Inter-Domain Routing S. PrevidiInternet-Draft Huawei TechnologiesIntended status: Standards Track K. Talaulikar, Ed.Expires: December 29, 2019 C. Filsfils Cisco Systems, Inc. H. Gredler RtBrick Inc. M. Chen Huawei Technologies June 27, 2019BGP Link-State extensions for Segment Routingdraft-ietf-idr-bgp-ls-segment-routing-ext-16Abstract 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 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 inBCP14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.Status of This Memo This Internet-Draft is submitted in full conformance with the provisions ofBCP 78 andBCP 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 athttps://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."Previdi, et al. Expires December 29, 2019 [Page 1]
Internet-Draft BGP LS extensions for Segment Routing June 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 toBCP 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 Contents1. Introduction . . . . . . . . . . . . . . . . . . . . . . . .32. BGP-LS Extensions for Segment Routing . . . . . . . . . . . .52.1. Node Attributes TLVs . . . . . . . . . . . . . . . . . .52.1.1. SID/Label TLV . . . . . . . . . . . . . . . . . . . .52.1.2. SR Capabilities TLV . . . . . . . . . . . . . . . . .62.1.3. SR Algorithm TLV . . . . . . . . . . . . . . . . . .82.1.4. SR Local Block TLV . . . . . . . . . . . . . . . . .82.1.5. SRMS Preference TLV . . . . . . . . . . . . . . . . .102.2. Link Attribute TLVs . . . . . . . . . . . . . . . . . . .112.2.1. Adjacency SID TLV . . . . . . . . . . . . . . . . . .112.2.2. LAN Adjacency SID TLV . . . . . . . . . . . . . . . .122.2.3. L2 Bundle Member Attribute TLV . . . . . . . . . . .142.3. Prefix Attribute TLVs . . . . . . . . . . . . . . . . . .162.3.1. Prefix SID TLV . . . . . . . . . . . . . . . . . . .172.3.2. Prefix Attribute Flags TLV . . . . . . . . . . . . .182.3.3. Source Router Identifier (Source Router-ID) TLV . . .192.3.4. Range TLV . . . . . . . . . . . . . . . . . . . . . .192.4. Equivalent IS-IS Segment Routing TLVs/Sub-TLVs . . . . .21 2.5. Equivalent OSPFv2/OSPFv3 Segment Routing TLVs/Sub-TLVs . 223. IANA Considerations . . . . . . . . . . . . . . . . . . . . .253.1. TLV/Sub-TLV Code Points Summary . . . . . . . . . . . . .254. Manageability Considerations . . . . . . . . . . . . . . . .255. Security Considerations . . . . . . . . . . . . . . . . . . .266. Contributors . . . . . . . . . . . . . . . . . . . . . . . .277. Acknowledgements . . . . . . . . . . . . . . . . . . . . . .288. References . . . . . . . . . . . . . . . . . . . . . . . . .288.1. Normative References . . . . . . . . . . . . . . . . . .288.2. Informative References . . . . . . . . . . . . . . . . .30 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . .30Previdi, et al. Expires December 29, 2019 [Page 2]
Internet-Draft BGP LS extensions for Segment Routing June 20191. 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 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 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. In order to address the need for applications that require topological visibility across IGP areas, or even across Autonomous Systems (AS), the BGP-LS address-family/sub-address-family have been defined to allow BGP to carry Link-State information. The BGP Network Layer Reachability Information (NLRI) encoding format for BGP-LS and a new BGP Path Attribute called the BGP-LS attribute are defined in [RFC7752]. The identifying key of each Link-State object, namely a node, link, or prefix, is encoded in the NLRI and the properties of the object are encoded in the BGP-LS attribute.Previdi, et al. Expires December 29, 2019 [Page 3]
Internet-Draft BGP LS extensions for Segment Routing June 2019 +------------+ | Consumer | +------------+ ^ | v +-------------------+ | BGP Speaker | +-----------+ | (Route-Reflector) | | Consumer | +-------------------+ +-----------+ ^ ^ ^ ^ | | | | +---------------+ | +-------------------+ | | | | | v v v v +-----------+ +-----------+ +-----------+ | BGP | | BGP | | BGP | | Speaker | | Speaker | . . . | Speaker | +-----------+ +-----------+ +-----------+ ^ ^ ^ | | | IGP IGP IGP Figure 1: Link State info collection 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) 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. 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.Previdi, et al. Expires December 29, 2019 [Page 4]
