--- 1/draft-ietf-idr-bgp-ls-segment-routing-ext-15.txt 2019-06-27 11:13:07.931643267 -0700 +++ 2/draft-ietf-idr-bgp-ls-segment-routing-ext-16.txt 2019-06-27 11:13:07.999644983 -0700 @@ -1,24 +1,24 @@ Inter-Domain Routing S. Previdi Internet-Draft Huawei Technologies Intended status: Standards Track K. Talaulikar, Ed. -Expires: December 1, 2019 C. Filsfils +Expires: December 29, 2019 C. Filsfils Cisco Systems, Inc. H. Gredler RtBrick Inc. M. Chen Huawei Technologies - May 30, 2019 + June 27, 2019 BGP Link-State extensions for Segment Routing - draft-ietf-idr-bgp-ls-segment-routing-ext-15 + draft-ietf-idr-bgp-ls-segment-routing-ext-16 Abstract Segment Routing (SR) allows for a flexible definition of end-to-end paths by encoding paths as sequences of topological sub-paths, called "segments". These segments are advertised by routing protocols e.g. by the link state routing protocols (IS-IS, OSPFv2 and OSPFv3) within IGP topologies. This document defines extensions to the BGP Link-state address-family @@ -39,43 +39,43 @@ 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 December 1, 2019. + This Internet-Draft will expire on December 29, 2019. Copyright Notice Copyright (c) 2019 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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. BGP-LS Extensions for Segment Routing . . . . . . . . . . . . 4 + 2. BGP-LS Extensions for Segment Routing . . . . . . . . . . . . 5 2.1. Node Attributes TLVs . . . . . . . . . . . . . . . . . . 5 - 2.1.1. SID/Label Sub-TLV . . . . . . . . . . . . . . . . . . 5 + 2.1.1. SID/Label TLV . . . . . . . . . . . . . . . . . . . . 5 2.1.2. SR Capabilities TLV . . . . . . . . . . . . . . . . . 6 2.1.3. SR Algorithm TLV . . . . . . . . . . . . . . . . . . 8 2.1.4. SR Local Block TLV . . . . . . . . . . . . . . . . . 8 2.1.5. SRMS Preference TLV . . . . . . . . . . . . . . . . . 10 2.2. Link Attribute TLVs . . . . . . . . . . . . . . . . . . . 11 2.2.1. Adjacency SID TLV . . . . . . . . . . . . . . . . . . 11 2.2.2. LAN Adjacency SID TLV . . . . . . . . . . . . . . . . 12 2.2.3. L2 Bundle Member Attribute TLV . . . . . . . . . . . 14 2.3. Prefix Attribute TLVs . . . . . . . . . . . . . . . . . . 16 2.3.1. Prefix SID TLV . . . . . . . . . . . . . . . . . . . 17 @@ -92,41 +92,41 @@ 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 8.1. Normative References . . . . . . . . . . . . . . . . . . 28 8.2. Informative References . . . . . . . . . . . . . . . . . 30 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30 1. Introduction Segment Routing (SR) allows for a flexible definition of end-to-end paths by combining sub-paths called "segments". A segment can - represent any instruction; topological or service-based. A segment + represent any instruction: topological or service-based. A segment can have a local semantic to an SR node or global semantic within a domain. Within IGP topologies, an SR path is encoded as a sequence of topological sub-paths, called "IGP segments". These segments are advertised by the link-state routing protocols (IS-IS, OSPFv2 and OSPFv3). [RFC8402] defines the Link-State IGP segments - Prefix, Node, Anycast and Adjacency segments. Prefix segments, by default, represent an ECMP-aware shortest-path to a prefix, as per the state of the IGP topology. Adjacency segments represent a hop over a specific adjacency between two nodes in the IGP. A prefix segment is typically a multi-hop path while an adjacency segment, in most of the cases, is a one-hop path. Node and anycast segments are variations of the prefix segment with their specific characteristics. When Segment Routing is enabled in an IGP domain, segments are advertised in the form of Segment Identifiers (SIDs). The IGP link- state routing protocols have been extended to advertise SIDs and - other SR-related information. IGP extensions are described in: IS-IS - [I-D.ietf-isis-segment-routing-extensions], OSPFv2 + other SR-related information. IGP extensions are described for: IS- + IS [I-D.ietf-isis-segment-routing-extensions], OSPFv2 [I-D.ietf-ospf-segment-routing-extensions] and OSPFv3 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. Using these extensions, Segment Routing can be enabled within an IGP domain. Segment Routing (SR) allows advertisement of single or multi-hop paths. The flooding scope for the IGP extensions