Internet Engineering Task Force L. Ginsberg, Ed. Internet-Draft Cisco Systems Intended status: Standards Track A. Przygienda Expires: April 25, 2018 Juniper Networks S. Aldrin Google J. Zhang Juniper Networks, Inc. October 22, 2017 BIER support via ISIS draft-ietf-bier-isis-extensions-06 Abstract Specification of an ISIS extension to support BIER domains and sub- domains. 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 RFC 2119 [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 April 25, 2018. Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. Ginsberg, et al. Expires April 25, 2018 [Page 1] Internet-Draft draft-ietf-bier-isis-extensions October 2017 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 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 4. Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. BIER Domains and Sub-Domains . . . . . . . . . . . . . . 4 4.2. Advertising BIER Information . . . . . . . . . . . . . . 5 5. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.1. Multi Topology and Sub-Domain . . . . . . . . . . . . . . 5 5.2. Encapsulation . . . . . . . . . . . . . . . . . . . . . . 5 5.3. BIER Algorithm . . . . . . . . . . . . . . . . . . . . . 5 5.4. Label advertisements for MPLS Encapsulation . . . . . . . 6 5.5. BFR-id Advertisements . . . . . . . . . . . . . . . . . . 6 5.6. Reporting Misconfiguration . . . . . . . . . . . . . . . 6 5.7. Flooding Reduction . . . . . . . . . . . . . . . . . . . 6 6. Packet Formats . . . . . . . . . . . . . . . . . . . . . . . 6 6.1. BIER Info sub-TLV . . . . . . . . . . . . . . . . . . . . 6 6.2. BIER MPLS Encapsulation sub-sub-TLV . . . . . . . . . . . 7 6.3. Optional BIER sub-domain BSL conversion sub-sub-TLV . . . 8 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 9.1. Normative References . . . . . . . . . . . . . . . . . . 9 9.2. Informative References . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction Bit Index Explicit Replication (BIER) [I-D.draft-ietf-bier-architecture-08] defines an architecture where all intended multicast receivers are encoded as bitmask in the Multicast packet header within different encapsulations such as [I-D.draft-ietf-bier-mpls-encapsulation-10]. A router that receives such a packet will forward the packet based on the Bit Position in the packet header towards the receiver(s), following a precomputed tree for each of the bits in the packet. Each receiver is represented by a unique bit in the bitmask. Ginsberg, et al. Expires April 25, 2018 [Page 2] Internet-Draft draft-ietf-bier-isis-extensions October 2017 This document presents necessary extensions to the currently deployed ISIS for IP [RFC1195] protocol to support distribution of information necessary for operation of BIER domains and sub-domains. This document defines a new TLV to be advertised by every router participating in BIER signaling. 2. Terminology Some of the terminology specified in [I-D.draft-ietf-bier-architecture-08] is replicated here and extended by necessary definitions: BIER: Bit Index Explicit Replication (The overall architecture of forwarding multicast using a Bit Position). BIER-OL: BIER Overlay Signaling. (The method for the BFIR to learn about BFER's). BFR: Bit Forwarding Router (A router that participates in Bit Index Multipoint Forwarding). A BFR is identified by a unique BFR- prefix in a BIER domain. BFIR: Bit Forwarding Ingress Router (The ingress border router that inserts the BM into the packet). Each BFIR must have a valid BFR- id assigned. BFER: Bit Forwarding Egress Router. A router that participates in Bit Index Forwarding as leaf. Each BFER must be a BFR. Each BFER must have a valid BFR-id assigned. BFT: Bit Forwarding Tree used to reach all BFERs in a domain. BIER sub-domain: A further distinction within a BIER domain identified by its unique sub-domain identifier. A BIER sub-domain can support multiple BitString Lengths. BFR-id: An optional, unique identifier for a BFR within a BIER sub- domain. Invalid BFR-id: Unassigned BFR-id. The special value 0 is reserved for this purpose. BAR BIER Algorithm. Algorithm used to calculate unicast nexthops Ginsberg, et al. Expires April 25, 2018 [Page 3] Internet-Draft draft-ietf-bier-isis-extensions October 2017 3. IANA Considerations This document adds the following new sub-TLV to the registry of sub- TLVs for TLVs 235, 237 [RFC5120] and TLVs 135,236 [RFC5305],[RFC5308]. Value: 32 (suggested - to be assigned by IANA) Name: BIER Info This document also introduces a new registry for sub-sub-TLVs for the BIER Info sub-TLV added above. The registration policy is Expert Review as defined in [RFC8126]. This registry is part of the "IS-IS TLV Codepoints" registry. The name of the registry is "sub-sub-TLVs for BIER Info sub-TLV". The defined values are: Type Name ---- ---- 1 BIER MPLS Encapsulation 3 BIER sub-domain BSL conversion 4. Concepts 4.1. BIER Domains and Sub-Domains An ISIS signalled BIER domain is aligned with the scope of distribution of BFR-prefixes that identify the BFRs within ISIS. ISIS acts in such a case as the supporting BIER underlay. Within such a domain, the extensions defined in this document advertise BIER information for one or more BIER sub-domains. Each sub-domain is uniquely identified