| Internet-Draft | BGP-SPF SR | October 2024 |
| Zhang & Dong | Expires 24 April 2025 | [Page] |
For network scenarios such as Massively Scaled Data Centers (MSDCs), BGP is extended for Link-State (LS) distribution and the Shortest Path First (SPF) algorithm based calculation. BGP-LS SPF leverages the mechanisms of both BGP protocol and BGP-LS protocol extensions. Segment Routing (SR) provides a source routing mechanism that allows a flow to be restricted to a specific topological path, while maintaining per-flow state only at the ingress node(s) to the SR domain. In some networks, it may be useful to enable SR based source routing mechanism together with BGP-LS SPF. This document proposes to introduce the BGP Link-State (BGP-LS) extensions for segment routing to the BGP-LS SPF SAFI.¶
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 24 April 2025.¶
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.¶
For network scenarios such as Massively Scaled Data Centers (MSDCs), BGP is extended for Link-State (LS) distribution and the Shortest Path First (SPF) algorithm based calculation. BGP-LS-SPF leverages the mechanisms of both BGP protocol [RFC4271] and BGP-LS protocol extensions [RFC9552], with the extensions to BGP-LS attribute and new NLRI selection rules defined in [I-D.ietf-lsvr-bgp-spf].¶
Segment Routing (SR) leverages the source routing paradigm. A node steers a packet through an ordered list of instructions, called "segments". SR provides a mechanism that allows a flow to be restricted to a specific topological path, while maintaining per-flow state only at the ingress node(s) to the SR domain. SR can be applied to the MPLS architecture (SR-MPLS) as defined in [RFC8660], and can also be applied to the IPv6 architecture (SRv6) as defined in [RFC8754] and [RFC8986].¶
In networks where BGP-LS-SPF is used as the underlay routing protocol, it may be useful to enable SR based source routing mechanism for traffic engineering and optimization. This document proposes to introduce the BGP Link-State (BGP-LS) extensions for segment routing to the BGP-LS-SPF SAFI. Both the extensions for SR-MPLS and SRv6 are specified.¶
In general, most of the BGP-LS extensions for SR can be applied to BGP-LS SPF SAFI, only a few extensions are not applicable to BGP-LS SPF. For accuracy and documentation, the following subsections list the BGP-LS SR extensions which are introduced to BGP-LS SPF.¶
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.¶
When SR-MPLS is enabled in BGP-LS SPF, The following TLVs SHOULD be supported.¶
| Type | Description | Reference |
|---|---|---|
| 1161 | SID/Label | RFC 9085 |
| 1034 | SR Capabilities | RFC 9085 |
| 1035 | SR Algorithm | RFC 9085 |
| 1036 | SR Local Block | RFC 9085 |
| 1037 | SRMS Preference | RFC 9085 |
The following Link Attribute TLVs SHOULD be supported:¶
| Type | Description | Reference |
|---|---|---|
| 1099 | Adjacency SID TLV | RFC 9085 |
| 1172 | L2 Bundle Member Attributes TLV | RFC 9085 |
| Type | Description | Reference |
|---|---|---|
| 1158 | Prefix-SID | RFC 9085 |
| 1159 | Range | RFC 9085 |
| 1170 | Prefix Attribute Flags | RFC 9085 |
| 1171 | Source Router Identifier | RFC 9085 |
| 1174 | Source OSPF Router-ID | RFC 9085 |
When SRv6 is enabled with BGP-LS SPF, The following extensions SHOULD be supported.¶
The following Node Attribute TLVs SHOULD be supported for SRv6:¶
| Type | Description | Reference |
|---|---|---|
| 1138 | SRv6 Capabilities TLV | RFC 9514 |
| 266 | Node MSD TLV | RFC 8814 |
The following Link Attribute TLVs SHOULD be supported for SRv6:¶
| Type | Description | Reference |
|---|---|---|
| 1106 | SRv6 End.X SID TLV | RFC 9514 |
The following Prefix Attribute TLVs SHOULD be supported for SRv6:¶
| Type | Description | Reference |
|---|---|---|
| 1162 | SRv6 Locator TLV | RFC 9514 |
When SRv6 SIDs need to be advertised in BGP-SPF, the NLRI type for SRv6 SID SHOULD be supported in BGP-LS SPF SAFI:¶
| Type | NLRI Type | Reference |
|---|---|---|
| 6 | SRv6 SID NLRI | RFC 9514 |
The SRv6 SID Information TLV SHOULD be carried in the SRv6 SID NLRI.¶
| Type | NLRI Type | Reference |
|---|---|---|
| 518 | SRv6 SID Information TLV | RFC 9514 |
The following TLVs MAY be carried in the BGP-LS Attribute associated with the SRv6 SID NLRI:¶
| Type | NLRI Type | Reference |
|---|---|---|
| 1250 | SRv6 Endpoint Behavior TLV | RFC 9514 |
| 1251 | SRv6 PeerNode SID TLV | RFC 9514 |
| 1252 | SRv6 SID Structure TLV | RFC 9514 |
This document introduces no additional security vulnerabilities in addition to the ones as described in [RFC9552].¶
The authors would like to thank XXX for the review and discussion of this document.¶