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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DMM Working Group S. Matsushima 3 Internet-Draft SoftBank 4 Intended status: Standards Track C. Filsfils 5 Expires: January 9, 2020 M. Kohno 6 P. Camarillo 7 Cisco Systems, Inc. 8 D. Voyer 9 Bell Canada 10 C. Perkins 11 Futurewei 12 July 8, 2019 14 Segment Routing IPv6 for Mobile User Plane 15 draft-ietf-dmm-srv6-mobile-uplane-05 17 Abstract 19 This document shows the applicability of SRv6 (Segment Routing IPv6) 20 to the user-plane of mobile networks. The network programming nature 21 of SRv6 accomplish mobile user-plane functions in a simple manner. 22 The statelessness of SRv6 and its ability to control both service 23 layer path and underlying transport can be beneficial to the mobile 24 user-plane, providing flexibility, end-to-end network slicing and SLA 25 control for various applications. This document describes the SRv6 26 mobile user plane behavior and defines the SID functions for that. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at http://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on January 9, 2020. 45 Copyright Notice 47 Copyright (c) 2019 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (http://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 63 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3 64 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 65 2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 4 66 2.3. Predefined SRv6 Functions . . . . . . . . . . . . . . . . 4 67 3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 5 68 4. A 3GPP Reference Architecture . . . . . . . . . . . . . . . . 6 69 5. User-plane behaviors . . . . . . . . . . . . . . . . . . . . 7 70 5.1. Traditional mode . . . . . . . . . . . . . . . . . . . . 7 71 5.1.1. Packet flow - Uplink . . . . . . . . . . . . . . . . 8 72 5.1.2. Packet flow - Downlink . . . . . . . . . . . . . . . 8 73 5.1.3. IPv6 user-traffic . . . . . . . . . . . . . . . . . . 9 74 5.2. Enhanced Mode . . . . . . . . . . . . . . . . . . . . . . 9 75 5.2.1. Packet flow - Uplink . . . . . . . . . . . . . . . . 10 76 5.2.2. Packet flow - Downlink . . . . . . . . . . . . . . . 11 77 5.2.3. IPv6 user-traffic . . . . . . . . . . . . . . . . . . 11 78 5.3. Enhanced mode with unchanged gNB GTP behavior . . . . . . 11 79 5.3.1. Interworking with IPv6 GTP . . . . . . . . . . . . . 12 80 5.3.2. Interworking with IPv4 GTP . . . . . . . . . . . . . 15 81 5.3.3. Extensions to the interworking mechanisms . . . . . . 17 82 6. SRv6 SID Mobility Functions . . . . . . . . . . . . . . . . . 18 83 6.1. Args.Mob.Session . . . . . . . . . . . . . . . . . . . . 18 84 6.2. End.MAP . . . . . . . . . . . . . . . . . . . . . . . . . 18 85 6.3. End.M.GTP6.D . . . . . . . . . . . . . . . . . . . . . . 19 86 6.4. End.M.GTP6.E . . . . . . . . . . . . . . . . . . . . . . 19 87 6.5. End.M.GTP4.E . . . . . . . . . . . . . . . . . . . . . . 20 88 6.6. T.M.GTP4.D . . . . . . . . . . . . . . . . . . . . . . . 21 89 6.7. End.Limit: Rate Limiting function . . . . . . . . . . . . 22 90 7. SRv6 supported 3GPP PDU session types . . . . . . . . . . . . 22 91 8. Network Slicing Considerations . . . . . . . . . . . . . . . 23 92 9. Control Plane Considerations . . . . . . . . . . . . . . . . 23 93 10. Security Considerations . . . . . . . . . . . . . . . . . . . 24 94 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 95 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24 96 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24 97 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 98 14.1. Normative References . . . . . . . . . . . . . . . . . . 24 99 14.2. Informative References . . . . . . . . . . . . . . . . . 25 100 Appendix A. Implementations . . . . . . . . . . . . . . . . . . 27 101 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 103 1. Introduction 105 In mobile networks, mobility management systems provide connectivity 106 while mobile nodes move. While the control-plane of the system 107 signals movements of a mobile node, the user-plane establishes a 108 tunnel between the mobile node and its anchor node over IP-based 109 backhaul and core networks. 111 This document shows the applicability of SRv6 (Segment Routing IPv6) 112 to those mobile networks. SRv6 provides source routing to networks 113 so that operators can explicitly indicate a route for the packets to 114 and from the mobile node. SRv6 endpoint nodes serve as the anchors 115 of mobile user-plane. 117 2. Conventions and Terminology 119 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 120 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 121 document are to be interpreted as described in [RFC2119]. 123 2.1. Terminology 125 o AMBR: Aggregate Maximum Bit Rate 126 o APN: Access Point Name (commonly used to identify a network or 127 class of service) 128 o BSID: SR Binding SID [RFC8402] 129 o CNF: Cloud-native Network Function 130 o gNB: gNodeB 131 o NH: The IPv6 next-header field. 132 o NFV: Network Function Virtualization 133 o PDU: Packet Data Unit 134 o Session: TBD... 135 o SID: A Segment Identifier which represents a specific segment in a 136 segment routing domain. 137 o SRH: The Segment Routing Header. 138 [I-D.ietf-6man-segment-routing-header] 139 o TEID: Tunnel Endpoint Identifier 140 o UE: User Equipment 141 o UPF: User Plane Function 142 o VNF: Virtual Network Function 144 2.2. Conventions 146 o NH=SRH means that NH is 43 with routing type 4. 147 o Multiple SRHs may be present inside each packet, but they must 148 follow each other. The next-header field of each SRH, except the 149 last one, must be NH-SRH (43 type 4). 150 o For simplicity, no other extension headers are shown except the 151 SRH. 152 o The SID type used in this document is IPv6 address (also called 153 SRv6 Segment or SRv6 SID). 154 o gNB::1 is an IPv6 address (SID) assigned to the gNB. 155 o U1::1 is an IPv6 address (SID) assigned to UPF1. 156 o U2::1 is an IPv6 address (SID) assigned to UPF2. 157 o U2:: is some other IPv6 address (SID) assigned to UPF2. 