by a subdomain-id. Each subdomain is associated with a single ISIS topology [RFC5120], which may be any of the topologies supported by ISIS. Local configuration controls which pairs are supported by a router. The mapping of sub- domains to topologies MUST be consistent within a BIER flooding domain. Each BIER sub-domain has as its unique attributes the encapsulation used and the type of tree it is using to forward BIER frames (currently always SPF). Additionally, per supported bitstring length in the sub-domain, each router will advertise the necessary label ranges to support it. Ginsberg, et al. Expires April 25, 2018 [Page 4] Internet-Draft draft-ietf-bier-isis-extensions October 2017 4.2. Advertising BIER Information BIER information advertisements are associated with a new sub-TLV in the extended reachability TLVs. BIER information is always associated with a host prefix which MUST be a node address for the advertising node. The following restrictions apply: o Prefix length MUST be 32 for an IPv4 prefix or 128 for an IPv6 prefix o When the Prefix Attributes Flags sub-TLV is present N flag MUST be set. [RFC7794] o BIER sub-TLVs MUST be included when a prefix reachability advertisement is leaked between levels. 5. Procedures 5.1. Multi Topology and Sub-Domain A given sub-domain is supported within one and only one topology. All routers in the flooding scope of the BIER sub-TLVs MUST advertise the same sub-domain within the same multi-topology. A router receiving an advertisement which does not match the locally configured pair MUST report a misconfiguration of the received pair. All received BIER advertisements associated with the conflicting pair MUST be ignored. 5.2. Encapsulation All routers in the flooding scope of the BIER TLVs MUST advertise the same encapsulation for a given . A router discovering encapsulation advertised that is different from its own MUST report a misconfiguration of a specific . All received BIER advertisements associated with the conflicting pair MUST be ignored. 5.3. BIER Algorithm All routers in the flooding scope of the BIER TLVs MUST advertise a supported algorithm for a given . The specified algorithm is used when calculating the optimal path. Currently only the default algorithm "SPF" is defined - which has a reserved value of 0. The supported algorithm MUST be consistent for all routers supporting a given . A router receiving an advertisement with a BAR which does not match the locally configured value MUST report a misconfiguration of the received pair. All received BIER Ginsberg, et al. Expires April 25, 2018 [Page 5] Internet-Draft draft-ietf-bier-isis-extensions October 2017 advertisements associated with the conflicting pair MUST be ignored. 5.4. Label advertisements for MPLS Encapsulation A router that desires to participate in MUST advertise for each bitstring length it supports in a label range size that guarantees to cover the maximum BFR-id injected into (which implies a certain maximum set id per bitstring length as described in [I-D.draft-ietf-bier-architecture-08]). Any router that violates this condition MUST be excluded from BIER BFTs for . 5.5. BFR-id Advertisements Each BFER/BFIR MAY advertise with its TLV the BFR-id that it has administratively chosen. A valid BFR-id MUST be unique within the flooding scope of the BIER advertisments. All BFERs/BFIRs MUST detect advertisement of duplicate valid BFR-IDs for a given . When such duplication is detected all of the routers advertising duplicates MUST be treated as if they did not advertise a valid BFR- id. This implies they cannot act as BFER or BFIR in that . 5.6. Reporting Misconfiguration Whenever an advertisement is received which violates any of the constraints defined in this document the receiving router MUST report the misconfiguration. Such reports SHOULD be dampened to avoid excessive logging output. 5.7. Flooding Reduction BIER domain information SHOULD change infrequently. Frequent changes will increase the number of Link State PDU (LSP) updates and negatively impact performance in the network. 6. Packet Formats All ISIS BIER information is carried within the TLVs 235, 237 [RFC5120] or TLVs 135 [RFC5305], or TLV 236 [RFC5308]. 6.1. BIER Info sub-TLV This sub-TLV carries the information for the BIER sub-domains that the router participates in as BFR. This sub-TLV MAY appear multiple times in a given prefix-reachability TLV - once for each sub-domain supported in the associated topology. Ginsberg, et al. Expires April 25, 2018 [Page 6] Internet-Draft draft-ietf-bier-isis-extensions October 2017 The sub-TLV advertises a single combination followed by optional sub-sub-TLVs as described in the following sections. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BAR | subdomain-id | BFR-id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | sub-sub-TLVs (variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: as indicated in IANA section. Length: variable BAR BIER Algorithm. 0 is the only supported value defined in this document. Other values may be defined in the future. 8 bits subdomain-id: Unique value identifying the BIER sub-domain. 