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(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 30, 2011) is 4685 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 R. White 6 Expires: January 1, 2012 A. Zinin 7 Cisco Systems, Inc. 8 D. McPherson 9 Verisign, Inc. 10 June 30, 2011 12 OSPF Stub Router Advertisement 13 draft-ietf-ospf-rfc3137bis-00 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 January 1, 2012. 41 Copyright Notice 43 Copyright (c) 2011 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. Compatibility issues . . . . . . . . . . . . . . . . . . . . . 4 62 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 63 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4 64 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 65 7.1. Normative References . . . . . . . . . . . . . . . . . . . 5 66 7.2. Informative References . . . . . . . . . . . . . . . . . . 5 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 69 1. Motivation 71 In some situations, it may be advantageous to inform routers in a 72 network not to use a specific router as a transit point, but still 73 route to it. Possible situations include the following: 75 o The router is in a critical condition (for example, has very high 76 CPU load or does not have enough memory to store all LSAs or build 77 the routing table). 79 o Graceful introduction and removal of the router to/from the 80 network. 82 o Other (administrative or traffic engineering) reasons. 84 Note that the proposed solution does not remove the router from the 85 topology view of the network (as could be done by just flushing that 86 router's router-LSA), but prevents other routers from using it for 87 transit routing, while still routing packets to the router's own IP 88 addresses, i.e., the router is announced as a stub. 90 It must be emphasized that the proposed solution provides real 91 benefits in networks designed with at least some level of redundancy 92 so that traffic can be routed around the stub router. Otherwise, 93 traffic destined for the networks reachable through such a stub 94 router will be still routed through it. 96 2. Requirements Language 98 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 99 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 100 document are to be interpreted as described in [RFC2119]. 102 3. Proposed Solution 104 The solution described in this document solves two challenges 105 associated with the outlined problem. In the description below, 106 router X is the router announcing itself as a stub. 108 1) Making other routers prefer routes around router X while 109 performing the Dijkstra calculation. 111 2) Allowing other routers to reach IP prefixes directly connected to 112 router X. 114 Note that it would be easy to address issue 1) alone by just flushing 115 router X's router-LSA from the domain. However, it does not solve 116 problem 2), since other routers will not be able to use links to 117 router X in Dijkstra (no back link), and because router X will not 118 have links to its neighbors. 120 To address both problems, router X announces its router-LSA to the 121 neighbors with the costs of all non-stub links (links of the types 122 other than 3) set to LSInfinity (16-bit value 0xFFFF, rather than 24- 123 bit value 0xFFFFFF used in summary and AS-external LSAs). 125 The solution above applies to both OSPFv2 [RFC2328] and OSPFv3 126 [RFC5340]. 128 4. Compatibility issues 130 Some inconsistency may be seen when the network is constructed of the 131 routers that perform intra-area Dijkstra calculation as specified in 132 [RFC1247] (discarding link records in router-LSAs that have 133 LSInfinity cost value) and routers that perform it as specified in 134 [RFC1583] and higher (do not treat links with LSInfinity cost as 135 unreachable). Note that this inconsistency will not lead to routing 136 loops, because if there are some alternate paths in the network, both 137 types of routers will agree on using them rather than the path 138 through the stub router. If the path through the stub router is the 139 only one, the routers of the first type will not use the stub router 140 for transit (which is the desired behavior), while the routers of the 141 second type will still use this path. 143 5. Security Considerations 145 The technique described in this document does not introduce any new 146 security issues into the OSPF protocol. 148 6. Acknowledgements 150 The authors of this document do not make any claims on the 151 originality of the ideas described. Among other people, we would 152 like to acknowledge Henk Smit for being part of one of the initial 153 discussions around this topic. 155 We would also like to thank Shishio Tsuchiya, Gunter Van de Velde and 156 Tomohiro Yamagata for reminding us of the need to document the OSPFv3 157 behavior. 159 7. References 161 7.1. Normative References 163 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 164 Requirement Levels", BCP 14, RFC 2119, March 1997. 166 7.2. Informative References 168 [RFC1247] Moy, J., "OSPF Version 2", RFC 1247, July 1991. 170 [RFC1583] Moy, J., "OSPF Version 2", RFC 1583, March 1994. 172 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. 174 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 175 for IPv6", RFC 5340, July 2008. 177 Authors' Addresses 179 Alvaro Retana 180 Hewlett-Packard Co. 181 2610 Wycliff Road 182 Raleigh, NC 27607 183 USA 185 Email: alvaro.retana@hp.com 187 Liem Nguyen 188 Cisco Systems, Inc. 189 3750 Cisco Way 190 San Jose, CA 95134 191 USA 193 Email: lhnguyen@cisco.com 195 Russ White 196 Cisco Systems, Inc. 197 7025 Kit Creek Rd. 198 Research Triangle Park, NC 27709 199 USA 201 Email: russwh@cisco.com 202 Alex Zinin 203 Cisco Systems, Inc. 204 Capital Tower, 168 Robinson Rd. 205 Singapore, Singapore 068912 206 Singapore 208 Email: azinin@cisco.com 210 Danny McPherson 211 Verisign, Inc. 212 21345 Ridgetop Circle 213 Dulles, VA 20166 214 USA 216 Email: dmcpherson@verisign.com