PCE Working Group M. Koldychev
Internet-Draft S. Sivabalan
Updates: 8231 (if approved) Ciena Corporation
Intended status: Standards Track S. Sidor
Expires: 3 October 2025 Cisco Systems, Inc.
C. Barth
Juniper Networks, Inc.
S. Peng
Huawei Technologies
H. Bidgoli
Nokia
1 April 2025
Path Computation Element Communication Protocol (PCEP) Extensions for
Segment Routing (SR) Policy Candidate Paths
draft-ietf-pce-segment-routing-policy-cp-25
Abstract
A Segment Routing (SR) Policy is an ordered list of instructions,
called "segments" that represent a source-routed policy. Packet
flows are steered into an SR Policy on a node where it is
instantiated, called a headend node. 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), 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 of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on 3 October 2025.
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
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. SR Policy Identifier . . . . . . . . . . . . . . . . . . 5
3.2. SR Policy Candidate Path Identifier . . . . . . . . . . . 6
3.3. SR Policy Candidate Path Attributes . . . . . . . . . . . 6
4. SR Policy Association (SRPA) . . . . . . . . . . . . . . . . 6
4.1. Association Parameters . . . . . . . . . . . . . . . . . 7
4.2. Association Information . . . . . . . . . . . . . . . . . 9
4.2.1. SR Policy Name TLV . . . . . . . . . . . . . . . . . 9
4.2.2. SR Policy Candidate Path Identifier TLV . . . . . . . 10
4.2.3. SR Policy Candidate Path Name TLV . . . . . . . . . . 11
4.2.4. SR Policy Candidate Path Preference TLV . . . . . . . 12
5. SR Policy Signaling Extensions . . . . . . . . . . . . . . . 13
5.1. SR Policy Capability TLV . . . . . . . . . . . . . . . . 13
5.2. Computation Priority TLV . . . . . . . . . . . . . . . . 14
5.3. Explicit Null Label Policy (ENLP) TLV . . . . . . . . . . 15
5.4. Invalidation TLV . . . . . . . . . . . . . . . . . . . . 16
5.4.1. Drop-upon-invalid applies to SR Policy . . . . . . . 17
5.5. Update to RFC 8231 . . . . . . . . . . . . . . . . . . . 18
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
6.1. Association Type . . . . . . . . . . . . . . . . . . . . 18
6.2. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 19
6.3. PCEP Errors . . . . . . . . . . . . . . . . . . . . . . . 19
6.4. TE-PATH-BINDING TLV Flag field . . . . . . . . . . . . . 20
6.5. SR Policy Invalidation Operational State . . . . . . . . 21
6.6. SR Policy Invalidation Configuration State . . . . . . . 21
6.7. SR Policy Capability TLV Flag field . . . . . . . . . . . 22
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 22
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7.1. Cisco . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.2. Juniper . . . . . . . . . . . . . . . . . . . . . . . . . 23
8. Security Considerations . . . . . . . . . . . . . . . . . . . 24
9. Manageability Considerations . . . . . . . . . . . . . . . . 24
9.1. Control of Function and Policy . . . . . . . . . . . . . 24
9.2. Information and Data Models . . . . . . . . . . . . . . . 24
9.3. Liveness Detection and Monitoring . . . . . . . . . . . . 24
9.4. Verify Correct Operations . . . . . . . . . . . . . . . . 24
9.5. Requirements On Other Protocols . . . . . . . . . . . . . 25
9.6. Impact On Network Operations . . . . . . . . . . . . . . 25
10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 25
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
11.1. Normative References . . . . . . . . . . . . . . . . . . 25
11.2. Informative References . . . . . . . . . . . . . . . . . 27
Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction
Segment Routing (SR) Policy Architecture [RFC9256] details the
concepts of Segment Routing (SR) Policy [RFC8402] and approaches to
steering traffic into an SR Policy.
Path Computation Element Communication Protocol (PCEP) Extensions for
Segment 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 SR networks. Although PCEP extensions
introduced in [RFC8664] are defined for creation of SR-TE tunnels,
these are not SR Policies and lack many important features described
in [RFC9256].
PCEP Extensions for Establishing Relationships Between Sets of Label
Switched Paths (LSPs) [RFC8697] introduces a generic mechanism to
create a grouping of LSPs which is called an 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 SR Policy
and a LSP corresponds to a Candidate Path. The unit of signaling in
PCEP is the LSP, thus all the information related to SR Policy is
carried at the Candidate Path level.
