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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'SL' is mentioned on line 138, but not defined == Unused Reference: 'RFC2629' is defined on line 274, but no explicit reference was found in the text ** Obsolete normative reference: RFC 2629 (Obsoleted by RFC 7749) == Outdated reference: A later version (-11) exists of draft-ietf-teas-actn-poi-applicability-03 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 SPRING Working Group J. Dong 3 Internet-Draft Huawei Technologies 4 Intended status: Standards Track Z. Du 5 Expires: April 27, 2022 China Mobile 6 October 24, 2021 8 SRv6 for Inter-Layer Network Programming 9 draft-dong-spring-srv6-inter-layer-programming-02 11 Abstract 13 This document defines a new SRv6 network function which can be used 14 for SRv6 inter-layer network programming. It is a variant of the 15 End.X function. Instead of pointing to an L3 adjacency, this 16 function points to an underlay interface. Such a interface can stand 17 for a underlay link or path/connection between two routers, which may 18 be invisible in the L3 topology. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at https://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on April 27, 2022. 37 Copyright Notice 39 Copyright (c) 2021 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (https://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Requirements Language and Terminology . . . . . . . . . . . . 3 56 3. END.XU Function . . . . . . . . . . . . . . . . . . . . . . . 3 57 4. Use Case for SRv6 Underlay Interface Function . . . . . . . . 4 58 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 59 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 60 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 61 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 62 8.1. Normative References . . . . . . . . . . . . . . . . . . 7 63 8.2. Informative References . . . . . . . . . . . . . . . . . 7 64 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 66 1. Introduction 68 In many scenarios, operator owns a multi-layered network. In that 69 case, cross-layer design and optimization mechanisms are more 70 efficient in resource utilization and SLA assurance, but normally are 71 also considered more complicated. As an IP/MPLS based technology, 72 Segment Routing (SR) normally does not need to care about the network 73 layers beneath the IP layer. One exception is as described in 74 [RFC8668], IS-IS is extended to advertise the link attributes and 75 Segment Identifiers (SIDs) of Layer 2 (L2) bundle members, so that 76 operator can control traffic flows to traverse a particular 77 individual L2 link which comprises the L2 bundle interface 79 In [RFC8986], it is described that for an outgoing interface bundle 80 made of 10 member links, up to 11 End.X local SIDs for that bundle 81 need to be allocated. One END.X for the bundle itself and then up to 82 one END.X for each member link. However, there are some differences 83 between the normal END.X function for the bundle and the END.X 84 function for the member link, as they are not at the same network 85 layer. Moreover, besides the L2 bundle use case, there are other 86 types of underlay interfaces or connections, which can be integrated 87 and programmed using SRv6. This document aims to define a unified 88 SRv6 function to support those inter-layer network programming in 89 SRv6. 91 As another example, the underlay of the IP network can be an optical 92 network. In many today's IP and optical transport networks, IP 93 network and optical network are maintained separately, and in most 94 cases, the optical network works as an underlay which is invisible to 95 the IP network. However, the optical path resource and the IP path 96 resource may not be one-to-one mapped so that some resource in 97 optical network can not be fully used. In some cases, there may be 98 some optical paths that is not visible in the L3 IP topology, and 99 thus they can not be used to carry IP traffic. 