idnits 2.17.1 draft-zzhang-bess-mvpn-regional-segmentation-01.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack a both a reference to RFC 2119 and the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords. RFC 2119 keyword, line 144: '... MAY be defined as a BGP neighbor gr...' RFC 2119 keyword, line 193: '... ingress PE MUST also attach a Route...' RFC 2119 keyword, line 194: '...d the local RBRs MUST be provisioned t...' RFC 2119 keyword, line 197: '... The local RBRs MUST remove the RT-RB...' RFC 2119 keyword, line 208: '...d limitation, it SHOULD request an add...' (4 more instances...) -- The abstract seems to indicate that this document updates RFC7524, but the header doesn't have an 'Updates:' line to match this. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (October 25, 2021) is 913 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-12) exists of draft-ietf-bess-bgp-multicast-controller-07 == Outdated reference: A later version (-04) exists of draft-zzhang-idr-rt-derived-community-01 == Outdated reference: A later version (-14) exists of draft-ietf-bess-evpn-bum-procedure-updates-11 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 routing Z. Zhang 3 Internet-Draft Juniper Networks 4 Intended status: Standards Track October 25, 2021 5 Expires: April 28, 2022 7 MVPN Inter/Intra-region Tunnel Segmentation 8 draft-zzhang-bess-mvpn-regional-segmentation-01 10 Abstract 12 RFC7524 specifies procedures for Inter-Area Point-to-Multipoint 13 Segmented Label Switched Paths (aka MVPN tunnel segmentation). This 14 document updates RFC7524 by extending the inter-area segmentation 15 concept to inter-region and intra-region segmentation where a region 16 is no longer tied to an IGP area. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at https://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on April 28, 2022. 35 Copyright Notice 37 Copyright (c) 2021 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (https://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 1.1. Tunnel Segmentation . . . . . . . . . . . . . . . . . . . 2 54 1.2. Intra-region Segmentation . . . . . . . . . . . . . . . . 3 55 1.3. Bud Node Support . . . . . . . . . . . . . . . . . . . . 3 56 2. Specifications . . . . . . . . . . . . . . . . . . . . . . . 3 57 2.1. Inter-region Segmentation . . . . . . . . . . . . . . . . 3 58 2.2. Intra-region Segmentation . . . . . . . . . . . . . . . . 4 59 2.3. Bud Node Support . . . . . . . . . . . . . . . . . . . . 5 60 3. Security Considerations . . . . . . . . . . . . . . . . . . . 6 61 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 62 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 63 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 64 6.1. Normative References . . . . . . . . . . . . . . . . . . 6 65 6.2. Informative References . . . . . . . . . . . . . . . . . 7 66 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 68 1. Introduction 70 1.1. Tunnel Segmentation 72 [RFC6514] specifies (among other things) inter-AS MVPN tunnel 73 segmentation procedures and [RFC7524] specifies inter-area MVPN 74 tunnel segmentation procedures. The procedures for inter-AS and 75 inter-area are similar in that the segmentation points - ASBRs or 76 ABRs - change the PMSI Tunnel Attribute (PTA) attached to I/S-PMSI 77 routes to specify the type and identification of tunnel to be used in 78 the next AS/area, when they re-advertise the PMSI routes into the 79 next AS/area. 81 This change of tunnel at the segmentation points and stitching of 82 upstream and downstream tunnel segments not only allows different 83 tunnel technology/instance to be used in different AS/area, but also 84 limits the replication of traffic to only PEs and segmentation points 85 in the local AS/area, instead of to all PEs. 87 The inter-area segmentation points are route reflectors and when they 88 re-advertise the x-PMSI routes to different downstream areas they may 89 use different BGP neighbor groups so that different tunnel type/ 90 identification can be encoded in PTA for different downstream areas. 91 If the ABR is also responsible for reflecting the routes to PEs in 92 the same area, the ABR does not modify the PTA (because of that those 93 local PEs are also put into a different neighbor group). 95 As a result, a segmentation point will likely have different neighbor 96 groups (one group for each area) so that the PTA and Inter-Area P2MP 97 Segmented Next-Hop Extended Community (referred to as Segmentation 98 EC) can be set accordingly when it re-advertise the x-PMSI routes. 