Path Computation Element Communication Protocol (PCEP) Extensions for Segment Routing (SR) Policy Candidate Paths
draft-ietf-pce-segment-routing-policy-cp-18
Document | Type | Active Internet-Draft (pce WG) | |
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Authors | Mike Koldychev , Siva Sivabalan , Colby Barth , Shuping Peng , Hooman Bidgoli | ||
Last updated | 2024-11-20 (Latest revision 2024-10-14) | ||
Replaces | draft-barth-pce-segment-routing-policy-cp | ||
RFC stream | Internet Engineering Task Force (IETF) | ||
Intended RFC status | Proposed Standard | ||
Formats | |||
Reviews |
GENART Last Call review
by Robert Sparks
Ready w/issues
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Additional resources | Mailing list discussion | ||
Stream | WG state | Submitted to IESG for Publication | |
Associated WG milestone |
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Document shepherd | Dhruv Dhody | ||
Shepherd write-up | Show Last changed 2024-07-05 | ||
IESG | IESG state | Waiting for AD Go-Ahead::Revised I-D Needed | |
Action Holders | |||
Consensus boilerplate | Yes | ||
Telechat date | (None) | ||
Responsible AD | Roman Danyliw | ||
Send notices to | dd@dhruvdhody.com | ||
IANA | IANA review state | IANA OK - Actions Needed |
draft-ietf-pce-segment-routing-policy-cp-18
PCE Working Group M. Koldychev Internet-Draft S. Sivabalan Updates: 8231 (if approved) Ciena Corporation Intended status: Standards Track C. Barth Expires: 17 April 2025 Juniper Networks, Inc. S. Peng Huawei Technologies H. Bidgoli Nokia 14 October 2024 Path Computation Element Communication Protocol (PCEP) Extensions for Segment Routing (SR) Policy Candidate Paths draft-ietf-pce-segment-routing-policy-cp-18 Abstract Segment Routing (SR) allows a node to steer a packet flow along any path. SR Policy is an ordered list of segments (i.e., instructions) 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 the SR Policy. Additionally, this document updates RFC 8231 to allow stateful bring up 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." This Internet-Draft will expire on 17 April 2025. Koldychev, et al. Expires 17 April 2025 [Page 1] Internet-Draft PCEP SR Policy October 2024 Copyright Notice Copyright (c) 2024 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 . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. SR Policy Identifier . . . . . . . . . . . . . . . . . . 4 3.2. SR Policy Candidate Path Identifier . . . . . . . . . . . 5 3.3. SR Policy Candidate Path Attributes . . . . . . . . . . . 5 4. SR Policy Association . . . . . . . . . . . . . . . . . . . . 5 4.1. Association Parameters . . . . . . . . . . . . . . . . . 6 4.2. Association Information . . . . . . . . . . . . . . . . . 8 4.2.1. SR Policy Name TLV . . . . . . . . . . . . . . . . . 8 4.2.2. SR Policy Candidate Path Identifier TLV . . . . . . . 9 4.2.3. SR Policy Candidate Path Name TLV . . . . . . . . . . 10 4.2.4. SR Policy Candidate Path Preference TLV . . . . . . . 11 5. Other Mechanisms . . . . . . . . . . . . . . . . . . . . . . 11 5.1. SR Policy Capability TLV . . . . . . . . . . . . . . . . 11 5.2. Computation Priority TLV . . . . . . . . . . . . . . . . 13 5.3. Explicit Null Label Policy (ENLP) TLV . . . . . . . . . . 13 5.4. Invalidation TLV . . . . . . . . . . . . . . . . . . . . 14 5.4.1. Drop-upon-invalid applies to SR Policy . . . . . . . 16 5.5. Specified-BSID-only . . . . . . . . . . . . . . . . . . . 16 5.6. Stateless Operation . . . . . . . . . . . . . . . . . . . 16 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 6.1. Association Type . . . . . . . . . . . . . . . . . . . . 17 6.2. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 17 6.3. PCEP Errors . . . . . . . . . . . . . . . . . . . . . . . 18 6.4. TE-PATH-BINDING TLV Flag field . . . . . . . . . . . . . 19 6.5. SR Policy Candidate Path Protocol Origin field . . . . . 19 6.6. SR Policy Explicit Null Label Policy field . . . . . . . 20 6.7. SR Policy Invalidation Drop Operational State . . . . . . 21 6.8. SR Policy Invalidation Drop Configuration State . . . . . 22 7. Implementation Status . . . . . . . . . . . . . . . . . . . . 22 Koldychev, et al. Expires 17 April 2025 [Page 2] Internet-Draft PCEP SR Policy October 2024 7.1. Cisco . . . . . . . . . . . . . . . . . . . . . . . . . . 23 7.2. Juniper . . . . . . . . . . . . . . . . . . . . . . . . . 23 8. Security Considerations . . . . . . . . . . . . . . . . . . . 