158 o A SID list is represented as where S1 is the first 159 SID to visit, S2 is the second SID to visit and S3 is the last SID 160 to visit along the SR path. 161 o (SA,DA) (S3, S2, S1; SL) represents an IPv6 packet with: 163 * IPv6 header with source and destination addresses SA and DA 164 respectively, and next-header SRH, with SID list 165 with SegmentsLeft = SL 166 * The payload of the packet is not represented. 167 o Note the difference between the <> and () symbols: 168 represents a SID list where S1 is the first SID and S3 is the last 169 SID. (S3, S2, S1; SL) represents the same SID list but encoded in 170 the SRH format where the rightmost SID in the SRH is the first SID 171 and the leftmost SID in the SRH is the last SID. When referring 172 to an SR policy in a high-level use-case, it is simpler to use the 173 notation. When referring to an illustration of the 174 detailed behavior, the (S3, S2, S1; SL) notation is more 175 convenient. 176 o SRH[SL] represents the SID pointed by the SL field in the first 177 SRH. In our example, SRH[2] represents S1, SRH[1] represents S2 178 and SRH[0] represents S3. 179 o SRH[SL] can be different from the DA of the IPv6 header. 181 2.3. Predefined SRv6 Functions 183 The following functions are defined in 184 [I-D.ietf-spring-srv6-network-programming]. 186 o End.DT4 means to decapsulate and forward using a specific IPv4 187 table lookup. 189 o End.DT6 means to decapsulate and forward using a specific IPv6 190 table lookup. 191 o End.DX4 means to decapsulate the packet and forward through a 192 particular outgoing interface -or set of OIFs- configured with the 193 SID. 194 o End.DX6 means to decapsulate and forward through a particular 195 outgoing interface -or set of OIFs- configured with the SID. 196 o End.DX2 means to decapsulate the L2 frame and forward through a 197 particular outgoing interface -or set of OIFs- configured with the 198 SID. 199 o End.T means to forward using a specific IPv6 table lookup. 200 o End.X means to forward through a link configured with the SID. 201 o T.Encaps.Red means encapsulation without pushing SRH (resulting in 202 "Reduced" packet size). 203 o PSP means Penultimate Segment Pop. The packet is subsequently 204 forwarded without the popped SRH. 206 New SRv6 functions are defined in Section 6 to support the needs of 207 the mobile user plane. 209 3. Motivation 211 Mobility networks are becoming more challenging to operate. On one 212 hand, traffic is constantly growing, and latency requirements are 213 more strict; on the other-hand, there are new use-cases like NFV that 214 are also challenging network management. 216 The current architecture of mobile networks does not take into 217 account the underlying transport. The user-plane is rigidly 218 fragmented into radio access, core and service networks, connected by 219 tunneling according to user-plane roles such as access and anchor 220 nodes. These factors have made it difficult for the operator to 221 optimize and operate the data-path. 223 In the meantime, applications have shifted to use IPv6, and network 224 operators have started adopting IPv6 as their IP transport. SRv6, 225 the IPv6 dataplane instantiation of Segment Routing [RFC8402], 226 integrates both the application data-path and the underlying 227 transport layer into a single protocol, allowing operators to 228 optimize the network in a simplified manner and removing forwarding 229 state from the network. It is also suitable for virtualized 230 environments, VNF/CNF to VNF/CNF networking. 232 SRv6 specifies network-programming (see 233 [I-D.ietf-spring-srv6-network-programming]). Applied to mobility, 234 SRv6 can provide the user-plane functions needed for mobility 235 management. SRv6 takes advantage of underlying transport awareness 236 and flexibility to improve mobility user-plane functions. 238 The use-cases for SRv6 mobility are discussed in 239 [I-D.camarilloelmalky-springdmm-srv6-mob-usecases]. 241 4. A 3GPP Reference Architecture 243 This section presents a reference architecture and possible 244 deployment scenarios. 246 Figure 1 shows a reference diagram from the 5G packet core 247 architecture [TS.23501]. 249 The user plane described in this document does not depend on any 250 specific architecture. The 5G packet core architecture as shown is 251 based on the latest 3GPP standards at the time of writing this draft. 252 Other architectures can be seen in [I-D.gundavelli-dmm-mfa] and 253 [WHITEPAPER-5G-UP]. 255 +-----+ 256 | AMF | 257 +-----+ 258 / | [N11] 259 [N2] / +-----+ 260 +------/ | SMF | 261 / +-----+ 262 / / \ 263 / / \ [N4] 264 / / \ ________ 265 / / \ / \ 266 +--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \ 267 |UE|------| gNB |------| UPF1 |--------| UPF2 |--------- \ DN / 268 +--+ +-----+ +------+ +------+ \________/ 270 Figure 1: 3GPP 5G Reference Architecture 272 o gNB: gNodeB 273 o UPF1: UPF with Interfaces N3 and N9 274 o UPF2: UPF with Interfaces N9 and N6 275 o SMF: Session Management Function 276 o AMF: Access and Mobility Management Function 277 o DN: Data Network e.g. operator services, Internet access 279 This reference diagram does not depict a UPF that is only connected 280 to N9 interfaces, although the description in this document also work 281 for such UPFs. 283 Each session from an UE gets assigned to a UPF. Sometimes multiple 284 UPFs may be used, providing richer service functions. A UE gets its 285 IP address from the DHCP block of its UPF. The UPF advertises that 286 IP address block toward the Internet, ensuring that return traffic is 287 routed to the right UPF. 289 5. User-plane behaviors 291 This section describes some mobile user-plane behaviors using SRv6. 293 In order to simplify the adoption of SRv6, we present two different 294 "modes" that vary with respect to the use of SRv6. The first one is 295 the "Traditional mode", which inherits the current 3GPP mobile user- 296 plane. In this mode there is no change to mobility networks 297 architecture, except that GTP-U [TS.29281] is replaced by SRv6. 299 The second mode is the "Enhanced mode". In this mode the SR policy 300 contains SIDs for Traffic Engineering and VNFs, which results in 301 effective end-to-end network slices. 