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Venaas 5 Expires: November 2, 2018 Cisco Systems 6 May 1, 2018 8 Use of PIM Address List Hello across address families 9 draft-ietf-pim-ipv4-prefix-over-ipv6-nh-02.txt 11 Abstract 13 In the PIM Sparse Mode standard there is an Address List Hello option 14 used to list secondary addresses of an interface. Usually the 15 addresses would be of the same address family as the primary address. 16 In this document we provide a use case for listing secondary 17 addresses that are from a different family. In particular, Multi- 18 Protocol BGP (MP-BGP) has support for distributing next-hop 19 information for multiple address families using one AFI/SAFI Network 20 Layer Reachability Information (NLRI). When using this combined with 21 PIM, the Address List Hello option can be used to determine which PIM 22 neighbor to use as RPF neighbor. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at https://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on November 2, 2018. 41 Copyright Notice 43 Copyright (c) 2018 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (https://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 This document may contain material from IETF Documents or IETF 57 Contributions published or made publicly available before November 58 10, 2008. The person(s) controlling the copyright in some of this 59 material may not have granted the IETF Trust the right to allow 60 modifications of such material outside the IETF Standards Process. 61 Without obtaining an adequate license from the person(s) controlling 62 the copyright in such materials, this document may not be modified 63 outside the IETF Standards Process, and derivative works of it may 64 not be created outside the IETF Standards Process, except to format 65 it for publication as an RFC or to translate it into languages other 66 than English. 68 Table of Contents 70 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 71 2. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 4 72 3. Security Considerations . . . . . . . . . . . . . . . . . . . 4 73 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 74 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 75 5.1. Normative References . . . . . . . . . . . . . . . . . . 4 76 5.2. Informative References . . . . . . . . . . . . . . . . . 4 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 79 1. Introduction 81 The PIM Sparse Mode standard [RFC7761] defines an Address List Hello 82 option used to list secondary addresses of an interface. It 83 specifies that the addresses listed SHOULD be of the same address 84 family as the primary address. It was not anticipated that it could 85 be useful to list addresses of a different address family. This 86 document describes a use-case for listing different address families. 88 While use of MP-BGP along with [RFC5549] enables one routing protocol 89 session to exchange next-hop info for both IPv4 and IPv6 prefixes, 90 forwarding plane needs additional procedures to enable forwarding in 91 data-plane. For example, when a IPv4 prefix is learnt over IPv6 92 next-hop, forwarding plane resolves the MAC-Address (L2-Adjacency) 93 for IPv6 next-hop and uses it as destination-mac while doing inter- 94 subnet forwarding. While it's simple to find the required 95 information for unicast forwarding, multicast forwarding in same 96 scenario poses additional requirements. 98 Multicast traffic is forwarding on a tree build by multicast routing 99 protocols such as PIM. Multicast routing protocols are address 100 family dependent and hence a system enabled with IPv4 and IPv6 101 multicast routing will have two PIM sessions one for each of the AF. 102 Also, Multicast routing protocol uses Unicast reachability 103 information to find unique Reverse Path Forwarding Neighbor. Further 104 it sends control messages such as PIM Join to form the tree. Now 105 when a PIMv4 session needs to initiate new multicast tree in event of 106 discovering new receiver It consults Unicast control plane to find 107 next-hop information. While this multicast tree can be Shared or 108 Shortest Path tree, PIMv4 will need a PIMv4 neighbor to send join. 109 However, the Unicast control plane can provide IPv6 next-hop as 110 explained earlier and hence we need certain procedures to find 111 corresponding PIMv4 neighbor address. This address is vital for 112 correct prorogation of join and furthermore to build multicast tree. 113 This document describes various approaches along with their use-cases 114 and pros-cons. 116 Figure 1: Example Topology 118 +-------------+ +-------------+ 119 | | | | 120 | Router1 1::1/64 1::2/64 Router2 | 121 10.1.1.1/32--+ +--------I1---------| +-+PIM receiver 122 | 1.1.1.1/24 1.1.1.2/24 | 123 | + + | 124 | | | | 125 +-------------+ +-------------+ 127 In example topology, Router1 and Router2 are PIMv4 and PIMv6 128 neighbors on Interface I1. Router2 learns prefix 10.1.1.1/32's next- 129 hop as 1::1/64 on Interface I1 as advertised by Router1 using BGP 130 IPV6 NLRI.But in order to send (10.1.1.1/32, multicast-group) PIMv4 131 join on Interface I1, Router2 needs to find corresponding PIMv4 132 neighbor. In case there are multiple PIMv4 neighbors on same 133 Interface I1, problem is aggravated. 135 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 136 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 137 document are to be interpreted as described in BCP 14, [RFC2119]. 139 2. Solution 141 A PIM router can advertise its locally configured IPv6 addresses on 142 the interface in PIMv4 Hello messages as per [RFC7761] section 4.3.4. 143 Same applies for IPv4 address in PIMv6 Hello. PIM will keep this 144 info for each neighbor in Neighbor-cache along with DR-priority, 145 hold-time etc. Once IPv6 Next-hop is notified to PIMv4, it will look 146 into neighbors on the notified RPF-interface and find PIMv4 neighbor 147 advertising same IPv6 local address in secondary Neighbor-list. If 148 such a match is found, that particular neighbor will be uses as IPv4 149 RPF-Neighbor for initiating upstream join. 151 This method is valid for networks enabled with PIMv4 and PIMv6 both 152 as well for the networks enabled with only PIMv4 with IPv6 BGP 153 session or PIMv6 with IPv4 BGP session. This method does't required 154 any additional config changes in the network. 156 3. Security Considerations 158 There are no new security considerations. 160 4. IANA Considerations 162 There are no IANA considerations. 164 5. References 166 5.1. Normative References 168 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 169 Requirement Levels", BCP 14, RFC 2119, 170 DOI 10.17487/RFC2119, March 1997, 171 . 173 5.2. Informative References 175 [RFC5549] Le Faucheur, F. and E. Rosen, "Advertising IPv4 Network 176 Layer Reachability Information with an IPv6 Next Hop", 177 RFC 5549, DOI 10.17487/RFC5549, May 2009, 178 . 180 [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., 181 Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent 182 Multicast - Sparse Mode (PIM-SM): Protocol Specification 183 (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March 184 2016, . 186 Authors' Addresses 188 Ashutosh Gupta 189 Avi Networks 190 5155 Old Ironsides Dr. Suite 100 191 Santa Clara, CA 95054 192 USA 194 Email: ashutosh@avinetworks.com 196 Stig Venaas 197 Cisco Systems 198 821 Alder Drive 199 San Jose, CA 95035 200 USA 202 Email: stig@cisco.com