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Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). 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 Intended status: Informational A. Lindem 5 Expires: January 14, 2013 Ericsson 6 July 13, 2012 8 OSPF Incremental Link State Database Synchronization 9 draft-retana-ospf-ils-01 11 Abstract 13 The ability of OSPF to transport non-routing information to be used 14 by other applications was defined by the Opaque LSA Option. In order 15 to not impact the convergence of routing information, this document 16 describes a simple process to incrementally synchronize the routing 17 and non-routing information residing in an OSPF link-state database. 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 http://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 January 14, 2013. 36 Copyright Notice 38 Copyright (c) 2012 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 (http://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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 2. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3 55 3. Incremental LSDB Synchronization Process . . . . . . . . . . . 3 56 3.1. Graceful Restart . . . . . . . . . . . . . . . . . . . . . 4 57 3.2. Flooding and Database Synchronization . . . . . . . . . . . 5 58 4. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 5 59 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 60 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 61 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 62 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 63 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 64 8.2. Informative References . . . . . . . . . . . . . . . . . . 6 65 Appendix A. Changes between the -00 and -01 versions. . . . . . . 7 66 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 68 1. Introduction 70 Opaque LSAs [RFC5250] provide the ability for OSPFv2 [RFC2328] to 71 transport non-routing information to be used by other applications. 72 A similar capability exists in OSPFv3 [RFC5340] through the use of 73 the U-bit and an appropriate LSA Function Code. Throughout this 74 document Opaque LSAs and ones with unrecognized link-state types will 75 be referred to simply as "opaque". 77 The presence of opaque information in the OSPF Link-State Database 78 (LSDB) may result in longer database exchange times, especially in 79 cases where the amount of data is significantly larger than the 80 routing-specific information. In order to not impact the convergence 81 of routing information, this document describes a simple process to 82 incrementally synchronize the information residing in an OSPF LSDB. 83 The process uses existing mechanisms. 85 2. Requirements Language 87 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 88 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 89 document are to be interpreted as described in [RFC2119]. 91 3. Incremental LSDB Synchronization Process 93 The Incremental LSBD Synchronization (ILS) process consists of the 94 following steps: 96 LSA Prioritization 97 The contents of the local LSDB are classified to determine 98 which LSAs require prioritized synchronization. 100 In general, LSAs containing routing-specific information MUST 101 be classified as requiring prioritized synchronization, while 102 other LSAs MAY be classified as not requiring it. 104 All routers in the OSPF routing domain should use the same 105 criteria for LSA prioritization. While this is not required 106 for correct OSPF operation, it is required for deterministic 107 operation of the applications using the opaque LSAs. 109 Prioritized LSDB Synchronization 110 This step corresponds to the adjacency establishment process 111 as described in [RFC2328]. 113 LSAs classified as not requiring prioritized synchronization 114 MUST NOT be included in Database Description (DBD) Packets 115 during the Database Exchange Process. The OSPF routing table 116 structure SHOULD be calculated before moving on to the next 117 step. 119 Final LSDB Synchronization 120 In this step, any remaining LSAs in the LSDB SHOULD be 121 synchronized. The routers MUST use the Out-of-Band LSDB 122 Resynchronization [RFC4811] (OOB Resync) mechanism, which 123 provides a way to resynchronize the LSDB without affecting 124 the advertised neighbor state. 126 The process is described in terms of LSAs containing (or not) 127 routing-specific information, but it may be generalized to include 128 any other criteria considered significant in the local network and 129 protocol instance. 131 The last step in the process MAY be used recursively to achieve an 132 incremental LSDB synchronization through different types of data, 133 making it also applicable to environments where only non-routing 134 information exists. 136 3.1. Graceful Restart 138 The restart of the OSPF software in a router also presents an 139 opportunity for LSDB synchronization. Because the restarting router 140 is still in the forwarding path, it is important for the routing 141 information in the LSDB to be synchronized as fast as possible. ILS 142 can be used, with minor modifications, to reduce the synchronization 143 time and the probability of network topology changes. 