capability TLV Flag field . . . . . . . . . . . 22 Field
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 23
7.1. Cisco . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.2. Juniper . . . . . . . . . . . . . . . . . . . . . . . . . 24
8. Security Considerations . . . . . . . . . . . . . . . . . . . 24
9.
8. Manageability Considerations . . . . . . . . . . . . . . . . 24
9.1.
8.1. Control of Function and Policy . . . . . . . . . . . . . 25
9.2.
8.2. Information and Data Models . . . . . . . . . . . . . . . 25
9.3.
8.3. Liveness Detection and Monitoring . . . . . . . . . . . . 25
9.4.
8.4. Verify Correct Operations . . . . . . . . . . . . . . . . 25
9.5.
8.5. Requirements On on Other Protocols . . . . . . . . . . . . . 25
9.6.
8.6. Impact On on Network Operations . . . . . . . . . . . . . . 25
10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 26
11.
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
11.1.
9.1. Normative References . . . . . . . . . . . . . . . . . . 26
11.2.
9.2. Informative References . . . . . . . . . . . . . . . . . 28
Appendix A.
Acknowledgements
Contributors . . . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction
Segment
"Segment Routing (SR) Policy Architecture Architecture" [RFC9256] details the concepts
of Segment Routing (SR) Policy [RFC8402] and approaches to steering
traffic into an SR Policy.
Path
"Path Computation Element Communication Protocol (PCEP) Extensions
for Segment Routing Routing" [RFC8664] specifies extensions to the PCEP that
allow a stateful Path Computation Element (PCE) to compute and
initiate Traffic Engineering (TE) paths, as well as a Path
Computation Client (PCC) to request a path subject to certain
constraints and optimization criteria in an SR domain. Although PCEP
extensions introduced in [RFC8664] enables enable the creation of SR-TE
paths, these do not constitute SR Policies as defined in [RFC9256] and therefore [RFC9256].
Therefore, they lack support for:
* Association of SR Policy Candidate Paths signaled via PCEP with
Candidate Paths of the same SR Policy signaled via other sources
(e.g., local configuration or BGP).
* Association of an SR Policy with an intent via color, enabling
headend-based steering of BGP service routes over SR Policies
provisioned via PCEP.
PCEP
"Path Computation Element Communication Protocol (PCEP) Extensions
for establishing relationships Establishing Relationships between sets Sets of Label Switched Paths (LSPs)
(LSPs)" [RFC8697] introduces a generic mechanism to create a grouping
of LSPs which that is called an Association. "Association".
An SR Policy is associated with one or more candidate paths. A
candidate path is the unit for signaling of an SR Policy to a headend as
described in Section 2.2 of [RFC9256]. This document extends
[RFC8664] to support signaling SR Policy Candidate Paths as LSPs and
to signal Candidate Path membership in an SR Policy by means of the
Association mechanism. A PCEP Association corresponds to a an SR
Policy and a an LSP corresponds to a Candidate Path. The unit of
signaling in PCEP is the LSP, thus thus, all the information related to an
SR Policy is carried at the Candidate Path level.
Also, this document updates Section 5.8.2 of [RFC8231], making the
use of Path Computation Request (PCReq) and Path Computation Reply
(PCRep) messages optional for LSPs setup that are set up using Path Setup
Type 1
(Segment (for Segment Routing) [RFC8664] and Path Setup Type 3 (SRv6) (for
SRv6) [RFC9603] with the aim of reducing the PCEP message exchanges
and simplifying implementation.
1.1. 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.
2. Terminology
This document uses the following terms defined in [RFC5440]: ERO,
PCC, PCE,
* Explicit Route Object (ERO)
* Path Computation Client (PCC)
* Path Computation Element (PCE)
* PCEP Peer, and Peer
* PCEP speaker. speaker
This document uses the following term defined in [RFC3031]: LSP.
* Label Switched Path (LSP)
This document uses the following term defined in [RFC9552]: BGP-LS.
* Border Gateway Protocol - Link State (BGP-LS)
The following other terms are used in this document:
Endpoint: The IPv4 or IPv6 endpoint address of an SR Policy, as
described in Section 2.1 of [RFC9256].
Color: The 32-bit color of an SR Policy, as described in Section 2.1
of [RFC9256].
Protocol-Origin: The protocol that was used to create a Candidate
Path, as described in Section 2.3 of [RFC9256].
Originator: A device that created a Candidate Path, as described in
Section 2.4 of [RFC9256].
Discriminator: Distinguishes Candidate Paths created by the same
device, as described in Section 2.5 of [RFC9256].
Association Parameters: As described in [RFC8697], refers parameters: Refers to the key data that uniquely
identifies an Association.
Association Information: As Association, as described in Section 6.1.4 of [RFC8697],
refers [RFC8697].
Association information: Refers to information related to
Association Type. Type, as described in Section 6.1.4 of [RFC8697].
SR Policy LSP: An LSP setup using Path Setup Type [RFC8408] 1
(Segment (for
Segment Routing) or 3 (SRv6). (for SRv6).
SR Policy Association: Association (SRPA): A new association type Association Type used to group
candidate paths belonging to the same SR Policy. Depending on the
discussion context, it can refer to the PCEP ASSOCIATION object of
an SR Policy type or to a group of LSPs that belong to the
association.
The base PCEP specification [RFC4655] originally defined the use of
the PCE architecture for MPLS and GMPLS networks with LSPs
instantiated using the RSVP-TE signaling protocol. Over time,
support for additional path setup types, types such as SRv6, SRv6 has been
introduced [RFC9603]. The term "LSP" is used extensively in PCEP
specifications and,
specifications, and in the context of this document, refers to a
Candidate Path within an SR Policy, which may be an SRv6 path (still
represented using the LSP Object object as specified in [RFC8231]. [RFC8231]).
3. Overview
The SR Policy is represented by a new type of PCEP Association,
called the SR Policy Association (SRPA) (see Section 4). The SR
Policy Candidate Paths of a specific SR Policy are the LSPs within
the same SRPA. The extensions in this document specify the encoding
of a single segment list within an SR Policy Candidate Path.
Encoding of multiple segment lists is outside the scope of this
document and is specified in [I-D.ietf-pce-multipath]. [PCEP-MULTIPATH].
An SRPA carries three pieces of information: SR Policy Identifier, SR
Policy Candidate Path Identifier, and SR Policy Candidate Path
Attribute(s).