for Segment routing is IGP area-wide. Consequently, the contents of a Link State Database (LSDB) or a Traffic Engineering Database (TED) has the scope of an IGP area and therefore, by using the IGP alone it is not enough to construct segments across multiple IGP Area or AS boundaries. @@ -174,22 +174,23 @@ EBGP peers). An external component connects to the route-reflector to obtain this information (perhaps moderated by a policy regarding what information is or isn't advertised to the external component) as described in [RFC7752]. This document describes extensions to BGP-LS to advertise the SR information. An external component (e.g., a controller) can collect SR information from across an SR domain (as described in [RFC8402]) and construct the end-to-end path (with its associated SIDs) that need to be applied to an incoming packet to achieve the desired end- - to-end forwarding. The SR domain may be comprised of a single AS or - multiple ASes. + to-end forwarding. SR operates within a trusted domain consisting of + a single or multiple ASes managed by the same administrative entity + e.g. within a single provider network. 2. BGP-LS Extensions for Segment Routing This document defines SR extensions to BGP-LS and specifies the TLVs and sub-TLVs for advertising SR information within the BGP-LS Attribute. Section 2.4 and Section 2.5 lists the equivalent TLVs and sub-TLVs in IS-IS, OSPFv2 and OSPFv3 protocols. BGP-LS [RFC7752] defines the BGP-LS NLRI that can be a Node NLRI, a Link NLRI or a Prefix NLRI. BGP-LS [RFC7752] defines the TLVs that @@ -211,45 +212,45 @@ | 1036 | SR Local Block | Section 2.1.4 | | 1037 | SRMS Preference | Section 2.1.5 | +------+-----------------+---------------+ Table 1: Node Attribute TLVs These TLVs should only be added to the BGP-LS Attribute associated with the Node NLRI describing the IGP node that is originating the corresponding IGP TLV/sub-TLV described below. -2.1.1. SID/Label Sub-TLV +2.1.1. SID/Label TLV The SID/Label TLV is used as a sub-TLV by the SR Capabilities (Section 2.1.2) and Segment Routing Local Block (SRLB) (Section 2.1.4) TLVs. This information is derived from the protocol specific advertisements. - o IS-IS, as defined by the SID/Label sub-TLV in + o IS-IS, as defined by the SID/Label sub-TLV in section 2.3 of [I-D.ietf-isis-segment-routing-extensions]. - o OSPFv2/OSPFv3, as defined by the SID/Label sub-TLV in - [I-D.ietf-ospf-segment-routing-extensions] and + o OSPFv2/OSPFv3, as defined by the SID/Label sub-TLV in section 2.1 + of [I-D.ietf-ospf-segment-routing-extensions] and section 3.1 of [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. - The TLV and has the following format: + The TLV has the following format: 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID/Label (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - Figure 2: SID/Label sub-TLV Format + Figure 2: SID/Label TLV Format Where: Type: 1161 Length: Variable. Either 3 or 4 depending whether the value is encoded as a label or as an index/SID. SID/Label: If length is set to 3, then the 20 rightmost bits represent a label (the total TLV size is 7) and the 4 leftmost @@ -257,89 +258,89 @@ represents a 32 bit SID (the total TLV size is 8). 2.1.2. SR Capabilities TLV The SR Capabilities TLV is used in order to advertise the node's SR Capabilities including its Segment Routing Global Base (SRGB) range(s). In the case of IS-IS, the capabilities also include the IPv4 and IPv6 support for the SR-MPLS forwarding plane. This information is derived from the protocol specific advertisements. - o IS-IS, as defined by the SR Capabilities sub-TLV in + o IS-IS, as defined by the SR Capabilities sub-TLV in section 3.1 of [I-D.ietf-isis-segment-routing-extensions]. - o OSPFv2/OSPFv3, as defined by the SID/Label Range TLV in - [I-D.ietf-ospf-segment-routing-extensions]. OSPFv3 leverages the - same TLV as defined for OSPFv2. + o OSPFv2/OSPFv3, as defined by the SID/Label Range TLV in section + 3.2 of [I-D.ietf-ospf-segment-routing-extensions]. OSPFv3 + leverages the same TLV as defined for OSPFv2. The SR Capabilities TLV has the following format: 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 | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Range Size 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | SID/Label sub-TLV 1 (variable) // + | SID/Label