BIER Working Group IJ. Wijnands Internet-Draft Cisco Systems Intended status: Informational X. Xu Expires: October 15, 2018 Alibaba Group H. Bidgoli Nokia April 13, 2018 An Optional Encoding of the BIFT-id Field in the non-MPLS BIER Encapsulation draft-ietf-bier-non-mpls-bift-encoding-00 Abstract Bit Index Explicit Replication (BIER) is an architecture that provides optimal multicast forwarding through a "multicast domain", without requiring intermediate routers to maintain any per-flow state or to engage in an explicit tree-building protocol. The Multicast packet is encapsulated using a BIER Header and transported through an MPLS or non-MPLS network. When MPLS is used as the transport, the Bit Indexed Forwarding Table (BIFT) is identified by a MPLS Label. When non-MPLS transport is used, the BIFT is identified by a 20bit value. This document describes one way of encoding the 20bit value. 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 15, 2018. Copyright Notice Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. Wijnands, et al. Expires October 15, 2018 [Page 1]
Internet-Draft Non-MPLS BIER BIFT-id Encapsulation April 2018 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 and Definitions . . . . . . . . . . . . . . . . . 3 3. Specification of Requirements . . . . . . . . . . . . . . . . 3 4. The Bit Index Forwarding Table . . . . . . . . . . . . . . . 3 5. The Non-MPLS Static BIFT Encoding . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 4 9. Normative References . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction Bit Index Explicit Replication (BIER) [RFC8279] is an architecture that provides optimal multicast forwarding through a "multicast domain", without requiring intermediate routers to maintain any per- flow state or to engage in an explicit tree-building protocol. The Multicast packet is encapsulated [RFC8296] using a BIER Header and transported through an MPLS or non-MPLS network. When MPLS is used as the transport, the Bit Indexed Forwarding Table (BIFT) is identified by a MPLS Label. When non-MPLS transport is used, the BIFT is identified by a 20bit value. This document describes one way of encoding the 20bit value, based on the Sub-Domain (SD), Set Identifier (SI) and BitStringLength (BSL) values. The BIER architecture requires that a BFR has a BIFT for every combination of <SD, SI, BSL> that is being used. When processing a BIER packet, the correct BIFT is inferred from the BIFT-id field of the encapsulation. When the non-MPLS encapsulation is used in a given BIER domain, it may be desirable for the a BIFT-id to be unique in that domain. This document describes an OPTIONAL method that can be used to form domain-wide unique BIFT-ids based on the <SD, SI, BSL> triples. If in the future the BIER architecture is extented with an additonal BIFT argument, this encoding does not generate domain-wide unique idenifiers anymore. Wijnands, et al. Expires October 15, 2018 [Page 2]
Internet-Draft Non-MPLS BIER BIFT-id Encapsulation April 2018 This encoding, if used, is only for the convenience of the network adminstrators. When forwarding a BIER packet, the BIFT-id is used as an opaque 20-bit value that identifies a BIFT; the forwarding procedures do not parse the 20-bit value, they just use it as a lookup key. 2. Terminology and Definitions Readers of this document are assumed to be familiar with the terminology and concepts of the documents listed as Normative References. For convenience, some of the more frequently used terms appear below. BIER: Bit Indexed Explicit Replication. BIFT-id: Bit Indexed Forwarding Table Identifier. 3. Specification of Requirements 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]. 4. The Bit Index Forwarding Table In MPLS networks a BIER label is allocated for each Bit Index Forwarding Table (BIFT) from the platform specific, downstream label database ([RFC8296]). This label is associated with a particular combination of BIER Sub-Domain (SD), Set Identifier (SI) and BitStringLength (BSL). In order for the network to know which MPLS label represents a particular combination of <SD, SI, BS>, this mapping has to be advertised through the network. This is currently done through an IGP or BGP. In MPLS networks this is not a drawback as the MPLS label has to be advertised anyway. When the non-MPLS encoding is chosen, there is no need to advertise the BIFT-id to <SD, SI, BSL> mapping if the BIFT-id is domain-wide unique. For this reason we're defining an encoding that MAY be used by operators to compute the domain-wide unique BIFT-id values from the SD, SI and BSL. Although the BIFT-id is not expected to change, it may change when the BSL mismatch procedures [RFC8279] section 6.10.2 are applied. Wijnands, et al. Expires October 15, 2018 [Page 3]
Internet-Draft Non-MPLS BIER BIFT-id Encapsulation April 2018 5. The Non-MPLS Static BIFT Encoding Find below the first 32 bits of the BIER header, encoding the SD, SI and BSL into the 20 bit BIFT-id field. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BSL | SD | SI | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |-------- 20 bit BIFT-id Field ---------| Figure 1 BSL: This 4-bit field encodes the length in bits of the BitString. These are the same values as documented in [RFC8296]. SD: This is a 8-bit field that encodes the Sub-Domain as described in [RFC8279]. SI: This is a 8-bit field that encodes the Set-ID as described in [RFC8279]. TC: This is a 3-bit field set to 000 (following [RFC8296]). S: This is a 1-bit field set to 1 (following [RFC8296]). TTL: See [RFC8296]. 6. Security Considerations This document does not introduce any new security considerations other than already discussed in [RFC8279]. 7. IANA Considerations There is no IANA consideration. 8. Acknowledgments The authors like to thank the following people for their comments and contributions to this document; Eric Rosen, Neale Ranns, Jeffrey Zhang. Wijnands, et al. Expires October 15, 2018 [Page 4]
Internet-Draft Non-MPLS BIER BIFT-id Encapsulation April 2018 9. Normative References [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>. [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Przygienda, T., and S. Aldrin, "Multicast Using Bit Index Explicit Replication (BIER)", RFC 8279, DOI 10.17487/RFC8279, November 2017, <https://www.rfc-editor.org/info/rfc8279>. [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation for Bit Index Explicit Replication (BIER) in MPLS and Non- MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 2018, <https://www.rfc-editor.org/info/rfc8296>. Authors' Addresses IJsbrand Wijnands Cisco Systems De Kleetlaan 6a Diegem 1831 Belgium Email: ice@cisco.com Xiaohu Xu Alibaba Group Email: xiaohu.xxh@alibaba-inc.com Hooman Bidgoli Nokia 600 March Rd. Ottawa, Ontario K2K 2E6 Canada Email: hooman.bidgoli@nokia.com Wijnands, et al. Expires October 15, 2018 [Page 5]