This document also specifies some additional information that is not
encoded as part of an SRPA: Computation Priority computation priority of the LSP, Explicit
Null Label Policy for the unlabeled IP packets and Drop-upon-invalid Drop-Upon-Invalid
behavior for traffic steering when the LSP is operationally down (see
Section 5).
4. SR Policy Association (SRPA)
Per [RFC8697], LSPs are associated with other LSPs with which they
interact by adding them to a common association group. An
association group is uniquely identified by the combination of the
following fields in the ASSOCIATION object (Section 6.1 of
[RFC8697]): Association Type, Association ID, Association Source, and
(if present) Global Association Source, or Extended Association ID.
These fields are referred to as Association Parameters "association parameters"
(Section 4.4).
[RFC8697] specifies the ASSOCIATION Object object with two Object-Types for
IPv4 and IPv6 which that includes the field "Association Type". Association Type. This
document defines a new Association type Type (6) "SR Policy Association"
for an SRPA.
[RFC8697] specifies the mechanism for the capability advertisement of
the Association Types supported by a PCEP speaker by defining an
ASSOC-Type-List TLV to be carried within an OPEN object. This
capability exchange for the SR Policy Association SRPA Type MUST be done before using the
SRPA. To that aim, a PCEP speaker MUST include the SRPA Type (6) in
the ASSOC-Type-List TLV and MUST receive the same from the PCEP peer
before using the SRPA (Section 6.1).
An SRPA MUST be assigned for all SR Policy LSPs by the PCEP speaker
originating the LSP if the capability was advertised by both PCEP
speakers. If the above condition is not satisfied, then the
receiving PCEP speaker MUST send a PCErr message with with:
* Error-Type = 6 "Mandatory Object Missing", Error-Value Missing"
* Error-value = TBD1 22 "Missing SR Policy
Association". Association"
A given LSP MUST belong to at most one SRPA, SRPA at most, since an SR Policy
Candidate Path cannot belong to multiple SR Policies. If a PCEP
speaker receives a PCEP message requesting to join more than one SRPA
for the same LSP, then the PCEP speaker MUST send a PCErr message
with
with:
* Error-Type = 26 "Association Error", Error-Value Error"
* Error-value = 7 "Cannot join the association group". group"
The existing behavior for the use of Binding SID (BSID) with an SR
Policy is already documented in [RFC9604]. If BSID value allocation failed,
failed because of conflict with the BSID used by another policy, then
the PCEP peer MUST send a PCErr message with with:
* Error-Type = 32 "Binding label/SID failure" and
* Error-value = 2 "Unable to allocate the specified binding value". value"
4.1. SR Policy Identifier
The SR Policy Identifier uniquely identifies an SR Policy [RFC9256]
within the SR domain. The SR Policy Identifier is assigned by the
PCEP peer originating the LSP and MUST be uniform across all the PCEP
sessions. Candidate Paths within an SR Policy MUST carry the same SR
Policy Identifiers in their SRPAs. Candidate Paths within an SR
Policy MUST NOT change their SR Policy Identifiers for the lifetime
of the PCEP session. If the above conditions are not satisfied, the
receiving PCEP speaker MUST send a PCEP Error (PCErr) message with with:
* Error-Type = 26 "Association Error" and Error Value
* Error-value = 20 "SR Policy Identifier
Mismatch". Mismatch"
The SR Policy Identifier consists of:
* Headend router where the SR Policy originates.
* Color of the SR Policy ([RFC9256], Section 2.1).
* Endpoint of the SR Policy ([RFC9256], Section 2.1).
4.2. SR Policy Candidate Path Identifier
The SR Policy Candidate Path Identifier uniquely identifies the SR
Policy Candidate Path within the context of an SR Policy. The SR
Policy Candidate Path Identifier is assigned by the PCEP peer
originating the LSP. Candidate Paths within an SR Policy MUST NOT
change their SR Policy Candidate Path Identifiers for the lifetime of
the PCEP session. Two or more Candidate Paths within an SR Policy
MUST NOT carry the same SR Policy Candidate Path Identifiers in their
SRPAs. If the above conditions are not satisfied, the PCEP speaker
MUST send a PCErr message with with:
* Error-Type = 26 "Association Error" and Error
Value
* Error-value = 21 "SR Policy Candidate Path Identifier Mismatch". Mismatch"
The SR Policy Candidate Path Identifier consists of:
* Protocol Origin Protocol-Origin ([RFC9256], Section 2.3). 2.3)
* Originator ([RFC9256], Section 2.4). 2.4)
* Discriminator ([RFC9256], Section 2.5). 2.5)
4.3. SR Policy Candidate Path Attributes
SR Policy Candidate Path Attributes carry optional, non-key
information about a Candidate Path and MAY change during the lifetime
of an LSP. SR Policy Candidate Path Attributes consists consist of:
* Candidate Path preference ([RFC9256], Section 2.7). 2.7)
* Candidate Path name ([RFC9256], Section 2.6). 2.6)
* SR Policy name ([RFC9256], Section 2.1). 2.1)
4.4. Association Parameters
Per Section 2.1 of [RFC9256], an SR Policy is identified through the
<headend, color, endpoint>
<Headend, Color, Endpoint> tuple.
The Association Parameters consists association parameters consist of:
*
Association Type: Set to 6 "SR Policy Association".
*
Association Source (IPv4/IPv6): Set to the headend value of the SR
Policy, as defined in [RFC9256] [RFC9256], Section 2.1.
*
Association ID (16-bit): (16 bit): Always set to the numeric value "1".
* 1.
Extended Association ID TLV: Mandatory TLV for SR Policy
Association. an SRPA. Encodes the
Color and Endpoint of the SR Policy (Figure 1).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 31 | Length = 8 or 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Color |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Endpoint ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Extended Association ID TLV Format
Type: 31 for the Extended Association ID TLV, type = 31 TLV [RFC8697].
Length: 8 octets if IPv4 address or 20 octets if IPv6 address is
encoded in the Endpoint field.
Color: unsigned Unsigned non-zero 32-bit integer value, SR Policy color
per Section 2.1 of [RFC9256].
Endpoint: can Can be either IPv4 (4 octets) or IPv6 address (16
octets). This value MAY be different from the one contained in
the Destination address field in the END-POINTS object, or in
the Tunnel Endpoint Address field in the LSP-IDENTIFIERS TLV
(Section 2.1 of [RFC9256]).
