BIER Z. Zhang Internet-Draft ZTE Corporation Intended status: Standards Track Z. Zhang, Ed. Expires: August 26, 2021 Juniper Networks I. Wijnands Individual M. Mishra Cisco Systems H. Bidgoli Nokia G. Mishra, Ed. Verizon February 22, 2021 Supporting BIER in IPv6 Networks (BIERin6) draft-zhang-bier-bierin6-09 Abstract BIER is a new architecture for the forwarding of multicast data packets without requiring per-flow state inside the network. This document describes how the existing BIER encapsulation specified in RFC 8296 works in an IPv6 non-MPLS network, referred to as BIERin6. Specifically, like in an IPv4 network, BIER can work over L2 links directly or over tunnels. In case of IPv6 tunneling, a new IP "Next Header" type is to be assigned for BIER. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. Status of This Memo 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 Zhang, et al. Expires August 26, 2021 [Page 1] Internet-Draft BIERin6 February 2021 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 August 26, 2021. Copyright Notice Copyright (c) 2021 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. BIER over L2/Tunnels . . . . . . . . . . . . . . . . . . 3 1.2. Considerations of Requirements for BIER in IPv6 Networks 3 2. IPv6 Header . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. IPv6 Options Considerations . . . . . . . . . . . . . . . 5 3. BIER Header . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. IPv6 Encapsulation Advertisement . . . . . . . . . . . . . . 6 4.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.2. Inter-area prefix redistribution . . . . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 8.2. Informative References . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction BIER [RFC8279] is a new architecture for the forwarding of multicast data packets. It provides optimal forwarding through a "multicast domain" and it does not precondition construction of a multicast distribution tree, nor does it require intermediate nodes to maintain any per-flow state. Zhang, et al. Expires August 26, 2021 [Page 2] Internet-Draft BIERin6 February 2021 This document specifies non-MPLS BIER forwarding in an IPv6 [RFC8200] environment, referred to as BIERin6, using non-MPLS BIER encapsulation specified in [RFC8296]. MPLS BIER forwarding in IPv6 is outside the scope of this document. This document uses terminology defined in [RFC8279] and [RFC8296]. 1.1. BIER over L2/Tunnels [RFC8296] defines the BIER encapsulation format in MPLS and non-MPLS environment. In case of non-MPLS environment, a BIER packet is the payload of an "outer" encapsulation, which has a "next header" codepoint that is set to a value that means "non-MPLS BIER". This "BIER over L2/Tunnel" model can be used as is in an IPv6 non-mpls environment, and is referred to as BIERin6. If a BFR needs to tunnel BIER packets to another BFR, e.g. per [RFC8279] Section 6.9, while any type of tunnel will work, for best efficiency native IPv6 encapsulation can be used with the destination address being the downstream BFR and the Next Header field set to a to-be-assigned value for "non-MPLS BIER". +---------------+------------------------ | IPv6 header | BIER header + data | | | Next Header = | | BIER | +---------------+------------------------ Between two directly connected BFRs, a BIER header can directly follow link layer header, e.g., an Ethernet header (with the Ethertype set to 0xAB37). Optionally, IPv6 encapsulation can be used even between directly connected BFRs (i.e. one-hop IPv6 tunneling) in the following two cases: o An operator mandates all traffic to be carried in IPv6. o A BFR does not have BIER support in its "fast forwarding path" and relies on "slow/software forwarding path", e.g. in environments like [RFC7368] where high throughput multicast forwarding performance is not critical. 