--- 1/draft-ietf-idr-bgp-ls-segment-routing-ext-14.txt 2019-05-30 07:16:51.436907440 -0700 +++ 2/draft-ietf-idr-bgp-ls-segment-routing-ext-15.txt 2019-05-30 07:16:51.540910069 -0700 @@ -1,35 +1,35 @@ Inter-Domain Routing S. Previdi Internet-Draft Huawei Technologies Intended status: Standards Track K. Talaulikar, Ed. -Expires: November 9, 2019 C. Filsfils +Expires: December 1, 2019 C. Filsfils Cisco Systems, Inc. H. Gredler RtBrick Inc. M. Chen Huawei Technologies - May 8, 2019 + May 30, 2019 BGP Link-State extensions for Segment Routing - draft-ietf-idr-bgp-ls-segment-routing-ext-14 + draft-ietf-idr-bgp-ls-segment-routing-ext-15 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 draft defines extensions to the BGP Link-state address-family in - order to carry segment routing information via BGP. + This document defines extensions to the BGP Link-state address-family + in order to carry segment routing information via BGP. 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. Status of This Memo @@ -39,21 +39,21 @@ 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 November 9, 2019. + This Internet-Draft will expire on December 1, 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 @@ -63,24 +63,24 @@ 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 2.1. Node Attributes TLVs . . . . . . . . . . . . . . . . . . 5 2.1.1. SID/Label Sub-TLV . . . . . . . . . . . . . . . . . . 5 2.1.2. SR Capabilities TLV . . . . . . . . . . . . . . . . . 6 - 2.1.3. SR Algorithm TLV . . . . . . . . . . . . . . . . . . 7 + 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 . . . . . . . . . . . . . . . . . . . 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 2.3.2. Prefix Attribute Flags TLV . . . . . . . . . . . . . 18 2.3.3. Source Router Identifier (Source Router-ID) TLV . . . 19 2.3.4. Range TLV . . . . . . . . . . . . . . . . . . . . . . 19 2.4. Equivalent IS-IS Segment Routing TLVs/Sub-TLVs . . . . . 21 2.5. Equivalent OSPFv2/OSPFv3 Segment Routing TLVs/Sub-TLVs . 22 @@ -92,35 +92,35 @@ 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 - can have a local semantic to an SR node or global within a domain. - Within IGP topologies an SR path is encoded as a sequence of - topological sub-paths, called "IGP segments". These segments are + 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. + 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 [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. @@ -159,37 +159,37 @@ +-----------+ +-----------+ +-----------+ | BGP | | BGP | | BGP | | Speaker | | Speaker | . . . | Speaker | +-----------+ +-----------+ +-----------+ ^ ^ ^ | | | IGP IGP IGP Figure 1: Link State info collection - Figure 1 describes a typical deployment scenario. In each IGP area, + Figure 1 denotes a typical deployment scenario. In each IGP area, one or more nodes are configured with BGP-LS. These BGP speakers form an IBGP mesh by connecting to one or more route-reflectors. This way, all BGP speakers (specifically the route-reflectors) obtain Link-State information from all IGP areas (and from other ASes from 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) then 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. + 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. 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 @@ -232,36 +232,36 @@ [I-D.ietf-ospf-segment-routing-extensions] and [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. The TLV and 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) | + | SID/Label (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: SID/Label sub-TLV Format Where: Type: 1161 - Length: Either 3 or 4 depending whether the value is encoded as a - label or an index/SID. + 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). If length is set to - 4, then the value represents a 32 bit SID (the total TLV size is - 8). + represent a label (the total TLV size is 7) and the 4 leftmost + bits are set to 0. If length is set to 4, then the value + 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 @@ -275,23 +275,31 @@ 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 | + | Range Size 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - // SID/Label sub-TLV (variable) // + | SID/Label sub-TLV 1 (variable) // + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + ... + + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Range Size N | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | SID/Label sub-TLV N (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: SR Capabilities TLV Format Where: Type: 1034 Length: Variable. Minimum length is 12. @@ -326,34 +334,33 @@ [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 | | - +- -+ - | | - + + + | Algorithm 1 | Algorithm... | Algorithm N | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: SR Algorithm TLV Format Where: Type: 1035 Length: Variable. Minimum length is 1 and maximum can be 256. - Algorithm: 1 octet identifying the algorithm. + Algorithm: One or more fields of 1 octet each identifying the + algorithm. 