1 octet BFR-id: A 2 octet field encoding the BFR-id, as documented in [I-D.draft-ietf-bier-architecture-08]. If no BFR-id has been assigned this field is set to the invalid BFR-id. 6.2. BIER MPLS Encapsulation sub-sub-TLV This sub-sub-TLV carries the information for the BIER MPLS encapsulation including the label range for a specific bitstring length for a certain . It is advertised within the BIER Info sub-TLV (Section 6.1) . This sub-sub-TLV MAY appear multiple times within a single BIER info sub-TLV. On violation of any of the following conditions, the receiving router MUST ignore the encapsulating BIER Info sub-TLV. o Label ranges in multiple sub-sub-TLV MUST NOT overlap. o Bitstring lengths in multiple sub-sub-TLVs MUST NOT be identical. o The sub-sub-TLV MUST include the required bitstring lengths encoded in precisely the same way as in [I-D.draft-ietf-bier-mpls-encapsulation-10]. o The label range size MUST be greater than 0. Ginsberg, et al. Expires April 25, 2018 [Page 7] Internet-Draft draft-ietf-bier-isis-extensions October 2017 o All labels in the range MUST represent valid label values 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Lbl Range Size|BS Len | Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: value of 1 indicating MPLS encapsulation. Length: 4 Local BitString Length (BS Len): Encoded bitstring length as per [I- D.draft-ietf-bier-mpls-encapsulation-10]. 4 bits. Label Range Size: Number of labels in the range used on encapsulation for this BIER sub-domain for this bitstring length, 1 octet. The size of the label range is determined by the number of Set Identifiers (SI) (section 1 of [I-D.ietf-bier- architecture]) that are used in the network. Each SI maps to a single label in the label range. The first label is for SI=0, the second label is for SI=1, etc. Label: First label of the range, 20 bits. The labels are as defined in [I-D.draft-ietf-bier-mpls-encapsulation-10]. 6.3. Optional BIER sub-domain BSL conversion sub-sub-TLV This sub-sub-TLV indicates whether the BFR is capable of imposing a different Bit String Length (BSL) than the one it received in a BIER encapsulated packet. Such a capability may allow future, advanced tree types which ensure simple migration procedures from one BSL to another in a given or prevent stable blackholes in scenarios where not all routers support the same set of BSLs in a given . Conversions are supported only between the set of BSLs advertised as supported by the router. It is carried within the BIER Info sub-TLV (Section 6.1). This sub-sub-TLV is optional and its absence indicates that the router is NOT capable of imposing different BSLs but will always forward the packet with the BSL unchanged. This sub-sub-TLV MAY occur at most once in a given BIER info sub-TLV. If multiple occurences of this sub-sub-TLV are received in a given BIER info sub-TLV the encapsulating sub-TLV MUST be ignored. Ginsberg, et al. Expires April 25, 2018 [Page 8] Internet-Draft draft-ietf-bier-isis-extensions October 2017 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: value of 3 indicating BIER sub-domain BSL Conversion Length: 0 7. Security Considerations Implementations must assure that malformed TLV and Sub-TLV permutations do not result in errors which cause hard protocol failures. 8. Acknowledgements The RFC is aligned with the [I-D.draft-ietf-bier-ospf-bier-extensions-08] draft as far as the protocol mechanisms overlap. Many thanks for comments from (in no particular order) Hannes Gredler, Ijsbrand Wijnands, Peter Psenak and Chris Bowers. 9. References 9.1. Normative References [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and dual environments", RFC 1195, DOI 10.17487/RFC1195, December 1990, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [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, . [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, . Ginsberg, et al. Expires April 25, 2018 [Page 9] Internet-Draft draft-ietf-bier-isis-extensions October 2017 [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, DOI 10.17487/RFC5308, October 2008, . [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, . 9.2. Informative References [I-D.draft-ietf-bier-architecture-08] Wijnands et al., IJ., "Stateless Multicast using Bit Index Explicit Replication Architecture", internet-draft draft- ietf-bier-architecture-08.txt, Sep 2017. [I-D.draft-ietf-bier-mpls-encapsulation-10] Wijnands et al., IJ., "Bit Index Explicit Replication using MPLS encapsulation", internet-draft draft-ietf-bier- mpls-encapsulation-10.txt, Sep 2017. [I-D.draft-ietf-bier-ospf-bier-extensions-08] Psenak et al., P., "OSPF Extension for Bit Index Explicit Replication", internet-draft draft-ietf-bier-ospf-bier- extensions-08.txt, Oct 2017. [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, . Authors' Addresses Les Ginsberg (editor) Cisco Systems 510 McCarthy Blvd. Milpitas, CA 95035 USA Email: ginsberg@cisco.com Tony Przygienda Juniper Networks Email: prz@juniper.net Ginsberg, et al. Expires April 25, 2018 [Page 10] Internet-Draft draft-ietf-bier-isis-extensions October 2017 Sam Aldrin Google 1600 Amphitheatre Parkway Mountain View, CA USA Email: aldrin.ietf@gmail.com Jeffrey (Zhaohui) Zhang Juniper Networks, Inc. 10 Technology Park Drive Westford, MA 01886 USA Email: zzhang@juniper.net Ginsberg, et al. Expires April 25, 2018 [Page 11]