If a PCEP speaker receives an SRPA object whose Association
Parameters association
parameters do not follow the above specification, then the PCEP
speaker MUST send a PCErr message with with:
* Error-Type = 26 "Association
Error", Error-Value Error"
* Error-value = 20 "SR Policy Identifier Mismatch". Mismatch"
The encoding choice of the Association Parameters association parameters in this way is
meant to guarantee that there is no possibility of a race condition
when multiple PCEP speakers want to associate the same SR Policy at
the same time. By adhering to this format, all PCEP speakers come up
with the same Association Parameters association parameters independently of each other
based on the SR Policy parameters [RFC9256].
The last hop of a computed SR Policy Candidate Path MAY differ from
the Endpoint contained in the <headend, color, endpoint> <Headend, Color, Endpoint> tuple. An
example use case is to terminate the SR Policy before reaching the
Endpoint and have decapsulated traffic be forwarded the rest of the
path to the Endpoint node using the native Interior Gateway Protocol
(IGP) path(s). In this example, the destination of the SR Policy
Candidate Paths will be some node before the Endpoint, but the
Endpoint value is still used at the headend to steer traffic with
that Endpoint IP address into the SR Policy. The Destination of the
SR Policy Candidate Path is signaled using the END-POINTS object and/
or the LSP-IDENTIFIERS TLV, per the usual PCEP procedure. When
neither the END-POINTS object nor the LSP-IDENTIFIERS TLV is present,
the PCEP speaker MUST extract the destination from the Endpoint field
in the SRPA Extended Association ID TLV.
SR Policy with Color-Only steering is signaled with the Endpoint
value set to unspecified, i.e., 0.0.0.0 for IPv4 or :: for IPv6, per
Section 8.8. 8.8 of [RFC9256].
4.5. Association Information
The SRPA object may carry the following TLVs:
*
SRPOLICY-POL-NAME TLV (Section 4.5.1): (optional) encodes the SR
Policy Name string.
*
SRPOLICY-CPATH-ID TLV (Section 4.5.2): (mandatory) encodes the SR
Policy Candidate Path Identifier.
*
SRPOLICY-CPATH-NAME TLV (Section 4.5.3): (optional) encodes the SR
Policy Candidate Path string name.
*
SRPOLICY-CPATH-PREFERENCE TLV (Section 4.5.4): (optional) encodes
the SR Policy Candidate Path preference value.
When a mandatory TLV is missing from an SRPA object, the PCEP speaker
MUST send a PCErr message with with:
* Error-Type = 6 "Mandatory Object
Missing", Error-Value Missing"
* Error-value = 21 "Missing SR Policy Mandatory TLV". TLV"
Only one TLV instance of each TLV type can be carried in an SRPA
object, and only the first occurrence is processed. Any others MUST
be silently ignored.
4.5.1. SR Policy Name SRPOLICY-POL-NAME TLV
The SRPOLICY-POL-NAME TLV (Figure 2) is an optional TLV for the SRPA
object. It is RECOMMENDED that the size of the name for the SR
Policy is limited to 255 bytes. Implementations MAY choose to
truncate long names to 255 bytes to simplify interoperability with
other protocols.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ SR Policy Name ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: SRPOLICY-POL-NAME TLV Format
Type: 56 for "SRPOLICY-POL-NAME" the SRPOLICY-POL-NAME TLV.
Length: indicates Indicates the length of the value portion of the TLV in
octets and MUST be greater than 0. The TLV MUST be zero-padded so
that the TLV is 4-octet aligned. Padding is not included in the
Length field.
SR Policy Name: SR Policy name, as defined in Section 2.1 of
[RFC9256]. It MUST be a string of printable ASCII [RFC0020]
characters, without a NULL terminator.
4.5.2. SR Policy Candidate Path Identifier SRPOLICY-CPATH-ID TLV
The SRPOLICY-CPATH-ID TLV (Figure 3) is a mandatory TLV for the SRPA
object.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Proto. Origin Proto-Origin | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator ASN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Originator Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: SRPOLICY-CPATH-ID TLV Format
Type: 57 for "SRPOLICY-CPATH-ID" the SRPOLICY-CPATH-ID TLV.
Length: 28.
Protocol Origin:
Protocol-Origin: 8-bit unsigned integer value that encodes the
protocol origin.
Protocol-Origin. The values of this field are specified in the
IANA registry "SR Policy Protocol Origin" under the "Segment
Routing" registry group, which was is introduced in Section 8.4 of
[I-D.ietf-idr-bgp-ls-sr-policy].
[ADV-SR-POLICY]. Note that in the PCInitiate message [RFC8281],
the Protocol Origin Protocol-Origin is always set to 10 - "PCEP (In PCEP or when
BGP-LS Producer is PCE)". The "SR Policy Protocol Origin" IANA
registry includes a combination of values intended for use in PCEP
and BGP-LS. When the registry contains two variants of values
associated with the mechanism or protocol used for provisioning of
the Candidate Path, for example 1 - "PCEP" and 10 - "PCEP (In PCEP
or when BGP-LS Producer is PCE)", the "(In PCEP or when BGP-LS
Producer is PCE)" PCE)", then variants MUST be used in PCEP.
Reserved: This field MUST be set to zero on transmission and MUST be
ignored on receipt.
Originator Autonomous System Number (ASN): Represented as a 32-bit
unsigned integer value, part of the originator identifier, as
specified in Section 2.4 of [RFC9256]. When sending a PCInitiate
message [RFC8281], the PCE is the originator of the Candidate
Path. If the PCE is configured with an ASN, then it MUST set it, otherwise it;
otherwise, the ASN is set to 0.
Originator Address: Represented as a 128-bit value as specified in
Section 2.4 of [RFC9256]. When sending a PCInitiate message, the
PCE is acting as the originator and therefore MAY set this to an
address that it owns.
Discriminator: 32-bit unsigned integer value that encodes the
Discriminator of the Candidate Path, as specified in Section 2.5
of [RFC9256]. This is the field that mainly distinguishes
different SR Policy Candidate Paths, coming from the same
originator. It is allowed to be any number in the 32-bit range.
4.5.3. SR Policy Candidate Path Name SRPOLICY-CPATH-NAME TLV
The SRPOLICY-CPATH-NAME TLV (Figure 4) is an optional TLV for the
SRPA object. It is RECOMMENDED that the size of the name for the SR
Policy is limited to 255 bytes. Implementations MAY choose to
truncate long names to 255 bytes to simplify interoperability with
other protocols.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ SR Policy Candidate Path Name ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: SRPOLICY-CPATH-NAME TLV Format
Type: 58 for "SRPOLICY-CPATH-NAME" the SRPOLICY-CPATH-NAME TLV.
