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Wang 3 Internet-Draft China Telecom 4 Intended status: Standards Track Z. Hu 5 Expires: April 1, 2021 Huawei Technologies 6 G. Mishra 7 Verizon Inc. 8 September 28, 2020 10 Passive Interface Attribute 11 draft-wang-lsr-passive-interface-attribute-03 13 Abstract 15 This document describes the mechanism that can be used to 16 differentiate the passive interfaces from the normal interfaces 17 within ISIS or OSPF domain. 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at https://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on April 1, 2021. 36 Copyright Notice 38 Copyright (c) 2020 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (https://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 2. Conventions used in this document . . . . . . . . . . . . . . 3 55 3. Scenario Description . . . . . . . . . . . . . . . . . . . . 3 56 4. Passive Interface Attribute . . . . . . . . . . . . . . . . . 4 57 4.1. ISIS Passive Interface Attribute . . . . . . . . . . . . 4 58 4.2. OSPF Passive Interface Attribute . . . . . . . . . . . . 5 59 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 60 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 61 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 5 62 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 63 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 64 8.2. Informative References . . . . . . . . . . . . . . . . . 6 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 67 1. Introduction 69 Passive interfaces are used commonly within an operators enterprise 70 or service provider networks. One of the most common use cases for 71 passive interface is in a data center Layer 2 and Layer 3 TOR(Top of 72 Rack) switch where the inter connected link between the TOR switches 73 and uplink to the Core switch are only a few links and a majority of 74 the links are Layer 3 VLAN Switched Virtual Interface Default 75 Gateways trunked betwen the TOR switches servicing Layer 2 broadcast 76 domains. In this scenario all the VLANs are made passive as it is 77 recommended to limit the number of network LSAs between routers and 78 switches to avoid unnecessary hello processing overhead. 80 Another common use case is an inter-as routing scenario where the 81 same routing protocol but diffent IGP instance is running between the 82 adjacent BGP domains. Using passive interface on the inter-as 83 tiepoint connections can ensure that prefixes contained within a 84 domain are only reachable within the domain itself and not allow the 85 link state database to be merged between domain which could result in 86 undesirable consequences. 88 For operator which runs different IGP domains that interconnect with 89 each other, there is desire to obtain the inter-as topology 90 information as described in 91 [I-D.ietf-idr-bgpls-inter-as-topology-ext]. If the router that runs 92 BGP-LS is within one IGP domain and can distinguish passive 93 interfaces from other interfaces with transit neighbor, it is then 94 easy for the router to report these passive links using BGP-LS to 95 centralized PCE controller. 97 But OSPF and ISIS have no capabilities to flag such passive 98 interface. 100 This document defines the protocol extension for OSPF and ISIS for 101 the prefix that comes from passive interface. 103 2. Conventions used in this document 105 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 106 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 107 document are to be interpreted as described in [RFC2119] . 109 3. Scenario Description 111 Figure 1 illustrates the topology scenario when ISIS/OSPF is running 112 in different domain. B1, B3 are border routers within IGP domain A, 113 B2, B4 are border routers within domain B. S1-S4 are the internal 114 routers within domain A, T1-T4 are the internal routers within domain 115 B. The two domain are interconnected via the links between B1/B2 and 116 B3/B4. 118 Passive interfaces are enabled in the links between B1/B2 and B3/B4 119 respectively. For domain A and B, the S2/T1 router that runs ISIS/ 120 OSPF can't extract the passives links from the normal links and 121 report it to PCE controller via the BGP-LS protocol. They can only 122 judge the passive interfaces from other characteristics, such as no 123 IGP neighbor on this link. Such judgement can extract these passive 124 links but it is not accurate, because it covers also the situation 125 when there are some issues to establish the ISIS adjacency/OSPF 126 neighbor but not the passive interface. 