2.1.4. SR Local Block TLV The SR Local Block (SRLB) TLV contains the range(s) of labels the node has reserved for local SIDs. Local SIDs are used, e.g., in IGP (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 @@ -373,23 +380,31 @@ 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 | + | Range Size 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - // SID/Label sub-TLV (variable) // + | SID/Label sub-TLV 1 (variable) // + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + ... + + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Range Size N | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | SID/Label sub-TLV N (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: SRLB TLV Format Where: Type: 1036 Length: Variable. Minimum length is 12. @@ -440,21 +455,21 @@ +-+-+-+-+-+-+-+-+ Figure 6: SRMS Preference TLV Format Where: Type: 1037 Length: 1. - Preference: 1 octet. Unsigned 8 bit SRMS preference. + Preference: 1 octet carrying a 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 | @@ -477,64 +492,64 @@ 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | SID/Label/Index (variable) | + | SID/Label/Index (variable) // +---------------------------------------------------------------+ Figure 7: Adjacency SID TLV Format Where: Type: 1099 - Length: Variable, 7 or 8 depending on Label or Index encoding of - the SID - + 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 [I-D.ietf-isis-segment-routing-extensions]. * OSPFv2 Adj-SID flags are defined in [I-D.ietf-ospf-segment-routing-extensions]. * OSPFv3 Adj-SID flags are defined in [I-D.ietf-ospf-segment-routing-extensions]. - Weight: Weight used for load-balancing purposes. + Weight: 1 octet carrying the weight used for load-balancing + purposes. Reserved: 2 octets that SHOULD be set to 0 and MUST be ignored on receipt. SID/Index/Label: * IS-IS: Label or index value as defined in [I-D.ietf-isis-segment-routing-extensions]. * OSPFv2: Label or index value as defined in [I-D.ietf-ospf-segment-routing-extensions]. * OSPFv3: Label or index value as defined in [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. The Flags and, as an extension, the SID/Index/Label fields of this - TLV need to be interpreted accordingly to the respective underlying - IS-IS, OSPFv2 or OSPFv3 protocol. The Protocol-ID of the BGP-LS Link - NLRI should be used to determine the underlying protocol - specification for parsing these fields. + 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 @@ -555,21 +570,21 @@ | Flags | Weight | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OSPF Neighbor ID / IS-IS System-ID | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | SID/Label/Index (variable) | + | SID/Label/Index (variable) // +---------------------------------------------------------------+ Figure 8: LAN Adjacency SID TLV Format 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 @@ -579,44 +594,45 @@ * IS-IS LAN Adj-SID flags are defined in [I-D.ietf-isis-segment-routing-extensions]. * OSPFv2 LAN Adj-SID flags are defined in [I-D.ietf-ospf-segment-routing-extensions]. * OSPFv3 LAN Adj-SID flags are defined in [I-D.ietf-ospf-segment-routing-extensions]. - Weight: Weight used for load-balancing purposes. + Weight: 1 octet carrying the weight used for load-balancing + purposes. Reserved: 2 octets that SHOULD be set to 0 and MUST be 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 [I-D.ietf-isis-segment-routing-extensions]. * OSPFv2: Label or index value as defined in [I-D.ietf-ospf-segment-routing-extensions]. * OSPFv3: Label or index value as defined in [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. The Neighbor ID, Flags and, as an extension, the SID/Index/Label - fields of this TLV need to be interpreted accordingly to the - respective underlying IS-IS, OSPFv2 or OSPFv3 protocol. The - Protocol-ID of the BGP-LS Link NLRI should be used to determine the - underlying protocol specification for parsing these fields. + 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 The L2 Bundle Member Attribute TLV identifies an L2 Bundle Member 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 @@ -627,37 +643,35 @@ IS-IS [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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - // Link attribute sub-TLVs(variable) // + | Link attribute sub-TLVs(variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 9: L2 Bundle Member Attributes TLV Format Where: Type: 1172 Length: Variable. - L2 Bundle Member Descriptor: A Link Local Identifier as defined in - [RFC4202]. + L2 Bundle Member Descriptor: 4 octets field that carries a Link + Local Identifier as defined in [RFC4202]. Link attributes for L2 Bundle Member Links are advertised as sub-TLVs of the L2 Bundle Member Attribute TLV. The sub-TLVs are identical to existing BGP-LS TLVs as identified in the table below. +-------------+------------------------------------+----------------+ | TLV Code | Description | Reference | | Point | | Document | +-------------+------------------------------------+----------------+ | 1088 | Administrative group (color) | [RFC7752] | @@ -712,30 +726,30 @@ 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | SID/Index/Label (variable) | + | SID/Index/Label (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 10: Prefix SID TLV Format Where: Type: 1158 - Length: Variable, 7 or 8 depending on Label or Index encoding of + 