101 Following the SRv6 network programming concept in [RFC8986], we can 102 use a new SRv6 function to identify a specific optical path, and put 103 the corresponding SRv6 SID into an integrated SRv6 SID list. The 104 optical path can be either OTN based or DWDM based. Besides the 105 optical paths, it is also possible to use the SRv6 function to 106 identify other underlay paths/connenctions, such as a back-to-back 107 Ethernet connection, or some pre-configured tunnels. 109 The SRv6 function mentioned above can be considered as a variant of 110 the END.X function defined in [RFC8986], so that it is suggested to 111 define a new SRv6 function for it. This document defines the 112 operation of this new SRv6 function, and describes some use cases of 113 this SRv6 underlay interface function. 115 2. Requirements Language and Terminology 117 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 118 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 119 "OPTIONAL" in this document are to be interpreted as described in 120 [RFC2119] when they appear in ALL CAPS. When these words are not in 121 ALL CAPS (such as "should" or "Should"), they have their usual 122 English meanings, and are not to be interpreted as [RFC2119] key 123 words. 125 3. END.XU Function 127 This section defines the new SRv6 underlay interface function. 129 The "Endpoint with cross-connect to an underlay interface" function 130 (End.XU for short) is a variant of the End.X function defined in 131 [RFC8986]. 133 When N receives a packet destined to S and S is a local End.XU SID, N 134 does: 136 1. IF NH=SRH and SL > 0 137 2. decrement SL 138 3. update the IPv6 DA with SRH[SL] 139 4. forward to underlay interface bound to the SID S 140 5. ELSE IF NH!=SRH 141 6. Send an ICMP parameter problem message; drop the packet 142 7. ELSE 143 8. drop the packet 145 Note that the underlay interface or connection in step 4 SHOULD be 146 established before this function and the associated SID is announced 147 into the network. 149 This End.XU function can be announced using IGP or BGP-LS in a 150 similar way to the announcement of END.X function. The detailed 151 protocol extension will be described in a separate document. 153 4. Use Case for SRv6 Underlay Interface Function 155 Assuming that an operator owns both the IP and optical network, and 156 the operator needs to deploy E2E service across IP and optical 157 network, with traditional approaches the planning and service 158 provisioning would be complex and time consuming due of the manual 159 synergy needed between the operator's IP team and optical team. With 160 the popularity of SR and SRv6, one straightforward way is to use a 161 SID list that integrates the path in both the IP layer and the 162 optical layer. 164 As the optical layer is not packet based, normally source routing 165 mechanism can not be directly used in the optical network. However, 166 we can expose the abstracted optical path and its associated 167 attribute and resource information into the network control system of 168 the IP network, by using the SRv6 End.XU function defined in this 169 document, so that E2E inter-layer paths can be programmed to meet 170 some specific traffic's SLA, such as low latency. 172 ----- ----- ----- 173 | P1 |--------| P2 |--------| P3 | 174 ----- ----- ----- 175 / |. |. |. \ 176 ----- / | . | . | . \ ----- 177 | P7 | | . | . | . | P8 | 178 ----- \ | . | . | ./ ----- 179 \ | . | . | / . 180 ----- . ----- . ----- . 181 | P4 |-------| P5 |--------| P6 | . 182 ----- . ----- . ----- . 183 . . . . . . 184 . ===== . ===== . ===== 185 . | O1 |----------| O2 |--------| O3 | 186 . ===== . ===== . ===== 187 . | . | . | 188 . | . | . | 189 . | . | . | 190 . | . | . | 191 .| .| .| 192 ===== ===== ===== 193 | O4 |----------| O5 |--------| O6 | 194 ===== ===== ===== 195 Figure 1. IP and Optical Layered Network Topology 197 In Figure 1, P1 to P8 are IP nodes, and O1 to O6 are optical nodes. 198 Assume we need to deploy a low latency path between P7 and P8. 199 According to traditional segment routing in IP layer, perhaps we can 200 choose the path along {P7, P1, P2, P3, P8}. But if an optical path 201 from O1 to O3 exists, and the End.XU function defined in this 202 document is used to announce this path into the IP domain with 203 specific attributes, the headend node or controller in IP domain can 204 choose the path along {P7, P1, END.XU, P3, P8} which provides lower 205 latency than the normal paths. 