100 The provisioning of a RR with these different neighbor groups for 101 segmentation purpose can actually be done on any router (as a 102 segmentation point) - not necessarily on an ABR. As a result, the 103 procedures in RFC7524, while specified for inter-area, can be 104 extended inter-regiona as well - the segmentation points can be any 105 border routers between arbitrarily defined "regions". 107 This concept is already described in Section 6 of 108 [I-D.ietf-bess-evpn-bum-procedure-updates], but specified formally in 109 this document for MVPN. 111 1.2. Intra-region Segmentation 113 Even with the inter-area segmentation extended to inter-region, when 114 a regional border router (RBR) reflects routes to PEs in the same 115 region, it does not modify the PTA or Segmentation EC. But if the 116 RBR also modifies the two attributes when reflecting routes to the 117 local PEs, tunnel segmentation is achieved even intra-region - both 118 the upstream and downstream tunnel segments are in the same region. 120 This Intra-region Segmentation is one way to achieve Assisted 121 Replication in MVPN: a PE sends traffic to assisting replicators who 122 will then relay traffic to other PEs (even in the same region). 124 1.3. Bud Node Support 126 A segmentation point may have both local receivers off a VRF and 127 downstream receivers off a remote PE for traffic arriving on an 128 upstream segment. This segmentation point is referred to a bud node, 129 just like that a node can be both a transit and leaf node for a P2MP 130 tree. 132 Depending on implementation, a bud node may need to receive two 133 copies of a packet, one for local delivery and one for remote 134 delivery. If so, the bud node may request the upstream PE or 135 segmentation point to send two copies. 137 2. Specifications 139 2.1. Inter-region Segmentation 141 The procedures in RFC7524 are extended to beyond IGP area-based. A 142 provider network can be arranged into "regions" connected by 143 "Regional Border Routers" (RBRs). On a segmentation point a region 144 MAY be defined as a BGP neighbor group - all peers in the group are 145 subject to the same export policy, which can be used to control the 146 modification of attributes for the purpose of segmentation. 148 RFC7524 procedures apply as is, though "area" is replaced with 149 "region" and "Area Border Router" (ABR) is replaced with "Regional 150 Border Router" (RBR). 152 The concept of Per-region Aggregation, as explained in Section 6.1 of 153 [I-D.ietf-bess-evpn-bum-procedure-updates], is also applicable to 154 MVPN. A future revision of this document will specify details of 155 Per-region Aggregation for MVPN. 157 2.2. Intra-region Segmentation 159 The following procedures are applicable for intra-region 160 segmentation. One use of intra-region segmentation is for Assisted 161 Replication where PE-PE traffic goes through a relay point (assisting 162 replicator). 164 If it is known that the local PEs are only peered with the RBRs (as 165 RRs and segmentation points), the PEs and RBRs follow the procedures 166 in RFC7524. In addition, the local RBRs modify the PTA and 167 Segmentation EC even when they re-advertise x-PMSI routes to PEs in 168 the ingress region, thus achieving Intra-region Segmentation. 170 Otherwise (i.e., if a local PE may import BGP-MVPN routes directly 171 unless with the modified procedures specified below), the following 172 modified procedures apply: 174 o When an ingress PE advertises an x-PMSI route, it attaches an 175 Extended Community (EC) derived from the Route Target for the VPN 176 (RT-VPN) [I-D.zzhang-idr-rt-derived-community] but not the RT-VPN 177 itself. Call this EC as EC-VPN. The route also carry a 178 Segmentation EC as specified in RFC7524. 180 o When the local RBRs (as RRs and segmentation points) receive this 181 route, it replaces the EC-VPN with the corresponding RT-VPN (the 182 EC-VPN and RT-VPN can be derived from each other), and then re- 183 advertise the route to its peers, with the Segmentation EC and PTA 184 modified as specified in RFC7524. The modification applies even 185 when re-advertising to peers in the same ingress region. 187 This is to ensure that local egress PEs will only import the routes 188 re-advertised by the RBRs after the modification of PTA and 189 Segmentation EC. 191 Additionally, if there are intermediate RRs between the ingress PE 192 and local RBRs, and Route Target Constrain [RFC4684] is in use, the 193 ingress PE MUST also attach a Route Target (referred to as RT-RBR) 194 and the local RBRs MUST be provisioned to import routes with RT-RBR 195 (otherwise the intermediate RRs will not re-advertise the routes 196 towards the RBRs because the routes carry only EC-VPN but not RT- 197 VPN). The local RBRs MUST remove the RT-RBR when they re-advertise 198 the routes. 