23 9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 23 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 10.1. Normative References . . . . . . . . . . . . . . . . . . 24 10.2. Informative References . . . . . . . . . . . . . . . . . 25 Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 25 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 1. Introduction Segment Routing Policy Architecture [RFC9256] details the concepts of SR Policy and approaches to steering traffic into an SR Policy. PCEP Extensions for Segment Routing [RFC8664] specifies extensions to the Path Computation Element Protocol (PCEP) that allow a stateful PCE to compute and initiate Traffic Engineering (TE) paths, as well as a PCC to request a path subject to certain constraint(s) and optimization criteria in SR networks. Although [RFC8664] was originally used to create SR-TE tunnels, these are not SR Policies and lack many important features and details. PCEP Extensions for Establishing Relationships Between Sets of PCEP LSPs [RFC8697] introduces a generic mechanism to create a grouping of LSPs which is called an Association. This document extends [RFC8664] to support signaling SR Policy Candidate Paths as PCEP LSPs and to signal Candidate Path membership in an SR Policy by means of the Association mechanism. The PCEP Association corresponds to the SR Policy and the PCEP LSP corresponds to the Candidate Path. The unit of signaling in PCEP is the LSP, thus all the information is carried at the Candidate Path level. 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 The following terminologies are used in this document: Endpoint: The IPv4 or IPv6 endpoint address of an SR Policy, as described in [RFC9256] Section 2.1. Koldychev, et al. Expires 17 April 2025 [Page 3] Internet-Draft PCEP SR Policy October 2024 Color: The 32-bit color of an SR Policy, as described in [RFC9256] Section 2.1. Protocol-Origin: The protocol that was used to create the Candidate Path, as described in [RFC9256] Section 2.3. Originator: Device that created the Candidate Path, as described in [RFC9256] Section 2.4. Discriminator: Distinguishes Candidate Paths created by the same device, as described in [RFC9256] Section 2.5. SRPA: SR Policy Association. A new association type 'SR Policy Association' is used to group candidate paths belonging to the 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. Association Parameters: As described in [RFC8697], refers to the key data, that uniquely identifies the Association. Association Information: As described in [RFC8697], refers to the non-key information about the Association. 3. Overview The SR Policy is represented by a new type of PCEP Association, called the SR Policy Association (SRPA). The SR Candidate Paths of an SR Policy are the PCEP LSPs within the same SRPA. The subject of encoding multiple Segment Lists within an SR Policy Candidate Path is described in [I-D.ietf-pce-multipath]. The 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 SRPA: Computation Priority, Explicit Null Label Policy, Drop-upon-invalid behavior, and Specified-BSID-only. 3.1. SR Policy Identifier SR Policy Identifier uniquely identifies the SR Policy [RFC9256] within the network. SR Policy Identifier MUST be the same for all SR Policy Candidate Paths in the same SRPA. SR Policy Identifier MUST NOT change for a given SR Policy Candidate Path during its lifetime. SR Policy Identifier MUST be different for different SRPAs. When these rules are not satisfied, the PCEP speaker MUST send a PCErr Koldychev, et al. Expires 17 April 2025 [Page 4] Internet-Draft PCEP SR Policy October 2024 message with Error-Type = 26 "Association Error", Error Value = 20 "SR Policy Identifier Mismatch". SR Policy Identifier consist of: * Headend router where the SR Policy originates. * Color of SR Policy ([RFC9256] Section 2.1). * Endpoint of SR Policy ([RFC9256] Section 2.1). 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 NOT change for a given LSP during its lifetime. SR Policy Candidate Path Identifier MUST be different for distinct Candidate Paths within the same SRPA. When these rules are not satisfied, the PCEP speaker MUST send a PCErr message with Error- Type = 26 "Association Error", Error Value = 21 "SR Policy Candidate Path Identifier Mismatch". SR Policy Candidate Path Identifier consist 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 the Candidate Path and MAY change during the lifetime of the LSP. SR Policy Candidate Path Attributes consist of: * Candidate Path preference. * Candidate Path name. * SR Policy name. 4. SR Policy