1.2. Considerations of Requirements for BIER in IPv6 Networks [draft-ietf-bier-ipv6-requirements] lists mandatory and optional requirements for BIER in IPv6 Networks. As a solution based on the Zhang, et al. Expires August 26, 2021 [Page 3] Internet-Draft BIERin6 February 2021 BIER over L2/tunnel model [RFC8296], BIERin6 satisfies all the mandatory requirements. For the two optional requirements for fragmentation and Encapsulating Security Payload (ESP), they can be satisfied by one of two ways: o IPv6 based fragmentation/ESP: a BFIR encapsulates the payload in IPv6 with fragmentation and/or ESP header, and then the IPv6 packets are treated as BIER payload. o Generic Fragmentation/ESP [I-D.zzhang-tsvwg-generic-transport-functions]: a BFIR does generic fragmentation and/or ESP (without using IPv6 encapsulation) and the resulting packets are treated as BIER payload. Either way, the fragmentation/ESP is handled by a layer outside of BIER and then the resulting packets are treated as BIER payload. BIERin6 does support SRv6 based overlay services (e.g. MVPN/EVPN). One of the following methods can be used (relevant overlay signaling will be specified separately): o An ingress PE (which is a BFIR) can encapsulate customer packets with an IPv6 header (with optional fragmentation and ESP extension headers). The destination address is a multicast locator plus the Fucn/Arg portion that identifies the service. That IPv6 packet is then treated as BIER payload. An egress PE (which is a BFER) uses the standard SRv6 procedures to forward the IPv6 packet that is exposed after the BIER header is decapsulated. o Alternatively, since only the destination IPv6 address in the above-mentioned IPv6 header is used for service delimiting purpose, a new value can be assigned for the Proto field in the BIER header to indicate that an IPv6 address (instead of an entire IPv6 header) is added between the BIER header and original payload. BIERin6 being a solution based on [RFC8279] [RFC8296], ECMP is inherently supported by BFRs using the the 20-bit entropy field in the BIER header for the load balancing hash. When a BIER packet is transported over an IPv6 tunnel, the entropy value is copied into the 20-bit IPv6 Flow Label (instead of using local 5-tuple input key to a hash function to locally generate the stateless 20-bit flow label) so that routers along the tunnel can do ECMP based on Flow Labels. For a router along the tunnel doing deep packet inspection for ECMP purpose, if it understands BIER header it can go past the BIER header to look for the 5-tuple input key to a hash function, otherwise it Zhang, et al. Expires August 26, 2021 [Page 4] Internet-Draft BIERin6 February 2021 stops at the BIER header. In either case the router will not mistake the BIER header as an IP header so no misordering should happen. BIER has its own OAM functions independent of those related to the underlying links or tunnels. With BIERin6 following the "BIER over L2/tunnel" model, IPv6 OAM function and BIER OAM functions are used independently for their own purposes. Specifically, BIERin6 works with all of the following OAM methods, or any future methods that are based on the "BIER over L2/tunnel" model: o BIER OAM specified in [I-D.ietf-bier-ping] o BIER BFD specified in [I-D.ietf-bier-bfd] o BIER Performance Measurement specified in [I-D.ietf-bier-pmmm-oam] o BIER Path Maximum Transmission Unit Discovery specified in [I-D.ietf-bier-path-mtu-discovery] o BIER IOAM specified in [I-D.xzlnp-bier-ioam] 2. IPv6 Header Whenever IPv6 encapsulation is used for BIER forwarding, The Next Header field in the IPv6 Header (if there are no extension headers), or the Next Header field in the last extension header is set to TBD, indicating that the payload is a BIER packet. If the neighbor is directly connected, The destination address in IPv6 header SHOULD be the neighbor's link-local address on this router's outgoing interface, the source destination address SHOULD be this router's link-local address on the outgoing interface, and the IPv6 TTL MUST be set to 1. Otherwise, the destination address SHOULD be the BIER prefix of the BFR neighbor, the source address SHOULD be this router's BIER prefix, and the TTL MUST be large enough to get the packet to the BFR neighbor. The "Flow label" field in the IPv6 packet SHOULD be copied from the entropy field in the BIER encapsulation. 