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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 using Path Setup Type 1
(Segment Routing) [RFC8664] and Path Setup Type 3 (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]: PCC,
PCE, PCEP Peer, and PCEP speaker.
This document uses the following terms defined in [RFC3031]: LSP.
The following 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 to the key
data that uniquely identifies an Association.
Association Information: As described in Section 6.1.4 of [RFC8697],
refers to information related to Association Type.
SR Policy LSP: An LSP setup using Path Setup Type [RFC8408] 1
(Segment Routing) or 3 (SRv6).
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SR Policy Association: A new association type used to group
candidate paths belonging to same SR Policy. Depending on the
discussion context, it can refer to the PCEP ASSOCIATION object of
SR Policy type or to a group of LSPs that belong to the
association.
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
Candidate Paths of an SR Policy are the LSPs within the same SRPA.
Encoding multiple Segment Lists within an SR Policy Candidate Path is
described in [I-D.ietf-pce-multipath]. These considerations are not
covered here.
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 of the LSP, Explicit
Null Label Policy for the unlabeled IP packets and Drop-upon-invalid
behavior for traffic steering when the LSP is operationally down (see
Section 5).
3.1. SR Policy Identifier
SR Policy Identifier uniquely identifies an SR Policy [RFC9256]
within the network. SR Policy identifier is assigned by PCEP peer
originating the LSP. SR Policy Identifier MUST be the same for all
SR Policy Candidate Paths in the same SRPA. SR Policy Identifier
MUST be constant for a given SR Policy Candidate Path for the
lifetime of the PCEP session. SR Policy Identifier MUST be different
for different SRPAs. If the identifier is inconsistent among
Candidate Paths, changes during the lifetime of the PCEP session, or
is not unique across different SRPAs, the receiving PCEP speaker MUST
send a PCEP Error (PCErr) message with Error-Type = 26 "Association
Error" and Error Value = 20 "SR Policy Identifier Mismatch". 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).
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3.2. SR Policy Candidate Path Identifier
SR Policy Candidate Path Identifier uniquely identifies the SR Policy
Candidate Path within the context of an SR Policy. SR Policy
Candidate Path Identifier MUST be constant for the lifetime of the
PCEP session. SR Policy Candidate Path Identifier MUST be different
for distinct Candidate Paths within the same SRPA. If SR Policy
Candidate Path Identifier changes during the lifetime of the PCEP
session or is not unique among distinct Candidate Paths, the PCEP
speaker MUST send a PCErr message with Error-Type = 26 "Association
Error" and Error Value = 21 "SR Policy Candidate Path Identifier
Mismatch". SR Policy Candidate Path Identifier consists of:
* Protocol Origin ([RFC9256], Section 2.3).
* Originator ([RFC9256], Section 2.4).
* Discriminator ([RFC9256], Section 2.5).
3.3. 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 of:
* Candidate Path preference ([RFC9256], Section 2.7).
* Candidate Path name ([RFC9256], Section 2.6).
* SR Policy name ([RFC9256], Section 2.1).
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 (Section 4.1).
[RFC8697] specifies the ASSOCIATION Object with two Object-Types for
IPv4 and IPv6 which includes the field "Association Type". This
document defines a new Association type (6) "SR Policy Association"
for SRPA.
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[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 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).
A given LSP MUST belong to at most one SRPA, 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 Error-Type = 26 "Association Error", Error-Value = 7 "Cannot
join the association group".
The existing behavior for the use of Binding SID with SR Policy is
already documented in [RFC9604]. If BSID value allocation failed,
because of conflict with BSID used by another policy, then PCEP peer
MUST send a PCErr message with Error-Type = 32 "Binding label/SID
failure" and Error-value = 2 "Unable to allocate the specified
binding value".
4.1. Association Parameters
Per Section 2.1 of [RFC9256], an SR Policy is identified through the
<headend, color, endpoint> tuple.
The Association Parameters consists 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] Section 2.1.
* Association ID (16-bit): Always set to the numeric value "1".
* Extended Association ID TLV: Mandatory TLV for SR Policy
Association. Encodes the Color and Endpoint of the SR Policy
(Figure 1).
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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: Extended Association ID TLV, type = 31 [RFC8697].
Length: Either 8 or 20, depending on whether an IPv4 or IPv6 address
is encoded in the Endpoint field.
Color: SR Policy color value, MUST be non-zero per Section 2.1 of
[RFC9256].
Endpoint: can be either IPv4 or IPv6 address. 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 do not follow the above specification, then the PCEP
speaker MUST send a PCErr message with Error-Type = 26 "Association
Error", Error-Value = 20 "SR Policy Identifier Mismatch".
