Network Working Group J. Xie Internet-Draft Huawei Technologies Intended status: Standards Track L. Geng Expires: January 3, 2019 L. Wang China Mobile M. McBride G. Yan Huawei July 2, 2018 Segmented MVPN Using IP Lookup for BIER draft-xie-bier-mvpn-segmented-01 Abstract This document specifies an alternative of the control plane and data plane procedures that allow segmented MVPN using BIER. This allows the use of a more efficient explicit-tracking as the BIER overlay, with a slight change in the forwarding procedure of a segmentation point BFR by a lookup of the IP header. This document updates [I- D.ietf-bier-mvpn]. 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]. 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 January 3, 2019. Xie, et al. Expires January 3, 2019 [Page 1] Internet-Draft draft-xie-bier-mvpn-segmented-00 July 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 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Problem Statement and Considerations . . . . . . . . . . . . 3 3.1. Problem Statement . . . . . . . . . . . . . . . . . . . . 3 3.2. Considerations . . . . . . . . . . . . . . . . . . . . . 4 4. Segmented MVPN using IP Lookup for BIER . . . . . . . . . . . 4 4.1. Explicit-tracking using LIR-pF Flag . . . . . . . . . . . 4 4.2. Forwarding Procedure of Segmentation Point . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction When using BIER to transport an MVPN data packet through a BIER domain, an ingress PE functions as a BFIR (see [RFC8279]). The BFIR must determine the set of BFERs to which the packet needs to be delivered. This can be done through an explicit-tracking function using a LIR and/or LIR-pF flag in BGP MVPN routes, per the [RFC6513],[RFC6514],[RFC6625],[I-D.ietf-bess-mvpn-expl-track], and [I-D.ietf-bier-mvpn]. Using a LIR-pF Flag will bring some extra benefits, as [I-D.ietf- bier-mvpn] and [I-D.ietf-bess-mvpn-expl-track] have stated. But unfortunately, the LIR-pF explicit tracking for a segmented MVPN deployment is not allowed in the current draft [I-D.ietf-bier-mvpn], Xie, et al. Expires January 3, 2019 [Page 2] Internet-Draft draft-xie-bier-mvpn-segmented-00 July 2018 because the draft requires a per-flow upstream-assigned label to do the data-plane per-flow lookup on the segmentation point BFR. This document specifies an alternative of the control plane and data plane procedures that allow segmented MVPN using BIER in both segments. This allows the use of the more efficient LIR-pF explicit- tracking as the BIER overlay, with a slight change in the forwarding procedure of a segmentation point BFR by using IP lookup. This will bring some significant benefits to the segmented MVPN deployment, including: o Getting a much better multicast join latency by eliminating the round trip interaction of S-PMSI AD routes and Leaf AD routes. Especially, the S-PMSI A-D routes may need a data-driven procedure to trigger, and make the multicast join latency even worse. o Greatly reducing the number of S-PMSI A-D routes that BFIR and BFERs need to save. o Consolidated forwarding procedure of IP lookup for every BIER Overlay functioning routers, such as BFIR, BFER, segmentation point BFR, and segmentation point BFR with BFER function. 2. Terminology Readers of this document are assumed to be familiar with the terminology and concepts of the documents listed as Normative References. 3. Problem Statement and Considerations 3.1. Problem Statement BIER is a stateless multicast forwarding by introducing a multicast- specific BIER header in the data plane. The maximal number of BFERs a packet can reach is limited by the bit string length of a BIER header. For a network with many routers in multiple IGP areas (typically an Inter-Area network), it may be more expected to use a segmented MVPN when deploying BIER than traditional MVPN. However, it is not allowed in the [I-D.ietf-bier-mvpn] to use a LIR- pF explicit-tracking when deploying a segmented MVPN. This will lead to a low efficiency of explicit-tracking, and cause a worse multicast join latency. Here we take a scenario of inter-area segmented MVPN with both segments using BIER as an example. Xie, et al. Expires January 3, 2019 [Page 3] Internet-Draft draft-xie-bier-mvpn-segmented-00 July 2018 3.2. Considerations A BFIR is always needed to know