sub-TLV 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Range Size N | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | SID/Label sub-TLV N (variable) // + | SID/Label sub-TLV N // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: SR Capabilities TLV Format Where: Type: 1034 Length: Variable. Minimum length is 12. - Flags: 1 octet of flags as defined in + Flags: 1 octet of flags as defined in section 3.1 of [I-D.ietf-isis-segment-routing-extensions] for IS-IS. The flags - are not currently defined for OSPFv2 and OSPFv3 and SHOULD be set - to 0 and MUST be ignored on receipt. + are not currently defined for OSPFv2 and OSPFv3 and MUST be set to + 0 and ignored on receipt. - Reserved: 1 octet that SHOULD be set to 0 and MUST be ignored on - receipt. + Reserved: 1 octet that MUST be set to 0 and ignored on receipt. One or more entries, each of which have the following format: Range Size: 3 octet with a non-zero value indicating the number of labels in the range. - SID/Label sub-TLV (as defined in Section 2.1.1) which encodes - the first label in the range. Since the SID/Label sub-TLV is - used to indicate the first label of the SRGB range, only label - encoding is valid under the SR Capabilities TLV. + SID/Label TLV (as defined in Section 2.1.1) used as sub-TLV + which encodes the first label in the range. Since the SID/ + Label TLV is used to indicate the first label of the SRGB + range, only label encoding is valid under the SR Capabilities + TLV. 2.1.3. SR Algorithm TLV The SR Algorithm TLV is used in order to advertise the SR Algorithms supported by the node. This information is derived from the protocol specific advertisements. - o IS-IS, as defined by the SR-Algorithm sub-TLV in + o IS-IS, as defined by the SR-Algorithm sub-TLV in section 3.2 of [I-D.ietf-isis-segment-routing-extensions]. - o OSPFv2/OSPFv3, as defined by the SR-Algorithm TLV in - [I-D.ietf-ospf-segment-routing-extensions]. OSPFv3 leverages the - same TLV as defined for OSPFv2. + o OSPFv2/OSPFv3, as defined by the SR-Algorithm TLV in section 3.1 + of [I-D.ietf-ospf-segment-routing-extensions]. OSPFv3 leverages + the same TLV as defined for OSPFv2. The SR Algorithm TLV has the following format: 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Algorithm 1 | Algorithm... | Algorithm N | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -362,114 +363,115 @@ (IS-IS, OSPF) for Adjacency-SIDs, and may also be allocated by components other than IGP protocols. As an example, an application or a controller may instruct a node to allocate a specific local SID. Therefore, in order for such applications or controllers to know the range of local SIDs available, it is required that the node advertises its SRLB. This information is derived from the protocol specific advertisements. - o IS-IS, as defined by the SR Local Block sub-TLV in + o IS-IS, as defined by the SR Local Block sub-TLV in section 3.3 of [I-D.ietf-isis-segment-routing-extensions]. - o OSPFv2/OSPFv3, as defined by the SR Local Block TLV in - [I-D.ietf-ospf-segment-routing-extensions]. OSPFv3 leverages the - same TLV as defined for OSPFv2. + o OSPFv2/OSPFv3, as defined by the SR Local Block TLV in section + 3.3. of [I-D.ietf-ospf-segment-routing-extensions]. OSPFv3 + leverages the same TLV as defined for OSPFv2. The SRLB TLV has the following format: 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 | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Range Size 1 | + | Sub-Range Size 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | SID/Label sub-TLV 1 (variable) // + | SID/Label sub-TLV 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Range Size N | + | Sub-Range Size N | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | SID/Label sub-TLV N (variable) // + | SID/Label sub-TLV N // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: SRLB TLV Format Where: Type: 1036 Length: Variable. Minimum length is 12. - Flags: 1 octet of flags. The flags are as defined in - [I-D.ietf-isis-segment-routing-extensions] for IS-IS. The flags - are not currently defined for OSPFv2 and OSPFv3 and SHOULD be set - to 0 and MUST be ignored on receipt. + Flags: 1 octet of flags. The flags are as defined in section 3.3 + of [I-D.ietf-isis-segment-routing-extensions] for IS-IS. The + flags are not currently defined for OSPFv2 and OSPFv3 and MUST