Internet-Draft BGP LS extensions for Segment Routing June 20192. 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 andSection 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 map link-state information to BGP-LS NLRI within the BGP-LS Attribute. This document adds additional BGP-LS Attribute TLVs in order to encode SR information. It does not introduce any changes to the encoding of the BGP-LS NLRIs.2.1. Node Attributes TLVs The following Node Attribute TLVs are defined: +------+-----------------+---------------+ | Type | Description | Section | +------+-----------------+---------------+ | 1161 | SID/Label |Section 2.1.1 | | 1034 | SR Capabilities |Section 2.1.2 | | 1035 | SR Algorithm |Section 2.1.3 | | 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 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 section 2.3 of [I-D.ietf-isis-segment-routing-extensions]. o OSPFv2/OSPFv3, as defined by the SID/Label sub-TLV in section 2.1 of [I-D.ietf-ospf-segment-routing-extensions] andsection 3.1 of [I-D.ietf-ospf-ospfv3-segment-routing-extensions].Previdi, et al. Expires December 29, 2019 [Page 5]
Internet-Draft BGP LS extensions for Segment Routing June 2019 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 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 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 section 3.1 of [I-D.ietf-isis-segment-routing-extensions]. o OSPFv2/OSPFv3, as defined by the SID/Label Range TLV insection3.2 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:Previdi, et al. Expires December 29, 2019 [Page 6]
Internet-Draft BGP LS extensions for Segment Routing June 2019 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 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Range Size N | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 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 MUST be set to 0 and 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 TLV (as defined inSection 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.Previdi, et al. Expires December 29, 2019 [Page 7]
Internet-Draft BGP LS extensions for Segment Routing June 20192.1.3. 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 section 3.2 of [I-D.ietf-isis-segment-routing-extensions]. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: SR Algorithm TLV Format Where: Type: 1035 Length: Variable. Minimum length is 1 and maximum can be 256. 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 advertises its SRLB. This information is derived from the protocol specific advertisements.Previdi, et al. Expires December 29, 2019 [Page 8]
Internet-Draft BGP LS extensions for Segment Routing June 2019 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 insection3.3. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Range Size 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID/Label sub-TLV 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Range Size N | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 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 MUST be set to 0 and ignored on receipt.Previdi, et al. Expires December 29, 2019 [Page 9]
Internet-Draft BGP LS extensions for Segment Routing June 2019 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 TLV (as defined inSection 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 section 3.4 of [I-D.ietf-isis-segment-routing-extensions]. o OSPFv2/OSPFv3, as defined by the SRMS Preference TLV insection3.4 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.Previdi, et al. Expires December 29, 2019 [Page 10]
Internet-Draft BGP LS extensions for Segment Routing June 2019 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 | | 1172 | L2 Bundle Member TLV |Section 2.2.3 | +------+-----------------------+---------------+ 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 (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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID/Label/Index (variable) // +---------------------------------------------------------------+ Figure 7: Adjacency SID TLV Format Where: Type: 1099Previdi, et al. Expires December 29, 2019 [Page 11]
