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Wang 3 Internet-Draft China Telecom 4 Intended status: Standards Track Z. Hu 5 Expires: February 27, 2021 Huawei Technologies 6 August 26, 2020 8 Passive Interface Attribute 9 draft-wang-lsr-passive-interface-attribute-01 11 Abstract 13 This document describes the mechanism that can be used to 14 differentiate the passive interfaces from the normal interfaces 15 within ISIS domain. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at https://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on February 27, 2021. 34 Copyright Notice 36 Copyright (c) 2020 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (https://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 2. Conventions used in this document . . . . . . . . . . . . . . 2 53 3. Scenario Description . . . . . . . . . . . . . . . . . . . . 3 54 4. Passive Interface Attribute . . . . . . . . . . . . . . . . . 4 55 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 56 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 57 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 4 58 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 59 8.1. Normative References . . . . . . . . . . . . . . . . . . 5 60 8.2. Informative References . . . . . . . . . . . . . . . . . 5 61 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 63 1. Introduction 65 Passive interfaces are used commonly within operator or enterprise 66 networks, especially at the boundary of different IGP domains. Using 67 passive interface can keep the address that associated with it is 68 reachable within the domain it belongs to but no other link 69 information is leaked to the other side in another domain. 71 For operator which runs different IGP domains that interconnect with 72 each other, there is desire that to get the inter-as topology 73 information as that described in 74 [I-D.ietf-idr-bgpls-inter-as-topology-ext]. If the router that run 75 BGP-LS within one IGP domain can distinguish the passive 76 interfaces(also the links between two boundary) from the other normal 77 interfaces, then it is easy for them to report these link in the 78 "Stub Link NLRI" via the BGP-LS. 80 OSPF has the mechanism as described in [RFC2328] to label the passive 81 interface, but ISIS protocol has no such attribute to label the 82 passive interface. 84 This document introduces the mechanism that can be used in such 85 situation, to label the passive interface via the newly defined 86 passive interface attribute. 88 2. Conventions used in this document 90 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 91 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 92 document are to be interpreted as described in [RFC2119] . 94 3. Scenario Description 96 Figure 1 illustrates the topology scenario when ISIS/OSPF is running 97 in different domain. B1, B3 are border routers within IGP domain A, 98 B2, B4 are border routers within domain B. S1-S4 are the internal 99 routers within domain A, T1-T4 are the internal routers within domain 100 B. The two domain are interconnected via the links between B1/B2 and 101 B3/B4. 103 Passive interfaces are enabled in the links between B1/B2 and B3/B4 104 respectively. For domain B, the T1 router that runs OSPF can extract 105 the passives links from the normal links and report it to IP SDN 106 controller via the BGP-LS protocol. But for domain A, the S2 router 107 that runs ISIS can only judge the passive interfaces from other 108 characteristics, such as no IGP neighbor on this link. Such 109 judgement can extract these passive links but it is not exactly, 110 because it covers also the situation when there is some issues to 111 establish the ISIS adjacency but not the passive interface. 113 The passive interfaces are also often used in the edge router which 114 connects the server, for example in the router S1/S4 and T2/T4 in 115 Figure 1. Knowing these interfaces are correctly configured will 116 also benefit the management of these interfaces. 118 The method to label these passive interface explicitly is necessary 119 then. 121 +-----------------+ 122 +----+IP SDN Controller+----+ 123 | +-----------------+ | 124 | | 125 |BGP-LS |BGP-LS 126 | | 127 +---------------+-----+ +-----+--------------+ 128 | +--+ +-++ ++-+ +-++ +|-+ +--+| 129 | |S1+--------+S2+---+B1+-----------+B2+---+T1+--------+T2|| 130 | +-++ N1 +-++ ++-+ +-++ ++++ N2 +-++| 131 | | | | | || | | 132 | | | | | || | | 133 | +-++ +-++ ++-+ +-++ ++++ +-++| 134 | |S4+--------+S3+---+B3+-----------+B4+---+T3+--------+T4|| 135 | +--+ +--+ ++-+ +-++ ++-+ +--+| 136 | | | | 137 | | | | 138 | Domain A(ISIS) | | Domain B(OSPF) | 139 +---------------------+ +--------------------+ 141 Figure 1: Inter-AS Domain Scenarios 143 4. Passive Interface Attribute 145 [RFC7794] defines the "IPv4/IPv6 Extended Reachability Attribute 146 Flags" sub-TLV to advertise the additional flags associated with a 147 given prefix advertisement. Currently, only X(Bit 0),R(Bit 1),N(Bit 148 2), E(Bit 3) flags are defined, here we propose another bit(Bit 4 is 149 desired) to be assigned by the IANA for the passive interface 150 attribute, as illustrated in the following Figure2: 152 0 1 2 3 4 5 6 7... 153 +-+-+-+-+-+-+-+-+... 154 |X|R|N|E|P ... 155 +-+-+-+-+-+-+-+-+... 156 Figure 2: Prefix Attribute Flags 157 P-flag: Passive Flag(Bit 4) 158 Set for local interface that is configured as passive interface. 160 When the interfaces on one router be configured as the passive 161 interface, the P-flag bit will be set in the "IPv4/IPv6 Extended 162 Reachability Attribute Flags" sub-TLV. This sub-TLV will be included 163 in the TLV 135, TLV 235, TLV 236 and TLV 237 as necessary and be 164 flooded within the ISIS domain. 166 The router receives such advertisement can then easily distinguish 167 the passive interfaces from the normal interface, and report them to 168 the SDN controller if it run the BGP-LS protocol. 170 5. Security Considerations 172 Security concerns for ISIS are addressed in [RFC5304] and[RFC5310] 174 Advertisement of the additional information defined in this document 175 introduces no new security concerns. 177 6. IANA Considerations 179 IANA is requested to allocate the P-bit (bit position 4 is desired) 180 from the "Bit Values for Prefix Attribute Flags Sub-TLV" registry. 182 7. Acknowledgement 184 Thanks Shunwan Zhang, Tony Li, Les Ginsberg and Robert Raszuk for 185 their suggestions and comments on this idea. 187 8. References 189 8.1. Normative References 191 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 192 Requirement Levels", BCP 14, RFC 2119, 193 DOI 10.17487/RFC2119, March 1997, 194 . 196 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 197 DOI 10.17487/RFC2328, April 1998, 198 . 200 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 201 Authentication", RFC 5304, DOI 10.17487/RFC5304, October 202 2008, . 204 [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., 205 and M. Fanto, "IS-IS Generic Cryptographic 206 Authentication", RFC 5310, DOI 10.17487/RFC5310, February 207 2009, . 209 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 210 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 211 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 212 March 2016, . 214 8.2. Informative References 216 [I-D.ietf-idr-bgpls-inter-as-topology-ext] 217 Wang, A., Chen, H., Talaulikar, K., and S. Zhuang, "BGP-LS 218 Extension for Inter-AS Topology Retrieval", draft-ietf- 219 idr-bgpls-inter-as-topology-ext-08 (work in progress), 220 April 2020. 222 Authors' Addresses 224 Aijun Wang 225 China Telecom 226 Beiqijia Town, Changping District 227 Beijing 102209 228 China 230 Email: wangaj3@chinatelecom.cn 231 Zhibo Hu 232 Huawei Technologies 233 Huawei Bld., No.156 Beiqing Rd. 234 Beijing 100095 235 China 237 Email: huzhibo@huawei.com