be + set to 0 and ignored on receipt. - Reserved: 1 octet that SHOULD be set to 0 and MUST be ignored on - receipt. + Reserved: 1 octet that MUST be set to 0 and ignored on receipt. - One or more entries, each of which have the following format: + One or more entries corresponding to sub-range(s), each of which + have the following format: Range Size: 3 octet value indicating the number of labels in the range. - SID/Label sub-TLV (as defined in Section 2.1.1) which encodes - the first label in the range. Since the SID/Label sub-TLV is - used to indicate the first label of the SRLB range, only label - encoding is valid under the SR Local Block TLV. + SID/Label TLV (as defined in Section 2.1.1) used as sub-TLV + which encodes the first label in the sub-range. Since the SID/ + Label TLV is used to indicate the first label of the SRLB sub- + range, only label encoding is valid under the SR Local Block + TLV. 2.1.5. SRMS Preference TLV The Segment Routing Mapping Server (SRMS) Preference TLV is used in order to associate a preference with SRMS advertisements from a particular source. [I-D.ietf-spring-segment-routing-ldp-interop] specifies the SRMS functionality along with SRMS preference of the node advertising the SRMS Prefix-to-SID Mapping ranges. This information is derived from the protocol specific advertisements. - o IS-IS, as defined by the SRMS Preference sub-TLV in + o IS-IS, as defined by the SRMS Preference sub-TLV in section 3.4 of [I-D.ietf-isis-segment-routing-extensions]. - o OSPFv2/OSPFv3, as defined by the SRMS Preference TLV in - [I-D.ietf-ospf-segment-routing-extensions]. OSPFv3 leverages the - same TLV as defined for OSPFv2. + o OSPFv2/OSPFv3, as defined by the SRMS Preference TLV in section + 3.4 of [I-D.ietf-ospf-segment-routing-extensions]. OSPFv3 + leverages the same TLV as defined for OSPFv2. The SRMS Preference TLV has the following format: 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 6: SRMS Preference TLV Format Where: Type: 1037 Length: 1. - Preference: 1 octet carrying a unsigned 8 bit SRMS preference. + Preference: 1 octet carrying an unsigned 8 bit SRMS preference. 2.2. Link Attribute TLVs The following Link Attribute TLVs are are defined: +------+-----------------------+---------------+ | Type | Description | Section | +------+-----------------------+---------------+ | 1099 | Adjacency SID TLV | Section 2.2.1 | | 1100 | LAN Adjacency SID TLV | Section 2.2.2 | @@ -479,23 +481,24 @@ Table 2: Link Attribute TLVs These TLVs should only be added to the BGP-LS Attribute associated with the Link NLRI describing the link of the IGP node that is originating the corresponding IGP TLV/sub-TLV described below. 2.2.1. Adjacency SID TLV The Adjacency SID TLV is used in order to advertise information related to an Adjacency SID. This information is derived from Adj- - SID sub-TLV of IS-IS [I-D.ietf-isis-segment-routing-extensions], - OSPFv2 [I-D.ietf-ospf-segment-routing-extensions] and OSPFv3 - [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. + SID sub-TLV of IS-IS (section 2.2.1 of + [I-D.ietf-isis-segment-routing-extensions]), OSPFv2 (section 6.1 of + [I-D.ietf-ospf-segment-routing-extensions]) and OSPFv3 (section 7.1 + of [I-D.ietf-ospf-ospfv3-segment-routing-extensions]). The Adjacency SID TLV has the following format: 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 | Weight | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -500,72 +503,73 @@ | Flags | Weight | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID/Label/Index (variable) // +---------------------------------------------------------------+ Figure 7: Adjacency SID TLV Format Where: Type: 1099 - Length: Variable. Either 7 or 8 depending on Label or Index encoding of the SID + Flags. 