Internet-Draft BGP LS extensions for Segment Routing June 2019 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 section 2.2.1 of [I-D.ietf-isis-segment-routing-extensions]. * 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 section 7.1 of [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. Weight: 1 octet carrying the weight used for load-balancing purposes. The use of weight is described insection 3.4 of [RFC8402]. 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 section 2.2.1 of [I-D.ietf-isis-segment-routing-extensions]. * 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 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.Previdi, et al. Expires December 29, 2019 [Page 12]
Internet-Draft BGP LS extensions for Segment Routing June 2019 This information is derived from LAN-Adj-SID sub-TLV of IS-IS (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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OSPF Neighbor ID / IS-IS System-ID | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 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 section 2.2.2 of [I-D.ietf-isis-segment-routing-extensions]. * 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 section 7.2 of [I-D.ietf-ospf-segment-routing-extensions].Previdi, et al. Expires December 29, 2019 [Page 13]
Internet-Draft BGP LS extensions for Segment Routing June 2019 Weight: 1 octet carrying the weight used for load-balancing purposes. The use of weight is described insection 3.4 of [RFC8402]. 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 section 2.2.2 of [I-D.ietf-isis-segment-routing-extensions]. * 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 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 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 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 (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:Previdi, et al. Expires December 29, 2019 [Page 14]
Internet-Draft BGP LS extensions for Segment Routing June 2019 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) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 9: L2 Bundle Member Attributes TLV Format Where: Type: 1172 Length: Variable. 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.Previdi, et al. Expires December 29, 2019 [Page 15]
Internet-Draft BGP LS extensions for Segment Routing June 2019 +-------------+------------------------------------+----------------+ | TLV Code | Description | Reference | | Point | | Document | +-------------+------------------------------------+----------------+ | 1088 | Administrative group (color) | [RFC7752] | | 1089 | Maximum link bandwidth | [RFC7752] | | 1090 | Max. reservable link bandwidth | [RFC7752] | | 1091 | Unreserved bandwidth | [RFC7752] | | 1092 | TE default metric | [RFC7752] | | 1093 | Link protection type | [RFC7752] | | 1099 | Adjacency Segment Identifier (Adj- |Section 2.2.1 | | | SID) TLV | | | 1100 | LAN Adjacency Segment Identifier |Section 2.2.2 | | | (Adj-SID) TLV | | | 1114 | Unidirectional link delay | [RFC8571] | | 1115 | Min/Max Unidirectional link delay | [RFC8571] | | 1116 | Unidirectional Delay Variation | [RFC8571] | | 1117 | Unidirectional packet loss | [RFC8571] | | 1118 | Unidirectional residual bandwidth | [RFC8571] | | 1119 | Unidirectional available bandwidth | [RFC8571] | | 1120 | Unidirectional bandwidth | [RFC8571] | | | utilization | | +-------------+------------------------------------+----------------+ Table 3: BGP-LS Attribute TLVs also used as sub-TLVs of L2 Bundle Member Attribute TLV2.3. Prefix Attribute TLVs The following Prefix Attribute TLVs are defined: +------+------------------------+---------------+ | Type | Description | Section | +------+------------------------+---------------+ | 1158 | Prefix SID |Section 2.3.1 | | 1159 | Range |Section 2.3.4 | | 1170 | Prefix Attribute Flags |Section 2.3.2 | | 1171 | Source Router-ID |Section 2.3.3 | +------+------------------------+---------------+ 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.Previdi, et al. Expires December 29, 2019 [Page 16]
