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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. '0' -- Possible downref: Non-RFC (?) normative reference: ref. '2' Summary: 6 errors (**), 0 flaws (~~), 4 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Internet Engineering Task Force Christian E. Hopps 2 INTERNET-DRAFT NextHop Technologies 3 Expires September 2001 2 April 2001 5 Routing IPv6 with IS-IS 6 8 Status of this Memo 10 This document is an Internet-Draft and is in full conformance with 11 all provisions of Section 10 of RFC2026. 13 Internet-Drafts are working documents of the Internet Engineering 14 Task Force (IETF), its areas, and its working groups. Note that 15 other groups may also distribute working documents as Internet- 16 Drafts. 18 Internet-Drafts are draft documents valid for a maximum of six months 19 and may be updated, replaced, or obsoleted by other documents at any 20 time. It is inappropriate to use Internet- Drafts as reference 21 material or to cite them other than as "work in progress." 23 The list of current Internet-Drafts can be accessed at 24 http://www.ietf.org/ietf/1id-abstracts.txt 26 The list of Internet-Draft Shadow Directories can be accessed at 27 http://www.ietf.org/shadow.html. 29 Copyright Notice 31 Copyright (C) The Internet Society (2001). All Rights Reserved. 33 Abstract 35 This draft specifies a method for exchanging IPv6 routing information 36 using the IS-IS routing protocol [0]. The method utilizes the same 37 mechanisms described in RFC 1195 [1]. This is accomplished by adding 38 2 new TLVs and defining their use. These new TLVs are patterned from 39 the ones described in "IS-IS extensions for Traffic Engineering" [2]. 41 Just as in RFC 1195 [1] with IPv4 and OSI, this method allows one to 42 route both IPv4 and IPv6 using a single intra-domain routing 43 protocol. 45 1. Terms 47 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 48 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 49 document are to be interpreted as described in RFC 2119. 51 2. Overview 53 IS-IS is an extendible intra-domain routing protocol. Each router in 54 the routing domain issues an LSP that contains information pertaining 55 to that router. The LSP contains typed variable length data often 56 referred to as TLVs (type-length-values). We extend the protocol 57 with 2 new TLVs to carry information required to perform IPv6 58 routing. 60 In [1] a method is described to route both OSI and IPv4. We utilize 61 this same method with some minor changes to allow for IPv6. To do so 62 we must define 2 new TLVs, namely "IPv6 Reachability" and "IPv6 63 Interface Address" and a new IPv6 protocol identifier. In our new 64 TLVs we utilize the extended metrics and up/down semantics of [2]. 66 3. IPv6 Reachability TLV 68 The "IPv6 Reachability" TLV is TLV type 236 (0xEC). 70 [1] defines 2 Reachability TLVs, "IP Internal Reachability 71 Information" and "IP External Reachability Information". We provide 72 the equivalent IPv6 data with the "IPv6 Reachability" TLV and an 73 "external" bit. 75 The "IPv6 Reachability" TLV describes network reachability through 76 the specification of a routing prefix, metric information, a bit to 77 indicate if the prefix is being advertised down from a higher level, 78 a bit to indicate if the prefix is being distributed from another 79 routing protocol and optionally the existence of sub-TLVs to allow 80 for later extension. This data is represented by the following 81 structure: 83 4 octets of metric information 84 1 octet of control information 85 1 bit of up/down information 86 1 bit indicating external origination 87 (e.g., from another routing protocol) 88 1 bit indicating the existence of sub-TLVs 89 5 reserved bits which must be zero and ignored 90 1 octet of prefix length 91 0-16 octets of prefix 92 0-249 optional octets of sub-TLVs, if present consisting of 93 1 octet of length of sub-TLVs 94 0-248 octets of sub-TLVs 96 This structure may appear any number of times (including none) within 97 the TLV. 99 As is described in [2], "the up/down bit is set to 0 when a prefix is 100 first injected into IS-IS. If a prefix is redistributed from a 101 higher level to a lower level (e.g., level two to level one), the bit 102 shall be set to 1 to indicate that the prefix has travelled down the 103 hierarchy. If a prefix is redistributed from an area to another area 104 at the same level then the up/down bit shall be set to 1." 106 If the prefix was distributed into IS-IS from another routing 107 protocol the external bit shall be set to 1. This information is 108 useful when distributing prefixes from IS-IS to other protocols. 110 If the sub-TLV bit is set to 0 then the optional octets of sub-TLVs 111 are not present. Otherwise the bit is 1 and the octet following the 112 prefix will contain the length of the sub-TLV portion of the 113 structure. 