Length: indicates Indicates the length of the value portion of the TLV in
octets and MUST be greater than 0. The TLV MUST be zero-padded so
that the TLV is 4-octet aligned. Padding is not included in the
Length field.
SR Policy Candidate Path Name: SR Policy Candidate Path Name, as
defined in Section 2.6 of [RFC9256]. It MUST be a string of
printable ASCII characters, without a NULL terminator.
4.5.4. SR Policy Candidate Path Preference SRPOLICY-CPATH-PREFERENCE TLV
The SRPOLICY-CPATH-PREFERENCE TLV (Figure 5) is an optional TLV for
the SRPA object. If the TLV is absent, then the default Preference
value is 100, per Section 2.7 of [RFC9256].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Preference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: SRPOLICY-CPATH-PREFERENCE TLV Format
Type: 59 for "SRPOLICY-CPATH-PREFERENCE" the SRPOLICY-CPATH-PREFERENCE TLV.
Length: 4.
Preference: 32-bit unsigned integer value that encodes the
preference of the Candidate Path as defined in Section 2.7 of
[RFC9256].
5. SR Policy Signaling Extensions
This section introduces mechanisms described for SR Policies in
[RFC9256] to PCEP. These extensions do not make use of the SRPA for
signaling in PCEP PCEP, and therefore cannot rely on the Association
capability negotiation in the ASSOC-Type-List TLV and separate
capability negotiation is required.
This document specifies four new TLVs to be carried in the OPEN or
LSP object. Only one TLV instance of each type can be carried, and
only the first occurrence is processed. Any others MUST be ignored.
5.1. SR Policy Capability SRPOLICY-CAPABILITY TLV
The SRPOLICY-CAPABILITY TLV (Figure 6) is a TLV for the OPEN object.
It is used at session establishment to learn the peer's capabilities
with respect to SR Policy. Implementations that support SR Policy
MUST include the SRPOLICY-CAPABILITY TLV in the OPEN object if the
extension is enabled. In addition, the ASSOC-Type-List TLV
containing SRPA Type (6) MUST be present in the OPEN object, as
specified in Section 4.
If a PCEP speaker receives an SRPA but the SRPOLICY-CAPABILITY TLV is
not exchanged, then the PCEP speaker MUST send a PCErr message with
Error- Type
Error-Type = 10 ("Reception "Reception of an invalid object") object" and Error-Value Error-value =
TBD2 ("Missing 44
"Missing SRPOLICY-CAPABILITY TLV") TLV" and MUST then close the PCEP
session.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |L| |I|E|P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: SRPOLICY-CAPABILITY TLV Format
Type: 71 for "SRPOLICY-CAPABILITY" the SRPOLICY-CAPABILITY TLV.
Length: 4.
Flags (32 bits):
Flags: 32 bits. The following flags are currently defined:
*
P-flag (Computation Priority): If set to '1' 1 by a PCEP speaker, the P flag
P-flag indicates that the PCEP speaker supports the handling of
the COMPUTATION-PRIORITY TLV for the SR Policy (Section 5.2.1).
If this flag is set to 0, then the receiving PCEP speaker MUST
NOT send the COMPUTATION-PRIORITY TLV and MUST ignore it on
receipt.
* E-Flag
E-flag (Explicit NULL Label Policy): If set to '1' 1 by a PCEP
speaker, the E flag E-flag indicates that the PCEP speaker supports
the handling of the Explicit Null Label Policy (ENLP) TLV for
the SR Policy (Section 5.2.2). If this flag is set to 0, then
the receiving PCEP speaker MUST NOT send the ENLP TLV and MUST
ignore it on receipt.
* I-Flag
I-flag (Invalidation): If set to '1' 1 by a PCEP speaker, the I flag I-flag
indicates that the PCEP speaker supports the handling of the
INVALIDATION TLV for the SR Policy (Section 5.2.3). If this
flag is set to 0, then the receiving PCEP speaker MUST NOT send
the INVALIDATION TLV and MUST ignore it on receipt.
* L-Flag
L-flag (Stateless Operation): If set to '1' 1 by a PCEP speaker, the
L flag
L-flag indicates that the PCEP speaker supports the stateless
(PCReq/PCRep) operations for the SR Policy (Section 5.3). If
the PCE set this flag to 0, then the PCC MUST NOT send PCReq
messages to this PCE for the SR Policy.
Unassigned bits MUST be set to '0' 0 on transmission and MUST be ignored
on receipt. More flags can be assigned in the future per
(Section 6.7).
5.2. LSP Object TLVs
This section is introducing three new TLVs to be carried in the LSP
object introduced in Section 7.3 of [RFC8231].
5.2.1. Computation Priority COMPUTATION-PRIORITY TLV
The COMPUTATION-PRIORITY TLV (Figure 7) is an optional TLV. It is
used to signal the numerical computation priority, as specified in
Section 2.12 of [RFC9256]. If the TLV is absent from the LSP object object,
and the P-flag in the SRPOLICY-CAPABILITY TLV is set to 1, a default
Priority value of 128 is used.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Priority | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: COMPUTATION-PRIORITY TLV Format
Type: 68 for "COMPUTATION-PRIORITY" the COMPUTATION-PRIORITY TLV.
Length: 4.
Priority: 8-bit unsigned integer value that encodes numerical
priority with which this LSP is to be recomputed by the PCE upon
topology change. Lowest The lowest value is the highest priority.
Reserved: This field MUST be set to zero on transmission and MUST be
ignored on receipt.
5.2.2. Explicit Null Label Policy (ENLP) TLV
To steer an unlabeled IP packet into an SR policy Policy for the MPLS data
plane, it is necessary to push a label stack of one or more labels on
that packet. The Explicit NULL Label Policy (ENLP) TLV is an
optional TLV for the LSP object used to indicate whether an Explicit
NULL Label [RFC3032] must be pushed on an unlabeled IP packet before
any other labels. The contents of this TLV are used by the SR Policy
Manager
manager as described in Section 4.1 of [RFC9256]. If an ENLP TLV is
not present, the decision of whether to push an Explicit NULL label
on a given packet is a matter of local configuration. Note that
Explicit Null is currently only defined for SR-MPLS and not for SRv6.