303 In both, the Traditional and the Enhanced modes, we assume that the 304 gNB as well as the UPFs are SR-aware (N3, N9 and -potentially- N6 305 interfaces are SRv6). 307 We introduce two mechanisms for interworking with legacy access 308 networks (N3 interface is unmodified). In these document we 309 introduce them applied to the Enhanced mode, although they could be 310 used in combination with the Traditional mode as well. 312 One of these mechanisms is designed to interwork with legacy gNBs 313 using GTP/IPv4. The second method is designed to interwork with 314 legacy gNBs using GTP/IPv6. 316 This document uses SRv6 functions defined in 317 [I-D.ietf-spring-srv6-network-programming] as well as new SRv6 318 functions designed for the mobile user plane. The new SRv6 functions 319 are detailed in Section 6. 321 5.1. Traditional mode 323 In the traditional mode, the existing mobile UPFs remain unchanged 324 except for the use of SRv6 as the data plane instead of GTP-U. There 325 is no impact to the rest of mobile system. 327 In existing 3GPP mobile networks, an UE PDU Session is mapped 1-for-1 328 with a specific GTP tunnel (TEID). This 1-for-1 mapping is mirrored 329 here to replace GTP encapsulation with the SRv6 encapsulation, while 330 not changing anything else. There will be a unique SRv6 SID 331 associated with each UE PDU Session. 333 The traditional mode minimizes the changes required to the mobile 334 system; it is a good starting point for forming a common basis. 336 Our example topology is shown in Figure 2. In traditional mode the 337 gNB and the UPFs are SR-aware. In the descriptions of the uplink and 338 downlink packet flow, A is an IPv6 address of the UE, and Z is an 339 IPv6 address reachable within the Data Network DN. A new SRv6 340 function End.MAP, defined in Section 6.2, is used. 342 ________ 343 SRv6 SRv6 / \ 344 +--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \ 345 |UE|------| gNB |------| UPF1 |--------| UPF2 |--------- \ DN / 346 +--+ +-----+ +------+ +------+ \________/ 347 SRv6 node SRv6 node SRv6 node 349 Figure 2: Traditional mode - example topology 351 5.1.1. Packet flow - Uplink 353 The uplink packet flow is as follows: 355 UE_out : (A,Z) 356 gNB_out : (gNB, U1::1) (A,Z) -> T.Encaps.Red 357 UPF1_out: (gNB, U2::1) (A,Z) -> End.MAP 358 UPF2_out: (A,Z) -> End.DT4 or End.DT6 360 When the UE packet arrives at the gNB, the gNB performs a 361 T.Encaps.Red operation. Since there is only one SID, there is no 362 need to push an SRH. gNB only adds an outer IPv6 header with IPv6 DA 363 U1::1. U1::1 represents an anchoring SID specific for that session 364 at UPF1. gNB obtains the SID U1::1 from the existing control plane 365 (N2 interface). 367 When the packet arrives at UPF1, the SID U1::1 identifies a local 368 End.MAP function. End.MAP replaces U1::1 by U2::1, that belongs to 369 the next UPF (U2). 371 When the packet arrives at UPF2, the SID U2::1 corresponds to an 372 End.DT function. UPF2 decapsulates the packet, performs a lookup in 373 a specific table associated with that mobile network and forwards the 374 packet toward the data network (DN). 376 5.1.2. Packet flow - Downlink 378 The downlink packet flow is as follows: 380 UPF2_in : (Z,A) 381 UPF2_out: (U2::, U1::1) (Z,A) -> T.Encaps.Red 382 UPF1_out: (U2::, gNB::1) (Z,A) -> End.MAP 383 gNB_out : (Z,A) -> End.DX4 or End.DX6 385 When the packet arrives at the UPF2, the UPF2 maps that flow into a 386 UE PDU Session. This UE PDU Session is associated with the segment 387 endpoint . UPF2 performs a T.Encaps.Red operation, 388 encapsulating the packet into a new IPv6 header with no SRH since 389 there is only one SID. 391 Upon packet arrival on UPF1, the SID U1::1 is a local End.MAP 392 function. This function maps the SID to the next anchoring point and 393 replaces U1::1 by gNB::1, that belongs to the next hop. 395 Upon packet arrival on gNB, the SID gNB::1 corresponds to an End.DX4 396 or End.DX6 function. The gNB decapsulates the packet, removing the 397 IPv6 header and all its extensions headers, and forwards the traffic 398 toward the UE. 400 5.1.3. IPv6 user-traffic 402 For IPv6 user-traffic it is RECOMMENDED to perform encapsulation. 403 However based on local policy, a service provider MAY choose to do 404 SRH insertion. The main benefit is a lower overhead(40B less). In 405 such case, the functions used are T.Insert.Red at gNB, End.MAP at 406 UPF1 and End.T at UPF2 on Uplink, T.Insert.Red at UPF2, End.MAP at 407 UPF1 and End.X at gNB on Downlink. 409 5.2. Enhanced Mode 411 Enhanced mode improves scalability, traffic steering and service 412 programming [I-D.xuclad-spring-sr-service-programming], thanks to the 413 use of multiple SIDs, instead of a single SID as done in the 414 Traditional mode. 416 The main difference is that the SR policy MAY include SIDs for 417 traffic engineering and service programming in addition to the UPFs 418 SIDs. 420 The gNB control-plane (N2 interface) is unchanged, specifically a 421 single IPv6 address is given to the gNB. 423 o The gNB MAY resolve the IP address into a SID list using a 424 mechanism like PCEP, DNS-lookup, small augment for LISP control- 425 plane, etc. 427 Note that the SIDs MAY use the arguments Args.Mob.Session if required 428 by the UPFs. 430 Figure 3 shows an Enhanced mode topology. In the Enhanced mode, the 431 gNB and the UPF are SR-aware. The Figure shows two service segments, 432 S1 and C1. S1 represents a VNF in the network, and C1 represents a 433 constraint path on a router requiring Traffic Engineering. S1 and C1 434 belong to the underlay and don't have an N4 interface, so they are 435 not considered UPFs. 437 +----+ SRv6 _______ 438 SRv6 --| C1 |--[N3] / \ 439 +--+ +-----+ [N3] / +----+ \ +------+ [N6] / \ 440 |UE|----| gNB |-- SRv6 / SRv6 --| UPF2 |------\ DN / 441 +--+ +-----+ \ [N3]/ TE +------+ \_______/ 442 SRv6 node \ +----+ / SRv6 node 443 -| S1 |- 444 +----+ 445 SRv6 node 446 CNF 448 Figure 3: Enhanced mode - Example topology 450 5.2.1. Packet flow - Uplink 452 The uplink packet flow is as follows: 454 UE_out : (A,Z) 455 gNB_out : (gNB, S1)(U2::1, C1; SL=2)(A,Z)-> T.Encaps.Red 456 S1_out : (gNB, C1)(U2::1, C1; SL=1 (A,Z) 457 C1_out : (gNB, U2::1)(A,Z) -> PSP 458 UPF2_out: (A,Z) -> End.DT4 or End.DT6 460 UE sends its packet (A,Z) on a specific bearer to its gNB. gNB's 461 control plane associates that session from the UE(A) with the IPv6 462 address B and GTP TEID T. gNB's control plane does a lookup on B to 463 find the related SID list . 