BESS Z. Zhang Internet-Draft L. Giuliano Intended status: Standards Track Juniper Networks Expires: March 31, 2018 September 27, 2017 MVPN and MSDP SA Interoperation draft-zzhang-bess-mvpn-msdp-sa-interoperation-00 Abstract This document specifies the procedures for interoperation between MVPN Source Active routes and customer MSDP Source Active routes, which is useful for MVPN provider networks offering services to customers with an existing MSDP infrastructure. Without the procedures described in this document, VPN-specific MSDP sessions are required among the PEs that are customer MSDP peers. 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 March 31, 2018. 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 Zhang & Giuliano Expires March 31, 2018 [Page 1] Internet-Draft mvpn-sa-msdp September 2017 (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. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2.1. MVPN RPT-SPT Mode . . . . . . . . . . . . . . . . . . . . 4 3. Specification . . . . . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 6. Normative References . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Terminologies Familiarity with MVPN and MSDP protocols and procedures is assumed. Some terminologies are listed below for convenience. o ASM: Any source multicast. o SPT: Source-specific Shortest-path Tree. o C-S: A multicast source address, identifying a multicast source located at a VPN customer site. o C-G: A multicast group address used by a VPN customer. o C-RP: A multicast Rendezvous Point for a VPN customer. o EC: Extended Community. 2. Introduction Section "14. Supporting PIM-SM without Inter-Site Shared C-Trees" of [RFC6514] specifies the procedures for MVPN PEs to discover (C-S,C-G) via MVPN Source Active A-D routes and then send (C-S,C-G) C-multicast routes towards the ingress PEs, to establish SPTs for customer ASM flows for which they have downstream receivers. (C-*,C-G) C-multicast routes are not sent among the PEs so inter-site shared C-Trees are not used and the method is generally referred to as "spt- only" mode. Zhang & Giuliano Expires March 31, 2018 [Page 2] Internet-Draft mvpn-sa-msdp September 2017 With this mode, the MVPN Source Active routes are functionally similar MSDP Source-Active messages [RFC3618]. One or more of the PEs, say PE1, either act as a C-RP and learn of (C-S,C-G) via PIM Register messages, or have MSDP sessions with some MSDP peers and learn (C-S,C-G) via MSDP SA messages. In either case, PE1 will then originate MVPN SA routes for other PEs to learn the (C-S,C-G). [RFC6514] only specifies that a PE receiving the MVPN SA routes, say PE2, will advertise (C-S,C-G) C-multicast routes if it has corresponding (C-*,C-G) state learnt from its CE. PE2 may also have MSDP sessions with other C-RPs at its site, but [RFC6514] does not specify that it advertise MSDP SA messages to those MSDP peers for the (C-S,C-G) that it learns via MVPN SA routes. PE2 would need to have an MSDP session with PE1 (that advertised the MVPN SA messages) to learn the sources via MSDP SA messages, for it to advertise the MSDP SA to its local peers. To make things worse, unless blocked by policy control, PE2 would in turn advertise MVPN SA routes because of those MSDP SA messages that it receives from PE1, which are redundant and unnecessary. Also notice that the PE1-PE2 MSDP session is VPN- specific, while the BGP sessions over which the MVPN routes are advertised are not. If a PE does advertise MSDP SA messages based on received MVPN SA routes, the VPN-specific MSDP sessions are no longer needed. Additionally, this MVPN/MSDP SA interoperation has the following inherent benefits for a BGP based solution. o MSDP SA refreshes are replaced with BGP hard state. o Route Reflectors can be used instead of having peer-to-peer sessions. o BGP route propagation/selection rules remove the need for RPF checking required by MSDP. o VPN extranet mechanisms can be used to propagate (C-S,C-G) information across VPNs with flexible policy control. While MSDP Source Active routes contain the source, group and RP address of a given multicast flow, MVPN Source Active routes only contain the source and group. MSDP requires the RP address information in order to perform peer-RPF. Therefore, this document describes how to convey the RP address information into the MVPN Source Active route using an Extended Community so this information can be shared with an existing MSDP infrastructure. Zhang & Giuliano Expires March 31, 2018 [Page 3] Internet-Draft mvpn-sa-msdp September 2017 2.1. MVPN RPT-SPT Mode For comparison, another method of supporting customer ASM is generally referred to "rpt-spt" mode. Section "13. Switching from a Shared C-Tree to a Source C-Tree" of [RFC6514] specifies the MVPN SA procedures for that mode, but those SA routes are replacement for PIM-ASM assert and (s,g,rpt) prune mechanisms, not for source discovery purpose. MVPN/MSDP SA interoperation for the "rpt-spt" mode is outside of the scope of this document. In the rest of the document, the "spt-only" mode is assumed. 3. Specification When an MVPN PE advertises an MVPN SA route, it SHOULD attach an "MVPN SA RP-address Extended Community". This is a Transitive IPv4- Address-Specific Extended Community. The Local Administrative field is set to zero and the Global Administrative field is set to an RP address determined as the following: o If the (C-S,C-G) is learnt as result of PIM Register mechanism, the local RP address in the VRF is used. o If the (C-S,C-G) is learnt as result of incoming MSDP SA messages, the RP address in the selected MSDP SA message is used. If an MVPN PE has one or more MSDP sessions and receives an MVPN SA route that is selected as the best MVPN SA route for a given (C-S,C-G), the PE generates an MSDP SA and transmits it to those MSDP peers. The Global Administrative field in the MVPN SA RP-address EC of the MVPN SA route is used to populate the RP address of the MSDP SA. If the MVPN SA route does not have the EC, the local RP address of the VRF is be used to populate the RP address field of the MSDP SA. If an MVPN PE receives the withdraw of an MVPN SA route, a new best MVPN SA route for the (C-S,C-G) may be selected. A new MSDP SA message is advertised if the RP address determined according to the newly selected best MVPN SA route is different from before. If there is no MVPN SA route left for the (C-S,C-G), the previously advertised MSDP SA message will not be refreshed and will eventually time out. 4. IANA Considerations This document introduces a new Transitive IPv4 Address Specific Extended Community "MVPN SA RP-address Extended Community". An IANA request is submitted for a subcode of 0x20 (pending approval and subject to change) in the Transitive IPv4-Address-Specific Extended Community Sub-Types registry. Zhang & Giuliano Expires March 31, 2018 [Page 4] Internet-Draft mvpn-sa-msdp September 2017 5. Acknowledgements The authors Eric Rosen for his review, comments, questions and suggestions for this document. The authors also thank Yajun Liu for her review and comments. 6. 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, . [RFC3618] Fenner, B., Ed. and D. Meyer, Ed., "Multicast Source Discovery Protocol (MSDP)", RFC 3618, DOI 10.17487/RFC3618, October 2003, . [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, . Authors' Addresses Zhaohui Zhang Juniper Networks EMail: zzhang@juniper.net Lenny Giuliano Juniper Networks EMail: lenny@juniper.net Zhang & Giuliano Expires March 31, 2018 [Page 5]