IDR Working Group U. Chunduri Internet-Draft Huawei USA Intended status: Standards Track April 2, 2018 Expires: October 4, 2018 BGP Link-State extensions for NSPF ID draft-chunduri-idr-bgp-ls-nspfid-00 Abstract Non Shortest Paths (NSPs) used in routing protocols e.g. by the link state routing protocols (IS-IS, OSPFv2 and OSPFv3) within IGP topologies. NSPs help to reduce the data plane path overhead, mitigate from MTU issues as well as performance related issues in certain data planes and allows granular traffic accounting in the network. NSPs are created locally by operator or can be provisioned through PCE or Yang from outside. This document describes a mechanism by which NSP information currently active in the network using the BGP routing protocol by defining extensions to BGP Link- state address-family. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC2119 [RFC2119]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on October 4, 2018. Chunduri Expires October 4, 2018 [Page 1] Internet-Draft BGP Link-State extensions for NSPF ID April 2018 Copyright Notice Copyright (c) 2018 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3 2. NSPF ID TLVs Supported by a Node . . . . . . . . . . . . . . 3 3. Elements of Procedure and Encoding . . . . . . . . . . . . . 4 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 7.2. Informative References . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction In a network implementing source routing, packets may be transported through the use of segment identifiers (SIDs), where a SID uniquely identifies a segment as defined in [I-D.ietf-spring-segment-routing]. Usage of Non Shortest Paths (NSPs) with SR SIDs by the link state routing protocols ( IS-IS, OSPFv2 and OSPFv3) within IGP topologies can reduce the data plane path overhead, mitigate from MTU and performance related issues and allow granular traffic accounting in the network. IGP NSP extensions are detailed in [I-D.ct-isis-nspfid-for-sr-paths] and [I-D.ct-ospf-nspfid-for-sr-paths] darfts. NSP Forwarding Identifier (NSPF ID) TLV can be associated with allows advertisement of multi-hop Traffic Engineered (TE) paths, Fast Re- Route (FRR) or certain chained paths. The flooding scope for the IGP extensions for NSPs is IGP area/domain. Consequently, the contents of a Link State Database (LSDB) or a Traffic Engineering Database (TED) has the scope of an IGP area/domain and therefore by using the Chunduri Expires October 4, 2018 [Page 2] Internet-Draft BGP Link-State extensions for NSPF ID April 2018 IGP alone it is not enough to construct NSPs across multiple IGP Area or AS boundaries. Even though an entity like PCE provisions the NSPs at the ingress node, not all NSPs are active and advertised in IGPs as these could be subjected to the local policies of ingress node. Also NSPs can be potentially created locally by operators too; it is critical to have a complete view of currently active NSPs in the network for creating end-to-end paths crossing multiple IGP areas and AS boundaries. This document describes extensions to BGP-LS to advertise NSP information. An external component, which is a BGP-LS [RFC7752] speaker (e.g., a controller) then can collect NSP information in the "north bound" direction across IGP areas or ASes and construct the end-to-end path that need to be applied to an incoming packet to achieve the desired end-to-end forwarding. 1.1. Acronyms IGP - Interior Gateway Protocols MTU - Maximum Transferrable Unit NSP - Non Shortest Path SID - Segment Identifier SR - Segment Routing TE - Traffic Engineering 2. NSPF ID TLVs Supported by a Node This section defines a new TLV, NSPF ID TLV in BGP-LS Node Attributes of Node NLRI and describes the encoding of the same. The BGP-LS Node attribute, NSPF-ID TLV has the following format: Chunduri Expires October 4, 2018 [Page 3] Internet-Draft BGP Link-State extensions for NSPF ID April 2018 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MT-ID | AF | Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix Len | FEC Prefix | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // FEC Prefix (continued, variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // NSPF-ID Encoding // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Node attribute - NSPF ID TLV Format Type - TBD (IANA) from BGP-LS