128 For passive interfaces that are used in the edge router or switches 129 which connects the server, for example in the router S1/S4 and T2/T4 130 in Figure 1, knowing these interfaces are correctly configured will 131 also benefit the management of them. 133 The method to label these passive interfaces explicitly is necessary 134 then. 136 +-----------------+ 137 +----+IP SDN Controller+----+ 138 | +-----------------+ | 139 | | 140 |BGP-LS |BGP-LS 141 | | 142 +---------------+-----+ +-----+--------------+ 143 | +--+ +-++ ++-+ +-++ +|-+ +--+| 144 | |S1+--------+S2+---+B1+-----------+B2+---+T1+--------+T2|| 145 | +-++ N1 +-++ ++-+ +-++ ++++ N2 +-++| 146 | | | | | || | | 147 | | | | | || | | 148 | +-++ +-++ ++-+ +-++ ++++ +-++| 149 | |S4+--------+S3+---+B3+-----------+B4+---+T3+--------+T4|| 150 | +--+ +--+ ++-+ +-++ ++-+ +--+| 151 | | | | 152 | | | | 153 | Domain A(ISIS) | | Domain B(OSPF) | 154 +---------------------+ +--------------------+ 156 Figure 1: Inter-AS Domain Scenarios 158 4. Passive Interface Attribute 160 4.1. ISIS Passive Interface Attribute 162 [RFC7794] defines the "IPv4/IPv6 Extended Reachability Attribute 163 Flags" sub-TLV to advertise the additional flags associated with a 164 given prefix advertisement. We propose new bit(Bit 5 is desired) to 165 be assigned by the IANA for the passive interface attribute, as 166 illustrated in Figure2: 168 0 1 2 3 4 5 6 7 169 +-+-+-+-+-+-+-+-+ 170 |X|R|N|E|A|U 171 +-+-+-+-+-+-+-+-+ 172 Figure 2: Prefix Attribute Flags 174 U-flag: Unactive Flag(Bit 5) 175 Set for local interface that is configured as passive interface. 177 When the interfaces on one router be configured as the passive 178 interface, the U-flag bit will be set in the "IPv4/IPv6 Extended 179 Reachability Attribute Flags" sub-TLV. This sub-TLV will be included 180 in the TLV 135, TLV 235, TLV 236 and TLV 237 as necessary and be 181 flooded within the ISIS domain. 183 4.2. OSPF Passive Interface Attribute 185 [RFC5340] defines the "Prefix Option field" in "Intra-Area-Prefix- 186 LSAs" LSA to describe the prefix capabilities. The bits in this 187 field can be defined to flag the prefix is coming from the passive 188 interface. We propose new bit(Bit 1 is desired) to be assigned by 189 the IANA for the passive interface, as illustrated in Figure 3: 191 0 1 2 3 4 5 6 7 192 +--+--+--+--+--+-+--+--+ 193 | | | U|DN| P|x|LA|NU| 194 +--+--+--+--+--+-+--+--+ 196 Figure 3: The PrefixOptions Field 198 U-flag: Unactive Flag(Bit 2) 199 Set for local interface that is configured as passive interface. 201 When the interfaces on one router be configured as the passive 202 interface, the U-flag bit will be set in the "Prefix Option field" of 203 Intra-Area-Prefix-LSAs. 205 The router receives such advertisement can then easily distinguish 206 the passive interfaces from the normal interface, and reports them to 207 the PCE controller if it run the BGP-LS protocol. 209 5. Security Considerations 211 Security concerns for ISIS are addressed in [RFC5304] and[RFC5310] 213 Advertisement of the additional information defined in this document 214 introduces no new security concerns. 216 6. IANA Considerations 218 IANA is requested to allocate the U-bit (bit position 5 is desired) 219 from the "Bit Values for Prefix Attribute Flags Sub-TLV" registry of 220 ISIS TLV codepoint. 222 IANA is requested to allocate the U-bit(bit position 2 is desired) 223 from the "OSPFv3 Prefix Options" registry of OSPFv3 Parameters 224 codepoint. 226 7. Acknowledgement 228 Thanks Shunwan Zhang, Tony Li, Les Ginsberg and Robert Raszuk for 229 their suggestions and comments on this idea. 231 8. References 233 8.1. Normative References 235 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 236 Requirement Levels", BCP 14, RFC 2119, 237 DOI 10.17487/RFC2119, March 1997, 238 . 240 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 241 Authentication", RFC 5304, DOI 10.17487/RFC5304, October 242 2008, . 244 [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., 245 and M. Fanto, "IS-IS Generic Cryptographic 246 Authentication", RFC 5310, DOI 10.17487/RFC5310, February 247 2009, . 249 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 250 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 251 . 253 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 254 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 255 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 256 March 2016, . 258 8.2. Informative References 260 [I-D.ietf-idr-bgpls-inter-as-topology-ext] 261 Wang, A., Chen, H., Talaulikar, K., and S. Zhuang, "BGP-LS 262 Extension for Inter-AS Topology Retrieval", draft-ietf- 263 idr-bgpls-inter-as-topology-ext-08 (work in progress), 264 April 2020. 266 Authors' Addresses 268 Aijun Wang 269 China Telecom 270 Beiqijia Town, Changping District 271 Beijing 102209 272 China 274 Email: wangaj3@chinatelecom.cn 275 Zhibo Hu 276 Huawei Technologies 277 Huawei Bld., No.156 Beiqing Rd. 278 Beijing 100095 279 China 281 Email: huzhibo@huawei.com 283 Gyan S. Mishra 284 Verizon Inc. 285 13101 Columbia Pike 286 Silver Spring MD 20904 287 United States of America 289 Email: gyan.s.mishra@verizon.com