465 When gNB transmits the packet, it contains all the segments of the SR 466 policy. The SR policy can include segments for traffic engineering 467 (C1) and for service programming (S1). 469 Nodes S1 and C1 perform their related Endpoint functionality and 470 forward the packet. 472 When the packet arrives at UPF2, the active segment (U2::1) is an 473 End.DT4/6 which performs the decapsulation (removing the IPv6 header 474 with all its extension headers) and forwards toward the data network. 476 5.2.2. Packet flow - Downlink 478 The downlink packet flow is as follows: 480 UPF2_in : (Z,A) -> UPF2 maps the flow w/ 481 SID list 482 UPF2_out: (U2::1, C1)(gNB, S1; SL=2)(Z,A) -> T.Encaps.Red 483 C1_out : (U2::1, S1)(gNB, S1; SL=1)(Z,A) 484 S1_out : (U2::1, gNB)(Z,A) -> PSP 485 gNB_out : (Z,A) -> End.DX4 or End.DX6 487 When the packet arrives at the UPF2, the UPF2 maps that particular 488 flow into a UE PDU Session. This UE PDU Session is associated with 489 the policy . The UPF2 performs a T.Encaps.Red 490 operation, encapsulating the packet into a new IPv6 header with its 491 corresponding SRH. 493 The nodes C1 and S1 perform their related Endpoint processing. 495 Once the packet arrives at the gNB, the IPv6 DA corresponds to an 496 End.DX4 or End.DX6 (depending on the underlying traffic). The gNB 497 decapsulates the packet, removing the IPv6 header and all its 498 extensions headers and forwards the traffic toward the UE. 500 5.2.3. IPv6 user-traffic 502 For IPv6 user-traffic it is RECOMMENDED to perform encapsulation. 503 However based on local policy, a service provider MAY choose to do 504 SRH insertion. The main benefit is a lower overhead. In such case, 505 the functions used are T.Insert.Red at gNB and End.T at UPF2 on 506 Uplink, T.Insert.Red at UPF2 and End.X at gNB on Downlink. 508 5.3. Enhanced mode with unchanged gNB GTP behavior 510 This section describes two mechanisms for interworking with legacy 511 gNBs that still use GTP: one for IPv4, the other for IPv6. 513 In the interworking scenarios as illustrated in Figure 4, gNB does 514 not support SRv6. gNB supports GTP encapsulation over IPv4 or IPv6. 515 To achieve interworking, a SR Gateway (SRGW-UPF1) entity is added. 516 The SRGW maps the GTP traffic into SRv6. 518 The SRGW is not an anchor point, and maintains very little state. 519 For this reason, both IPv4 and IPv6 methods scale to millions of UEs. 521 _______ 522 IP GTP SRv6 / \ 523 +--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \ 524 |UE|------| gNB |------| UPF1 |--------| UPF2 |---------\ DN / 525 +--+ +-----+ +------+ +------+ \_______/ 526 SR Gateway SRv6 node 528 Figure 4: Example topology for interworking 530 5.3.1. Interworking with IPv6 GTP 532 In this interworking mode the gNB uses GTP over IPv6 via the N3 533 interface 535 Key points: 537 o The gNB is unchanged (control-plane or user-plane) and 538 encapsulates into GTP (N3 interface is not modified). 539 o The 5G Control-Plane (N2 interface) is unmodified; one IPv6 540 address is needed (i.e. a BSID at the SRGW). 541 o The SRGW removes GTP, finds the SID list related to DA, and adds 542 SRH with the SID list. 543 o There is no state for the downlink at the SRGW. 544 o There is simple state in the uplink at the SRGW; using Enhanced 545 mode results in fewer SR policies on this node. A SR policy can 546 be shared across UEs. 547 o When a packet from the UE leaves the gNB, it is SR-routed. This 548 simplifies network slicing [I-D.hegdeppsenak-isis-sr-flex-algo]. 549 o In the uplink, the IPv6 DA BSID steers traffic into an SR policy 550 when it arrives at the SRGW-UPF1. 552 An example topology is shown in Figure 5. In this mode the gNB is an 553 unmodified gNB using IPv6/GTP. The UPFs are SR-aware. As before, 554 the SRGW maps IPv6/GTP traffic to SRv6. 556 S1 and C1 are two service segments. S1 represents a VNF in the 557 network, and C1 represents a router configured for Traffic 558 Engineering. 560 +----+ 561 IPv6/GTP -| S1 |- ___ 562 +--+ +-----+ [N3] / +----+ \ / 563 |UE|--| gNB |- SRv6 / SRv6 \ +----+ +------+ [N6] / 564 +--+ +-----+ \ [N9]/ VNF -| C1 |---| UPF2 |------\ DN 565 GTP \ +------+ / +----+ +------+ \___ 566 -| UPF1 |- SRv6 SRv6 567 +------+ TE 568 SR Gateway 570 Figure 5: Enhanced mode with unchanged gNB IPv6/GTP behavior 572 5.3.1.1. Packet flow - Uplink 574 The uplink packet flow is as follows: 576 UE_out : (A,Z) 577 gNB_out : (gNB, B)(GTP: TEID T)(A,Z) -> Interface N3 unmodified 578 (IPv6/GTP) 579 SRGW_out: (SRGW, S1)(U2::1, C1; SL=2)(A,Z) -> B is an End.M.GTP6.D 580 SID at the SRGW 581 S1_out : (SRGW, C1)(U2::1, C1; SL=1)(A,Z) 582 C1_out : (SRGW, U2::1)(A,Z) -> PSP 583 UPF2_out: (A,Z) -> End.DT4 or End.DT6 585 The UE sends a packet destined to Z toward the gNB on a specific 586 bearer for that session. The gNB, which is unmodified, encapsulates 587 the packet into IPv6, UDP and GTP headers. The IPv6 DA B, and the 588 GTP TEID T are the ones received in the N2 interface. 590 The IPv6 address that was signalled over the N2 interface for that UE 591 PDU Session, B, is now the IPv6 DA. B is an SRv6 Binding SID at the 592 SRGW. Hence the packet is routed to the SRGW. 594 When the packet arrives at the SRGW, the SRGW identifies B as an 595 End.M.GTP6.D Binding SID (see Section 6.3). Hence, the SRGW removes 596 the IPv6, UDP and GTP headers, and pushes an IPv6 header with its own 597 SRH containing the SIDs bound to the SR policy associated with this 598 BindingSID. There is one instance of the End.M.GTP6.D SID per PDU 599 type. 601 S1 and C1 perform their related Endpoint functionality and forward 602 the packet. 604 When the packet arrives at UPF2, the active segment is (U2::1) which 605 is bound to End.DT4/6. UPF2 then decapsulates (removing the outer 606 IPv6 header with all its extension headers) and forwards the packet 607 toward the data network. 