207 The creation of the optical path from O1 to O3 may be requested 208 either by the headend IP node P7 or the IP network controller (not 209 shown in the Figure). The creation should be done by the optical 210 network controller (not shown in the Figure), so that P7 or IP 211 network controller needs to inform the path requirements to the 212 optical network controller. The details of the process are out of 213 scope of this document, and may refer to 214 [I-D.ietf-teas-actn-poi-applicability]. 216 We can also use the topology in Figure 1 to show another use case. 217 Assume there are two optical paths between P1 and P2. One is {O1, 218 O2} , and the other is {O1, O4, O5, O2}. We can assign two End.XU 219 functions for these two underlay paths separately. One is P1::C2 for 220 the path {O1, O2}, and the other is P1::C45 for the path {O1, O4, O5, 221 O2}. The headend P7 or the IP network controller will be informed 222 about the two SRv6 functions and the associated path attributes, so 223 that the headend or the controller can program different end-to-end 224 inter-layer paths using integrated SID lists for services with 225 different SLA requirement. 227 Assume the path {O1, O2} is owned by the operator with a higher 228 reliability, and the path {O1, O4, O5, O2} is not totally owned by 229 the operator, i.e., they are partly rented. In this use case, for 230 the traffic with high reliability requirement, the integrated SID 231 list implemented in P7 would be . The ellipsis 232 means some other possible SRv6 functions can be added along the path. 233 For traffic with normal reliability requirement, the integrated SID 234 list programmed in P7 can be . Before the 235 announcement of the two functions, the node P1 needs to map the 236 P1::C12 function to the optical path {O1, O2}, and map P1::C45 to the 237 optical path {O1, O4, O5, O2}. 239 5. Security Considerations 241 TBD 243 6. IANA Considerations 245 This document defines a new SRv6 function called END.XU. 247 IANA is requested to allocate four new code points from the "SRv6 248 Endpoint Behaviors" sub-registry in the "Segment-routing with IPv6 249 data plane (SRv6) Parameters" registry: 251 +-------+--------+---------------------------+-----------+ 252 | Value | Hex | Endpoint function | Reference | 253 +-------+--------+---------------------------+-----------+ 254 | TBA | TBA | End.XU (no PSP, no USP) | [This.ID] | 255 | TBA | TBA | End.XU with PSP | [This.ID] | 256 | TBA | TBA | End.XU with USP | [This.ID] | 257 | TBA | TBA | End.XU with PSP&USP | [This.ID] | 258 +-------+--------+---------------------------+-----------+ 260 7. Acknowledgements 262 The authors would like to thank Xiaodong Chang for his review and 263 comments. 265 8. References 267 8.1. Normative References 269 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 270 Requirement Levels", BCP 14, RFC 2119, 271 DOI 10.17487/RFC2119, March 1997, 272 . 274 [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, 275 DOI 10.17487/RFC2629, June 1999, 276 . 278 [RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, 279 D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 280 (SRv6) Network Programming", RFC 8986, 281 DOI 10.17487/RFC8986, February 2021, 282 . 284 8.2. Informative References 286 [I-D.ietf-teas-actn-poi-applicability] 287 Peruzzini, F., Bouquier, J., Busi, I., King, D., and D. 288 Ceccarelli, "Applicability of Abstraction and Control of 289 Traffic Engineered Networks (ACTN) to Packet Optical 290 Integration (POI)", draft-ietf-teas-actn-poi- 291 applicability-03 (work in progress), July 2021. 293 [RFC8668] Ginsberg, L., Ed., Bashandy, A., Filsfils, C., Nanduri, 294 M., and E. Aries, "Advertising Layer 2 Bundle Member Link 295 Attributes in IS-IS", RFC 8668, DOI 10.17487/RFC8668, 296 December 2019, . 298 Authors' Addresses 300 Jie Dong 301 Huawei Technologies 302 Huawei Campus, No.156 Beiqing Road 303 Beijing, 100095 304 China 306 Email: jie.dong@huawei.com 307 Zongpeng Du 308 China Mobile 309 No.32 XuanWuMen West Street 310 Beijing, 100053 311 China 313 Email: duzongpeng@foxmail.com