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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 mpls Z. Zhang 3 Internet-Draft A. Deshmukh 4 Intended status: Standards Track R. Singh 5 Expires: January 3, 2019 Juniper Networks 6 July 2, 2018 8 RSVP-TE P2MP Tunnels on RMR 9 draft-zzhang-mpls-rmr-rsvp-p2mp-00 11 Abstract 13 This document specifies the optimization in RSVP-TE P2MP tunnel 14 signaling over Resilient MPLS Rings (RMR). 16 Requirements Language 18 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 19 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 20 document are to be interpreted as described in RFC2119. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on January 3, 2019. 39 Copyright Notice 41 Copyright (c) 2018 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2. Specification . . . . . . . . . . . . . . . . . . . . . . . . . 4 58 2.1. RMR Object . . . . . . . . . . . . . . . . . . . . . . . . 4 59 2.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 5 60 2.2.1. PATH Message/State . . . . . . . . . . . . . . . . . . 5 61 2.2.2. RESV Message/State . . . . . . . . . . . . . . . . . . 6 62 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 63 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 64 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 65 5.1. Normative References . . . . . . . . . . . . . . . . . . . 6 66 5.2. Informative References . . . . . . . . . . . . . . . . . . 6 68 1. Introduction 70 Traditional RSVP-TE P2MP tunnel signaling could be quite involving. 71 With RMR, this could be significantly simplifed: 73 There is no need for ERO/RRO/SERO/SRRO or hop by hop rouing. The 74 tunnel ingress simply sends PATH messages in one or both directions 75 of the ring, depending on how leaves are best reached. The only needs to list the tunnel leaves, and a 77 transit router does not need to "branch" a PATH message into multiple 78 ones Therefore, unless there are many tunnel leaves on a huge ring, a 79 single PATH message is enough. In the rare situation of a large 80 tunnel with many leaves to list, a small number of PATH messages 81 should suffice. Additionally, there is no need to signal and 82 maintain individual sub-LSPs (one for each leaf) any more. As a 83 result, corresponding PATH/RESV state is also reduced. Each node 84 only needs to maintain a single PATH state and a single RESV state 85 for each P2MP tunnel, and the RESV state does not need to track 86 individual leaves - it just need to track if a RESV is received from 87 downstream and/or if this node itself is a leaf. 89 A RESV message is triggered to the PHOP when the RESV state is first 90 created (either because the node is a leaf or because a RESV message 91 is received from downstream) and it is refreshed periodically. A 92 RESV Tear is sent when the RESV state is deleted (when the node is no 93 longer a Leaf and the RESV from downstream has timed out or a RESV 94 Tear is received). 96 Optionally, the tunnel ingress may not need to list any/all leaves. 97 It could simply send the PATH message around the ring, with the listing the root itself. Through methods 99 outside the scope of this document, a node determines if it is a leaf 100 of the tunnel, and if yes, it will send back a RESV message. With 101 this, a single PATH message is surely enough. 103 In this document, leaves in are 104 referred to as explicit leaves, and leaves not listed there but self- 105 determined by ring nodes are referred to as implicit leaves. There 106 could be both explicit and implicit leaves for a tunnel. The ingress 107 allows implicit leaves by including itself as the last one in the 108 . 110 Optionally, the RESV message could also include a to list all the leaves on the established tunnel so 112 that the each node knows its downstream leaves. In that case, when 113 the set of downstream leaves changes, a RESV message with the new 114 is triggered. 116 Adding/removing explicit leaves is straighforward. The ingress 117 simply sends a triggered PATH message with new . As it passes around the ring, each node determines 119 if it is an explicit leaf and updates its state accordingly. The 120 triggered PATH message does not have to go all the way to the last 121 leaf - if on a node the in the to-be- 122 sent PATH message is the same as what was sent before, the triggered 123 PATH message will not be sent further. 125 To indicate that the tunnel signaling is with above mentioned RMR 126 optimizations, a new object is included in the PATH message to 127 specify the Ring ID and direction. 