609 5.3.1.2. Packet flow - Downlink 611 The downlink packet flow is as follows: 613 UPF2_in : (Z,A) -> UPF2 maps the flow with 614 615 UPF2_out: (U2::1, C1)(gNB, SRGW::TEID, S1; SL=3)(Z,A) -> T.Encaps.Red 616 C1_out : (U2::1, S1)(gNB, S1; SL=2)(Z,A) 617 S1_out : (U2::1, SRGW::TEID)(gNB, SRGW::TEID, S1, SL=1)(Z,A) 618 SRGW_out: (SRGW, gNB)(GTP: TEID=T)(Z,A) -> SRGW/96 is End.M.GTP6.E 619 gNB_out : (Z,A) 621 When a packet destined to A arrives at the UPF2, the UPF2 performs a 622 lookup in the table associated to A and finds the SID list . The UPF2 performs a T.Encaps.Red operation, 624 encapsulating the packet into a new IPv6 header with its 625 corresponding SRH. 627 C1 and S1 perform their related Endpoint processing. 629 Once the packet arrives at the SRGW, the SRGW identifies the active 630 SID as an End.M.GTP6.E function. The SRGW removes the IPv6 header 631 and all its extensions headers. The SRGW generates new IPv6, UDP and 632 GTP headers. The new IPv6 DA is the gNB which is the last SID in the 633 received SRH. The TEID in the generated GTP header is an argument of 634 the received End.M.GTP6.E SID. The SRGW pushes the headers to the 635 packet and forwards the packet toward the gNB. There is one instance 636 of the End.M.GTP6.E SID per PDU type. 638 Once the packet arrives at the gNB, the packet is a regular IPv6/GTP 639 packet. The gNB looks for the specific radio bearer for that TEID 640 and forward it on the bearer. This gNB behavior is not modified from 641 current and previous generations. 643 5.3.1.3. Scalability 645 For the downlink traffic, the SRGW is stateless. All the state is in 646 the SRH inserted by the UPF2. The UPF2 must have the UE states since 647 it is the UE's session anchor point. 649 For the uplink traffic, the state at the SRGW does not necessarily 650 need to be unique per UE PDU Session; the state state can be shared 651 among UEs. This enables much more scalable SRGW deployments compared 652 to a solution holding millions of states, one or more per UE. 654 5.3.1.4. IPv6 user-traffic 656 For IPv6 user-traffic it is RECOMMENDED to perform encapsulation. 657 However based on local policy, a service provider MAY choose to do 658 SRH insertion. The main benefit is lower overhead. 660 5.3.2. Interworking with IPv4 GTP 662 In this interworking mode the gNB uses GTP over IPv4 in the N3 663 interface 665 Key points: 667 o The gNB is unchanged and encapsulates packets into GTP (the N3 668 interface is not modified). 669 o In the uplink, traffic is classified by SRGW's Uplink Classifier 670 and steered into an SR policy. The SRGW is a UPF1 functionality 671 and can coexist with UPF1's Uplink Classifier functionality. 672 o SRGW removes GTP, finds the SID list related to DA, and adds a SRH 673 with the SID list. 675 An example topology is shown in Figure 6. In this mode the gNB is an 676 unmodified gNB using IPv4/GTP. The UPFs are SR-aware. As before, 677 the SRGW maps the IPv4/GTP traffic to SRv6. 679 S1 and C1 are two service segment endpoints. S1 represents a VNF in 680 the network, and C1 represents a router configured for Traffic 681 Engineering. 683 +----+ 684 IPv4/GTP -| S1 |- ___ 685 +--+ +-----+ [N3] / +----+ \ / 686 |UE|--| gNB |- SRv6 / SRv6 \ +----+ +------+ [N6] / 687 +--+ +-----+ \ [N9]/ VNF -| C1 |---| UPF2 |------\ DN 688 GTP \ +------+ / +----+ +------+ \___ 689 -| UPF1 |- SRv6 SRv6 690 +------+ TE 691 SR Gateway 693 Figure 6: Enhanced mode with unchanged gNB IPv4/GTP behavior 695 5.3.2.1. Packet flow - Uplink 697 The uplink packet flow is as follows: 699 gNB_out : (gNB, B)(GTP: TEID T)(A,Z) -> Interface N3 700 unchanged IPv4/GTP 701 SRGW_out: (SRGW, S1)(U2::1, C1; SL=2)(A,Z) -> T.M.GTP4.D function 702 S1_out : (SRGW, C1)(U2::1, C1; SL=1)(A,Z) 703 C1_out : (SRGW, U2::1) (A,Z) -> PSP 704 UPF2_out: (A,Z) -> End.DT4 or End.DT6 706 The UE sends a packet destined to Z toward the gNB on a specific 707 bearer for that session. The gNB, which is unmodified, encapsulates 708 the packet into a new IPv4, UDP and GTP headers. The IPv4 DA, B, and 709 the GTP TEID are the ones received at the N2 interface. 711 When the packet arrives at the SRGW for UPF1, the SRGW has an Uplink 712 Classifier rule for incoming traffic from the gNB, that steers the 713 traffic into an SR policy by using the function T.M.GTP4.D. The SRGW 714 removes the IPv4, UDP and GTP headers and pushes an IPv6 header with 715 its own SRH containing the SIDs related to the SR policy associated 716 with this traffic. The SRGW forwards according to the new IPv6 DA. 718 S1 and C1 perform their related Endpoint functionality and forward 719 the packet. 721 When the packet arrives at UPF2, the active segment is (U2::1) which 722 is bound to End.DT4/6 which performs the decapsulation (removing the 723 outer IPv6 header with all its extension headers) and forwards toward 724 the data network. 726 5.3.2.2. Packet flow - Downlink 728 The downlink packet flow is as follows: 730 UPF2_in : (Z,A) -> UPF2 maps flow with SID 731 732 UPF2_out: (U2::1, C1)(SRGW::SA:DA:TEID, S1; SL=2)(Z,A) ->T.Encaps.Red 733 C1_out : (U2::1, S1)(SRGW::SA:DA:TEID, S1; SL=1)(Z,A) 734 S1_out : (U2::1, SRGW::SA:DA:TEID)(Z,A) 735 SRGW_out: (SA, DA)(GTP: TEID=T)(Z,A) -> End.M.GTP4.E 736 gNB_out : (Z,A) 738 When a packet destined to A arrives at the UPF2, the UPF2 performs a 739 lookup in the table associated to A and finds the SID list . The UPF2 performs a T.Encaps.Red operation, 741 encapsulating the packet into a new IPv6 header with its 742 corresponding SRH. 744 The nodes C1 and S1 perform their related Endpoint processing. 746 Once the packet arrives at the SRGW, the SRGW identifies the active 747 SID as an End.M.GTP4.E function. The SRGW removes the IPv6 header 748 and all its extensions headers. The SRGW generates an IPv4, UDP and 749 GTP headers. The IPv4 SA and DA are received as SID arguments. The 750 TEID in the generated GTP header is also the arguments of the 751 received End.M.GTP4.E SID. The SRGW pushes the headers to the packet 752 and forwards the packet toward the gNB. 754 When the packet arrives at the gNB, the packet is a regular IPv4/GTP 755 packet. The gNB looks for the specific radio bearer for that TEID 756 and forward it on the bearer. This gNB behavior is not modified from 757 current and previous generations. 