1 octet value which should be set as: - * IS-IS Adj-SID flags are defined in + * IS-IS Adj-SID flags are defined in section 2.2.1 of [I-D.ietf-isis-segment-routing-extensions]. - * OSPFv2 Adj-SID flags are defined in + * OSPFv2 Adj-SID flags are defined in section 6.1 of [I-D.ietf-ospf-segment-routing-extensions]. - * OSPFv3 Adj-SID flags are defined in - [I-D.ietf-ospf-segment-routing-extensions]. + * OSPFv3 Adj-SID flags are defined in section 7.1 of + [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. Weight: 1 octet carrying the weight used for load-balancing - purposes. + purposes. The use of weight is described in section 3.4 of + [RFC8402]. - Reserved: 2 octets that SHOULD be set to 0 and MUST be ignored on - receipt. + Reserved: 2 octets that MUST be set to 0 and ignored on receipt. SID/Index/Label: - * IS-IS: Label or index value as defined in + * IS-IS: Label or index value as defined in section 2.2.1 of [I-D.ietf-isis-segment-routing-extensions]. - * OSPFv2: Label or index value as defined in + * OSPFv2: Label or index value as defined in section 6.1 of [I-D.ietf-ospf-segment-routing-extensions]. - * OSPFv3: Label or index value as defined in + * OSPFv3: Label or index value as defined in section 7.1 of [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. The Flags and, as an extension, the SID/Index/Label fields of this TLV are interpreted according to the respective underlying IS-IS, OSPFv2 or OSPFv3 protocol. The Protocol-ID of the BGP-LS Link NLRI is used to determine the underlying protocol specification for parsing these fields. 2.2.2. LAN Adjacency SID TLV For a LAN, normally a node only announces its adjacency to the IS-IS pseudo-node (or the equivalent OSPF Designated and Backup Designated Routers). The LAN Adjacency Segment TLV allows a node to announce adjacencies to all other nodes attached to the LAN in a single instance of the BGP-LS Link NLRI. Without this TLV, the corresponding BGP-LS link NLRI would need to be originated for each additional adjacency in order to advertise the SR TLVs for these neighbor adjacencies. This information is derived from LAN-Adj-SID sub-TLV of IS-IS - [I-D.ietf-isis-segment-routing-extensions] and LAN Adj-SID sub-TLV of - OSPFv2 [I-D.ietf-ospf-segment-routing-extensions] and OSPFv3 - [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. + (section 2.2.2 of [I-D.ietf-isis-segment-routing-extensions]) and LAN + Adj-SID sub-TLV of OSPFv2 (section 6.2 of + [I-D.ietf-ospf-segment-routing-extensions]) and OSPFv3 (section 7.2 + of [I-D.ietf-ospf-ospfv3-segment-routing-extensions]). The LAN Adjacency SID TLV has the following format: 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 | Weight | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -585,47 +589,47 @@ Where: Type: 1100 Length: Variable. For IS-IS it would be 13 or 14 depending on Label or Index encoding of the SID. For OSPF it would be 11 or 12 depending on Label or Index encoding of the SID. Flags. 1 octet value which should be set as: - * IS-IS LAN Adj-SID flags are defined in + * IS-IS LAN Adj-SID flags are defined in section 2.2.2 of [I-D.ietf-isis-segment-routing-extensions]. - * OSPFv2 LAN Adj-SID flags are defined in + * OSPFv2 LAN Adj-SID flags are defined in section 6.2 of [I-D.ietf-ospf-segment-routing-extensions]. - * OSPFv3 LAN Adj-SID flags are defined in + * OSPFv3 LAN Adj-SID flags are defined in section 7.2 of [I-D.ietf-ospf-segment-routing-extensions]. Weight: 1 octet carrying the weight used for load-balancing - purposes. + purposes. The use of weight is described in section 3.4 of + [RFC8402]. - Reserved: 2 octets that SHOULD be set to 0 and MUST be ignored on - receipt. + Reserved: 2 octets that MUST be set to 0 and ignored on receipt. Neighbor ID: 6 octets for IS-IS for the System-ID and 4 octets for OSPF for the OSPF Router-ID of the neighbor. SID/Index/Label: - * IS-IS: Label or index value as defined in + * IS-IS: Label or index value as defined in section 2.2.2 of [I-D.ietf-isis-segment-routing-extensions]. - * OSPFv2: Label or index value as defined in + * OSPFv2: Label or index value as defined in section 6.2 of [I-D.ietf-ospf-segment-routing-extensions]. - * OSPFv3: Label or index value as defined in + * OSPFv3: Label or index value as defined in section 7.2 of [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. The Neighbor ID, Flags and, as an extension, the SID/Index/Label fields of this TLV are interpreted according to the respective underlying IS-IS, OSPFv2 or OSPFv3 protocol. The Protocol-ID of the BGP-LS Link NLRI is used to determine the underlying protocol specification for parsing these fields. 