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 [I-D.ietf-isis-segment-routing-extensions]. * OSPFv2 Prefix SID flags are defined in [I-D.ietf-ospf-segment-routing-extensions]. @@ -752,157 +766,158 @@ * IS-IS: Label or index value as defined in [I-D.ietf-isis-segment-routing-extensions]. * OSPFv2: Label or index value as defined in [I-D.ietf-ospf-segment-routing-extensions]. * OSPFv3: Label or index value as defined in [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. The Flags and, as an extension, the SID/Index/Label fields of this - TLV need to be interpreted accordingly to the respective underlying - IS-IS, OSPFv2 or OSPFv3 protocol. The Protocol-ID of the BGP-LS - Prefix NLRI should be used to determine the underlying protocol - specification for parsing these fields. + 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]. 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) // + | Flags (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 11: Prefix Attribute Flags TLV Format Where: Type: 1170 - Length: variable. + 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] * OSPFv2 flags correspond to the Flags field of the OSPFv2 Extended Prefix TLV defined in [RFC7684] * OSPFv3 flags map to the Prefix Options field defined in [RFC5340] and extended via [RFC8362] - The Flags field of this TLV need to be interpreted accordingly to the + 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 should be used to determine the - underlying protocol specification for parsing these fields. + 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]. 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 6 octet Router-ID // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 12: Source Router-ID TLV Format Where: Type: 1171 - Length: 4 or 16 in case of IS-IS and 4 in case of OSPF. + 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. - A Prefix NLRI, that been advertised with a Range TLV, is considered - as a normal routing prefix (i.e. prefix reachability) unless there is - also an IGP metric TLV (TLV 1095) attached to it. + 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 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - // sub-TLVs // + | sub-TLVs // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 13: Range TLV Format Where: Type: 1159 - Length: Variable, 11 or 12 depending on Label or Index encoding of + 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]. * OSPFv2 OSPF Extended Prefix Range TLV flags are defined in [I-D.ietf-ospf-segment-routing-extensions]. * OSPFv3 Extended Prefix Range TLV flags are defined in [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. Reserved: 1 octet that SHOULD be set to 0 and MUST be ignored on receipt. Range Size: 2 octets as defined in [I-D.ietf-ospf-segment-routing-extensions]. - The Flags field of this TLV need to be interpreted accordingly to the - respective underlying IS-IS, OSPFv2 or OSPFv3 protocol. The consumer - of the BGP-LS interested in this TLV information MUST check the - Protocol-ID of the BGP-LS Prefix NLRI and refer to the underlying - protocol specification in order to parse this field. + 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 Prefix-SID sub-TLV OSPFv2/OSPFv3: OSPFv2/OSPFv3 Extended Prefix Range TLV Prefix SID sub-TLV @@ -1064,23 +1079,23 @@ | | sub-TLV | | | | (TBD) | | +-----------+------------+------------------------------------------+ Table 7: OSPFv3 Segment Routing Extensions TLVs/Sub-TLVs 3. IANA Considerations Early allocation of codepoints has been done by IANA for this document from the registry "BGP-LS Node Descriptor, Link Descriptor, - Prefix Descriptor, and Attribute TLVs" based on Table 8. The column - "IS-IS TLV/Sub-TLV" defined in the registry does not require any - value and should be left empty. + Prefix Descriptor, and Attribute TLVs" under the "BGP-LS Parameters" + registry based on Table 8. The column "IS-IS TLV/Sub-TLV" defined in + the registry does not require any value and should be left empty. 3.1. TLV/Sub-TLV Code Points Summary This section contains the global table of all TLVs/sub-TLVs defined in this document. +----------------+-----------------------------+---------------+ | TLV Code Point | Description | Reference | +----------------+-----------------------------+---------------+ | 1034 | SR Capabilities | Section 2.1.2 | @@ -1228,21 +1243,21 @@ [I-D.ietf-isis-l2bundles] Ginsberg, L., Bashandy, A., Filsfils, C., Nanduri, M., and E. Aries, "Advertising L2 Bundle Member Link Attributes in IS-IS", draft-ietf-isis-l2bundles-07 (work in progress), May 2017. [I-D.ietf-isis-segment-routing-extensions] Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., Gredler, H., and B. Decraene, "IS-IS Extensions for Segment Routing", draft-ietf-isis-segment-routing- - extensions-24 (work in progress), April 2019. + extensions-25 (work in progress), May 2019. [I-D.ietf-lsr-ospf-prefix-originator] Wang, A., Lindem, A., Dong, J., Talaulikar, K., and P. Psenak, "OSPF Extension for Prefix Originator", draft- ietf-lsr-ospf-prefix-originator-00 (work in progress), February 2019. [I-D.ietf-ospf-ospfv3-segment-routing-extensions] Psenak, P. and S. Previdi, "OSPFv3 Extensions for Segment Routing", draft-ietf-ospf-ospfv3-segment-routing-