Internet-Draft BGP LS extensions for Segment Routing June 20192.3.1. 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 (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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 the SID Flags: 1 octet value which should be set as: * 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 section 5 of [I-D.ietf-ospf-segment-routing-extensions]. * OSPFv3 Prefix SID flags are defined in section 6 of [I-D.ietf-ospf-segment-routing-extensions]. Algorithm: 1 octet value identify the algorithm. The semantics of algorithm are described insection 3.1.1 of [RFC8402]. Reserved: 2 octets that MUST be set to 0 and ignored on receipt. SID/Index/Label:Previdi, et al. Expires December 29, 2019 [Page 17]
Internet-Draft BGP LS extensions for Segment Routing June 2019 * 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 section 5 of [I-D.ietf-ospf-segment-routing-extensions]. * 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 insection 2.1 of [RFC7684], for OSPFv3 in section A.4.1.1 of [RFC5340] and for IS- IS insection 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) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 11: Prefix Attribute Flags TLV Format Where: 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 insection 2.1 of [RFC7794]Previdi, et al. Expires December 29, 2019 [Page 18]
Internet-Draft BGP LS extensions for Segment Routing June 2019 * OSPFv2 flags correspond to the Flags field of the OSPFv2 Extended Prefix TLV defined insection 2.1 of [RFC7684] * OSPFv3 flags map to the Prefix Options field defined in section A.4.1.1 of [RFC5340] and extended insection 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 insection 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 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 extensionsPrevidi, et al. Expires December 29, 2019 [Page 19]
Internet-Draft BGP LS extensions for Segment Routing June 2019 [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 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 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 13: Range TLV Format 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 section 2.4.1 of [I-D.ietf-isis-segment-routing-extensions]. * OSPFv2 OSPF Extended Prefix Range TLV flags are defined in section 4 of [I-D.ietf-ospf-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 MUST be set to 0 and ignored on receipt.Previdi, et al. Expires December 29, 2019 [Page 20]
Internet-Draft BGP LS extensions for Segment Routing June 2019 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 Prefix-SID sub-TLV OSPFv2/OSPFv3: OSPFv2/OSPFv3 Extended Prefix Range TLV Prefix SID sub-TLV BGP-LS: Range TLV Prefix-SID TLV (used as a sub-TLV in this context) The prefix-to-SID mapping information for the BGP-LS Prefix-SID TLV (used as sub-TLV in this context) is encoded as described inSection 2.3.1.2.4. Equivalent IS-IS Segment Routing TLVs/Sub-TLVs This section illustrate the IS-IS Segment Routing Extensions TLVs and sub-TLVs mapped to the ones defined in this document. The following table, illustrates for each BGP-LS TLV, its equivalence in IS-IS.Previdi, et al. Expires December 29, 2019 [Page 21]
Internet-Draft BGP LS extensions for Segment Routing June 2019 +------------+---------------+--------------------------------------+ | Descriptio | IS-IS TLV | Reference | | n | /sub-TLV | | +------------+---------------+--------------------------------------+ | SR Capabil | SR- | [I-D.ietf-isis-segment-routing-exten | | ities | Capabilities | sions] | | | sub-TLV (2) | | | SR | SR-Algorithm | [I-D.ietf-isis-segment-routing-exten | | Algorithm | sub-TLV (19) | sions] | | SR Local | SR Local | [I-D.ietf-isis-segment-routing-exten | | Block | Block sub-TLV | sions] | | | (22) | | | SRMS | SRMS | [I-D.ietf-isis-segment-routing-exten | | Preference | Preference | sions] | | | sub-TLV (19) | | | Adjacency | Adj-SID sub- | [I-D.ietf-isis-segment-routing-exten | | SID | TLV (31) | sions] | | LAN | LAN-Adj-SID | [I-D.ietf-isis-segment-routing-exten | | Adjacency | sub-TLV (32) | sions] | | SID | | | | Prefix SID | Prefix-SID | [I-D.ietf-isis-segment-routing-exten | | | sub-TLV (3) | sions] | | Range | SID/Label | [I-D.ietf-isis-segment-routing-exten | | | Binding TLV | sions] | | | (149) | | | SID/Label | SID/Label | [I-D.ietf-isis-segment-routing-exten | | | sub-TLV (1) | sions] | | Prefix | Prefix | [RFC7794] | | Attribute | Attributes | | | Flags | Flags sub-TLV | | | | (4) | | | Source | IPv4/IPv6 | [RFC7794] | | Router-ID | Source Router | | | | ID sub-TLV | | | | (11/12) | | | L2 Bundle | L2 Bundle | [I-D.ietf-isis-l2bundles] | | Member | Member | | | Attributes | Attributes | | | | TLV (25) | | +------------+---------------+--------------------------------------+ Table 5: IS-IS Segment Routing Extensions TLVs/Sub-TLVs2.5. Equivalent OSPFv2/OSPFv3 Segment Routing TLVs/Sub-TLVs This section illustrate the OSPFv2 and OSPFv3 Segment Routing Extensions TLVs and sub-TLVs mapped to the ones defined in this document.Previdi, et al. Expires December 29, 2019 [Page 22]
Internet-Draft BGP LS extensions for Segment Routing June 2019 The following table, illustrates for each BGP-LS TLV, its equivalence in OSPFv2 and OSPFv3. +------------+-------------+----------------------------------------+ | Descriptio | OSPFv2 TLV | Reference | | n | /sub-TLV | | +------------+-------------+----------------------------------------+ | SR Capabil | SID/Label | [I-D.ietf-ospf-segment-routing-extensi | | ities | Range TLV | ons] | | | (9) | | | SR | SR- | [I-D.ietf-ospf-segment-routing-extensi | | Algorithm | Algorithm | ons] | | | TLV (8) | | | SR Local | SR Local | [I-D.ietf-ospf-segment-routing-extensi | | Block | Block TLV | ons] | | | (14) | | | SRMS | SRMS | [I-D.ietf-ospf-segment-routing-extensi | | Preference | Preference | ons] | | | TLV (15) | | | Adjacency | Adj-SID | [I-D.ietf-ospf-segment-routing-extensi | | SID | sub-TLV (2) | ons] | | LAN | LAN Adj-SID | [I-D.ietf-ospf-segment-routing-extensi | | Adjacency | sub-TLV (3) | ons] | | SID | | | | Prefix SID | Prefix SID | [I-D.ietf-ospf-segment-routing-extensi | | | sub-TLV (2) | ons] | | Range | OSPF | [I-D.ietf-ospf-segment-routing-extensi | | | Extended | ons] | | | Prefix | | | | Range TLV | | | | (2) | | | SID/Label | SID/Label | [I-D.ietf-ospf-segment-routing-extensi | | | sub-TLV (1) | ons] | | Prefix | Flags of | [RFC7684] | | Attribute | OSPFv2 | | | Flags | Extended | | | | Prefix TLV | | | | (1) | | | Source | Prefix | [I-D.ietf-lsr-ospf-prefix-originator] | | Router-ID | Source | | | | Router-ID | | | | sub-TLV | | | | (TBD) | | +------------+-------------+----------------------------------------+ Table 6: OSPFv2 Segment Routing Extensions TLVs/Sub-TLVsPrevidi, et al. Expires December 29, 2019 [Page 23]
Internet-Draft BGP LS extensions for Segment Routing June 2019 +-----------+------------+------------------------------------------+ | Descripti | OSPFv3 TLV | Reference | | on | /sub-TLV | | +-----------+------------+------------------------------------------+ | SR Capabi | SID/Label | [I-D.ietf-ospf-segment-routing-extension | | lities | Range TLV | s] | | | (9) | | | SR | SR- | [I-D.ietf-ospf-segment-routing-extension | | Algorithm | Algorithm | s] | | | TLV (8) | | | SR Local | SR Local | [I-D.ietf-ospf-segment-routing-extension | | Block | Block TLV | s] | | | (14) | | | SRMS Pref | SRMS | [I-D.ietf-ospf-segment-routing-extension | | erence | Preference | s] | | | TLV (15) | | | Adjacency | Adj-SID | [I-D.ietf-ospf-ospfv3-segment-routing-ex | | SID | sub-TLV | tensions] | | | (5) | | | LAN | LAN Adj- | [I-D.ietf-ospf-ospfv3-segment-routing-ex | | Adjacency | SID sub- | tensions] | | SID | TLV (6) | | | Prefix | Prefix SID | [I-D.ietf-ospf-ospfv3-segment-routing-ex | | SID | sub-TLV | tensions] | | | (4) | | | Range | OSPFv3 | [I-D.ietf-ospf-ospfv3-segment-routing-ex | | | Extended | tensions] | | | Prefix | | | | Range TLV | | | | (9) | | | SID/Label | SID/Label | [I-D.ietf-ospf-ospfv3-segment-routing-ex | | | sub-TLV | tensions] | | | (7) | | | Prefix | Prefix | [RFC8362] | | Attribute | Option | | | Flags | Fields of | | | | Prefix TLV | | | | types | | | | 3,5,6 | | | Source | Prefix | [I-D.ietf-lsr-ospf-prefix-originator] | | Router-ID | Source | | | | Router-ID | | | | sub-TLV | | | | (TBD) | | +-----------+------------+------------------------------------------+ Table 7: OSPFv3 Segment Routing Extensions TLVs/Sub-TLVsPrevidi, et al. Expires December 29, 2019 [Page 24]