the BFERs interested in a specific flow. This is a function of a BIER overlay defined in [RFC8279]. A segmentation point BFR in a segmented MVPN deployment, saying ABR, will play similar roles of both BFIR and BFER. It needs to do a disposition of a BIER Header, and then do an imposition of a new BIER Header. It requires the ABR router to maintain per-flow states, and especially, such per-flow states always include a set of BFERs who are intrested in a specific flow by using an explicit-tracking procedure. This behavior is completely different from a traditional segmented MVPN deployment, e.g, with both of the two segments using P2MP label switch. In a traditional segmented MVPN with both segments using P2MP label switch, it is expected to receive a MPLS packet and replicate to downstream routers after swap the MPLS Label. A lookup of IP packet is not expected. Also, in a traditional segmented MVPN deployment, an MPLS label represents a P-tunnel, which may carry one, many or even all multicast flow(s) of a VPN, so it is not always a per-flow state on the segmentation point router. In conclusion, the pattern of forwarding packets on segmentation points only by lookup of MPLS label mapped from multicast flow(s) is significantly unnecessary when BIER is introduced. Instead, doing a per-flow lookup of IP header on segmentation points is more efficient and consolidated. 4. Segmented MVPN using IP Lookup for BIER 4.1. Explicit-tracking using LIR-pF Flag In a scenario of Inter-area Segmented MVPN with both segments using BIER, the determination of the set of BFERs that need to receive the a specific multicast flow of (C-S1,C-G1) in each segment, can be obtained by using a LIR-pF flag. Suppose a topology of this: (Ingress PE)PE1-------P1-------ABR-------P2------PE2(Egress PE) | | | | Ingress Area | Egress Area | | ( BIER SD ) | ( BIER SD ) | Figure 1: Example topology PE1 is Ingress PE, and the area of { PE1 -- P1 -- ABR } is called an Ingress Area. Xie, et al. Expires January 3, 2019 [Page 4] Internet-Draft draft-xie-bier-mvpn-segmented-00 July 2018 PE2 is Egress PE, and the area of { ABR -- P2 -- PE2 } is called an Egress Area. The Ingress PE is configured to use a BIER tunnel type for a MVPN instance for the Ingress Area, and the ABR is configured to use a BIER tunnel type for the MVPN instance for the Egress Area. The Ingress PE originates a wildcard S-PMSI A-D route (C-*,C-*) and the PTA of that route has the following settings: o The LIR-pF and LIR flags be set. o The tunnel type be set to "BIER". o A non-zero MPLS label be specified. ABR receives the S-PMSI A-D route from the Ingress PE, and re- advertises the route to the Egress PE, with a PTA type "BIER", and PTA flags of LIR and LIR-pF, and a new non-zero upstream-assigned MPLS label allocated by ABR per-VPN. Egress PE receives the S-PMSI A-D route from the ABR, and checks if it need to response with a Leaf A-D route to this S-PMSI A-D route using the process of the "match for reception" and "match for tracking" as defined in [I-D.bess-mvpn-expl-track]. In this example, for a C-flow of (C-S1, C-G1), the checking result of "matched for tracking" is the S-PMSI(C-*, C-*), and the checking result of "matched for reception" is also the S-PMSI(C-*, C-*). Egress PE will then send a Leaf A-D route (RD, C-S1, C-G1, Root=PE1, Leaf=PE2) to the ABR with a PTA flag LIR-pF, and a Leaf A-D route (RD, C-*, C-*, Root=PE1, Leaf=PE2) without a PTA flag LIR-pF. ABR then has an explicit-tracking result of a new per-flow information of (RD, C-S1, C-G1, Root=PE1) with Egress PE as its leaf or BFER. ABR's "matched for tracking" result to this flow(RD, C-S1, C-G1, PE1) will then be updated with a new record, and ABR then sends a Leaf A-D route (RD, C-S1, C-G1, Root=PE1, Leaf=ABR) to Ingress PE. Ingress PE then has an explicit-tracking result of a new per-flow information of (RD, C-S1, C-G1, Root=PE1) with ABR as its leaf or BFER. From this procedure description one can see that: 1. The S-PMSI A-D(C-*, C-*) route is functioning as a per-VPN anchor of the upstream and the downstream(s), which can be called a BIER FEC in this document, saying BIER FEC(*,*). Xie, et al. Expires January 3, 2019 [Page 5] Internet-Draft draft-xie-bier-mvpn-segmented-00 July 2018 2. The Leaf A-D(S,G) routes are functioning as a per-flow anchor of the downstream(s) and the upstream, which are also BIER FECs accordingly, saying BIER FEC(S,G). 