200 2.3. Bud Node Support 202 This section applies only if the segmentation point can not both 203 route traffic arriving on the upstream segment to local receivers and 204 label switch the traffic to downstream segments due to implementation 205 limitation. 207 If a segmentation point is a bud node for a segmented x-PMSI tunnel 208 with the above mentioned limitation, it SHOULD request an additional 209 copy to be sent by the upstream RSVP neighbor if the upstream segment 210 is a RSVP-TE P2MP tunnel, or by the upstream PE/RBR when the upstream 211 segment is an IR or mLDP tunnel. 213 The RSVP-TE P2MP case is outside the scope of this document (though 214 there are known implementations). For the IR/mLDP case, it is done 215 by including a Tunnel Encapsulation Attribute (TEA) [RFC9012] in the 216 Leaf A-D route in response to the x-PMSI route for the upstream 217 segment. Note that the leaf A-D route is sent for this purpose even 218 if the Leaf Information Required (LIR) flag is not set in the x-PMSI 219 route (e.g. for mLDP tunnel). 221 The TEA includes one tunnel of a desired type (e.g. MPLS or Any 222 Encapsulation [I-D.ietf-bess-bgp-multicast-controller]) that is used 223 for the upstream PE/RBR to send the additional copy to this bud node. 224 The tunnel MUST include a Tunnel Egress Endpoint sub-TLV set to a 225 loal address on the bud node, and MUST include a Tree Label Stack 226 sub-TLV that includes a single label. The node MUST program a label 227 forwarding entry to pop the label and forward packet based on IP 228 lookup in a VRF identified by the label (while the tunnel label for 229 the upstream segment or the label in the PTA of the x-PMSI/Leaf route 230 for the upstream segment is used to stitch the upstream and 231 downstream segments together). 233 When the upstream PE/RBR decodes the TEA in the Leaf A-D route in 234 response to an x-PMSI A-D route that it (re-)advertises (even if it 235 did set the LIR flag in the x-PMSI A-D route), it SHOULD send an 236 extra copy via unicast tunneling with the label encoded in the Tree 237 Label Stack sub-TLV. If the extra copy is not sent the downstream 238 bud node segmentation point will not be able to send traffic to its 239 local receivers. 241 3. Security Considerations 243 No additional security considerations are needed beyond what are 244 discussed in RFC7524. 246 4. IANA Considerations 248 This document requests the IANA to create a "PMSI Tunnel Attribute 249 Extension sub-TLV Type Registry". Allocation from the registry is 250 First Come First Serve, with an initial allocation for "Additional 251 Label". 253 5. Acknowledgements 255 The author thanks Sanoj Vivekanandan for his review and comments. 257 6. References 259 6.1. Normative References 261 [I-D.ietf-bess-bgp-multicast-controller] 262 Zhang, Z., Raszuk, R., Pacella, D., and A. Gulko, 263 "Controller Based BGP Multicast Signaling", draft-ietf- 264 bess-bgp-multicast-controller-07 (work in progress), July 265 2021. 267 [I-D.zzhang-idr-rt-derived-community] 268 Zhang, Z., "Extended Communities Derived from Route 269 Targets", draft-zzhang-idr-rt-derived-community-01 (work 270 in progress), March 2021. 272 [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP 273 Encodings and Procedures for Multicast in MPLS/BGP IP 274 VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, 275 . 277 [RFC7524] Rekhter, Y., Rosen, E., Aggarwal, R., Morin, T., 278 Grosclaude, I., Leymann, N., and S. Saad, "Inter-Area 279 Point-to-Multipoint (P2MP) Segmented Label Switched Paths 280 (LSPs)", RFC 7524, DOI 10.17487/RFC7524, May 2015, 281 . 283 [RFC9012] Patel, K., Van de Velde, G., Sangli, S., and J. Scudder, 284 "The BGP Tunnel Encapsulation Attribute", RFC 9012, 285 DOI 10.17487/RFC9012, April 2021, 286 . 288 6.2. Informative References 290 [I-D.ietf-bess-evpn-bum-procedure-updates] 291 Zhang, Z., Lin, W., Rabadan, J., Patel, K., and A. 292 Sajassi, "Updates on EVPN BUM Procedures", draft-ietf- 293 bess-evpn-bum-procedure-updates-11 (work in progress), 294 October 2021. 296 [RFC4684] Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk, 297 R., Patel, K., and J. Guichard, "Constrained Route 298 Distribution for Border Gateway Protocol/MultiProtocol 299 Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual 300 Private Networks (VPNs)", RFC 4684, DOI 10.17487/RFC4684, 301 November 2006, . 303 Author's Address 305 Zhaohui Zhang 306 Juniper Networks 308 Email: zzhang@juniper.net