2.1. IPv6 Options Considerations For directly connected BIER routers, IPv6 Hop-by-Hop or Destination options are irrelevant and SHOULD NOT be inserted by BFIR on the BIERin6 packet. In this case IPv6 header, Next Header field should be set to TBD. Any IPv6 packet arriving on BFRs and BFERs, with multiple extension header where the last extension header has a Next Zhang, et al. Expires August 26, 2021 [Page 5] Internet-Draft BIERin6 February 2021 Header field set to TBD, SHOULD be discard and the node should transmit an ICMP Parameter Problem message to the source of the packet (BFIR) with an ICMP code value of TBD10 ('invalid options for BIERin6'). This also indicates that for disjoint BIER routers using IPv6 encapsulation, there SHOULD NOT be any IPv6 Hop-by-Hop or Destination options be present in a BIERin6 packet. In this case, if additional traffic engineering is required, IPv6 tunneling (i.e. BIERin6 over SRv6) can be implemented. 3. BIER Header The BIER header MUST be encoded per Section 2.2 of [RFC8296]. The BIFT-id is either encoded per [I-D.ietf-bier-non-mpls-bift-encoding] or per advertised by BFRs, as specified in [I-D.ietf-bier-lsr-ethernet-extensions]. 4. IPv6 Encapsulation Advertisement When IPv6 encapsulation is not required between directly connected BFRs, no signaling in addition to that specified in [I-D.ietf-bier-lsr-ethernet-extensions] is needed. Otherwise, a node that requires IPv6 encapsulation MUST advertise the BIER IPv6 transportation sub-sub-sub-TLV/sub-sub-TLV according to local configuration or policy in the BIER domain to request other BFRs to always use IPv6 encapsulation. In presence of multiple encapsulation possibilities hop-by-hop it is a matter of local policy which encapsulation is imposed and the receiving router MUST accept all encapsulations that it advertised. 4.1. Format The BIER IPv6 transportation is a new sub-sub-TLV of BIER Ethernet Encapsulation sub-TLV defined in OSPFv3, and a new sub-sub-sub-TLV of BIER Ethernet Encapsulation sub-sub-TLV defined in ISIS, as per [I-D.ietf-bier-lsr-ethernet-extensions]. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Zhang, et al. Expires August 26, 2021 [Page 6] Internet-Draft BIERin6 February 2021 o Type: For OSPF, value TBD1 (prefer 1) is used to indicate it is the IPv6 transportation sub-TLV. For ISIS, value TBD2 (prefer 1) is used to indicate it is the IPv6 transportation sub-sub-TLV. o Length: 0. 4.2. Inter-area prefix redistribution When BFR-prefixes are advertised across IGP areas per [I-D.ietf-bier-lsr-ethernet-extensions] or redistributed across protocol boundaries per [I-D.ietf-bier-prefix-redistribute], the BIER IPv6 transportation sub-sub-TLV or sub-sub-sub-TLV MAY be re- advertised/re-distributed as well. 5. IANA Considerations IANA is requested to assign a new "BIER" type for "Next Header" in the "Assigned Internet Protocol Numbers" registry. IANA is requested to assign a new "BIERin6" type for "invalid options" in the "ICMP code value" registry. IANA is requested to assign a new "IPv6 address" type in the "BIER Next Protocol Identifiers" registry. IANA is requested to assign a new "BIER IPv6 transportation Sub-sub- TLV" type in the "OSPFv3 BIER Ethernet Encapsulation sub-TLV" Registry. IANA is requested to set up a new "BIER IPv6 transportation Sub-sub- sub-TLV" type in the "IS-IS BIER Ethernet Encapsulation sub-sub-TLV" Registry. 6. Security Considerations General IPv6 and BIER security considerations apply. 7. Acknowledgement The authors would like to thank Tony Przygienda, Nagendra Kumar for their review and valuable comments. 8. References Zhang, et al. Expires August 26, 2021 [Page 7] Internet-Draft BIERin6 February 2021 8.1. 