Association As per [RFC8697], LSPs are associated with other LSPs with which they interact by adding them to a common association group. As described in [RFC8697], the association group is uniquely identified by the combination of the following fields in the ASSOCIATION object: Association Type, Association ID, Association Source, and (if present) Global Association Source or Extended Association ID, referred to as Association Parameters. Koldychev, et al. Expires 17 April 2025 [Page 5] Internet-Draft PCEP SR Policy October 2024 [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. [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 Types MUST be done before using the SRPA. Thus, the 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 SRPA. 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". 4.1. Association Parameters As per [RFC9256], an SR Policy is identified through the tuple <headend, color, endpoint>. The headend is encoded in the 'Association Source' field in the ASSOCIATION object. The color and endpoint are encoded as part of the Extended Association ID TLV. The Association Parameters (see Section 2) consist of: * Association Type: Part of the base ASSOCIATION object. Set to 6 "SR Policy Association". * Association Source (IPv4/IPv6): Part of the base ASSOCIATION object. Set to the headend value of the SR Policy, as defined in [RFC9256] Section 2.1. * Association ID (16-bit): Part of the base ASSOCIATION object. Always set to the numeric value "1". This 16-bit field does not store meaningful data, because neither the Color nor the Endpoint can fit in it. * Extended Association ID TLV: Mandatory TLV of the ASSOCIATION object. Encodes the Color and Endpoint of the SR Policy. MUST be in the format specified in Figure 1. Koldychev, et al. Expires 17 April 2025 [Page 6] Internet-Draft PCEP SR Policy October 2024 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 IPv4 or IPv6 address is encoded in the Endpoint field. Color: SR Policy color value, non-zero as per [RFC9256] Section 2.1. Endpoint: can be either IPv4 or IPv6. 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. If the 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 purpose of choosing the Association Parameters in this way is 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 [RFC9256] parameters. Thus, there is no chance that different PCEP speakers will come up with different Association Parameters for the same SR Policy. The last hop of the 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 go the rest of the way 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 head-end to steer traffic with that Endpoint IP into the SR Policy. The Destination of the SR Policy Candidate Path is signaled using the END-POINTS object and/or LSP-IDENTIFIERS TLV, as per the usual PCEP Koldychev, et al. Expires 17 April 2025 [Page 7] Internet-Draft PCEP SR Policy October 2024 procedures. When neither the END-POINTS object nor 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 End-Point value set to null, i.e., 0.0.0.0 for IPv4 or :: for IPv6, see [RFC9256] Section 8.8.1. 4.2. Association Information The SRPA object may carry the following TLVs: * SRPOLICY-POL-NAME TLV: (optional) encodes SR Policy Name string. * SRPOLICY-CPATH-ID TLV: (mandatory) encodes SR Policy Candidate Path Identifier. * SRPOLICY-CPATH-NAME TLV: (optional) encodes SR Policy Candidate Path string name. * SRPOLICY-CPATH-PREFERENCE TLV: (optional) encodes SR Policy Candidate Path preference value. Out of these TLVs, the SRPOLICY-CPATH-ID TLV is mandatory, all others are optional. When a mandatory TLV is missing from the 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". This document specifies four new TLVs to be carried in the SRPA object. Only one TLV instance of each type can be carried, and only the first occurrence is processed. Any others MUST be ignored. 4.2.1. SR Policy Name TLV The SRPOLICY-POL-NAME TLV is an optional 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ SR Policy Name ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: The SRPOLICY-POL-NAME TLV format Koldychev, et al. Expires 17 April 2025 [Page 8] Internet-Draft PCEP SR Policy October 2024 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. SR Policy Name: SR Policy name, as defined in [RFC9256]. It SHOULD be a string of printable ASCII characters, without a NULL terminator. 