2.2.3. L2 Bundle Member Attribute TLV @@ -633,22 +637,22 @@ link which in turn is associated with a parent L3 link. The L3 link is described by the Link NLRI defined in [RFC7752] and the L2 Bundle Member Attribute TLV is associated with the Link NLRI. The TLV MAY include sub-TLVs which describe attributes associated with the bundle member. The identified bundle member represents a unidirectional path from the originating router to the neighbor specified in the parent L3 Link. Multiple L2 Bundle Member Attribute TLVs MAY be associated with a Link NLRI. This information is derived from L2 Bundle Member Attributes TLV of - IS-IS [I-D.ietf-isis-l2bundles]. The equivalent functionality has - not been specified as yet for OSPF. + IS-IS (section 2 of [I-D.ietf-isis-l2bundles]). The equivalent + functionality has not been specified as yet for OSPF. The L2 Bundle Member Attribute TLV has the following format: 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | L2 Bundle Member Descriptor | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -713,23 +717,24 @@ Table 4: Prefix Attribute TLVs These TLVs should only be added to the BGP-LS Attribute associated with the Prefix NLRI describing the prefix of the IGP node that is originating the corresponding IGP TLV/sub-TLV described below. 2.3.1. Prefix SID TLV The Prefix SID TLV is used in order to advertise information related to a Prefix SID. This information is derived from Prefix-SID sub-TLV - of IS-IS [I-D.ietf-isis-segment-routing-extensions] and the Prefix - SID sub-TLV of OSPFv2 [I-D.ietf-ospf-segment-routing-extensions] and - OSPFv3 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. + of IS-IS (section 2.1 of [I-D.ietf-isis-segment-routing-extensions]) + and the Prefix SID sub-TLV of OSPFv2 (section 5 of + [I-D.ietf-ospf-segment-routing-extensions]) and OSPFv3 (section 6 of + [I-D.ietf-ospf-ospfv3-segment-routing-extensions]). The Prefix SID TLV has the following format: 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 | Algorithm | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -740,56 +745,57 @@ Where: Type: 1158 Length: Variable. 7 or 8 depending on Label or Index encoding of the SID Flags: 1 octet value which should be set as: - * IS-IS Prefix SID flags are defined in + * IS-IS Prefix SID flags are defined in section 2.1.1 of [I-D.ietf-isis-segment-routing-extensions]. - * OSPFv2 Prefix SID flags are defined in + * OSPFv2 Prefix SID flags are defined in section 5 of [I-D.ietf-ospf-segment-routing-extensions]. - * OSPFv3 Prefix SID flags are defined in + * OSPFv3 Prefix SID flags are defined in section 6 of [I-D.ietf-ospf-segment-routing-extensions]. - Algorithm: 1 octet value identify the algorithm. + Algorithm: 1 octet value identify the algorithm. The semantics of + algorithm are described in section 3.1.1 of [RFC8402]. - Reserved: 2 octets that SHOULD be set to 0 and MUST be ignored on - receipt. + Reserved: 2 octets that MUST be set to 0 and ignored on receipt. SID/Index/Label: - * IS-IS: Label or index value as defined in + * IS-IS: Label or index value as defined in section 2.1 of [I-D.ietf-isis-segment-routing-extensions]. - * OSPFv2: Label or index value as defined in + * OSPFv2: Label or index value as defined in section 5 of [I-D.ietf-ospf-segment-routing-extensions]. - * OSPFv3: Label or index value as defined in + * OSPFv3: Label or index value as defined in section 6 of [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. The Flags and, as an extension, the SID/Index/Label fields of this TLV are interpreted according to the respective underlying IS-IS, OSPFv2 or OSPFv3 protocol. The Protocol-ID of the BGP-LS Prefix NLRI is used to determine the underlying protocol specification for parsing these fields. 2.3.2. Prefix Attribute Flags TLV The Prefix Attribute Flags TLV carries IPv4/IPv6 prefix attribute - flags information. These flags are defined for OSPFv2 in [RFC7684], - for OSPFv3 in [RFC5340] and for IS-IS in [RFC7794]. + flags information. These flags are defined for OSPFv2 in section 2.1 + of [RFC7684], for OSPFv3 in section A.4.1.1 of [RFC5340] and for IS- + IS in section 2.1 of [RFC7794]. The Prefix Attribute Flags TLV has the following format: 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 (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -800,75 +806,76 @@ Type: 1170 Length: Variable. Flags: a variable length flag field (according to the length field). Flags are routing protocol specific and are to be set as below: * IS-IS flags correspond to the IPv4/IPv6 Extended Reachability - Attribute Flags defined in [RFC7794] + Attribute Flags defined in section 2.1 of [RFC7794] * OSPFv2 flags correspond to the Flags field of the OSPFv2 - Extended Prefix TLV defined in [RFC7684] + Extended Prefix TLV defined in section 2.1 of [RFC7684] - * OSPFv3 flags map to the Prefix Options field defined in - [RFC5340] and extended via [RFC8362] + * OSPFv3 flags map to the Prefix Options field defined in section + A.4.1.1 of [RFC5340] and extended in section 3.1 of [RFC8362] The Flags field of this TLV is interpreted according to the respective underlying IS-IS, OSPFv2 or OSPFv3 protocol. The Protocol-ID of the BGP-LS Prefix NLRI is used to determine the underlying protocol specification for parsing this field. 