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'I-D.ietf-teas-native-ip-scenarios') ** Obsolete normative reference: RFC 5316 (Obsoleted by RFC 9346) ** Obsolete normative reference: RFC 7752 (Obsoleted by RFC 9552) Summary: 3 errors (**), 0 flaws (~~), 10 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IDR Working Group A. Wang 3 Internet-Draft China Telecom 4 Intended status: Standards Track June 28, 2018 5 Expires: December 30, 2018 7 BGP-LS Extend for Inter-AS Topology Retrieval 8 draft-wang-idr-bgpls-inter-as-topology-ext-01 10 Abstract 12 This document describes the process to build BGP-LS key parameters in 13 Native IP multi-domain scenario and defines some new inter-AS TE 14 related TLVs for BGP-LS to let SDN controller retrieve the network 15 topology automatically under various environments. 17 Such process and extension can expand the usage of BGP-LS protocol to 18 multi- domain, enable the network operator to collect the connection 19 relationship between different AS domains and then calculate the 20 overall network topology automatically based on the information 21 provided by BGP-LS protocol. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at https://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on December 30, 2018. 40 Copyright Notice 42 Copyright (c) 2018 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (https://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 58 2. Conventions used in this document . . . . . . . . . . . . . . 3 59 3. Inter-AS Domain Scenarios. . . . . . . . . . . . . . . . . . 3 60 3.1. IS-IS/OSPF Inter-AS Native IP Scenario . . . . . . . . . 3 61 3.2. IS-IS/OSPF Inter-AS TE Scenario . . . . . . . . . . . . . 4 62 4. Inter-AS TE related TLVs . . . . . . . . . . . . . . . . . . 5 63 5. Topology Reconstruction. . . . . . . . . . . . . . . . . . . 5 64 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 65 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 66 8. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 5 67 9. Normative References . . . . . . . . . . . . . . . . . . . . 6 68 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 70 1. Introduction 72 BGP-LS [RFC7752] describes the methodology that using BGP protocol to 73 transfer the Link-State information. Such method can enable SDN 74 controller to collect the underlay network topology automatically, 75 but normally it can only get the information within one IGP domain. 76 If the operator has more than one IGP domain, and these domains 77 interconnect with each other, there is no general TLV within current 78 BGP- LS to transfer the interconnect information. 80 Draft [I-D.ietf-idr-bgpls-segment-routing-epe] defines some 81 extensions for exporting BGP peering node topology information 82 (including its peers, interfaces and peering ASs) in a way that is 83 exploitable in order to compute efficient BGP Peering Engineering 84 policies and strategies. Such information can also be used to 85 calculate the interconnection topology among different IGP domains, 86 but it requires the border routers to run BGP-LS protocol to collect 87 this information and report them to the PCE/SDN controller, which 88 restricts the deployment flexibility of BGP-LS protocol. 90 This draft analysizes the situations that the PCE/SDN controller 91 needs to get about the inter-connected information between different 92 AS domains, defines new TLVs to extend the BGP-LS protocol to 93 transfer the key information related to the interconnect TE topology. 94 After that, the SDN controller can then deduce the multi-domain 95 topology automatically based on the information from BGP-LS protocol. 97 2. Conventions used in this document 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 101 document are to be interpreted as described in RFC 2119 [RFC2119] . 103 3. Inter-AS Domain Scenarios. 105 Fig.1 illustrates the multi-domain scenarios that this draft 106 discussed. Normally, SDN Controller can get the topology of IGP A 107 and IGP B individually via the BGP-LS protocol, but it can't get the 108 topology connection information between these two IGP domains because 109 there is generally no IGP protocol run on the connected links. 111 +-----------------+ 112 +----+IP SDN Controller+----+ 113 | +-----------------+ | 114 | | 115 |BGP-LS |BGP-LS 116 | | 117 +---------------+-----+ +-----+--------------+ 118 | +--+ +-++ ++-+ +-++ +|-+ +--+| 119 | |S1+--------+S2+---+B1+-----------+B2+---+T1+--------+T2|| 120 | +-++ N1 +-++ ++-+ +-++ ++++ N2 +-++| 121 | | | | | || | | 122 | | | | | || | | 123 | +-++ +-++ ++-+ +-++ ++++ +-++| 124 | |S4+--------+S3+---+B3+-----------+B4+---+T3+--------+T4|| 125 | +--+ +--+ ++-+ +-++ ++-+ +--+| 126 | | | | 127 | | | | 128 | IGP A | | IGP B | 129 +---------------------+ +--------------------+ 131 Fig.1 Inter-AS Domain Scenarios 133 3.1. IS-IS/OSPF Inter-AS Native IP Scenario 135 When the IGP A or IGP B runs native IS-IS/OSPF protocol, the operator 136 often redistributes the IPv4/IPv6 prefixes of interconnect links into 137 IS-IS/OSPF protocol to ensure the inter-domain connectivity. 139 If the IGP runs IS-IS protocol, the redistributed link information 140 will be carried in IP External Reachability Information TLV within 141 the Level 2 PDU type that defined in [RFC1195], every router within 142 the IGP domain can deduce the redistributed router from the IS-IS 143 LSDB. 145 If the IGP runs OSPF protocol,[RFC2328]defines the type 5 external 146 LSA to transfer the external IPv4 routes; 147 [I-D.ietf-ospf-ospfv3-lsa-extend] defines the "External-Prefix TLV" 148 to transfer the external IPv6 routes; these LSAs have also the 149 advertising router information that initiates the redistribute 150 activity. Every router within IGP domain can also deduce the 151 redistributed router from the OSPF LSDB. 153 For prefix information that associated with each router, BGP-LS 154 [RFC7752] defines the Prefix NLRI which is illustrated below: 156 0 1 2 3 157 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 1 158 +-+-+-+-+-+-+-+-+ 159 | Protocol-ID | 160 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 161 | Identifier | 162 | (64 bits) | 163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 164 // Local Node Descriptors (variable) // 165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 166 // Prefix Descriptors (variable) // 167 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 169 Figure 2: The IPv4/IPv6 Topology Prefix NLRI Format 171 For these redistributed inter-domain links, their prefix information 172 should be included in the "Prefix Descriptor", and the associated 173 redistributed router information should be included in the "Local 174 Node Descriptors". 