Therefore, the receiving PCEP speaker MUST ignore the presence of
this TLV for SRv6 Policies.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ENLP | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Explicit Null Label Policy (ENLP) TLV Format
Type: 69 for "ENLP" the ENLP TLV.
Length: 4.
ENLP (Explicit
ENLP: Explicit NULL Label Policy): Policy. 8-bit unsigned integer value that
indicates whether Explicit NULL labels are to be pushed on
unlabeled IP packets that are being steered into a given SR policy.
Policy. The values of this field are specified in the IANA
registry "SR Policy ENLP Values" under the "Segment Routing"
registry group, which was introduced in Section 6.10 of [I-D.ietf-idr-sr-policy-safi]. [RFC9830].
Reserved: This field MUST be set to zero on transmission and MUST be
ignored on receipt.
The ENLP unassigned values may be used for future extensions extensions, and
implementations MUST ignore the ENLP TLV with unrecognized values.
The behavior signaled in this TLV MAY be overridden by local
configuration by the network operator based on their deployment
requirements. The Section 4.1 of [RFC9256] describes the behavior on the
headend for the handling of the explicit null label.
5.2.3. Invalidation INVALIDATION TLV
The INVALIDATION TLV (Figure 9) is an optional TLV. This TLV is used
to control traffic steering into an LSP when the LSP is operationally
down/invalid. In the context of SR Policy, this TLV facilitates the
Drop-upon-invalid
Drop-Upon-Invalid behavior, specified in Section 8.2 of [RFC9256].
Normally, if the LSP is down/invalid then it stops attracting
traffic; traffic that would have been destined for that LSP is
redirected somewhere else, such as via IGP or another LSP. The Drop-
upon-invalid
Upon-Invalid behavior specifies that the LSP keeps attracting traffic
and the traffic has to be dropped at the headend. Such an LSP is
said to be "in drop state". While in the drop state, the LSP
operational state is "UP", as indicated by the O-flag in the LSP
object. However, the ERO object MAY be empty, empty if no valid path has
been computed.
The INVALIDATION TLV is used in both directions between PCEP peers:
* PCE -> PCC: The PCE specifies to the PCC whether to enable or
disable
Drop-upon-invalid Drop-Upon-Invalid (Config).
* PCC -> PCE: The PCC reports the current setting of the Drop-upon-
invalid Drop-Upon-
Invalid (Config) and also whether the LSP is currently in the drop
state (Oper).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Oper | Config | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: INVALIDATION TLV Format
Type: 70 for "INVALIDATION" the INVALIDATION TLV.
Length: 4.
Oper: An 8-bit flag field that encodes the operational state of the
LSP. It MUST be set to 0 by the PCE when sending and MUST be
ignored by the PCC upon receipt. See Section 6.5 for IANA
information.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| |D|
+-+-+-+-+-+-+-+-+
Figure 10: Oper state State of Drop-upon-invalid feature Drop-Upon-Invalid Feature
* D: dropping Dropping - the LSP is actively dropping traffic as a
result of
Drop-upon-invalid Drop-Upon-Invalid behavior being activated.
* The unassigned bits in the Flag octet MUST be set to zero
upon transmission and MUST be ignored upon receipt.
Config: An 8-bit flag field that encodes the configuration of the
LSP. See Section 6.6 for IANA information.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| |D|
+-+-+-+-+-+-+-+-+
Figure 11: Config state State of Drop-upon-invalid feature Drop-Upon-Invalid Feature
* D: drop Drop enabled - the Candidate Path has Drop-upon-invalid Drop-Upon-Invalid
feature enabled.
* The unassigned bits in the Flag octet MUST be set to zero
upon transmission and MUST be ignored upon receipt.
Reserved: This field MUST be set to zero on transmission and MUST be
ignored on receipt.
5.2.3.1. Drop-upon-invalid applies Drop-Upon-Invalid Applies to SR Policy
The Drop-upon-invalid Drop-Upon-Invalid feature is somewhat special among the other SR
Policy features in the way that it is enabled/disabled. This feature
is enabled only on the whole SR Policy, not on a particular Candidate
Path of that SR Policy, i.e., when any Candidate Path has Drop-upon-
invalid Drop-Upon-
Invalid enabled, it means that the whole SR Policy has the feature
enabled. As stated in Section 8.1 of [RFC9256], an SR Policy is
invalid when all its Candidate Paths are invalid.
Once all the Candidate Paths of an SR Policy have become invalid,
then the SR Policy checks whether any of the Candidate Paths have
Drop-upon-invalid
Drop-Upon-Invalid enabled. If so, the SR Policy enters the drop
state and "activates" the highest preference Candidate Path which that has
the Drop-upon-invalid Drop-Upon-Invalid enabled. Note that only one Candidate Path
needs to be reported to the PCE with the D (dropping) flag set.
5.3. Update Updates to RFC 8231
Section 5.8.2 of [RFC8231], [RFC8231] allows delegation of an LSP in
operationally down state, but at the same time mandates the use of
PCReq before sending PCRpt. This document updates Section 5.8.2 of
[RFC8231], by making that section of [RFC8231] not applicable to SR
Policy LSPs. Thus, when a PCC wants to delegate an SR Policy LSP, it
MAY proceed directly to sending PCRpt, without first sending PCReq
and waiting for PCRep. This has the advantage of reducing the number
of PCEP messages and simplifying the implementation.
Furthermore, a PCEP speaker is not required to support PCReq/PCRep at
all for SR Policies. The PCEP speaker can indicate support for
PCReq/PCRep via the "L-Flag" L-flag in the SRPOLICY-CAPABILITY TLV (See (see
Section 5.1). When this flag is cleared, or when the SRPOLICY-
CAPABILITY TLV is absent, the given peer MUST NOT be sent PCReq/PCRep
messages for SR Policy LSPs. Conversely, when this flag is set, the
peer can receive and process PCReq/PCRep messages for SR Policy LSPs.
The above applies only to SR Policy LSPs and does not affect other
LSP types, such as RSVP-TE LSPs. For other LSP types, Section 5.8.2
of [RFC8231] continues to apply.
6. IANA Considerations
IANA maintains the "Path Computation Element Protocol (PCEP) Numbers"
registry at <https://www.iana.org/assignments/pcep>.
6.1. Association Type
This document defines a new association type: Association Type: SR Policy Association.