4.2.2. SR Policy Candidate Path Identifier TLV The SRPOLICY-CPATH-ID TLV 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 | MBZ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Originator ASN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Originator Address | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Discriminator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: The SRPOLICY-CPATH-ID TLV format Type: 57 for "SRPOLICY-CPATH-ID" TLV. Length: 28. Protocol Origin: 8-bit value that encodes the protocol origin, as specified in Section 6.5. Note that in the PCInitiate message [RFC8281], the Protocol Origin is always set to 10 (PCEP). MBZ: Must be zero. Koldychev, et al. Expires 17 April 2025 [Page 9] Internet-Draft PCEP SR Policy October 2024 Originator ASN: Represented as a 4-byte number, part of the originator identifier, as specified in [RFC9256] Section 2.4. If 2-byte ASNs are in use, the low-order 16 bits are used, and the high- order bits are set to 0. When sending a PCInitiate message [RFC8281], the PCE is the originator of the Candidate Path. AS number is not a PCE concept and PCE is not required to have one for itself. If the PCE has its AS number, then it MUST set it, otherwise the AS number can be set to 0. Originator Address: Represented as a 128-bit value where IPv4 address is encoded in the lowest 32 bits and high-order bits are set to 0, part of the originator identifier, as specified in [RFC9256] Section 2.4. 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 [RFC9256] Section 2.5. 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 is an optional 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ SR Policy Candidate Path Name ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: The 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. SR Policy Candidate Path Name: SR Policy Candidate Path Name, as defined in [RFC9256]. It SHOULD be a string of printable ASCII characters, without a NULL terminator. Koldychev, et al. Expires 17 April 2025 [Page 10] Internet-Draft PCEP SR Policy October 2024 4.2.4. SR Policy Candidate Path Preference TLV The SRPOLICY-CPATH-PREFERENCE TLV is an optional TLV for the SRPA object. If the TLV is absent, then default Preference value is 100, as 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: The 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]. 5. Other Mechanisms This section describes mechanisms that are standardized for SR Policies in [RFC9256], but 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 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. In addition, the ASSOC-Type-List TLV containing SRPA Type (6) MUST be present in the OPEN object, as specified in Section 4. Koldychev, et al. Expires 17 April 2025 [Page 11] Internet-Draft PCEP SR Policy October 2024 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|S|I|E|P| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: The SRPOLICY-CAPABILITY TLV format Type: 71 for "SRPOLICY-CAPABILITY TLV. Length: 4. P-flag: 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, see Section 5.2. If this flag is not set, then the PCEP speaker MUST NOT send the COMPUTATION-PRIORITY TLV and SHOULD ignore it on receipt. E-Flag: If set to '1' by a PCEP speaker, the E flag indicates that the PCEP speaker supports the handling of ENLP TLV for the SR Policy, see Section 5.3. If this flag is not set, then the PCEP speaker MUST NOT send the ENLP TLV and SHOULD ignore it on receipt. I-Flag: 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, see Section 5.4. If this flag is not set, then the PCEP speaker MUST NOT send the INVALIDATION TLV and SHOULD ignore it on receipt. S-Flag: If set to '1' by a PCEP speaker, the S flag indicates that the PCEP speaker supports the handling of "Specified-BSID-only" behavior for the SR Policy, see Section 5.5. If this flag is not set, then the PCEP speaker MUST NOT set the Specified-BSID-only flag in the TE-PATH-BINDING TLV and SHOULD ignore it on receipt. L-Flag: 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, see Section 5.6. If the PCE did not set this flag then the PCC SHOULD 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. Koldychev, et al. Expires 17 April 2025 [Page 12] Internet-Draft PCEP SR Policy October 2024 5.2. Computation Priority TLV The COMPUTATION-PRIORITY TLV 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 | MBZ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7: The COMPUTATION-PRIORITY TLV format Type: 68 for "COMPUTATION-PRIORITY" TLV. 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. The default value of priority is 128 (if this TLV is absent), see Section 2.12 of [RFC9256]. 