115 The prefix is "packed" in the data structure. That is, only the 116 required number of octets of prefix are present. This number can be 117 computed from the prefix length octet as follows: 119 prefix octets = integer of ((prefix length + 7) / 8) 121 Just as in [2], if a prefix is advertised with a metric larger than 122 MAX_V6_PATH_METRIC (0xFE000000), this prefix must not be considered 123 during the normal SPF computation. This will allow advertisement of 124 a prefix for purposes other than building the normal IPv6 routing 125 table. 127 4. IPv6 Interface Address TLV 129 The "IPv6 Interface Address" TLV is TLV type 232 (0xE8). 131 This TLV maps directly to [1]'s "IP Interface Address" TLV. We 132 necessarily modify the contents to be 0-15 16 octet IPv6 interface 133 addresses instead of 0-63 4 octet IPv4 interface address. 135 We further restrict the semantics of this TLV depending on where it 136 is advertised. For Hello PDUs the "Interfaces Address" TLV must 137 contain only the link-local IPv6 addresses assigned to the interface 138 which is sending the Hello. For LSPs the "Interfaces Address" TLVs 139 must contain only the non-link-local IPv6 addresses assigned to the 140 IS. 142 5. IPv6 NLPID 144 The value of the IPv6 NLPID is 142 (0x8E). 146 As with [1] and IPv4, if the IS supports IPv6 routing using IS-IS, it 147 must advertise this in the "NLPID" TLV by adding the IPv6 NLPID. 149 6. Operation 151 We utilize the same changes to [1] as made in [2] for the processing 152 of prefix information. These changes are both related to the SPF 153 calculation. 155 Since the metric space has been extended we need to redefine the 156 MAX_PATH_METRIC (1023) from the original specification in [1]. This 157 new value MAX_V6_PATH_METRIC is the same as in [2] (0xFE000000). If 158 during the SPF a path metric would exceed MAX_V6_PATH_METRIC it shall 159 be considered to be MAX_V6_PATH_METRIC. 161 The order of preference between paths for a given prefix must be 162 modified to consider the up/down bit. The new order of preference is 163 as follows (from best to worst). 165 1. Level 1 up prefix 166 2. Level 2 up prefix 167 3. Level 2 down prefix 168 4. Level 1 down prefix 170 If multiple paths have the same best preference then selection occurs 171 based on metric. Any remaining multiple paths should be considered 172 for equal-cost multi-path routing if the router supports this, otherwise 173 the router can select any one of the multiple paths. 175 7. Implementations 177 An implementation of this draft has been completed in GateD. 179 8. Security Considerations 181 This document raises no new security considerations. 183 9. References 185 [0] "Intermediate System to Intermediate System Intra-Domain Routeing 186 Exchange Protocol for use in Conjunction with the Protocol for 187 Providing the Connectionless-mode Network Service (ISO 8473)", ISO 188 10589, 1992. 190 [1] Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and Dual 191 Environments", RFC 1195, December 1990. 193 [2] Smit, H., and T. Li, "IS-IS extensions for Traffic Engineering", 194 Work in Progress, May 1999. 196 10. Author's Address 198 Christian E. Hopps 199 NextHop Technologies, Inc. 200 517 W. William Street, 201 Ann Arbor, MI 48103-4943 202 U.S.A. 203 Phone: +1 734 936 0291 204 Email: chopps@nexthop.com 206 11. Full Copyright Statement 208 Copyright (C) The Internet Society 2000. All Rights Reserved. 210 This document and translations of it may be copied and furnished to 211 others, and derivative works that comment on or otherwise explain it 212 or assist in its implementation may be prepared, copied, published 213 and distributed, in whole or in part, without restriction of any 214 kind, provided that the above copyright notice and this paragraph are 215 included on all such copies and derivative works. However, this 216 document itself may not be modified in any way, such as by removing 217 the copyright notice or references to the Internet Society or other 218 Internet organizations, except as needed for the purpose of 219 developing Internet standards in which case the procedures for 220 copyrights defined in the Internet Standards process must be 221 followed, or as required to translate it into languages other than 222 English. 224 The limited permissions granted above are perpetual and will not be 225 revoked by the Internet Society or its successors or assigns. 227 This document and the information contained herein is provided on an 228 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 229 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 230 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 231 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 232 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.