176 When such information is reported via the BGP-LS protocol, the PCE/ 177 SDN controller can construct the underlay inter-domain topology 178 according to procedure described in section 5 180 3.2. IS-IS/OSPF Inter-AS TE Scenario 182 [RFC5316] and [RFC5392] define the IS-IS and OSPF extensions 183 respectively to deal with the requirements for inter-AS traffic 184 engineering. They define some new sub-TLVs(Remote AS 185 Number、IPv4 Remote ASBR ID、IPv6 Remote ASBR ID) which 186 are associated with the inter-AS TE link TLVs to report the TE 187 topology between different domains. 189 These TLVs are flooded within the IGP domain automatically. If the 190 PCE/SDN controller can know these information via one of the interior 191 router that runs BGP-LS protocol, the PCE/SDN controller can rebuild 192 the inter-AS TE topology correctly. 194 4. Inter-AS TE related TLVs 196 This draft proposes to add three new TLVs that is included within the 197 inter-AS TE link NLRI to transfer the information via BGP-LS, which 198 are required to build the inter-AS related topology by the PCE/SDN 199 controller. 201 The following Link Descriptor TLVs are added into the Link NLRI in 202 BGP-LS protocol : 204 +-----------+---------------------+--------------+----------------+ 205 | TLV Code | Description |IS-IS/OSPF TLV| Reference | 206 | Point | | /Sub-TLV | (RFC/Section) | 207 +-----------+---------------------+--------------+----------------+ 208 | TBD |Remote AS Number | 24/21 | [RFC5316]/3.3.1| 209 | | | | [RFC5392]/3.3.1| 210 | TBD |IPv4 Remote ASBR ID | 25/22 | [RFC5316]/3.3.2| 211 | | | | [RFC5392]/3.3.2| 212 | TBD |IPv6 Remote ASBR ID | 26/24 | [RFC5316]/3.3.3| 213 | | | | [RFC5392]/3.3.3| 214 +-----------+---------------------+--------------+----------------+ 216 5. Topology Reconstruction. 218 When SDN Controller gets such information from BGP-LS protocol, it 219 should compares the proximity of the redistributed prefixes. If they 220 are under the same network scope, then it should find the 221 corresponding associated router information, build the link between 222 these two border routers. 224 After iterating the above procedures for all of the redistributed 225 prefixes, the SDN controller can then retrieve the connection 226 topology between different domains automatically. 228 6. Security Considerations 230 TBD. 232 7. IANA Considerations 234 TBD. 236 8. Acknowledgement 238 The author would like to thank Acee Lindem and Ketan Talaulikar for 239 their valuable comments and suggestions, thank also the comments from 240 Jeff Tantsura and Dhruv Dhody. 242 9. Normative References 244 [I-D.ietf-idr-bgp-ls-segment-routing-ext] 245 Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., 246 and M. Chen, "BGP Link-State extensions for Segment 247 Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-08 248 (work in progress), May 2018. 250 [I-D.ietf-idr-bgpls-segment-routing-epe] 251 Previdi, S., Filsfils, C., Patel, K., Ray, S., and J. 252 Dong, "BGP-LS extensions for Segment Routing BGP Egress 253 Peer Engineering", draft-ietf-idr-bgpls-segment-routing- 254 epe-15 (work in progress), March 2018. 256 [I-D.ietf-ospf-ospfv3-lsa-extend] 257 Lindem, A., Roy, A., Goethals, D., Vallem, V., and F. 258 Baker, "OSPFv3 LSA Extendibility", draft-ietf-ospf-ospfv3- 259 lsa-extend-23 (work in progress), January 2018. 261 [I-D.ietf-teas-native-ip-scenarios] 262 Wang, A., Huang, X., Qou, C., Huang, L., and K. Mi, "CCDR 263 Scenario, Simulation and Suggestion", draft-ietf-teas- 264 native-ip-scenarios-00 (work in progress), February 2018. 266 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 267 dual environments", RFC 1195, DOI 10.17487/RFC1195, 268 December 1990, . 270 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 271 Requirement Levels", BCP 14, RFC 2119, 272 DOI 10.17487/RFC2119, March 1997, 273 . 275 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 276 DOI 10.17487/RFC2328, April 1998, 277 . 279 [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in 280 Support of Inter-Autonomous System (AS) MPLS and GMPLS 281 Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316, 282 December 2008, . 284 [RFC5392] Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in 285 Support of Inter-Autonomous System (AS) MPLS and GMPLS 286 Traffic Engineering", RFC 5392, DOI 10.17487/RFC5392, 287 January 2009, . 289 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 290 S. Ray, "North-Bound Distribution of Link-State and 291 Traffic Engineering (TE) Information Using BGP", RFC 7752, 292 DOI 10.17487/RFC7752, March 2016, 293 . 295 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 296 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 297 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 298 March 2016, . 300 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 301 F. Baker, "OSPFv3 Link State Advertisement (LSA) 302 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 303 2018, . 305 Author's Address 307 Aijun Wang 308 China Telecom 309 Beiqijia Town, Changping District 310 Beijing, Beijing 102209 311 China 313 Email: wangaj.bri@chinatelecom.cn