759 5.3.2.3. Scalability 761 For the downlink traffic, the SRGW is stateless. All the state is in 762 the SRH inserted by the UPF. The UPF must have this UE-base state 763 anyway (since it is its anchor point). 765 For the uplink traffic, the state at the SRGW is dedicated on a per 766 UE/session basis according to an Uplink Classifier. There is state 767 for steering the different sessions on a SR policies. However, SR 768 policies are shared among several UE/sessions. 770 5.3.2.4. IPv6 user-traffic 772 For IPv6 user-traffic it is RECOMMENDED to perform encapsulation. 773 Based on local policy, a service provider MAY choose to do SRH 774 insertion. The main benefit is a lower overhead. 776 5.3.3. Extensions to the interworking mechanisms 778 In this section we presented two mechanisms for interworking with 779 gNBs that do not support SRv6. These mechanism are done to support 780 GTP over IPv4 and GTP over IPv6. 782 Even though we have presented these methods as an extension to the 783 "Enhanced mode", it is straightforward in its applicability to the 784 "Traditional mode". 786 Furthermore, although these mechanisms are designed for interworking 787 with legacy RAN at the N3 interface, these methods could also be 788 applied for interworking with a non-SRv6 capable UPF at the N9 789 interface (e.g. L3-anchor is SRv6 capable but L2-anchor is not). 791 6. SRv6 SID Mobility Functions 793 6.1. Args.Mob.Session 795 Args.Mob.Session provide per-session information for charging, 796 buffering and lawful intercept (among others) required by some mobile 797 nodes. The Args.Mob.Session argument format is used in combination 798 with End.Map, End.DT and End.DX functions. Note that proposed format 799 is applicable for 5G networks, while similar formats could be 800 proposed for legacy networks. 802 0 1 2 3 803 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 1 804 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 805 | QFI |R|U| PDU Session ID | 806 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 807 |PDU Sess(cont')| 808 +-+-+-+-+-+-+-+-+ 810 Args.Mob.Session format 812 o QFI: QoS Flow Identifier [TS.38415] 813 o R: Reflective QoS Indication [TS.23501]. This parameter indicates 814 the activaton of reflective QoS towards the UE for the transfered 815 packet. Reflective QoS enables the UE to map UL User Plane 816 traffic to QoS Flows without SMF provided QoS rules. 817 o U: Unused and for future use. MUST be 0 on transmission and 818 ignored on receipt. 819 o PDU Session ID: Identifier of PDU Session. The GTP-U equivalent 820 is TEID. 822 Since the SRv6 function is likely NOT to be instantiated per PDU 823 session, Args.Mob.Session helps the UPF to perform the functions 824 which require per QFI and/or per PDU Session granularity. 826 6.2. End.MAP 828 The "Endpoint function with SID mapping" function (End.MAP for short) 829 is used in several scenarios. Particularly in mobility, End.MAP is 830 used in the UPFs for the PDU Session anchor functionality. 832 When a SR node N receives a packet destined to S and S is a local 833 End.MAP SID, N does the following: 835 1. Lookup the IPv6 DA in the mapping table 836 2. update the IPv6 DA with the new mapped SID ;; Ref1 837 3. IF segment_list > 1 838 4. insert a new SRH 839 5. forward according to the new mapped SID 841 Ref1: The SIDs in the SRH are NOT modified. 843 6.3. End.M.GTP6.D 845 The "Endpoint function with IPv6/GTP decapsulation into SR policy" 846 function (End.M.GTP6.D for short) is used in interworking scenario 847 for the uplink toward from the legacy gNB using IPv6/GTP. Suppose, 848 for example, this SID is associated with an SR policy 849 and an IPv6 Source Address A. 851 When the SR Gateway node N receives a packet destined to S and S is a 852 local End.M.GTP6.D SID, N does: 854 1. IF NH=UDP & UDP_DST_PORT = GTP THEN 855 2. copy TEID to form SID S3 856 3. pop the IPv6, UDP and GTP headers 857 4. push a new IPv6 header with a SR policy in SRH 858 5. set the outer IPv6 SA to A 859 6. set the outer IPv6 DA to S1 860 7. set the outer IPv6 NH ;; Ref1 861 8. forward according to the S1 segment of the SRv6 Policy 862 9. ELSE 863 10. Drop the packet 865 Ref1: The NH is set based on the SID parameter. There is one 866 instantiation of the End.M.GTP6.D SID per PDU Session Type, hence the 867 NH is already known in advance. For the IPv4v6 PDU Session Type, in 868 addition we inspect the first nibble of the PDU to know the NH value. 870 The prefix of last segment(S3 in above example) SHOULD be followed by 871 an Arg.Mob.Session argument space which is used to provide the 872 session identifiers. 874 The prefix of A SHOULD be an End.M.GTP6.E SID instantiated at an SR 875 gateway. 877 6.4. End.M.GTP6.E 879 The "Endpoint function with encapsulation for IPv6/GTP tunnel" 880 function (End.M.GTP6.E for short) is used in interworking scenario 881 for the downlink toward the legacy gNB using IPv6/GTP. 883 The prefix of End.M.GTP6.E SID MUST be followed by the 884 Arg.Mob.Session argument space which is used to provide the session 885 identifiers. 887 When the SR Gateway node N receives a packet destined to S, and S is 888 a local End.M.GTP6.E SID, N does the following: 890 1. IF NH=SRH & SL = 1 THEN ;; Ref1 891 2. store SRH[0] in variable new_DA 892 3. store TEID in variable new_TEID from IPv6 DA ;; Ref2 893 4. pop IP header and all its extension headers 894 5. push new IPv6 header and GTP-U header 895 6. set IPv6 DA to new_DA 896 7. set IPv6 SA to A 897 8. set GTP_TEID to new_TEID 898 9. lookup the new_DA and forward the packet accordingly 899 10. ELSE 900 11. Drop the packet 902 Ref1: An End.M.GTP6.E SID MUST always be the penultimate SID. 904 Ref2: TEID is extracted from the argument space of the current SID. 906 The source address A SHOULD be an End.M.GTP6.D SID instantiated at an 907 SR gateway. 