2.3.3. Source Router Identifier (Source Router-ID) TLV The Source Router-ID TLV contains the IPv4 or IPv6 Router-ID of the originator of the Prefix. For the IS-IS protocol this is derived - from the IPv4/IPv6 Source Router ID sub-TLV as defined in [RFC7794]. - For the OSPF protocol, this is derived from the Prefix Source Router- - ID sub-TLV as defined in [I-D.ietf-lsr-ospf-prefix-originator]. + from the IPv4/IPv6 Source Router ID sub-TLV as defined in section 2.2 + of [RFC7794]. For the OSPF protocol, this is derived from the Prefix + Source Router-ID sub-TLV as defined in section 4 of + [I-D.ietf-lsr-ospf-prefix-originator]. The Source Router-ID TLV has the following format: 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | 4 or 6 octet Router-ID // + | 4 or 16 octet Router-ID // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 12: Source Router-ID TLV Format Where: Type: 1171 Length: Variable. 4 or 16 in case of IS-IS and 4 in case of OSPF. Router-ID: the IPv4 or IPv6 Router-ID in case of IS-IS and the OSPF Router-ID in the case of OSPF. 2.3.4. Range TLV The Range TLV is used in order to advertise a range of prefix-to-SID mappings as part of the Segment Routing Mapping Server (SRMS) functionality [I-D.ietf-spring-segment-routing-ldp-interop], as defined in the respective underlying IGP SR extensions - [I-D.ietf-ospf-segment-routing-extensions], - [I-D.ietf-ospf-ospfv3-segment-routing-extensions] and - [I-D.ietf-isis-segment-routing-extensions]. The information - advertised in the Range TLV is derived from the SID/Label Binding TLV - in the case of IS-IS and the OSPFv2/OSPFv3 Extended Prefix Range TLV - in the case of OSPFv2/OSPFv3. + [I-D.ietf-ospf-segment-routing-extensions] (section 4), + [I-D.ietf-ospf-ospfv3-segment-routing-extensions] (section 5) and + [I-D.ietf-isis-segment-routing-extensions] (section 2.4). The + information advertised in the Range TLV is derived from the SID/Label + Binding TLV in the case of IS-IS and the OSPFv2/OSPFv3 Extended + Prefix Range TLV in the case of OSPFv2/OSPFv3. A Prefix NLRI, that been advertised with a Range TLV, is considered a normal routing prefix (i.e. prefix reachability) only when there is also an IGP metric TLV (TLV 1095) associated it. Otherwise, it is considered only as the first prefix in the range for prefix-to-SID mapping advertisement. The format of the Range TLV is as follows: 0 1 2 3 @@ -885,34 +892,33 @@ Where: Type: 1159 Length: Variable. 11 or 12 depending on Label or Index encoding of the SID Flags: 1 octet value which should be set as: - * IS-IS SID/Label Binding TLV flags are defined in - [I-D.ietf-isis-segment-routing-extensions]. + * IS-IS SID/Label Binding TLV flags are defined in section 2.4.1 + of [I-D.ietf-isis-segment-routing-extensions]. * OSPFv2 OSPF Extended Prefix Range TLV flags are defined in - [I-D.ietf-ospf-segment-routing-extensions]. + section 4 of [I-D.ietf-ospf-segment-routing-extensions]. - * OSPFv3 Extended Prefix Range TLV flags are defined in - [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. + * OSPFv3 Extended Prefix Range TLV flags are defined in section 5 + of [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. - Reserved: 1 octet that SHOULD be set to 0 and MUST be ignored on - receipt. + Reserved: 1 octet that MUST be set to 0 and ignored on receipt. - Range Size: 2 octets as defined in - [I-D.ietf-ospf-segment-routing-extensions]. + Range Size: 2 octets that carry the number of prefixes that are + covered by the advertisement.. The Flags field of this TLV is interpreted according to the respective underlying IS-IS, OSPFv2 or OSPFv3 protocol. The Protocol-ID of the BGP-LS Prefix NLRI is used to determine the underlying protocol specification for parsing this field. The prefix-to-SID mappings are advertised using sub-TLVs as below: IS-IS: SID/Label Range TLV @@ -1158,24 +1164,27 @@ The extensions, specified in this document, do not introduce any new configuration or monitoring aspects in BGP or BGP-LS other than as discussed in [RFC7752]. The manageability aspects of the underlying SR features are covered by [I-D.ietf-spring-sr-yang], [I-D.ietf-isis-sr-yang] and [I-D.ietf-ospf-sr-yang]. 