3. The Tuple of (Root=PE1, RD) in S-PMSI (C-*, C-*) or Leaf AD(C-*, C-*) or Leaf AD(C-S, C-G) represents an VRF on the ABR implicitly. ABR knows the per-vpn infmation of a (Root=PE1, RD) tuple when receiving and re-advertising the S-PMSI A-D(*,*) route bound with a PTA, where: o Inbound SD (InSD): in PTA of the received S-PMSI(*,*) route. o Inbound VpnLabel (InVpnLabel): in PTA of the received S-PMSI(*,*) route. o Inbound BfirId (InBfirId): in PTA of the received S-PMSI(*,*) route. o Outbound SD(OutSD): in PTA of the re-advertised S-PMSI(*,*) route. o Outbound VpnLabel (OutVpnLabel): in PTA of the re-advertised S-PMSI(*,*) route. o Outbound BfirId (OutBfirId): in PTA of the re-advertised S-PMSI(*,*) route. ABR establishs a per-flow control-plane state accordingly like this: o Per-flow upstream state, according to the Leaf A-D (C-S, C-G) route send to the Ingress PE: (PE1, RD, C-S1, C-G1, InSD, InBfirId, InVpnLabel). o Per-flow downstream state(s), according to the Leaf A-D(C-S, C-G) route(s) received by the ABR from Egress PE(s): (PE1, RD, C-S1, C-G1, Leaf, OutSD, OutBfirId, OutVpnLabel). ABR knows the BIER Label(s) it allocated for InSD and OutSD, saying InBierLabel for InSD and OutBierLabel for OutSD, and thus it can establish the per-flow forwarding state: o Per-flow upstream forwarding state: (InBierLabel, InBfirId, InVpnLabel, C-S1, C-G1). o Per-flow downstream(s) forwarding state: (InBierLabel, InBfirId, InVpnLabel, C-S1, C-G1, Leaf, OutBfirId, OutVpnLabel, OutBitString) Xie, et al. Expires January 3, 2019 [Page 6] Internet-Draft draft-xie-bier-mvpn-segmented-00 July 2018 4.2. Forwarding Procedure of Segmentation Point The Forwarding procedure of a segmentation point BFR is a combination of a deposition and a re-imposition of the whole BIER header and the upstream-assigned Vpn Label. One can think it as swapping of a series of fields like below: o swapping the InBierLabel with an OutBierLabel. o swapping the InBfirId with an OutBfirId. o swapping the InVpnLabel with an OutVpnLabel. o swapping the InBitString with an OutBitString. The key of a per-flow lookup on ABR is a tuple of (InBierLabel, InBfirId, InVpnLabel) and a tuple of (C-S1, C-G1), representing a VRF and a flow respectively. All the elements are from a BIER packet, and such an IP lookup can be seen the same as an MFIB lookup, if the (InBierLabel, InBfirId, InVpnLabel) tuple is mapped to a VRF locally on the ABR. 5. Security Considerations The procedures of this document do not, in themselves, provide privacy, integrity, or authentication for the control plane or the data plane. 6. IANA Considerations No IANA allocation is required. 7. Acknowledgements TBD. 8. References 8.1. Normative References [I-D.ietf-bess-mvpn-expl-track] Dolganow, A., Kotalwar, J., Rosen, E., and Z. Zhang, "Explicit Tracking with Wild Card Routes in Multicast VPN", draft-ietf-bess-mvpn-expl-track-09 (work in progress), April 2018. Xie, et al. Expires January 3, 2019 [Page 7] Internet-Draft draft-xie-bier-mvpn-segmented-00 July 2018 [I-D.ietf-bier-mvpn] Rosen, E., Sivakumar, M., Aldrin, S., Dolganow, A., and T. Przygienda, "Multicast VPN Using BIER", draft-ietf-bier- mvpn-11 (work in progress), March 2018. [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February 2012, . [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP Encodings and Procedures for Multicast in MPLS/BGP IP VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, . [RFC6625] Rosen, E., Ed., Rekhter, Y., Ed., Hendrickx, W., and R. Qiu, "Wildcards in Multicast VPN Auto-Discovery Routes", RFC 6625, DOI 10.17487/RFC6625, May 2012, . [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, . 8.2. Informative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . Authors' Addresses Jingrong Xie Huawei Technologies Email: xiejingrong@huawei.com Liang Geng China Mobile Beijing 10053 Email: gengliang@chinamobile.com Xie, et al. Expires January 3, 2019 [Page 8] Internet-Draft draft-xie-bier-mvpn-segmented-00 July 2018 Lei Wang China Mobile Beijing 10053 Email: wangleiyjy@chinamobile.com Mike McBride Huawei Email: mmcbride7@gmail.com Gang Yan Huawei Email: yangang@huawei.com Xie, et al. Expires January 3, 2019 [Page 9]