5.3. Explicit Null Label Policy (ENLP) TLV To steer an unlabeled IP packet into an SR policy, it is necessary to create a label stack for that packet, and push one or more labels onto that stack. The Explicit NULL Label Policy (ENLP) TLV is an optional TLV 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 (SRPM) 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 PCEP speaker MUST ignore the presence of this TLV for SRv6 Policies. Koldychev, et al. Expires 17 April 2025 [Page 13] Internet-Draft PCEP SR Policy October 2024 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 | MBZ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8: The 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 section Section 6.6. The ENLP reserved values may be used for future extensions and implementations SHOULD ignore the ENLP TLV with these values. The behavior signaled in this TLV MAY be overridden by local configuration. 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 is an optional TLV for the LSP object. It is used to control traffic steering into the 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 and 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 head-end. 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). Koldychev, et al. Expires 17 April 2025 [Page 14] Internet-Draft PCEP SR Policy October 2024 * 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 | MBZ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 9: The INVALIDATION TLV format Type: 70 for "INVALIDATION" TLV. Length: 4. Oper: encodes the current state of the LSP, i.e., whether it is actively dropping traffic right now. This field can be set to non- zero values only by the PCC, it MUST be set to 0 by the PCE and MUST be ignored by the PCC. See Section Section 6.7 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 currently attracting traffic and actively dropping it. * The unassigned bits in the Flag octet MUST be set to zero upon transmission and MUST be ignored upon receipt. Config: encodes the current setting of the Drop-upon-invalid feature. See Section Section 6.8 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. Koldychev, et al. Expires 17 April 2025 [Page 15] Internet-Draft PCEP SR Policy October 2024 * The unassigned bits in the Flag octet MUST be set to zero upon transmission and MUST be ignored upon 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 essentially the whole SR Policy has the feature enabled. As stated in [RFC9256] Section 8.1, the SR Policy is invalid when all its Candidate Paths are invalid, therefore all Candidate Paths MUST be attempted for bring up before the SR Policy is declared invalid. Once all the Candidate Paths of the SR Policy have become invalid, then the SR Policy checks whether any of the Candidate Paths have Drop-upon-invalid enabled. If so, 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. Specified-BSID-only Specified-BSID-only functionality is defined in Section 6.2.3 of [RFC9256]. When specified-BSID-only is enabled for a particular binding SID, it means that the given binding SID is required to be allocated and programmed for the LSP to be operationally up. If the binding SID cannot be allocated or programmed for some reason, then the LSP must stay down. To signal specified-BSID-only, a new bit: S (Specified-BSID-only) is allocated in the "TE-PATH-BINDING TLV Flag field" of the TE-PATH- BINDING TLV [I-D.ietf-pce-binding-label-sid]. When this bit is set for a particular BSID, it means that the BSID follows the Specified- BSID-only behavior. It is possible to have a mix of BSIDs for the same LSP: some with S=1 and some with S=0. 5.6. Stateless Operation [RFC8231] Section 5.8.2, 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 [RFC8231] Section 5.8.2, by making this section 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. Koldychev, et al. Expires 17 April 2025 [Page 16] Internet-Draft PCEP SR Policy October 2024 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 SHOULD 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, [RFC8231] Section 5.8.2 continues to apply. 