BIER Workgroup H. Bidgoli, Ed. Internet Draft A. Dolganow Intended status: Standard Track J. Kotalwar Nokia Fengman Xu Verizon Expires: May 1, 2018 October 28, 2017 PIM Signaling Through BIER Core draft-hfa-bier-pim-signaling-00 Abstract Bit Index Explicit Replication (BIER) is an architecture that provides multicast forwarding through a "BIER domain" without requiring intermediate routers to maintain multicast related per-flow state. Neither does BIER require an explicit tree-building protocol for its operation. A multicast data packet enters a BIER domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs). The BFIR router adds a BIER header to the packet. Such header contains a bit-string in which each bit represents exactly one BFER to forward the packet to. The set of BFERs to which the multicast packet needs to be forwarded is expressed by the according set of bits switched on in BIER packet header. This document describes the procedure needed for PIM Joins and Prunes to be signaled through a BIER core. Allowing PIM routers to run traditional PIM multicast services through a BIER core. 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), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list Bidgoli, Xu et al. Expires May 1, 2018 [Page 1] Internet-Draft PIM Stitching Through BIER Core October 28, 2017 of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on October 8, 2017. Copyright Notice Copyright (c) 2017 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 (http://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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . . 3 2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . . 3 3. PIM Signaling Through BIER domain . . . . . . . . . . . . . . . 5 3.1. Ingress BBR procedure . . . . . . . . . . . . . . . . . . . 6 3.1.1. BIER packet construction at IBBR . . . . . . . . . . . 7 3.2. Signaling PIM through the BIER domain procedure . . . . . . 8 3.3. EBBR procedure . . . . . . . . . . . . . . . . . . . . . . 8 4. Datapath Forwarding . . . . . . . . . . . . . . . . . . . . . . 8 4.1. BFIR tracking of (S,G) . . . . . . . . . . . . . . . . . . 8 4.2. Datapath traffic flow . . . . . . . . . . . . . . . . . . . 9 5. PIM-ASM behavior . . . . . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 9 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 8.1. Normative References . . . . . . . . . . . . . . . . . . . 9 8.2. Informative References . . . . . . . . . . . . . . . . . . 9 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Bidgoli, Xu et al. Expires May 1, 2018 [Page 2] Internet-Draft PIM Stitching Through BIER Core October 28, 2017 1. Introduction Greenfield deployment of BIER might not be possible for some large network. These networks deploy traditional PIM multicast services in grt or in mvpns such as draft rosen multicast vpns. Typically, each portion of these large networks have their own mandates and requirements. Consider the case of converged core, where single core is used for fixed, business and wireless services. In this case there is a desire for next generation "lean" core. Where a single IGP protocol or SDN controller could enable unicast and multicast services. BIER is a natural fit for this core. That said because of cost and operational complexity the migration to BIER might fall into below categories: 1.Gradual migration of the network to BIER, starting with the "lean" core and eventually to access networks. 2.Migrating only the core to BIER and keeping traditional pim services in access. As an example, in wireless networks where there are thousands of cell site routers. Each cell site router is a leaf as such for scaling and cost it might be desired to keep traditional PIM multicast services in the access network. This draft explains the procedure to signal PIM joins and prunes through a BIER core, as such enable provisioning of traditional pim services through a BIER core. It should be noted that this "lean" core is usually a single IGP area. As such the procedures in this draft is concentrating on a single BIER IGP area. 2. Conventions used in this document 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]. 2.1. Definitions Some of the terminology specified in [I-D.draft-ietf-bier- architecture-05] is replicated here and extended by necessary definitions: BIER: Bidgoli, Xu et al. Expires May 1, 2018 [Page 3] Internet-Draft PIM Stitching Through BIER Core October 28, 2017 Bit Index Explicit Replication (The overall architecture of forwarding multicast using a Bit Position). 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. In this draft BIER will be used for forwarding and tunneling of control plain packet (i.e. PIM) and forwarding dataplain packets. BFIR is term used for dataplain packet forwarding. 