IANA is requested to confirm has made the following allocation assignment in the "ASSOCIATION Type
Field" registry within the "Path Computation Element Protocol (PCEP)
Numbers" registry group:
+-----------+-------------------------------------------+-----------+
+======+=======================+===========+
| Type | Name | Reference |
+-----------+-------------------------------------------+-----------+
+======+=======================+===========+
| 6 | SR Policy Association | This.I-D RFC 9862 |
+-----------+-------------------------------------------+-----------+
+------+-----------------------+-----------+
Table 1
6.2. PCEP TLV Type Indicators
This document defines eight new TLVs for carrying additional
information about SR Policy and SR Policy Candidate Paths. IANA is
requested to confirm has
made the following allocations assignments in the existing "PCEP TLV Type
Indicators" registry as follows:
+-----------+-------------------------------------------+-----------+ registry:
+=======+============================+===========+
| Value | Description | Reference |
+-----------+-------------------------------------------+-----------+
+=======+============================+===========+
| 56 | SRPOLICY-POL-NAME | This.I-D RFC 9862 |
+-----------+-------------------------------------------+-----------+
+-------+----------------------------+-----------+
| 57 | SRPOLICY-CPATH-ID | This.I-D RFC 9862 |
+-----------+-------------------------------------------+-----------+
+-------+----------------------------+-----------+
| 58 | SRPOLICY-CPATH-NAME | This.I-D RFC 9862 |
+-----------+-------------------------------------------+-----------+
+-------+----------------------------+-----------+
| 59 | SRPOLICY-CPATH-PREFERENCE | This.I-D RFC 9862 |
+-----------+-------------------------------------------+-----------+
+-------+----------------------------+-----------+
| 68 | COMPUTATION-PRIORITY | This.I-D RFC 9862 |
+-----------+-------------------------------------------+-----------+
+-------+----------------------------+-----------+
| 69 | EXPLICIT-NULL-LABEL-POLICY | This.I-D RFC 9862 |
+-----------+-------------------------------------------+-----------+
+-------+----------------------------+-----------+
| 70 | INVALIDATION | This.I-D RFC 9862 |
+-----------+-------------------------------------------+-----------+
+-------+----------------------------+-----------+
| 71 | SRPOLICY-CAPABILITY | This.I-D RFC 9862 |
+-----------+-------------------------------------------+-----------+
+-------+----------------------------+-----------+
Table 2
6.3. PCEP Errors
This document defines the following:
* one new Error-Value Error-value within the "Mandatory Object Missing" Error-Type, Error-
Type,
* two new Error-Values Error-values within the "Association Error" Error-Type Error-Type,
and
* one new Error-Value Error-value within the "Reception of an invalid object".
IANA is requested to confirm has made the following allocations within assignments in the "PCEP-ERROR Object
Error Types and Values" registry of the "Path Computation Element
Protocol (PCEP) Numbers" registry group.
+------------+------------------+-----------------------+-----------+
+============+================+======================+===========+
| Error-Type | Meaning | Error-value | Reference |
+------------+------------------+-----------------------+-----------+
+============+================+======================+===========+
| 6 | Mandatory Object | | [RFC5440] |
| | Object Missing | | |
+------------+------------------+-----------------------+-----------+
| +----------------+----------------------+-----------+
| | | 21: Missing SR | This.I-D RFC 9862 |
| | | Policy Mandatory TLV | |
+------------+------------------+-----------------------+-----------+
+------------+----------------+----------------------+-----------+
| 26 | Association | | [RFC8697] |
| | Error | | |
+------------+------------------+-----------------------+-----------+
| +----------------+----------------------+-----------+
| | | 20: SR Policy | This.I-D RFC 9862 |
| | | Identifers Mismatch | |
+------------+------------------+-----------------------+-----------+
| +----------------+----------------------+-----------+
| | | 21: SR Policy | This.I-D RFC 9862 |
| | | Candidate Path | |
| | | Identifier Mismatch | |
+------------+------------------+-----------------------+-----------+
+------------+----------------+----------------------+-----------+
Table 3
IANA is requested to make new allocations within has made the following assigments in the "PCEP-ERROR Object
Error Types and Values" registry of the "Path Computation Element
Protocol (PCEP) Numbers" registry group.
+------------+------------------+-----------------------+-----------+
+============+=================+=======================+===========+
| Error-Type | Meaning | Error-value | Reference |
+------------+------------------+-----------------------+-----------+
+============+=================+=======================+===========+
| 6 | Mandatory Object | | [RFC5440] |
| | Object Missing | | |
+------------+------------------+-----------------------+-----------+
| +-----------------+-----------------------+-----------+
| | TBD1: | 22: Missing SR Policy | This.I-D RFC 9862 |
| | | Policy Association | |
+------------+------------------+-----------------------+-----------+
+------------+-----------------+-----------------------+-----------+
| 10 | Reception of an | | [RFC5440] |
| | invalid object | | |
+------------+------------------+-----------------------+-----------+
| | | TBD2: Missing | This.I-D
| +-----------------+-----------------------+-----------+
| | | SRPOLICY-CAPABILITY 44: Missing SRPOLICY- | RFC 9862 |
| | | CAPABILITY TLV | |
+------------+------------------+-----------------------+-----------+
+------------+-----------------+-----------------------+-----------+
Table 4
6.4. TE-PATH-BINDING TLV Flag field
An earlier Field
A draft version of this document added a new bit within in the "TE-
PATH-BINDING "TE-PATH-
BINDING TLV Flag field" Field" registry of the "Path Computation Element
Protocol (PCEP) Numbers" registry group, which was also early allocated by the
IANA.
IANA is requested to mark has marked the bit position as deprecated.
+------------+------------------------------------------+-----------+
+=====+==================================+===========+
| Bit position | Description | Reference |
+--------------+----------------------------------------+-----------+
+=====+==================================+===========+
| 1 | Deprecated (Specified-BSID-only) | This.I-D RFC 9862 |
+--------------+----------------------------------------+-----------+
+-----+----------------------------------+-----------+
Table 5
6.5. SR Policy Invalidation Operational State
This document requests
IANA to has created and will maintain a new registry under the "Path
Computation Element Protocol (PCEP) Numbers" registry group. The new
registry is called "SR Policy Invalidation Operational Flags". New
values are to be assigned by "IETF review" Review" [RFC8126]. Each bit
should will
be tracked with the following qualities:
* Bit (counting from bit 0 as the most significant bit). bit)
* Description. Description
* Reference.