Node attributes registry. Length - Total length of the value field in bytes (variable). AF - See Section 3. MT-ID - is the multi-topology identifier defined in [RFC5120] with 4 most significant bits reset on transmission and ignored on receive. The remaining 12-bit field contains the MT-ID. For OSPFv2 this is as defined in [RFC4915]. For OSPFv3 it MUST be set to zero. Prefix Len - contains the length of the prefix in bits. FEC Prefix - represents the Forwarding Equivalence Class at the tail-end of the advertised NSP. Value of this field MUST be encoded as a 32-bit value for IPv4 "FEC Prefix". Value of this field MUST be 16 octets for IPv6 "FEC Prefix", encoded as an even multiple of 32-bit words, padded with zeroed bits as necessary. This encoding consumes ((PrefixLength + 31) / 32) 32-bit words. Flags: 1 octet field of NSPD ID TLV has flags as defined in respective IGP and encoded based on the Protocol-ID field in BGP- LS node NLRI. 3. Elements of Procedure and Encoding This TLV can be seen as having 3 logical section viz., encoding of FEC Prefix, encoding of NSPF-ID with description of ordered path with sub-TLVs and a set of optional non-NSP sub-TLVs which can be used to describe one or more parameters of the NSP. Out of the above only the first logical section i.e., encoding FEC Prefix is described here Chunduri Expires October 4, 2018 [Page 4] Internet-Draft BGP Link-State extensions for NSPF ID April 2018 in IGP agnostic way. The remaining 2 sections MUST be encoded as defined in [I-D.ct-isis-nspfid-for-sr-paths] and [I-D.ct-ospf-nspfid-for-sr-paths] darfts. This MUST be based on the Protocol-ID field as defined in section 3.2 of [RFC7752] 'The Node NLRI Format'. The advertisement of NSPF ID TLV in OSPF has following semantics: The OSPFv2/OSPFv3 "NSPF-ID Encoding" as defined in Section 2 is encoded in the BGP-LS Node Attribute and the format is as defined in [I-D.ct-ospf-nspfid-for-sr-paths] including all possible Non-NSP sub- TLVs. The flags and AF of the NSPF ID TLV are semantically mapped to the definition in [I-D.ct-ospf-nspfid-for-sr-paths] section 2 for OSPFv2 or section 3 for OSPFv3. The advertisement of NSPF ID TLV in IS-IS has following semantics: The IS-IS 'NSPF-ID Encoding' as defined in Section 2 is encoded in the BGP-LS Node Attribute and the format is as defined in [I-D.ct-isis-nspfid-for-sr-paths] including all possible Non-NSP sub- TLVs. The AF field for IS-IS MUST be set to zero. The flags of the NSPF ID TLV are semantically mapped to the definition in [I-D.ct-isis-nspfid-for-sr-paths] section 2. 4. Acknowledgements TBD. 5. IANA Considerations This document requests IANA to assign a code point from the "BGP-LS Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs" registry as follows: BGP-LS Node Attribute - NSPF ID TLV as described in Section 2. TLV # Name ----- ------------------------------ TBD NSPF ID TLV in Node attribute 6. Security Considerations This document does not introduce security issues beyond those discussed in [RFC7752] Chunduri Expires October 4, 2018 [Page 5] Internet-Draft BGP Link-State extensions for NSPF ID April 2018 7. References 7.1. Normative References [I-D.ct-isis-nspfid-for-sr-paths] Chunduri, U., Tantsura, J., and Y. Qu, "Usage of Non Shortest Path Forwarding (NSPF) IDs in IS-IS", draft-ct- isis-nspfid-for-sr-paths-01 (work in progress), March 2018. [I-D.ct-ospf-nspfid-for-sr-paths] Chunduri, U., Qu, Y., and J. Tantsura, "Usage of Non Shortest Path Forwarding (NSPF) IDs in OSPF", draft-ct- ospf-nspfid-for-sr-paths-00 (work in progress), March 2018. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [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, . 7.2. Informative References [I-D.ietf-spring-segment-routing] Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture", draft-ietf-spring-segment-routing-15 (work in progress), January 2018. [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", RFC 4915, DOI 10.17487/RFC4915, June 2007, . [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, DOI 10.17487/RFC5120, February 2008, . Chunduri Expires October 4, 2018 [Page 6] Internet-Draft BGP Link-State extensions for NSPF ID April 2018 Author's Address Uma Chunduri Huawei USA 2330 Central Expressway Santa Clara, CA 95050 USA Email: uma.chunduri@huawei.com Chunduri Expires October 4, 2018 [Page 7]