6. IANA Considerations 6.1. Association Type This document defines a new association type: SR Policy Association. IANA is requested to confirm the following early allocated codepoint assignment in the "ASSOCIATION Type Field" registry [RFC8697] within the "Path Computation Element Protocol (PCEP) Numbers" registry group: +-----------+-------------------------------------------+-----------+ | Type | Name | Reference | +-----------+-------------------------------------------+-----------+ | 6 | SR Policy Association | This.I-D | +-----------+-------------------------------------------+-----------+ 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 early allocated assignment of a new value for the existing "PCEP TLV Type Indicators" registry as follows: Koldychev, et al. Expires 17 April 2025 [Page 17] Internet-Draft PCEP SR Policy October 2024 +-----------+-------------------------------------------+-----------+ | 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 and two new Error-Values within the "Association Error" Error-Type. IANA is requested to confirm the early allocated new error values within the "PCEP-ERROR Object Error Types and Values" registry of the "Path Computation Element Protocol (PCEP) Numbers" registry group, as follows: +------------+------------------+-----------------------+-----------+ | 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 | | +------------+------------------+-----------------------+-----------+ Koldychev, et al. Expires 17 April 2025 [Page 18] Internet-Draft PCEP SR Policy October 2024 6.4. TE-PATH-BINDING TLV Flag field IANA is requested to confirm the early allocated new bit within the "TE-PATH-BINDING TLV Flag field" registry of the "Path Computation Element Protocol (PCEP) Numbers" registry group, as follows: +------------+------------------------------------------+-----------+ | Bit position | Description | Reference | +--------------+----------------------------------------+-----------+ | 1 | S (Specified-BSID-only) | This.I-D | +--------------+----------------------------------------+-----------+ 6.5. SR Policy Candidate Path Protocol Origin field Note to IANA (RFC editor to remove this before publication): The new registry creation request below is also present in the draft-ietf- idr-bgp-ls-sr-policy. IANA is requested to process the registry creation via the first of these two documents to reach the publication stage and the authors of the other document would update the IANA considerations suitably. Note that draft-ietf-idr-bgp-ls- sr-policy allocates different values in BGP. This document requests IANA to maintain a new registry under "Segment Routing Parameters" registry group. The new registry is called "SR Policy Protocol Origin". New values are to be assigned by "Specification Required" [RFC8126] using the guidelines for Designated Experts as specified in [RFC9256]. The registry contains the following codepoints: Koldychev, et al. Expires 17 April 2025 [Page 19] Internet-Draft PCEP SR Policy October 2024 +--------------+----------------------------------------+-----------+ | Value | Description | Reference | +--------------+----------------------------------------+-----------+ | 0 | Reserved (not to be used) | This.I-D | +--------------+----------------------------------------+-----------+ | 1-9 | Unassigned | This.I-D | +--------------+----------------------------------------+-----------+ | 10 | PCEP (in PCEP) | This.I-D | +--------------+----------------------------------------+-----------+ | 11-19 | Unassigned | This.I-D | +--------------+----------------------------------------+-----------+ | 20 | BGP SR Policy (in PCEP) | This.I-D | +--------------+----------------------------------------+-----------+ | 21-29 | Unassigned | This.I-D | +--------------+----------------------------------------+-----------+ | 30 | Configuration (CLI, YANG model via | This.I-D | | | NETCONF, etc.) (in PCEP) | | +--------------+----------------------------------------+-----------+ | 31-250 | Unassigned | This.I-D | +--------------+----------------------------------------+-----------+ | 251 - 255 | Private Use (not to be assigned by | This.I-D | | | |ANA) | | +--------------+----------------------------------------+-----------+ 6.6. SR Policy Explicit Null Label Policy field Note to IANA (RFC editor to remove this before publication): The new registry creation request below is also present in the draft-ietf- idr-sr-policy-safi. IANA is requested to process the registry creation via the first of these two documents to reach the publication stage and the authors of the other document would update the IANA considerations suitably. This document requests IANA to maintain a new registry under "Segment Routing Parameters" registry group. The new registry is called "SR Policy ENLP Values". New values are to be assigned by "Standards Action" [RFC8126]. The registry contains the following codepoints: Koldychev, et al. Expires 17 April 2025 [Page 20] Internet-Draft PCEP SR Policy October 2024 +----------+--------------------------------------------+-----------+ | Value | Description | Reference | +----------+--------------------------------------------+-----------+ | 0 | Reserved (not to be used). | This.I-D | +----------+--------------------------------------------+-----------+ | 1 | Push an IPv4 Explicit NULL label on an | This.I-D | | | unlabeled IPv4 packet, but do not push an | | | | IPv6 Explicit NULL label on an unlabeled | | | | IPv6 packet. | | +----------+--------------------------------------------+-----------+ | 2 | Push an IPv6 Explicit NULL label on an | This.I-D | | | unlabeled IPv6 packet, but do not push an | | | | IPv4 Explicit NULL label on an unlabeled | | | | IPv4 packet. | | +----------+--------------------------------------------+-----------+ | 3 | Push an IPv4 Explicit NULL label on an | This.I-D | | | unlabeled IPv4 packet, and push an IPv6 | | | | Explicit NULL label on an unlabeled IPv6 | | | | packet. | | +----------+--------------------------------------------+-----------+ | 4 | Do not push an Explicit NULL label. | This.I-D | +----------+--------------------------------------------+-----------+ | 5 - 255 | Reserved. | This.I-D | +----------+--------------------------------------------+-----------+ 6.7. SR Policy Invalidation Drop Operational State This document requests IANA to maintain a new registry under "Segment Routing Parameters" registry group. The new registry is called "SR Policy Invalidation Operational Flags". New values are to be assigned by "Standards Action" [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. | | +-------+-----------------------------------------------+-----------+ Koldychev, et al. Expires 17 April 2025 [Page 21] Internet-Draft PCEP SR Policy October 2024 6.8. SR Policy Invalidation Drop Configuration State This document requests IANA to maintain a new registry under "Segment Routing Parameters" registry group. The new registry is called "SR Policy Invalidation Configuration Flags". New values are to be assigned by "Standards Action" [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: drop enabled - the Drop-upon-invalid is | This.I-D | | | enabled on the LSP. | | +-------+-----------------------------------------------+-----------+ 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". Koldychev, et al. Expires 17 April 2025 [Page 22] Internet-Draft PCEP SR Policy October 2024 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] and [RFC9256] are applicable to this specification. 9. Acknowledgement Would like to thank Ketan Talaulikar, Dhruv Dhody, Stephane Litkowski, Boris Khasanov, Abdul Rehman, Alex Tokar, Praveen Kumar and Tom Petch for review and suggestions. 10. References Koldychev, et al. Expires 17 April 2025 [Page 23] Internet-Draft PCEP SR Policy October 2024 10.1. 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>. [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>. [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>. [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>. [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>. [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>. [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>. Koldychev, et al. Expires 17 April 2025 [Page 24] Internet-Draft PCEP SR Policy October 2024 [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>. [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>. [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>. [I-D.ietf-pce-binding-label-sid] Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S., and C. Li, "Carrying Binding Label/Segment Identifier (SID) in PCE-based Networks.", Work in Progress, Internet- Draft, draft-ietf-pce-binding-label-sid-16, 27 March 2023, <https://datatracker.ietf.org/doc/html/draft-ietf-pce- binding-label-sid-16>. 10.2. Informative References [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>. Appendix A. Contributors Koldychev, et al. Expires 17 April 2025 [Page 25] Internet-Draft PCEP SR Policy October 2024 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 Samuel Sidor Cisco Systems, Inc. Eurovea Central 3. Pribinova 10 811 09 Bratislava Slovakia Email: ssidor@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 Koldychev, et al. Expires 17 April 2025 [Page 26] Internet-Draft PCEP SR Policy October 2024 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 Koldychev, et al. Expires 17 April 2025 [Page 27]