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Giuliano 4 Intended status: Standards Track Juniper Networks 5 Expires: March 31, 2018 September 27, 2017 7 MVPN and MSDP SA Interoperation 8 draft-zzhang-bess-mvpn-msdp-sa-interoperation-00 10 Abstract 12 This document specifies the procedures for interoperation between 13 MVPN Source Active routes and customer MSDP Source Active routes, 14 which is useful for MVPN provider networks offering services to 15 customers with an existing MSDP infrastructure. Without the 16 procedures described in this document, VPN-specific MSDP sessions are 17 required among the PEs that are customer MSDP peers. 19 Requirements Language 21 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 22 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 23 document are to be interpreted as described in RFC2119. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at https://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on March 31, 2018. 42 Copyright Notice 44 Copyright (c) 2017 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (https://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 2 60 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 2.1. MVPN RPT-SPT Mode . . . . . . . . . . . . . . . . . . . . 4 62 3. Specification . . . . . . . . . . . . . . . . . . . . . . . . 4 63 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 64 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 65 6. Normative References . . . . . . . . . . . . . . . . . . . . 5 66 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 68 1. Terminologies 70 Familiarity with MVPN and MSDP protocols and procedures is assumed. 71 Some terminologies are listed below for convenience. 73 o ASM: Any source multicast. 75 o SPT: Source-specific Shortest-path Tree. 77 o C-S: A multicast source address, identifying a multicast source 78 located at a VPN customer site. 80 o C-G: A multicast group address used by a VPN customer. 82 o C-RP: A multicast Rendezvous Point for a VPN customer. 84 o EC: Extended Community. 86 2. Introduction 88 Section "14. Supporting PIM-SM without Inter-Site Shared C-Trees" of 89 [RFC6514] specifies the procedures for MVPN PEs to discover (C-S,C-G) 90 via MVPN Source Active A-D routes and then send (C-S,C-G) C-multicast 91 routes towards the ingress PEs, to establish SPTs for customer ASM 92 flows for which they have downstream receivers. (C-*,C-G) 93 C-multicast routes are not sent among the PEs so inter-site shared 94 C-Trees are not used and the method is generally referred to as "spt- 95 only" mode. 97 With this mode, the MVPN Source Active routes are functionally 98 similar MSDP Source-Active messages [RFC3618]. One or more of the 99 PEs, say PE1, either act as a C-RP and learn of (C-S,C-G) via PIM 100 Register messages, or have MSDP sessions with some MSDP peers and 101 learn (C-S,C-G) via MSDP SA messages. In either case, PE1 will then 102 originate MVPN SA routes for other PEs to learn the (C-S,C-G). 104 [RFC6514] only specifies that a PE receiving the MVPN SA routes, say 105 PE2, will advertise (C-S,C-G) C-multicast routes if it has 106 corresponding (C-*,C-G) state learnt from its CE. PE2 may also have 107 MSDP sessions with other C-RPs at its site, but [RFC6514] does not 108 specify that it advertise MSDP SA messages to those MSDP peers for 109 the (C-S,C-G) that it learns via MVPN SA routes. PE2 would need to 110 have an MSDP session with PE1 (that advertised the MVPN SA messages) 111 to learn the sources via MSDP SA messages, for it to advertise the 112 MSDP SA to its local peers. To make things worse, unless blocked by 113 policy control, PE2 would in turn advertise MVPN SA routes because of 114 those MSDP SA messages that it receives from PE1, which are redundant 115 and unnecessary. Also notice that the PE1-PE2 MSDP session is VPN- 116 specific, while the BGP sessions over which the MVPN routes are 117 advertised are not. 119 If a PE does advertise MSDP SA messages based on received MVPN SA 120 routes, the VPN-specific MSDP sessions are no longer needed. 121 Additionally, this MVPN/MSDP SA interoperation has the following 122 inherent benefits for a BGP based solution. 