129 Link/Node protection is achieved by tunneling packets to the next 130 node using the Ring LSP to that node in the other direction. This 131 does not need any additional signaling but is based on a reasonable 132 premise that unicast Ring LSPs are always in place. Once the ingress 133 learns the failure (through IGP discovery or through other error 134 detection/notification mechanisms), global repair kicks in to reach 135 some leaves via PATH message sent in the other direction. Before 136 global repair is finished, traffic continues to flow in the original 137 path except that at the failure point it is tunneled to the next 138 node. 140 If an RMR is just part of a general RSVP network the optimization can 141 also be applied on the ring nodes. If the tunnel ingress knows the 142 leaves that are on the ring, it could put all those leaves in the 143 single PATH message and construct the ERO/SERO only towards the entry 144 points on the ring. The entry points then includes the RMR object in 145 the PATH messages that they send. For leaves beyond the ring, the 146 ingress may include the exit points on the ring as loose hops in the 147 ERO/SERO, and when a ring node needs to send the PATH message off the 148 ring, it removes the RMR object. Details will be provided in future 149 revisions of this document. 151 2. Specification 153 2.1. RMR Object 155 The RMR object is a new object of the following: 157 o Class Name: RMR 159 o Class-Num: TBA1 (to be assigned by IANA) 161 o C-Type: TBA2 (to be assigned by IANA) 163 The format of the object content following the common object header 164 is the folowing: 166 0 1 2 3 167 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 1 168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 169 | Ring ID (4 octets) | 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 171 |D| Flags | Reserved | 172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 174 Following the 4-octect Ring ID, there is an 8-bit Flags field. The 175 first bit of the Flags field indicates the direction. If it is set, 176 it is clockwise direction. Otherwise, it is anti-clockwise. 178 2.2. Procedures 180 This section describes the differces in the procedures for ring nodes 181 to set up RSVP-TE P2MP tunnels across the ring, compared to the 182 conventional non-RMR-aware case. For now it is assumed that all 183 nodes (ingress, tranist, and leaves) on the tunnel are on the ring. 185 More details will be provided in future revisions. 187 2.2.1. PATH Message/State 189 The tunnel ingress includes the RMR object with the Ring ID and the 190 direction flag bit set accordingly. The explicit tunnel leaves are 191 encoded in the , and no ERO/SERO is 192 included. If the tunnel allows implicit leaves, the descriptor list 193 encodes the ingress itself as the last element. The message is sent 194 to the next node on the ring in the direction specified in the RMR 195 object, w/o using ERO/SERO or hop-by-hop routing. 197 When a node recevies a PATH message with the RMR object, it checks if 198 itself is listed in the , or if the encodes the tunnel ingress as the last 200 element and this node itself is an implicit leaf. If yes, it creates 201 corresponding RESV state and sends a RESV message to the PHOP. 203 The receiving node removes itself from the in the PATH message, and saves the list locally. The PATH 205 message is sent to the next node on the ring in the specified 206 direction if one of the following conditions is met: 208 o The encodes the tunnel ingress 209 itself as the last element. 211 o The is not empty and either the PATH 212 state is newly created or the is 213 different from the previously saved one. 215 If is empty and different from the 216 previously saved one, a PATH Teardown is sent instead with the saved 217 . 219 2.2.2. RESV Message/State 221 A ring node may know that it is a leaf when the PATH message is first 222 processed as described in the previous section. In case of implicit 223 leaves, it may become a leaf after the PATH messages has been 224 processed. A non-leaf node may also receive a RESV message from its 225 NHOP. In all cases, the node creates RESV state and sends a RESV 226 message to the PHOP, w/o encoding RRO/SRRO. 228 If a ring node was a leaf but stops being a leaf, either because it 229 is no longer listed in the or it is no 230 longer an implicit leaf, it removes/updates corresponding local 231 state. A RESV Teardown is sent to the PHOP if there is no RESV 232 received from its downstream. 234 3. Security Considerations 236 This document does not introduce new security risks? 238 4. Acknowledgements 240 5. References 242 5.1. Normative References 244 [I-D.ietf-mpls-rmr] Kompella, K. and L. Contreras, "Resilient MPLS 245 Rings", draft-ietf-mpls-rmr-04 (work in 246 progress), March 2017. 248 5.2. Informative References 250 Authors' Addresses 252 Zhaohui Zhang 253 Juniper Networks 255 EMail: zzhang@juniper.net 256 Abhishek Deshmukh 257 Juniper Networks 259 EMail: adeshmukh@juniper.net 261 Ravi Singh 262 Juniper Networks 264 EMail: ravis@juniper.net