5. Security Considerations The new protocol extensions introduced in this document augment the existing IGP topology information that is distributed via [RFC7752]. - The Security Considerations section of [RFC7752] also applies to - these extensions. The procedures and new TLVs defined in this - document, by themselves, do not affect the BGP-LS security model - discussed in [RFC7752]. + The advertisement of the SR link attribute information defined in + this document presents similar risk as associated with the existing + set of link attribute information as described in [RFC7752]. The + Security Considerations section of [RFC7752] also applies to these + extensions. The procedures and new TLVs defined in this document, by + themselves, do not affect the BGP-LS security model discussed in + [RFC7752]. The TLVs introduced in this document are used to propagate IGP defined information ([I-D.ietf-isis-segment-routing-extensions], [I-D.ietf-ospf-segment-routing-extensions] and [I-D.ietf-ospf-ospfv3-segment-routing-extensions]). These TLVs represent the SR information associated with the IGP node, link and prefix. The IGP instances originating these TLVs are assumed to support all the required security and authentication mechanisms (as described in [I-D.ietf-isis-segment-routing-extensions], [I-D.ietf-ospf-segment-routing-extensions] and @@ -1172,43 +1181,38 @@ The TLVs introduced in this document are used to propagate IGP defined information ([I-D.ietf-isis-segment-routing-extensions], [I-D.ietf-ospf-segment-routing-extensions] and [I-D.ietf-ospf-ospfv3-segment-routing-extensions]). These TLVs represent the SR information associated with the IGP node, link and prefix. The IGP instances originating these TLVs are assumed to support all the required security and authentication mechanisms (as described in [I-D.ietf-isis-segment-routing-extensions], [I-D.ietf-ospf-segment-routing-extensions] and - [I-D.ietf-ospf-ospfv3-segment-routing-extensions]) in order to prevent any security issue when propagating the TLVs into BGP-LS. - The advertisement of the link attribute information defined in this - document presents no additional risk beyond that associated with the - existing set of link attribute information already supported in - [RFC7752]. BGP-LS SR extensions enable traffic engineering use-cases within the Segment Routing domain. SR operates within a trusted domain [RFC8402] and its security considerations also apply to BGP-LS sessions when carrying SR information. The SR traffic engineering policies using the SIDs advertised via BGP-LS are expected to be used entirely within this trusted SR domain (e.g. between multiple AS/ domains within a single provider network). Therefore, precaution is - necessary to ensure that the SR information advertised via BGP-LS - sessions is limited to consumers in a secure manner within this - trusted SR domain. BGP peering sessions for address-families other - than Link-State may be setup to routers outside the SR domain. The - isolation of BGP-LS peering sessions is recommended to ensure that - BGP-LS topology information (including the newly added SR - information) is not advertised to an external BGP peering session - outside the SR domain. + necessary to ensure that the link-state information (including SR + information) advertised via BGP-LS sessions is limited to consumers + in a secure manner within this trusted SR domain. BGP peering + sessions for address-families other than Link-State may be setup to + routers outside the SR domain. The isolation of BGP-LS peering + sessions is recommended to ensure that BGP-LS topology information + (including the newly added SR information) is not advertised to an + external BGP peering session outside the SR domain. 6. Contributors The following people have substantially contributed to the editing of this document: Peter Psenak Cisco Systems Email: ppsenak@cisco.com