+-------+-----------------------------------------------+-----------+ Reference
+=======+==============================================+===========+
| Bit | Description | Reference |
+-------+-----------------------------------------------+-----------+
+=======+==============================================+===========+
| 0 - 6 | Unassigned | This.I-D |
+-------+-----------------------------------------------+-----------+
+-------+----------------------------------------------+-----------+
| 7 | D: dropping Dropping - the LSP is currently attracting | This.I-D RFC 9862 |
| | attracting traffic and actively dropping it. | |
+-------+-----------------------------------------------+-----------+
+-------+----------------------------------------------+-----------+
Table 6
6.6. SR Policy Invalidation Configuration State
This document requests
IANA to has created and will maintain a new registry under the "Path
Computation Element Protocol (PCEP) Numbers" registry group. The new
registry is called "SR Policy Invalidation Configuration Flags". New
values are to be assigned by "IETF review" Review" [RFC8126]. Each bit
should will
be tracked with the following qualities:
* Bit (counting from bit 0 as the most significant bit). bit)
* Description. Description
* Reference.
+-------+-----------------------------------------------+-----------+ Reference
+=======+==================================+===========+
| Bit | Description | Reference |
+-------+-----------------------------------------------+-----------+
+=======+==================================+===========+
| 0 - 6 | Unassigned. | This.I-D |
+-------+-----------------------------------------------+-----------+
+-------+----------------------------------+-----------+
| 7 | D: drop Drop enabled - the Drop-upon-invalid is Drop-Upon- | This.I-D RFC 9862 |
| | Invalid is enabled on the LSP. | |
+-------+-----------------------------------------------+-----------+
+-------+----------------------------------+-----------+
Table 7
6.7. SR Policy Capability TLV Flag field
This document requests Field
IANA to has created and will maintain a new registry under the "Path
Computation Element Protocol (PCEP) Numbers" registry group. The new
registry is called "SR Policy Capability TLV Flag Field". New values
are to be assigned by "IETF review" Review" [RFC8126]. Each bit should will be
tracked with the following qualities:
* Bit (counting from bit 0 as the most significant bit). bit)
* Description. Description
* Reference.
+--------+-----------------------------------------------+-----------+ Reference
+========+=====================================+===========+
| Bit | Description | Reference |
+--------+-----------------------------------------------+-----------+
+========+=====================================+===========+
| 0 - 26 | Unassigned | This.I-D RFC 9862 |
+--------+-----------------------------------------------+-----------+
+--------+-------------------------------------+-----------+
| 27 | Stateless Operation (L-Flag) (L-flag) | This.I-D RFC 9862 |
+--------+-----------------------------------------------+-----------+
+--------+-------------------------------------+-----------+
| 28 | Unassigned | This.I-D RFC 9862 |
+--------+-----------------------------------------------+-----------+
+--------+-------------------------------------+-----------+
| 29 | Invalidation (I-Flag) (I-flag) | This.I-D RFC 9862 |
+--------+-----------------------------------------------+-----------+
+--------+-------------------------------------+-----------+
| 30 | Explicit NULL Label Policy (E-Flag) (E-flag) | This.I-D RFC 9862 |
+--------+-----------------------------------------------+-----------+
+--------+-------------------------------------+-----------+
| 31 | Computation Priority (P-flag) | This.I-D RFC 9862 |
+--------+-----------------------------------------------+-----------+
+--------+-------------------------------------+-----------+
Table 8
7. Implementation Status
[Note to the RFC Editor - remove this section before publication, as
well as remove the reference to RFC 7942.]
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.
According to [RFC7942], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
7.1. Cisco
* Organization: Cisco Systems
* Implementation: IOS-XR PCC and PCE.
* Description: All features supported except Computation Priority,
Explicit NULL and Invalidation Drop.
* Maturity Level: Production.
* Coverage: Full.
* Contact: ssidor@cisco.com
7.2. Juniper
* Organization: Juniper Networks
* Implementation: PCC and PCE.
* Description: Everything in -05 except SR Policy Name TLV and SR
Policy Candidate Path Name TLV.
* Maturity Level: Production.
* Coverage: Partial.
* Contact: cbarth@juniper.net
8. Security Considerations
The information carried in the newly defined SRPA object and TLVs
could provide an eavesdropper with additional information about the
SR Policy.
The security considerations described in [RFC5440], [RFC8231],
[RFC8281], [RFC8664], [RFC8697], [RFC9256] [RFC9256], and [RFC9603] are
applicable to this specification.
As per [RFC8231], it is RECOMMENDED that these PCEP extensions can
only be activated on authenticated and encrypted sessions across PCEs
and PCCs belonging to the same administrative authority, using
Transport Layer Security (TLS) [RFC8253] as per the recommendations
and best current practices in [RFC9325].
9.
8. Manageability Considerations
All manageability requirements and considerations listed in
[RFC5440], [RFC8231], [RFC8664], [RFC9256], and [RFC9603] apply to
PCEP protocol extensions defined in this document. In addition,
requirements and considerations listed in this section apply.
9.1.
8.1. Control of Function and Policy
A PCE or PCC implementation MAY allow the capabilities specified in
Section 5.1 and the capability for support of an SRPA advertised in
the ASSOC-Type-List TLV to be enabled and disabled.
9.2.
8.2. Information and Data Models
[I-D.ietf-pce-pcep-srv6-yang]
[PCEP-SRv6-YANG] defines a YANG module with common building blocks
for PCEP Extensions extensions described in Section 4.
9.3.
8.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in [RFC5440], [RFC8664], and [RFC9256].
9.4.
8.4. Verify Correct Operations
Operation verification requirements already listed in [RFC5440],
[RFC8231], [RFC8664], [RFC9256], and [RFC9603] are applicable to
mechanisms defined in this document.
An implementation MUST allow the operator to view SR Policy
Identifier and SR Policy Candidate Path Identifier advertised in an
SRPA object.
An implementation SHOULD allow the operator to view the capabilities
defined in this document advertised by each PCEP peer.
An implementation SHOULD allow the operator to view LSPs associated
with a specific SR Policy Identifier.
9.5.
8.5. Requirements On on Other Protocols
The PCEP extensions defined in this document do not imply any new
requirements on other protocols.
9.6.
8.6. Impact On on Network Operations
The mechanisms defined in [RFC5440], [RFC8231], [RFC9256] [RFC9256], and
[RFC9603] also apply to the PCEP extensions defined in this document.