909 6.5. End.M.GTP4.E 911 The "Endpoint function with encapsulation for IPv4/GTP tunnel" 912 function (End.M.GTP4.E for short) is used in the downlink when doing 913 interworking with legacy gNB using IPv4/GTP. 915 When the SR Gateway node N receives a packet destined to S and S is a 916 local End.M.GTP4.E SID, N does: 918 1. IF (NH=SRH and SL = 0) or ENH=4 THEN 919 2. store IPv6 DA in buffer S 920 3. store IPv6 SA in buffer S' 921 4. pop the IPv6 header and its extension headers 922 5. push UDP/GTP headers with GTP TEID from S 923 6. push outer IPv4 header with SA, DA from S' and S 924 7. ELSE 925 8. Drop the packet 927 The End.M.GTP4.E SID in S has the following format: 929 0 127 930 +-----------------------+-------+----------------+---------+ 931 | SRGW-IPv6-LOC-FUNC |IPv4DA |Args.Mob.Session|0 Padded | 932 +-----------------------+-------+----------------+---------+ 933 128-a-b-c a b c 935 End.M.GTP4.E SID Encoding 937 S' has the following format: 939 0 127 940 +----------------------+--------+--------------------------+ 941 | Source UPF Prefix |IPv4 SA | any bit pattern(ignored) | 942 +----------------------+--------+--------------------------+ 943 128-a-b a b 945 IPv6 SA Encoding for End.M.GTP4.E 947 6.6. T.M.GTP4.D 949 The "Transit with tunnel decapsulation and map to an SRv6 policy" 950 function (T.M.GTP4.D for short) is used in the direction from legacy 951 user-plane to SRv6 user-plane network. 953 When the SR Gateway node N receives a packet destined to a IW- 954 IPv4-Prefix, N does: 956 1. IF Payload == UDP/GTP THEN 957 2. pop the outer IPv4 header and UDP/GTP headers 958 3. copy IPv4 DA, TEID to form SID B 959 4. copy IPv4 SA to form IPv6 SA B' 960 5. encapsulate the packet into a new IPv6 header ;;Ref1 961 6. set the IPv6 DA = B 962 7. forward along the shortest path to B 963 8. ELSE 964 9. Drop the packet 966 Ref1: The NH value is identified by inspecting the first nibble of 967 the inner payload. 969 The SID B has the following format: 971 0 127 972 +-----------------------+-------+----------------+---------+ 973 |Destination UPF Prefix |IPv4DA |Args.Mob.Session|0 Padded | 974 +-----------------------+-------+----------------+---------+ 975 128-a-b-c a b c 977 T.M.GTP4.D SID Encoding 979 The SID B MAY be an SRv6 Binding SID instantiated at the first UPF 980 (U1) to bind a SR policy [I-D.ietf-spring-segment-routing-policy]. 982 The prefix of B' SHOULD be an End.M.GTP4.E SID with its format 983 instantiated at an SR gateway with the IPv4 SA of the receiving 984 packet. 986 6.7. End.Limit: Rate Limiting function 988 The mobile user-plane requires a rate-limit feature. For this 989 purpose, we define a new function "End.Limit". The "End.Limit" 990 function encodes in its arguments the rate limiting parameter that 991 should be applied to this packet. Multiple flows of packets should 992 have the same group identifier in the SID when those flows are in an 993 same AMBR group. The encoding format of the rate limit segment SID 994 is as follows: 996 +----------------------+----------+-----------+ 997 | LOC+FUNC rate-limit | group-id | limit-rate| 998 +----------------------+----------+-----------+ 999 128-i-j i j 1001 End.Limit: Rate limiting function argument format 1003 If the limit-rate bits are set to zero, the node should not do rate 1004 limiting unless static configuration or control-plane sets the limit 1005 rate associated to the SID. 1007 7. SRv6 supported 3GPP PDU session types 1009 The 3GPP [TS.23501] defines the following PDU session types: 1011 o IPv4 1012 o IPv6 1013 o IPv4v6 1014 o Ethernet 1015 o Unstructured 1016 SRv6 supports all the 3GPP PDU session types without any protocol 1017 overhead by using the corresponding SRv6 functions (End.DX4, End.DT4 1018 for IPv4 PDU sessions; End.DX6, End.DT6, End.T for IPv6 PDU sessions; 1019 End.DT46 for IPv4v6 PDU sessions; End.DX2 for L2 PDU sessions; 1020 End.DX2 for Unstructured PDU sessions). 1022 8. Network Slicing Considerations 1024 A mobile network may be required to implement "network slices", which 1025 logically separate network resources. User-plane functions 1026 represented as SRv6 segments would be part of a slice. 1028 [I-D.ietf-spring-segment-routing-policy] describes a solution to 1029 build basic network slices with SR. Depending on the requirements, 1030 these slices can be further refined by adopting the mechanisms from: 1032 o IGP Flex-Algo [I-D.hegdeppsenak-isis-sr-flex-algo] 1033 o Inter-Domain policies 1034 [I-D.ietf-spring-segment-routing-central-epe] 1036 Furthermore, these can be combined with ODN/AS 1037 [I-D.ietf-spring-segment-routing-policy] for automated slice 1038 provisioning and traffic steering. 1040 Further details on how these tools can be used to create end to end 1041 network slices are documented in 1042 [I-D.ali-spring-network-slicing-building-blocks]. 1044 9. Control Plane Considerations 1046 This document focuses on user-plane behavior and its independence 1047 from the control plane. 1049 The control plane could be the current 3GPP-defined control plane 1050 with slight modifications to the N4 interface [TS.29244]. 1052 Alternatively, SRv6 could be used in conjunction with a new mobility 1053 control plane as described in LISP [I-D.rodrigueznatal-lisp-srv6], 1054 hICN [I-D.auge-dmm-hicn-mobility-deployment-options], MFA 1055 [I-D.gundavelli-dmm-mfa] or in conjunction with FPC 1056 [I-D.ietf-dmm-fpc-cpdp]. The analysis of new mobility control-planes 1057 and its applicability to SRv6 is out of the scope of this document. 1059 Section 11 allocates SRv6 endpoint function types for the new 1060 functions defined in this document. Control-plane protocols are 1061 expected to use these function type codes to signal each function. 1063 SRv6's network programming nature allows a flexible and dynamic UPF 1064 placement. 