Internet-Draft BGP LS extensions for Segment Routing June 20193. 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" 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 | | 1035 | SR Algorithm |Section 2.1.3 | | 1036 | SR Local Block |Section 2.1.4 | | 1037 | SRMS Preference |Section 2.1.5 | | 1099 | Adjacency SID |Section 2.2.1 | | 1100 | LAN Adjacency SID |Section 2.2.2 | | 1158 | Prefix SID |Section 2.3.1 | | 1159 | Range |Section 2.3.4 | | 1161 | SID/Label |Section 2.1.1 | | 1170 | Prefix Attribute Flags |Section 2.3.2 | | 1171 | Source Router-ID |Section 2.3.3 | | 1172 | L2 Bundle Member Attributes |Section 2.2.3 | +----------------+-----------------------------+---------------+ Table 8: Summary Table of TLV/Sub-TLV Codepoints4. Manageability Considerations This section is structured as recommended in [RFC5706]. The new protocol extensions introduced in this document augment the existing IGP topology information that is distributed via [RFC7752]. Procedures and protocol extensions defined in this document do not affect the BGP protocol operations and management other than as discussed in the Manageability Considerations section of [RFC7752]. Specifically, the malformed attribute tests for syntactic checks in the Fault Management section of [RFC7752] now encompass the new BGP- LS Attribute TLVs defined in this document. The semantic or content checking for the TLVs specified in this document and their association with the BGP-LS NLRI types or their BGP-LS Attribute is left to the consumer of the BGP-LS information (e.g. an application or a controller) and not the BGP protocol.Previdi, et al. Expires December 29, 2019 [Page 25]
Internet-Draft BGP LS extensions for Segment Routing June 2019 A consumer of the BGP-LS information retrieves this information over a BGP-LS session (referSection 1 and 2 of [RFC7752]). The handling of semantic or content errors by the consumer would be dictated by the nature of its application usage and hence is beyond the scope of this document. This document only introduces new Attribute TLVs and any syntactic error in them would result in only that specific attribute being discarded with an error log. The SR information introduced in BGP-LS by this specification, may be used by BGP-LS consumer applications like a SR path computation engine (PCE) to learn the SR capabilities of the nodes in the topology and the mapping of SR segments to those nodes. This can enable the SR PCE to perform path computations based on SR for traffic engineering use-cases and to steer traffic on paths different from the underlying IGP based distributed best path computation. Errors in the encoding or decoding of the SR information may result in the unavailability of such information to the SR PCE or incorrect information being made available to it. This may result in the SR PCE not being able to perform the desired SR based optimization functionality or to perform it in an unexpected or inconsistent manner. The handling of such errors by applications like SR PCE may be implementation specific and out of scope of this document. 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 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 toPrevidi, et al. Expires December 29, 2019 [Page 26]
Internet-Draft BGP LS extensions for Segment Routing June 2019 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. 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 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 Les Ginsberg Cisco Systems Email: ginsberg@cisco.com Acee Lindem Cisco Systems Email: acee@cisco.com Saikat Ray Individual Email: raysaikat@gmail.com Jeff Tantsura Apstra Inc. Email: jefftant.ietf@gmail.comPrevidi, et al. Expires December 29, 2019 [Page 27]
Internet-Draft BGP LS extensions for Segment Routing June 20197. Acknowledgements The authors would like to thank Jeffrey Haas, Aijun Wang, Robert Raszuk and Susan Hares for their review of this document and their comments. The authors would also like to thank Alvaro Retana for his extensive review and comments which helped correct issues and improve the document.8. References8.1. Normative References [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-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-extensions-23 (work in progress), January 2019. [I-D.ietf-ospf-segment-routing-extensions] Psenak, P., Previdi, S., Filsfils, C., Gredler, H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF Extensions for Segment Routing",draft-ietf-ospf-segment-routing-extensions-27 (work in progress), December 2018. [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>.Previdi, et al. Expires December 29, 2019 [Page 28]