145 Graceful OSPF Restart 146 Graceful OSPF Restart for OSPFv2 [RFC3623] and OSPFv3 147 [RFC5187] don't specify any changes to the adjacency 148 establishment process. 150 ILS can be used by the Helper Neighbor during the Grace 151 Period; if so, then the Helper Node MUST include any Grace- 152 LSAs in the DBD Packets during the Prioritized LSDB 153 Synchronization step. 155 OSPF Restart Signaling 156 OSPF Restart Signaling [RFC4812] defines a mechanism to 157 inform neighbors about a local restart, in which the LSDB 158 synchronization is achieved using OOB Resync. In other 159 words, the Prioritized LSDB Synchronization step would use 160 OOB Resync if the non-restarting router uses ILS. No other 161 changes to the process are needed. 163 3.2. Flooding and Database Synchronization 165 In order to maintain OSPF reliable flooding, separate neighbor 166 flooding state must be maintained for the lower priority LSAs and 167 used when determining whether a lower priority LSA has been flooded 168 or put on a neighbor's retransmission list. 170 The rules for flooding lower-priority LSAs and deleting lower 171 priority MaxAge LSAs are modified for ILS synchronization. Neighbor 172 state MUST be maintained as to whether low-priority LSAs have been 173 synchronized with a given neighbor. In this document, this lower 174 priority state will be referred to as ILS-state. This ILS-state will 175 not advance until a neighbor reaches Full state and will return to 176 Down ILS-state should the neighbor fall from Full state. 178 If a given neighbor's ILS-state is Exchange or higher, then lower 179 priority LSAs should be flooded to that neighbor. This similar to 180 the general LSA flooding rules in Section 13.1 of [RFC2328]. 182 Consistent with Section 14.1 in [RFC2328], a lower priority MaxAge 183 LSA cannot be removed the Link State Database if any the router is in 184 Exchange or Loading ILS-state. 186 If multiple ILS synchronizations are used for synchronization 187 different priorities of LSAs, separate ILS-state MUST be maintained 188 for each priority and the previously described rules MUST be applied 189 at each priority. 191 4. Backward Compatibility 193 The operation of ILS depends on the support of OOB Resync during 194 synchronization; no backwards compatibility issues exist there 195 [RFC4811]. If OOB Resync is not supported by one of the routers, 196 then the LSDB synchronization would fall back to the adjacency 197 establishment process as described in [RFC2328]. 199 If OOB Resync is supported, but ILS has not been implemented by all 200 the routers involved, the operation is still backwards compatible. 201 Note that the process (Section 3) depends on the database description 202 by the local router. In other words, a router may decide to not 203 fully describe the contents of its LSDB to its neighbor during the 204 adjacency establishment process, and later use OOB Resync to 205 incrementally describe the difference; the receiver doesn't need to 206 be aware of ILS. The benefits of ILS may only be partially realized 207 if not supported by all the routers involved in synchronization. 209 5. IANA Considerations 211 This memo includes no request to IANA. 213 6. Security Considerations 215 The process described in this document does not introduce any new 216 security issues into the OSPF protocol. 218 7. Acknowledgements 220 The authors would like to thank Abhay Roy and Liem Nguyen for their 221 comments, and Dimitri Papadimitriou for his comments and for 222 providing the motivation for this document. 224 8. References 226 8.1. Normative References 228 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 229 Requirement Levels", BCP 14, RFC 2119, March 1997. 231 [RFC4811] Nguyen, L., Roy, A., and A. Zinin, "OSPF Out-of-Band Link 232 State Database (LSDB) Resynchronization", RFC 4811, 233 March 2007. 235 8.2. Informative References 237 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. 239 [RFC3623] Moy, J., Pillay-Esnault, P., and A. Lindem, "Graceful OSPF 240 Restart", RFC 3623, November 2003. 242 [RFC4812] Nguyen, L., Roy, A., and A. Zinin, "OSPF Restart 243 Signaling", RFC 4812, March 2007. 245 [RFC5187] Pillay-Esnault, P. and A. Lindem, "OSPFv3 Graceful 246 Restart", RFC 5187, June 2008. 248 [RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The 249 OSPF Opaque LSA Option", RFC 5250, July 2008. 251 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 252 for IPv6", RFC 5340, July 2008. 254 Appendix A. Changes between the -00 and -01 versions. 256 o Added a new section explaining how to maintain reliable flooding 257 for the low priority LSAS. 259 o Updated authors and contact information. 261 Authors' Addresses 263 Alvaro Retana 264 Hewlett-Packard Co. 265 2610 Wycliff Road 266 Raleigh, NC 27607 267 USA 269 Email: alvaro.retana@hp.com 271 Acee Lindem 272 Ericsson 273 102 Carric Bend Court 274 Cary, NC 27519 275 USA 277 Email: acee.lindem@ericsson.com