The encoding choice of the 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 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> 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 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 LSP-IDENTIFIERS TLV, per
the usual PCEP procedure. When neither the END-POINTS object nor
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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. of [RFC9256].
4.2. Association Information
The SRPA object may carry the following TLVs:
* SRPOLICY-POL-NAME TLV (Section 4.2.1): (optional) encodes the SR
Policy Name string.
* SRPOLICY-CPATH-ID TLV (Section 4.2.2): (mandatory) encodes the SR
Policy Candidate Path Identifier.
* SRPOLICY-CPATH-NAME TLV (Section 4.2.3): (optional) encodes the SR
Policy Candidate Path string name.
* SRPOLICY-CPATH-PREFERENCE TLV (Section 4.2.4): (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 Error-Type = 6 "Mandatory Object
Missing", Error-Value = 21 "Missing SR Policy Mandatory 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.
4.2.1. SR Policy 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 symbolic 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.
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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" TLV.
Length: 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.
4.2.2. SR Policy Candidate Path Identifier 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 | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator ASN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Originator Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: SRPOLICY-CPATH-ID TLV Format
Type: 57 for "SRPOLICY-CPATH-ID" TLV.
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Length: 28.
Protocol Origin: 8-bit value that encodes the protocol origin. The
values of this field are specified in IANA registry "SR Policy
Protocol Origin" under "Segment Routing" registry group, which was
introduced in Section 8.4 of [I-D.ietf-idr-bgp-ls-sr-policy]. Note
that in the PCInitiate message [RFC8281], the 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)" 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 4-byte
number, 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 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 MUST set this to an address
that it owns.
Discriminator: 32-bit 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 Candidate Paths,
coming from the same originator. It is allowed to be any number in
the 32-bit range.
4.2.3. SR Policy Candidate Path 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 symbolic 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.
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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" TLV.
Length: 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.
4.2.4. SR Policy Candidate Path Preference TLV
The SRPOLICY-CPATH-PREFERENCE TLV (Figure 5) is an optional TLV for
the SRPA object. If the TLV is absent, then 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" TLV.
Length: 4.
Preference: Numerical preference of the Candidate Path as defined in
Section 2.7 of [RFC9256].
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5. SR Policy Signaling Extensions
This section introduces mechanisms that are described for SR Policies
in [RFC9256] to PCEP, but which do not make use of the SRPA for
signaling in PCEP. Since SRPA is not used, there needs to be a
separate capability negotiation.
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 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 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 SRPA but the SRPOLICY-CAPABILITY TLV is
not exchanged, then the PCEP speaker MUST send a PCErr message with
Error- Type = 10 ("Reception of an invalid object") and Error-Value =
TBD ("Missing SRPOLICY-CAPABILITY 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 TLV.
Length: 4.
Flags (32 bits):
The following flags are currently defined:
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* P-flag (Computation Priority): If set to '1' by a PCEP speaker,
the P flag indicates that the PCEP speaker supports the handling
of COMPUTATION-PRIORITY TLV for the SR Policy (Section 5.2). 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 (Explicit NULL Label Policy): If set to '1' by a PCEP
speaker, the E flag indicates that the PCEP speaker supports the
handling of Explicit Null Label Policy (ENLP) TLV for the SR
Policy (Section 5.3). 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 (Invalidation): If set to '1' by a PCEP speaker, the I flag
indicates that the PCEP speaker supports the handling of
INVALIDATION TLV for the SR Policy (Section 5.4). 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 (Stateless Operation): If set to '1' by a PCEP speaker, the
L flag indicates that the PCEP speaker supports the stateless
(PCReq/PCRep) operations for the SR Policy (Section 5.5). 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' on transmission and MUST be
ignored on receipt. More flags can be assigned in the future per
(Section 6.7).
5.2. Computation Priority TLV
The COMPUTATION-PRIORITY TLV (Figure 7) is an optional TLV for the
LSP object. 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 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" TLV.
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Length: 4.
Priority: Numerical priority with which this LSP is to be recomputed
by the PCE upon topology change. Lowest value is the highest
priority.
Reserved: This field MUST be set to zero on transmission and MUST be
ignored on receipt.
5.3. Explicit Null Label Policy (ENLP) TLV
To steer an unlabeled IP packet into an SR 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 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" TLV.
Length: 4.
ENLP (Explicit NULL Label Policy): Indicates whether Explicit NULL
labels are to be pushed on unlabeled IP packets that are being
steered into a given SR policy. The values of this field are
specified in IANA registry "SR Policy ENLP Values" under "Segment
Routing" registry group, which was introduced in Section 6.10 of
[I-D.ietf-idr-sr-policy-safi].