1066 10. Security Considerations 1068 TBD 1070 11. IANA Considerations 1072 IANA is requested to allocate, within the "SRv6 Endpoint Types" sub- 1073 registry belonging to the top-level "Segment-routing with IPv6 1074 dataplane (SRv6) Parameters" registry 1075 [I-D.ietf-spring-srv6-network-programming], the following values: 1077 +-------------+-----+-------------------+-----------+ 1078 | Value/Range | Hex | Endpoint function | Reference | 1079 +-------------+-----+-------------------+-----------+ 1080 | TBA | TBA | End.MAP | [This.ID] | 1081 | TBA | TBA | End.M.GTP6.D | [This.ID] | 1082 | TBA | TBA | End.M.GTP6.E | [This.ID] | 1083 | TBA | TBA | End.M.GTP4.E | [This.ID] | 1084 | TBA | TBA | End.Limit | [This.ID] | 1085 +-------------+-----+-------------------+-----------+ 1087 Table 1: SRv6 Mobile User-plane Endpoint Types 1089 12. Acknowledgements 1091 The authors would like to thank Daisuke Yokota, Bart Peirens, 1092 Ryokichi Onishi, Kentaro Ebisawa, Peter Bosch, Darren Dukes, Francois 1093 Clad, Sri Gundavelli, Sridhar Bhaskaran, Arashmid Akhavain, Ravi 1094 Shekhar and Aeneas Dodd-Noble for their useful comments of this work. 1096 13. Contributors 1098 Kentaro Ebisawa 1099 Toyota Motor Corporation 1100 Japan 1102 Email: ebisawa@toyota-tokyo.tech 1104 14. References 1106 14.1. Normative References 1108 [I-D.ietf-6man-segment-routing-header] 1109 Filsfils, C., Dukes, D., Previdi, S., Leddy, J., 1110 Matsushima, S., and d. daniel.voyer@bell.ca, "IPv6 Segment 1111 Routing Header (SRH)", draft-ietf-6man-segment-routing- 1112 header-21 (work in progress), June 2019. 1114 [I-D.ietf-spring-segment-routing-policy] 1115 Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d., 1116 bogdanov@google.com, b., and P. Mattes, "Segment Routing 1117 Policy Architecture", draft-ietf-spring-segment-routing- 1118 policy-03 (work in progress), May 2019. 1120 [I-D.ietf-spring-srv6-network-programming] 1121 Filsfils, C., Camarillo, P., Leddy, J., 1122 daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6 1123 Network Programming", draft-ietf-spring-srv6-network- 1124 programming-01 (work in progress), July 2019. 1126 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1127 Requirement Levels", BCP 14, RFC 2119, 1128 DOI 10.17487/RFC2119, March 1997, . 1131 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 1132 Decraene, B., Litkowski, S., and R. Shakir, "Segment 1133 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 1134 July 2018, . 1136 14.2. Informative References 1138 [I-D.ali-spring-network-slicing-building-blocks] 1139 Ali, Z., Filsfils, C., Camarillo, P., and d. 1140 daniel.voyer@bell.ca, "Building blocks for Slicing in 1141 Segment Routing Network", draft-ali-spring-network- 1142 slicing-building-blocks-01 (work in progress), March 2019. 1144 [I-D.auge-dmm-hicn-mobility-deployment-options] 1145 Auge, J., Carofiglio, G., Muscariello, L., and M. 1146 Papalini, "Anchorless mobility management through hICN 1147 (hICN-AMM): Deployment options", draft-auge-dmm-hicn- 1148 mobility-deployment-options-02 (work in progress), July 1149 2019. 1151 [I-D.camarillo-dmm-srv6-mobile-pocs] 1152 Camarillo, P., Filsfils, C., Bertz, L., Akhavain, A., 1153 Matsushima, S., and d. daniel.voyer@bell.ca, "Segment 1154 Routing IPv6 for mobile user-plane PoCs", draft-camarillo- 1155 dmm-srv6-mobile-pocs-02 (work in progress), April 2019. 1157 [I-D.camarilloelmalky-springdmm-srv6-mob-usecases] 1158 Camarillo, P., Filsfils, C., Elmalky, H., Matsushima, S., 1159 daniel.voyer@bell.ca, d., Cui, A., and B. Peirens, "SRv6 1160 Mobility Use-Cases", draft-camarilloelmalky-springdmm- 1161 srv6-mob-usecases-01 (work in progress), January 2019. 1163 [I-D.gundavelli-dmm-mfa] 1164 Gundavelli, S., Liebsch, M., and S. Matsushima, "Mobility- 1165 aware Floating Anchor (MFA)", draft-gundavelli-dmm-mfa-01 1166 (work in progress), September 2018. 1168 [I-D.hegdeppsenak-isis-sr-flex-algo] 1169 Psenak, P., Hegde, S., Filsfils, C., and A. Gulko, "ISIS 1170 Segment Routing Flexible Algorithm", draft-hegdeppsenak- 1171 isis-sr-flex-algo-02 (work in progress), February 2018. 1173 [I-D.ietf-dmm-fpc-cpdp] 1174 Matsushima, S., Bertz, L., Liebsch, M., Gundavelli, S., 1175 Moses, D., and C. Perkins, "Protocol for Forwarding Policy 1176 Configuration (FPC) in DMM", draft-ietf-dmm-fpc-cpdp-12 1177 (work in progress), June 2018. 1179 [I-D.ietf-spring-segment-routing-central-epe] 1180 Filsfils, C., Previdi, S., Dawra, G., Aries, E., and D. 1181 Afanasiev, "Segment Routing Centralized BGP Egress Peer 1182 Engineering", draft-ietf-spring-segment-routing-central- 1183 epe-10 (work in progress), December 2017. 1185 [I-D.rodrigueznatal-lisp-srv6] 1186 Rodriguez-Natal, A., Ermagan, V., Maino, F., Dukes, D., 1187 Camarillo, P., and C. Filsfils, "LISP Control Plane for 1188 SRv6 Endpoint Mobility", draft-rodrigueznatal-lisp-srv6-01 1189 (work in progress), January 2019. 1191 [I-D.xuclad-spring-sr-service-programming] 1192 Clad, F., Xu, X., Filsfils, C., daniel.bernier@bell.ca, 1193 d., Li, C., Decraene, B., Ma, S., Yadlapalli, C., 1194 Henderickx, W., and S. Salsano, "Service Programming with 1195 Segment Routing", draft-xuclad-spring-sr-service- 1196 programming-02 (work in progress), April 2019. 1198 [TS.23501] 1199 3GPP, , "System Architecture for the 5G System", 3GPP TS 1200 23.501 15.0.0, November 2017. 1202 [TS.29244] 1203 3GPP, , "Interface between the Control Plane and the User 1204 Plane Nodes", 3GPP TS 29.244 15.0.0, December 2017. 1206 [TS.29281] 1207 3GPP, , "General Packet Radio System (GPRS) Tunnelling 1208 Protocol User Plane (GTPv1-U)", 3GPP TS 29.281 15.1.0, 1209 December 2017. 1211 [TS.38415] 1212 3GPP, , "Draft Specification for 5GS container (TS 1213 38.415)", 3GPP R3-174510 0.0.0, August 2017. 1215 Appendix A. Implementations 1217 This document introduces new SRv6 functions. These functions have an 1218 open-source P4 implementation available in 1219 . 1221 There are also implementations in M-CORD NGIC and Open Air Interface 1222 (OAI). Further details can be found in 1223 [I-D.camarillo-dmm-srv6-mobile-pocs]. 1225 Authors' Addresses 1227 Satoru Matsushima 1228 SoftBank 1229 Tokyo 1230 Japan 1232 Email: satoru.matsushima@g.softbank.co.jp 1234 Clarence Filsfils 1235 Cisco Systems, Inc. 1236 Belgium 1238 Email: cf@cisco.com 1240 Miya Kohno 1241 Cisco Systems, Inc. 1242 Japan 1244 Email: mkohno@cisco.com 1246 Pablo Camarillo Garvia 1247 Cisco Systems, Inc. 1248 Spain 1250 Email: pcamaril@cisco.com 1251 Daniel Voyer 1252 Bell Canada 1253 Canada 1255 Email: daniel.voyer@bell.ca 1257 Charles E. Perkins 1258 Futurewei Inc. 1259 2330 Central Expressway 1260 Santa Clara, CA 95050 1261 USA 1263 Phone: +1-408-330-4586 1264 Email: charliep@computer.org