124 o MSDP SA refreshes are replaced with BGP hard state. 126 o Route Reflectors can be used instead of having peer-to-peer 127 sessions. 129 o BGP route propagation/selection rules remove the need for RPF 130 checking required by MSDP. 132 o VPN extranet mechanisms can be used to propagate (C-S,C-G) 133 information across VPNs with flexible policy control. 135 While MSDP Source Active routes contain the source, group and RP 136 address of a given multicast flow, MVPN Source Active routes only 137 contain the source and group. MSDP requires the RP address 138 information in order to perform peer-RPF. Therefore, this document 139 describes how to convey the RP address information into the MVPN 140 Source Active route using an Extended Community so this information 141 can be shared with an existing MSDP infrastructure. 143 2.1. MVPN RPT-SPT Mode 145 For comparison, another method of supporting customer ASM is 146 generally referred to "rpt-spt" mode. Section "13. Switching from a 147 Shared C-Tree to a Source C-Tree" of [RFC6514] specifies the MVPN SA 148 procedures for that mode, but those SA routes are replacement for 149 PIM-ASM assert and (s,g,rpt) prune mechanisms, not for source 150 discovery purpose. MVPN/MSDP SA interoperation for the "rpt-spt" 151 mode is outside of the scope of this document. In the rest of the 152 document, the "spt-only" mode is assumed. 154 3. Specification 156 When an MVPN PE advertises an MVPN SA route, it SHOULD attach an 157 "MVPN SA RP-address Extended Community". This is a Transitive IPv4- 158 Address-Specific Extended Community. The Local Administrative field 159 is set to zero and the Global Administrative field is set to an RP 160 address determined as the following: 162 o If the (C-S,C-G) is learnt as result of PIM Register mechanism, 163 the local RP address in the VRF is used. 165 o If the (C-S,C-G) is learnt as result of incoming MSDP SA messages, 166 the RP address in the selected MSDP SA message is used. 168 If an MVPN PE has one or more MSDP sessions and receives an MVPN SA 169 route that is selected as the best MVPN SA route for a given 170 (C-S,C-G), the PE generates an MSDP SA and transmits it to those MSDP 171 peers. The Global Administrative field in the MVPN SA RP-address EC 172 of the MVPN SA route is used to populate the RP address of the MSDP 173 SA. If the MVPN SA route does not have the EC, the local RP address 174 of the VRF is be used to populate the RP address field of the MSDP 175 SA. 177 If an MVPN PE receives the withdraw of an MVPN SA route, a new best 178 MVPN SA route for the (C-S,C-G) may be selected. A new MSDP SA 179 message is advertised if the RP address determined according to the 180 newly selected best MVPN SA route is different from before. If there 181 is no MVPN SA route left for the (C-S,C-G), the previously advertised 182 MSDP SA message will not be refreshed and will eventually time out. 184 4. IANA Considerations 186 This document introduces a new Transitive IPv4 Address Specific 187 Extended Community "MVPN SA RP-address Extended Community". An IANA 188 request is submitted for a subcode of 0x20 (pending approval and 189 subject to change) in the Transitive IPv4-Address-Specific Extended 190 Community Sub-Types registry. 192 5. Acknowledgements 194 The authors Eric Rosen for his review, comments, questions and 195 suggestions for this document. The authors also thank Yajun Liu for 196 her review and comments. 198 6. Normative References 200 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 201 Requirement Levels", BCP 14, RFC 2119, 202 DOI 10.17487/RFC2119, March 1997, 203 . 205 [RFC3618] Fenner, B., Ed. and D. Meyer, Ed., "Multicast Source 206 Discovery Protocol (MSDP)", RFC 3618, 207 DOI 10.17487/RFC3618, October 2003, 208 . 210 [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP 211 Encodings and Procedures for Multicast in MPLS/BGP IP 212 VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, 213 . 215 Authors' Addresses 217 Zhaohui Zhang 218 Juniper Networks 220 EMail: zzhang@juniper.net 222 Lenny Giuliano 223 Juniper Networks 225 EMail: lenny@juniper.net