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. In this draft BIER will be used for forwarding and tunneling of control plain packet (i.e. PIM) and forwarding dataplain packets. BFIR is term used for dataplain packet forwarding. BBR: BIER Boundary router. The router between the PIM domain and BIER domain. Maintains PIM adjacency for all routers attached to it on the PIM domain and terminates the PIM adjacency toward the BIER domain. IBBR: Ingress BIER Boundary Router. The ingress router from signaling point of view. It maintains PIM adjacency toward the PIM domain and determines if PIM joins and prunes arriving from PIM domain need to be signaled across the BIER domain. If so it terminates the PIM adjacency toward the BIER domain and signals the PIM joins/prunes through the BIER core. EBBR: Egress BIER Boundary Router. The egress router in BIER domain from signaling point of view. It terminates the BIER packet and forwards the signaled joins and prunes into PIM Domain. Bidgoli, Xu et al. Expires May 1, 2018 [Page 4] Internet-Draft PIM Stitching Through BIER Core October 28, 2017 BFT: Bit Forwarding Tree used to reach all BFERs in a domain. BIFT: Bit Index Forwarding Table. 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. 3. PIM Signaling Through BIER domain bbr bbr |--pim Domain--|-----bier domain-----|--pim domain--| S--( A )----------( B ) ---- ( C ) ---- ( D )----------( E )--h ebbr ibbr Sig <-----PIM-----|<--Bier Tunneling----|<----PIM------ (new) bfir bfer ------------->|--------BIER-------->|-------------> Datapatah (no change) Figure 1: bier boundary router As per figure 1, the procedures of PIM signaling is done at the BIER boundary router. The BIER boundary router (BBR) are connected to PIM capable routers toward the pim domain and BIER routers toward the bier domain. PIM routers in pim domain continue to send PIM state messages to the BBR. The BBR will create pim adjacency between all the PIM routers attach to it on the pim domain. That said the BBR does not propagate all PIM packets natively into the BIER domain. Instead when it determines that the PIM join or prune messages needs to be signaled through the BIER domain it will tunnel the PIM packet Bidgoli, Xu et al. Expires May 1, 2018 [Page 5] Internet-Draft PIM Stitching Through BIER Core October 28, 2017 through BIER network. This tunneling is only done for signaling purposes and not for creating a PIM adjacency between the two disjoint pim domains through the bier domain. The terminology ingress BBR (ibbr) and egress BBR (ebbr) are relative from signaling point of view. The ingress BBR will determine if an arriving pim join or prune needs to be signaled across the bier domain. While the egress BBR will determine if the bier packet is a signaling packet and propagate the packet to its attach pim domain. The BFER and BFIR are BBR from datapath point of view. It should be noted the new procedures in this draft are only applicable to signaling and there are no changes from datapath point of view. 3.1. Ingress BBR procedure IBBR will create pim adjacency to all pim routers attach to it toward the pim domain. When a PIM join or prune for certain (S,G) arrives, the IBBR first determines weather the join or prune is meant for a source that is reachable through the bier domain. As an example, this source is located on a disjoint PIM domain that is reachable through the BIER domain. If so the ibbr will try to resolve the source via an ebbr closest to the source. The procedure to find the ebbr (BFIR from datapath point of view) can be via many mechanisms and is beyond the scope of this draft. It should be noted that in most cases the BIER domain is a single IGP area. The PIM domains are part of the same IGP area as BIER domain(single area) or are stitched to the BIER domain via an ABR or ASBR. in either case the BBRs are all located in the same area as bier domain. Below are two examples of resolving ebbrs: 1.The ebbr can be an ABR or ASBR router in the same IGP area as bier domain. In this case the ebbr summarizes the route to the source, and as such the ebbr is the IGP source of this route. The IGP source information can be used for identifying the ebbr and resolving it. 2.If source and ebbr are within a single IGP area, the ebbr can be resolved via SPF calculation. As an example, the closest ebbr to the source. The ebbr BFR-ID is signaled via IGP to all BFRs, as Bidgoli, Xu et al. Expires May 1, 2018 [Page 6] Internet-Draft PIM Stitching Through BIER Core October 28, 2017 such making it possible to do SFP calculation. After discovering the EBBR and its BFR-ID (flooded via IGP BIER extension), the IBBR will construct the BIER header via the BIFT. The signaling packet, in this case the PIM join/prune packet, is encapsulated in the BIER header and transported through BIER domain to EBBR. On forwarding plane the IBBR will track all the PIM interfaces on the attach pim domain which are interested in a certain (S,G). It creates multicast states for arriving (S,G)s from pim domain, with incoming interface (RPF) as BIER "tunnel" interface and outgoing interface as the pim domain interface(s) on which PIM Join(s) were received on. If there is another PIM Join for the same multicast (S,G) entry on another interface arriving from pim domain, that interface gets added in the outgoing interface list as well. 3.1.1. BIER packet construction at IBBR The BIER header will be encoded with the BFR-id of the IBBR(with appropriate bit set in the bitstring) and the PIM signaling packet is then encapsulated in the packet. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BIFT-id | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Nibble | Ver | BSL | Entropy | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |OAM|Rsv| DSCP | Proto | BFIR-id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BitString (first 32 bits) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ BitString (last 32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ BIERHeader.Proto = IPv4 or IPv6 BIERHeader.BitString= Bit corresponding to the BFR-ID of the EBBR BIERHeader.BFIR-id = BFR-Id of the BER originating the encapsulated PIM packet, i.e. the IBBR. Bidgoli, Xu et al. Expires May 1, 2018 [Page 7] Internet-Draft PIM Stitching Through BIER Core October 28, 2017 Rest of the values in the BIER header are determined based on the network (MPLS/non-MPLS), capabilities (BSL), and network configuration. 3.2. Signaling PIM through the BIER domain procedure Throughout the BIER domain the BIER forwarding procedure is in par with draft-ietf-bier-architecture. No BIER router will examine the BIER packet encapsulating the PIM signaling packet. As such there is no multicast state build in the BIER domain. The packet will be forwarded through the BIER domain until it reaches the BER with matching BFR-ID as in the BIERHeader.Bitstring. This BER (EBBR) will remove the BIER header and examine the PIM IPv4 or IPv6 signaling packet farther. 3.3. EBBR procedure After receiving the BIER packet and determining this packet is a signaling packet. As such the EBBR will remove the BIER header from PIM packet and does a route lookup for the source of the pim packet, if the source is on a local attach pim domain, it forwards the PIM packet toward the source. With same token the EBBR creates a multicast state with incoming interface as same interface that PIM join packet was forwarded and outgoing interfaces of BIER tunnel with BIER-Header.BFIR-id as one of the BFER of the tunnel. The EBBR will also build a BIER reverse path forwarding table, using the BIERHeader.BFIR-id and the arriving PIM packet (S,G). This is explained in section 4.1. It should be noted EBBR will maintain PIM adjacency toward the PIM domain and all PIM routers which are connected to it. At this point the end-to-end multicast traffic flow setup is complete. 4. Datapath Forwarding 4.1. BFIR tracking of (S,G) For a specific Source and Group, BFIR (EBBR)should track all the interested BFERs via arriving PIM signaling from BIER Domain. BFIR should build its multicast tree with incoming interface (IIF) as PIM interface (in PIM domain) and out going interfaces OIFs set as the of the interested BFERs (in BIER Domain). Bidgoli, Xu et al. Expires May 1, 2018 [Page 8] Internet-Draft PIM Stitching Through BIER Core October 28, 2017 4.2. Datapath traffic flow When the multicast data traffic arrives on the BFIR (EBBR) the router will find all the interested BFERs for that specific (S,G). The router then constructs the BIERHeader.BitString with all the BFER interested in the group and will forward the packet to the BIER domain. The BFER(s) will accept the packets and remove the BIER header and forward the multicast packet as per pre-build multicast state for (G) and its outgoing interfaces. 5. PIM-ASM behavior In case of PIM ASM the procedure for LEAFs joining RP is same as above. The unicast (source registration) traffic from source to RP will be flooded throughout the BIER domain as regular unicast traffic without BIER involvement. 6. IANA Considerations This document contains no actions for IANA. 7. Security Considerations TBD 8. References 8.1. Normative References [BIER_ARCH] Wijnands, IJ., Rosen, E., Dolganow, A., Przygienda, T., and S. Aldrin, "Multicast using Bit Index Explicit Replication", internet-draft draft-ietf-bier-architecture-08, October 2016. 8.2. Informative References [BIER_MVPN] Rosen, E., Ed., Sivakumar, M., Wijnands, IJ., Aldrin, S., Dolganow, A., and T. Przygienda, "Multicast VPN Using Bier", internet-draft draft-ietf-bier-mvpn-08, January 2017. [ISIS_BIER_EXTENSIONS] Ginsberg, L., Przygienda, T., Aldrin, S., and Z. Zhang, "BIER Support via ISIS", internet-draft draft-ietf-bier- isis-extensions-06.txt, March 2017. [OSPF_BIER_EXTENSIONS] Psenak, P., Kumar, N., Wijnands, IJ., Dolganow, A., Przygienda, T., Zhang, Z., and S. Aldrin, "OSPF Extensions for Bit Index Explicit Replication", internet-draft draft- ietf-ospf-bier-extensions-09.txt, March 2017. Bidgoli, Xu et al. Expires May 1, 2018 [Page 9] Internet-Draft PIM Stitching Through BIER Core October 28, 2017 7. Acknowledgments Authors' Addresses Hooman Bidgoli (editor) Nokia 600 March Rd. Ottawa, Ontario K2K 2E6 Canada Email: hooman.bidgoli@nokia.com Fengman Xu Verizon 400 International PKWY Richardson, Tx 75081 US Email: fengman.xu@verizon.com Jayant Kotalwar Nokia 380 N Bernardo Ave, Mountain View, CA 94043 US Email: jayant.kotalwar@nokia.com Andrew Dolganow Nokia 750D Chai Chee Rd 06-06, Viva Business Park Singapore 469004 Email: Andrew.dolganow@nokia.com Bidgoli, Xu et al. Expires May 1, 2018 [Page 10]