idnits 2.17.1 draft-ietf-ospf-rfc3137bis-01.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack an Introduction section. ** The document seems to lack an IANA Considerations section. (See Section 2.2 of https://www.ietf.org/id-info/checklist for how to handle the case when there are no actions for IANA.) == The 'Obsoletes: ' line in the draft header should list only the _numbers_ of the RFCs which will be obsoleted by this document (if approved); it should not include the word 'RFC' in the list. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == The document doesn't use any RFC 2119 keywords, yet seems to have RFC 2119 boilerplate text. -- The document date (June 29, 2012) is 4317 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- -- Obsolete informational reference (is this intentional?): RFC 1247 (Obsoleted by RFC 1583) -- Obsolete informational reference (is this intentional?): RFC 1583 (Obsoleted by RFC 2178) Summary: 2 errors (**), 0 flaws (~~), 3 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Retana 3 Internet-Draft Hewlett-Packard Co. 4 Obsoletes: RFC3137 (if approved) L. Nguyen 5 Intended status: Informational A. Zinin 6 Expires: December 31, 2012 Cisco Systems, Inc. 7 R. White 8 D. McPherson 9 Verisign, Inc. 10 June 29, 2012 12 OSPF Stub Router Advertisement 13 draft-ietf-ospf-rfc3137bis-01 15 Abstract 17 This memo describes a backward-compatible technique that may be used 18 by OSPF (Open Shortest Path First) implementations to advertise 19 unavailability to forward transit traffic or to lower the preference 20 level for the paths through such a router. In some cases, it is 21 desirable not to route transit traffic via a specific OSPF router. 22 However, OSPF does not specify a standard way to accomplish this. 24 Status of this Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on December 31, 2012. 41 Copyright Notice 43 Copyright (c) 2012 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3 60 3. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . . 3 61 4. Deployment Considerations . . . . . . . . . . . . . . . . . . . 4 62 4.1. Other Solutions . . . . . . . . . . . . . . . . . . . . . . 4 63 5. Maximum Link Metric . . . . . . . . . . . . . . . . . . . . . . 4 64 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 65 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 66 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 67 8.1. Normative References . . . . . . . . . . . . . . . . . . . 5 68 8.2. Informative References . . . . . . . . . . . . . . . . . . 5 69 Appendix A. Changes between the -00 and -01 versions. . . . . . . 5 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 72 1. Motivation 74 In some situations, it may be advantageous to inform routers in a 75 network not to use a specific router as a transit point, but still 76 route to it. Possible situations include the following: 78 o The router is in a critical condition (for example, has very high 79 CPU load or does not have enough memory to store all LSAs or build 80 the routing table). 82 o Graceful introduction and removal of the router to/from the 83 network. 85 o Other (administrative or traffic engineering) reasons. 87 Note that the proposed solution does not remove the router from the 88 topology view of the network (as could be done by just flushing that 89 router's router-LSA), but prevents other routers from using it for 90 transit routing, while still routing packets to the router's own IP 91 addresses, i.e., the router is announced as a stub. 93 It must be emphasized that the proposed solution provides real 94 benefits in networks designed with at least some level of redundancy 95 so that traffic can be routed around the stub router. Otherwise, 96 traffic destined for the networks reachable through such a stub 97 router will be still routed through it. 99 2. Requirements Language 101 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 102 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 103 document are to be interpreted as described in [RFC2119]. 105 3. Proposed Solution 107 The solution described in this document solves two challenges 108 associated with the outlined problem. In the description below, 109 router X is the router announcing itself as a stub. 111 1) Making other routers prefer routes around router X while 112 performing the Dijkstra calculation. 