Reserved: This field MUST be set to zero on transmission and MUST be
ignored on receipt.
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The ENLP unassigned values may be used for future 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.
5.4. Invalidation TLV
The INVALIDATION TLV (Figure 9) is an optional TLV for the LSP
object. 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 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 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,
if no valid path has been computed.
The INVALIDATION TLV is used in both directions between PCEP peers:
* PCE -> PCC: PCE specifies to the PCC whether to enable or disable
Drop-upon-invalid (Config).
* PCC -> PCE: PCC reports the current setting of the 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" TLV.
Length: 4.
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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 of Drop-upon-invalid feature
* D: dropping - the LSP is actively dropping traffic as a result of
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 of Drop-upon-invalid feature
* D: drop enabled - the Candidate Path has 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.
5.4.1. Drop-upon-invalid applies to SR Policy
The 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 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.
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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 enabled. If so, the SR Policy enters the drop
state and "activates" the highest preference Candidate Path which has
the Drop-upon-invalid enabled. Note that only one Candidate Path
needs to be reported to the PCE with the D (dropping) flag set.
5.5. Update to RFC 8231
Section 5.8.2 of [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" in the SRPOLICY-CAPABILITY TLV (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: SR Policy Association.
IANA is requested to confirm the following allocation 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 |
+-----------+-------------------------------------------+-----------+
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6.2. PCEP TLV Type Indicators
This document defines eight new TLVs for carrying additional
information about SR Policy and SR Candidate Paths. IANA is
requested to confirm the following allocations in the existing "PCEP
TLV Type Indicators" registry as follows:
+-----------+-------------------------------------------+-----------+
| Value | Description | Reference |
+-----------+-------------------------------------------+-----------+
| 56 | SRPOLICY-POL-NAME | This.I-D |
+-----------+-------------------------------------------+-----------+
| 57 | SRPOLICY-CPATH-ID | This.I-D |
+-----------+-------------------------------------------+-----------+
| 58 | SRPOLICY-CPATH-NAME | This.I-D |
+-----------+-------------------------------------------+-----------+
| 59 | SRPOLICY-CPATH-PREFERENCE | This.I-D |
+-----------+-------------------------------------------+-----------+
| 68 | COMPUTATION-PRIORITY | This.I-D |
+-----------+-------------------------------------------+-----------+
| 69 | EXPLICIT-NULL-LABEL-POLICY | This.I-D |
+-----------+-------------------------------------------+-----------+
| 70 | INVALIDATION | This.I-D |
+-----------+-------------------------------------------+-----------+
| 71 | SRPOLICY-CAPABILITY | This.I-D |
+-----------+-------------------------------------------+-----------+
6.3. PCEP Errors
This document defines one new Error-Value within the "Mandatory
Object Missing" Error-Type, two new Error-Values within the
"Association Error" Error-Type and one new Error-Value within the
"Reception of an invalid object".
IANA is requested to confirm the following allocations within the
"PCEP-ERROR Object Error Types and Values" registry of the "Path
Computation Element Protocol (PCEP) Numbers" registry group.
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+------------+------------------+-----------------------+-----------+
| Error-Type | Meaning | Error-value | Reference |
+------------+------------------+-----------------------+-----------+
| 6 | Mandatory Object | | [RFC5440] |
| | Missing | | |
+------------+------------------+-----------------------+-----------+
| | | 21: Missing SR | This.I-D |
| | | Policy Mandatory TLV | |
+------------+------------------+-----------------------+-----------+
| 26 | Association | | [RFC8697] |
| | Error | | |
+------------+------------------+-----------------------+-----------+
| | | 20: SR Policy | This.I-D |
| | | Identifers Mismatch | |
+------------+------------------+-----------------------+-----------+
| | | 21: SR Policy | This.I-D |
| | | Candidate Path | |
| | | Identifier Mismatch | |
+------------+------------------+-----------------------+-----------+
IANA is requested to make new allocations within 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 |
+------------+------------------+-----------------------+-----------+
| 10 | Reception of an | | [RFC5440] |
| | invalid object | | |
+------------+------------------+-----------------------+-----------+
| | | TBA: Missing | This.I-D |
| | | SRPOLICY-CAPABILITY | |
| | | TLV | |
+------------+------------------+-----------------------+-----------+
6.4. TE-PATH-BINDING TLV Flag field
An earlier version of this document added new bit within the "TE-
PATH-BINDING TLV Flag field" registry of the "Path Computation
Element Protocol (PCEP) Numbers" registry group, which was also early
allocated by the IANA.