10. Acknowledgement
We would like to thank Abdul Rehman, Andrew Stone, Boris Khasanov,
Cheng Li, Dhruv Dhody, Gorry Fairhurst, Gyan Mishra, Huaimo Chen,
Ines Robles, Joseph Salowey, Ketan Talaulikar, Marina Fizgeer, Mike
Bishopm, Praveen Kumar, Robert Sparks, Roman Danyliw, Stephane
Litkowski, Tom Petch, Zoey Rose, Xiao Min, Xiong Quan for review and
suggestions.
11.
9. References
11.1.
9.1. Normative References
[RFC0020] Cerf, V., "ASCII format for network interchange", STD 80,
RFC 20, DOI 10.17487/RFC0020, October 1969,
<https://www.rfc-editor.org/info/rfc20>.
[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>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[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>.
[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>.
[RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for PCE-Initiated LSP Setup in a Stateful PCE
Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
<https://www.rfc-editor.org/info/rfc8281>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8408] Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J.
Hardwick, "Conveying Path Setup Type in PCE Communication
Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408,
July 2018, <https://www.rfc-editor.org/info/rfc8408>.
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.
[RFC8697] Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H.,
Dhody, D., and Y. Tanaka, "Path Computation Element
Communication Protocol (PCEP) Extensions for Establishing
Relationships between Sets of Label Switched Paths
(LSPs)", RFC 8697, DOI 10.17487/RFC8697, January 2020,
<https://www.rfc-editor.org/info/rfc8697>.
[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.
[RFC9325] Sheffer, Y., Saint-Andre, P., and T. Fossati,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, November
2022, <https://www.rfc-editor.org/info/rfc9325>.
[RFC9603] Li, C., Ed., Kaladharan, P., Sivabalan, S., Koldychev, M.,
and Y. Zhu, "Path Computation Element Communication
Protocol (PCEP) Extensions for IPv6 Segment Routing",
RFC 9603, DOI 10.17487/RFC9603, July 2024,
<https://www.rfc-editor.org/info/rfc9603>.
11.2.
9.2. Informative References
[I-D.ietf-idr-sr-policy-safi]
Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., and
D. Jain, "Advertising Segment Routing Policies in BGP",
Work in Progress, Internet-Draft, draft-ietf-idr-sr-
policy-safi-13, 6 February 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-sr-
policy-safi-13>.
[I-D.ietf-idr-bgp-ls-sr-policy]
[ADV-SR-POLICY]
Previdi, S., Talaulikar, K., Ed., Dong, J., Gredler, H.,
and J. Tantsura, "Advertisement of Segment Routing
Policies using BGP Link-State", Work in Progress, Internet-Draft, draft-
ietf-idr-bgp-ls-sr-policy-17, 6
March 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-
ls-sr-policy-17>.
[I-D.ietf-pce-multipath] <https://datatracker.ietf.org/doc/html/draft-
ietf-idr-bgp-ls-sr-policy-17>.
[PCEP-MULTIPATH]
Koldychev, M., Sivabalan, S., Saad, T., Beeram, V. P.,
Bidgoli, H., Yadav, B., Peng, S., and Mishra, G. S., and S. Mishra, "PCEP
Sidor, "Path Computation Element Communication Protocol
(PCEP) Extensions for Signaling Multipath Information",
Work in Progress, Internet-Draft, draft-ietf-pce-multipath-12, 8
October 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-pce-multipath-12>.
[I-D.ietf-pce-pcep-srv6-yang] draft-ietf-pce-
multipath-14, 5 September 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-pce-
multipath-14>.
[PCEP-SRv6-YANG]
Li, C., Sivabalan, S., Peng, S., Koldychev, M., and L.
Ndifor, "A YANG Data Model for Segment Routing (SR) Policy
and SR in IPv6 (SRv6) support in Path Computation Element
Communications Protocol (PCEP)", Work in Progress,
October 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-pce-pcep-srv6-yang-06>.
Internet-Draft, draft-ietf-pce-pcep-srv6-yang-07, 21 April
2025, <https://datatracker.ietf.org/doc/html/draft-ietf-
pce-pcep-srv6-yang-07>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[RFC9552] Talaulikar, K., Ed., "Distribution of Link-State and
Traffic Engineering Information Using BGP", RFC 9552,
DOI 10.17487/RFC9552, December 2023,
<https://www.rfc-editor.org/info/rfc9552>.
[RFC9604] Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S.,
and C. Li, Ed., "Carrying Binding Label/SID in PCE-Based
Networks", RFC 9604, DOI 10.17487/RFC9604, August 2024,
<https://www.rfc-editor.org/info/rfc9604>.
Appendix A.
[RFC9830] Previdi, S., Filsfils, C., Talaulikar, K., Ed., Mattes,
P., and D. Jain, "Advertising Segment Routing Policies in
BGP", RFC 9830, DOI 10.17487/RFC9830, September 2025,
<https://www.rfc-editor.org/info/rfc9830>.
Acknowledgements
We would like to thank Abdul Rehman, Andrew Stone, Boris Khasanov,
Cheng Li, Dhruv Dhody, Gorry Fairhurst, Gyan Mishra, Huaimo Chen,
Ines Robles, Joseph Salowey, Ketan Talaulikar, Marina Fizgeer, Mike
Bishopm, Praveen Kumar, Robert Sparks, Roman Danyliw, Stephane
Litkowski, Tom Petch, Zoey Rose, Xiao Min, Xiong Quan for review and
suggestions.
Contributors
Dhruv Dhody
Huawei
India
Email: dhruv.ietf@gmail.com
Cheng Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing,
Beijing
10095
China
Email: chengli13@huawei.com
Zafar Ali
Cisco Systems, Inc. Inc
Email: zali@cisco.com
Rajesh Melarcode
Cisco Systems, Inc.
2000 Innovation Dr.
Kanata,
Kanata Ontario
Canada
Email: rmelarco@cisco.com
Authors' Addresses
Mike Koldychev
Ciena Corporation
385 Terry Fox Dr.
Kanata Ontario K2K 0L1
Canada
Email: mkoldych@proton.me
Siva Sivabalan
Ciena Corporation
385 Terry Fox Dr.
Kanata Ontario K2K 0L1
Canada
Email: ssivabal@ciena.com
Samuel Sidor
Cisco Systems, Inc.
Eurovea Central 3.
811 09 Bratislava
Slovakia
Email: ssidor@cisco.com
Colby Barth
Juniper Networks, Inc.
Email: cbarth@juniper.net
Shuping Peng
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing
100095
China
Email: pengshuping@huawei.com
Hooman Bidgoli
Nokia
Email: hooman.bidgoli@nokia.com