114 2) Allowing other routers to reach IP prefixes directly connected to 115 router X. 117 Note that it would be easy to address issue 1) alone by just flushing 118 router X's router-LSA from the domain. However, it does not solve 119 problem 2), since other routers will not be able to use links to 120 router X in Dijkstra (no back link), and because router X will not 121 have links to its neighbors. 123 To address both problems, router X announces its router-LSA to the 124 neighbors with the costs of all non-stub links (links of the types 125 other than 3) set to MaxLinkMetric. 127 The solution above applies to both OSPFv2 [RFC2328] and OSPFv3 128 [RFC5340]. 130 4. Deployment Considerations 132 When using MaxLinkMetric, some inconsistency may be seen if the 133 network is constructed of routers that perform intra-area Dijkstra 134 calculation as specified in [RFC1247] (discarding link records in 135 router-LSAs that have a MaxLinkMetric cost value) and routers that 136 perform it as specified in [RFC1583] and higher (do not treat links 137 with MaxLinkMetric cost as unreachable). Note that this 138 inconsistency will not lead to routing loops, because if there are 139 some alternate paths in the network, both types of routers will agree 140 on using them rather than the path through the stub router. If the 141 path through the stub router is the only one, the routers of the 142 first type will not use the stub router for transit (which is the 143 desired behavior), while the routers of the second type will still 144 use this path. 146 4.1. Other Solutions 148 This document describes a technique that has been implemented and 149 deployed in a wide variety of networks. OSPFv3 [RFC5340] introduced 150 additional options to provide similar, if not better, control of the 151 forwarding topology; the R-bit and the V6-bit provide a more granular 152 indication of whether a router is active and/or whether it should be 153 used specifically for IPv6 traffic, respectively. 155 It is left to network operators to decide which technique to use in 156 their network. 158 5. Maximum Link Metric 160 Section 3 refers to the cost of all non-stub links as MaxLinkMetric, 161 which is a new fixed architectural value introduced in this document. 163 MaxLinkMetric 164 The metric value indicating that the link described by an LSA 165 should not be used as transit. Used in router-LSAs (see 166 Section 3). It is defined to be the 16-bit binary value of all 167 ones: 0xffff. 169 6. Security Considerations 171 The technique described in this document does not introduce any new 172 security issues into the OSPF protocol. 174 7. Acknowledgements 176 The authors of this document do not make any claims on the 177 originality of the ideas described. Among other people, we would 178 like to acknowledge Henk Smit for being part of one of the initial 179 discussions around this topic. 181 We would also like to thank Shishio Tsuchiya, Gunter Van de Velde, 182 Tomohiro Yamagata, Faraz Shamim and Acee Lindem who provided 183 significant input for the latest version of this document. 185 8. References 187 8.1. Normative References 189 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 190 Requirement Levels", BCP 14, RFC 2119, March 1997. 192 8.2. Informative References 194 [RFC1247] Moy, J., "OSPF Version 2", RFC 1247, July 1991. 196 [RFC1583] Moy, J., "OSPF Version 2", RFC 1583, March 1994. 198 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. 200 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 201 for IPv6", RFC 5340, July 2008. 203 Appendix A. Changes between the -00 and -01 versions. 205 o Defined a new architectural constant (MaxLinkMetric) to eliminate 206 any confusion about the interpretation of LSInfinity. 208 o Added a section to reference the R-bit and V6-bit in OSPFv3. 210 o Updated acks and contact information. 212 Authors' Addresses 214 Alvaro Retana 215 Hewlett-Packard Co. 216 2610 Wycliff Road 217 Raleigh, NC 27607 218 USA 220 Email: alvaro.retana@hp.com 222 Liem Nguyen 223 Cisco Systems, Inc. 224 3750 Cisco Way 225 San Jose, CA 95134 226 USA 228 Email: lhnguyen@cisco.com 230 Alex Zinin 231 Cisco Systems, Inc. 232 Capital Tower, 168 Robinson Rd. 233 Singapore, Singapore 068912 234 Singapore 236 Email: azinin@cisco.com 238 Russ White 239 Verisign, Inc. 240 12061 Bluemont Way 241 Reston, VA 20190 242 USA 244 Email: riwhite@verisign.com 245 Danny McPherson 246 Verisign, Inc. 247 21345 Ridgetop Circle 248 Dulles, VA 20166 249 USA 251 Email: dmcpherson@verisign.com