IANA is requested to cancel the early allocation made which is not
needed anymore. As per the instructions from the chairs, please mark
it as deprecated.
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+------------+------------------------------------------+-----------+
| Bit position | Description | Reference |
+--------------+----------------------------------------+-----------+
| 1 | Deprecated (Specified-BSID-only) | This.I-D |
+--------------+----------------------------------------+-----------+
6.5. SR Policy Invalidation Operational State
This document requests IANA to maintain a new registry under "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" [RFC8126]. Each bit
should be tracked with the following qualities:
* Bit (counting from bit 0 as the most significant bit).
* Description.
* Reference.
+-------+-----------------------------------------------+-----------+
| Bit | Description | Reference |
+-------+-----------------------------------------------+-----------+
| 0 - 6 | Unassigned | This.I-D |
+-------+-----------------------------------------------+-----------+
| 7 | D: dropping - the LSP is currently attracting | This.I-D |
| | traffic and actively dropping it. | |
+-------+-----------------------------------------------+-----------+
6.6. SR Policy Invalidation Configuration State
This document requests IANA to maintain a new registry under "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" [RFC8126]. Each bit
should be tracked with the following qualities:
* Bit (counting from bit 0 as the most significant bit).
* Description.
* Reference.
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+-------+-----------------------------------------------+-----------+
| Bit | Description | Reference |
+-------+-----------------------------------------------+-----------+
| 0 - 6 | Unassigned. | This.I-D |
+-------+-----------------------------------------------+-----------+
| 7 | D: drop enabled - the Drop-upon-invalid is | This.I-D |
| | enabled on the LSP. | |
+-------+-----------------------------------------------+-----------+
6.7. SR Policy Capability TLV Flag field
This document requests IANA to maintain a new registry under "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" [RFC8126]. Each bit should be
tracked with the following qualities:
* Bit (counting from bit 0 as the most significant bit).
* Description.
* Reference.
+--------+-----------------------------------------------+-----------+
| Bit | Description | Reference |
+--------+-----------------------------------------------+-----------+
| 0 - 26 | Unassigned | This.I-D |
+--------+-----------------------------------------------+-----------+
| 27 | Stateless Operation | This.I-D |
+--------+-----------------------------------------------+-----------+
| 28 | Unassigned | This.I-D |
+--------+-----------------------------------------------+-----------+
| 29 | Invalidation | This.I-D |
+--------+-----------------------------------------------+-----------+
| 30 | Explicit NULL Label Policy | This.I-D |
+--------+-----------------------------------------------+-----------+
| 31 | Computation Priority | This.I-D |
+--------+-----------------------------------------------+-----------+
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
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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
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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] 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. 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. 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 SRPA advertised in
ASSOC-Type-List TLV to be enabled and disabled.
9.2. Information and Data Models
[I-D.ietf-pce-pcep-srv6-yang] defines YANG module with common
building blocks for PCEP Extensions described in Section 4.
9.3. 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. Verify Correct Operations
Operation verification requirements already listed in [RFC5440],
[RFC8231], [RFC8664], [RFC9256], and [RFC9603] are applicable to
mechanisms defined in this document.
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An implementation MUST allow the operator to view SR Policy
Identifier and SR Policy Candidate Path Identifier advertised in 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 specific SR Policy Identifier.
9.5. Requirements On Other Protocols
The PCEP extensions defined in this document do not imply any new
requirements on other protocols.
9.6. Impact On Network Operations
The mechanisms defined in [RFC5440], [RFC8231], [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. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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>.
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[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>.
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[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. 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]
Previdi, S., Talaulikar, K., 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>.
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[I-D.ietf-pce-multipath]
Koldychev, M., Sivabalan, S., Saad, T., Beeram, V. P.,
Bidgoli, H., Yadav, B., Peng, S., and G. S. Mishra, "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]
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,
Internet-Draft, draft-ietf-pce-pcep-srv6-yang-06, 19
October 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-pce-pcep-srv6-yang-06>.
[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>.
[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>.
[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. Contributors
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Dhruv Dhody
Huawei
India
Email: dhruv.ietf@gmail.com
Cheng Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing, 10095
China
Email: chengli13@huawei.com
Zafar Ali
Cisco Systems, Inc.
Email: zali@cisco.com
Rajesh Melarcode
Cisco Systems, Inc.
2000 Innovation Dr.
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
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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
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