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, . [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, "IPv6 Flow Label Specification", RFC 6437, DOI 10.17487/RFC6437, November 2011, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, . [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, . [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, . [RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z. Zhang, "Bit Index Explicit Replication (BIER) Support via IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018, . 8.2. Informative References [I-D.ietf-bier-bar-ipa] Zhang, Z., Przygienda, T., Dolganow, A., Bidgoli, H., Wijnands, I., and A. Gulko, "BIER Underlay Path Calculation Algorithm and Constraints", draft-ietf-bier- bar-ipa-07 (work in progress), September 2020. Zhang, et al. Expires August 26, 2021 [Page 8] Internet-Draft BIERin6 February 2021 [I-D.ietf-bier-bfd] Xiong, Q., Mirsky, G., hu, f., and C. Liu, "BIER BFD", draft-ietf-bier-bfd-00 (work in progress), November 2020. [I-D.ietf-bier-idr-extensions] Xu, X., Chen, M., Patel, K., Wijnands, I., and T. Przygienda, "BGP Extensions for BIER", draft-ietf-bier- idr-extensions-07 (work in progress), September 2019. [I-D.ietf-bier-ipv6-requirements] McBride, M., Xie, J., Geng, X., Dhanaraj, S., Asati, R., Zhu, Y., Mishra, G., and Z. Zhang, "BIER IPv6 Requirements", draft-ietf-bier-ipv6-requirements-09 (work in progress), September 2020. [I-D.ietf-bier-lsr-ethernet-extensions] Dhanaraj, S., Yan, G., Wijnands, I., Psenak, P., Zhang, Z., and J. Xie, "LSR Extensions for BIER over Ethernet", draft-ietf-bier-lsr-ethernet-extensions-02 (work in progress), December 2020. [I-D.ietf-bier-non-mpls-bift-encoding] Wijnands, I., Mishra, M., Xu, X., and H. Bidgoli, "An Optional Encoding of the BIFT-id Field in the non-MPLS BIER Encapsulation", draft-ietf-bier-non-mpls-bift- encoding-03 (work in progress), November 2020. [I-D.ietf-bier-ospfv3-extensions] Psenak, P., Nainar, N., and I. Wijnands, "OSPFv3 Extensions for BIER", draft-ietf-bier-ospfv3-extensions-03 (work in progress), November 2020. [I-D.ietf-bier-path-mtu-discovery] Mirsky, G., Przygienda, T., and A. Dolganow, "Path Maximum Transmission Unit Discovery (PMTUD) for Bit Index Explicit Replication (BIER) Layer", draft-ietf-bier-path-mtu- discovery-09 (work in progress), November 2020. [I-D.ietf-bier-ping] Nainar, N., Pignataro, C., Akiya, N., Zheng, L., Chen, M., and G. Mirsky, "BIER Ping and Trace", draft-ietf-bier- ping-07 (work in progress), May 2020. [I-D.ietf-bier-pmmm-oam] Mirsky, G., Zheng, L., Chen, M., and G. Fioccola, "Performance Measurement (PM) with Marking Method in Bit Index Explicit Replication (BIER) Layer", draft-ietf-bier- pmmm-oam-09 (work in progress), December 2020. Zhang, et al. Expires August 26, 2021 [Page 9] Internet-Draft BIERin6 February 2021 [I-D.ietf-bier-prefix-redistribute] Zhang, Z., Bo, W., Zhang, Z., Wijnands, I., and Y. Liu, "BIER Prefix Redistribute", draft-ietf-bier-prefix- redistribute-00 (work in progress), August 2020. [I-D.xzlnp-bier-ioam] Min, X., Zhang, Z., Liu, Y., Nainar, N., and C. Pignataro, "Bit Index Explicit Replication (BIER) Encapsulation for In-situ OAM (IOAM) Data", draft-xzlnp-bier-ioam-01 (work in progress), January 2021. [I-D.zhang-bier-babel-extensions] Zhang, Z. and T. Przygienda, "BIER in BABEL", draft-zhang- bier-babel-extensions-04 (work in progress), November 2020. [I-D.zzhang-tsvwg-generic-transport-functions] Zhang, Z., Bonica, R., and K. Kompella, "Generic Transport Functions", draft-zzhang-tsvwg-generic-transport- functions-00 (work in progress), November 2020. [RFC7368] Chown, T., Ed., Arkko, J., Brandt, A., Troan, O., and J. Weil, "IPv6 Home Networking Architecture Principles", RFC 7368, DOI 10.17487/RFC7368, October 2014, . Authors' Addresses Zheng(Sandy) Zhang ZTE Corporation EMail: zhang.zheng@zte.com.cn Zhaohui Zhang (editor) Juniper Networks EMail: zzhang@juniper.net IJsbrand Wijnands Individual EMail: ice@braindump.be Zhang, et al. Expires August 26, 2021 [Page 10] Internet-Draft BIERin6 February 2021 Mankamana Mishra Cisco Systems EMail: mankamis@cisco.com Hooman Bidgoli Nokia EMail: hooman.bidgoli@nokia.com Gyan Mishra (editor) Verizon EMail: gyan.s.mishra@verizon.com Zhang, et al. Expires August 26, 2021 [Page 11]