Internet-Draft BGP LS extensions for Segment Routing June 2019 [RFC4202] Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)",RFC 4202, DOI 10.17487/RFC4202, October 2005, <https://www.rfc-editor.org/info/rfc4202>. [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6",RFC 5340, DOI 10.17487/RFC5340, July 2008, <https://www.rfc-editor.org/info/rfc5340>. [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement",RFC 7684, DOI 10.17487/RFC7684, November 2015, <https://www.rfc-editor.org/info/rfc7684>. [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and S. Ray, "North-Bound Distribution of Link-State and Traffic Engineering (TE) Information Using BGP",RFC 7752, DOI 10.17487/RFC7752, March 2016, <https://www.rfc-editor.org/info/rfc7752>. [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 and IPv6 Reachability",RFC 7794, DOI 10.17487/RFC7794, March 2016, <https://www.rfc-editor.org/info/rfc7794>. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase inRFC2119 Key Words",BCP 14,RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>. [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and F. Baker, "OSPFv3 Link State Advertisement (LSA) Extensibility",RFC 8362, DOI 10.17487/RFC8362, April 2018, <https://www.rfc-editor.org/info/rfc8362>. [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture",RFC 8402, DOI 10.17487/RFC8402, July 2018, <https://www.rfc-editor.org/info/rfc8402>. [RFC8571] Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of IGP Traffic Engineering Performance Metric Extensions",RFC 8571, DOI 10.17487/RFC8571, March 2019, <https://www.rfc-editor.org/info/rfc8571>.Previdi, et al. Expires December 29, 2019 [Page 29]
Internet-Draft BGP LS extensions for Segment Routing June 20198.2. Informative References [I-D.ietf-isis-sr-yang] Litkowski, S., Qu, Y., Sarkar, P., Chen, I., and J. Tantsura, "YANG Data Model for IS-IS Segment Routing",draft-ietf-isis-sr-yang-05 (work in progress), March 2019. [I-D.ietf-ospf-sr-yang] Yeung, D., Qu, Y., Zhang, Z., Chen, I., and A. Lindem, "YANG Data Model for OSPF SR (Segment Routing) Protocol",draft-ietf-ospf-sr-yang-07 (work in progress), March 2019. [I-D.ietf-spring-segment-routing-ldp-interop] Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., and S. Litkowski, "Segment Routing interworking with LDP",draft-ietf-spring-segment-routing-ldp-interop-15 (work in progress), September 2018. [I-D.ietf-spring-sr-yang] Litkowski, S., Qu, Y., Lindem, A., Sarkar, P., and J. Tantsura, "YANG Data Model for Segment Routing",draft-ietf-spring-sr-yang-12 (work in progress), February 2019. [RFC5706] Harrington, D., "Guidelines for Considering Operations and Management of New Protocols and Protocol Extensions",RFC 5706, DOI 10.17487/RFC5706, November 2009, <https://www.rfc-editor.org/info/rfc5706>.Authors' Addresses Stefano Previdi Huawei Technologies Rome Italy Email: stefano@previdi.net Ketan Talaulikar (editor) Cisco Systems, Inc. India Email: ketant@cisco.comPrevidi, et al. Expires December 29, 2019 [Page 30]
Internet-Draft BGP LS extensions for Segment Routing June 2019 Clarence Filsfils Cisco Systems, Inc. Brussels Belgium Email: cfilsfil@cisco.com Hannes Gredler RtBrick Inc. Email: hannes@rtbrick.com Mach(Guoyi) Chen Huawei Technologies Huawei Building, No. 156 Beiqing Rd. Beijing 100095 China Email: mach.chen@huawei.comPrevidi, et al. Expires December 29, 2019 [Page 31]Datatracker
draft-ietf-idr-bgp-ls-segment-routing-ext-16
This is an older version of an Internet-Draft that was ultimately published asRFC 9085.
| Document | Document type | This is an older version of an Internet-Draft that was ultimately published asRFC 9085. | |
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| Authors | Stefano Previdi,Ketan Talaulikar,Clarence Filsfils,Hannes Gredler,Mach Chen | ||
| Replaces | draft-gredler-idr-bgp-ls-segment-routing-ext | ||
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| Additional resources | Mailing list discussion |