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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group Christian Martin 2 INTERNET DRAFT Verizon 3 Expiration Date: January 2005 Brad Neal 4 Broadwing Communications 5 Stefano Previdi 6 July 2004 Cisco Systems 8 A Policy Control Mechanism in IS-IS Using Administrative Tags 9 11 1. Status of this Memo 13 This document is an Internet-Draft and is in full conformance with 14 all provisions of Section 10 of RFC 2026. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet- Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 2. Abstract 34 This document describes an extension to the IS-IS protocol to add 35 operational capabilities that allow for ease of management and 36 control over IP prefix distribution within an IS-IS domain. 37 This document enhances the IS-IS protocol by extending the 38 information that a Intermediate System (IS) [router] can place in 39 Link State Protocol Data Units (LSPs) for policy use. This 40 extension will provide operators with a mechanism to control IP 41 prefix distribution throughout multi-level IS-IS domains. 42 Additionally, the information can be placed in LSPs that have TLVs as 43 yet undefined, if this information is used to convey the same meaning 44 in these future TLVs as it is used in the currently defined TLVs. 46 3. Specification of Requirements 48 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 49 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 50 document are to be interpreted as described in [RFC 2119]. 52 4. Introduction 54 As defined in [2] and extended in [3], the IS-IS protocol may be used 55 to distribute IP prefix reachibility information throughout an IS-IS 56 domain. The IP prefix information is encoded as TLV type 128 and 130 57 in [2], with additional information carried in TLV 135 as specified 58 in [3] and TLV 235 as defined in [6]. In particular, the extended IP 59 Reachabilty TLV (135) contains support for a larger metric space, an 60 up/down bit to indicate redistribution between different levels in 61 the hierarchy, an IP prefix, and one or more sub-TLVs that can be 62 used to carry specific information about the prefix. TLV 235 is a 63 derivative of TLV 135, with the addition of MultiTopology membership 64 information [6]. 66 As of this writing no sub-TLVs have been defined; however, this draft 67 proposes 2 new sub-TLVs for both TLV 135 and TLV 235 that may be used 68 to carry administrative information about an IP prefix. 70 5. Sub-TLV Additions 72 This draft proposes 2 new "Administrative Tag" sub-TLVs to be added 73 to TLV 135 and 235. These TLVs specify one or more ordered, 32 or 64 74 bit unsigned integers that may be associated with an IP prefix. 75 Example uses of these tags include controlling redistribution between 76 levels and areas, different routing protocols, or multiple instances 77 of IS-IS running on the same router, or carrying BGP standard or 78 extended communites. 80 The methods for which their use is employed is beyond the scope of 81 this document and left to the implementer and/or operator. 83 The encoding of the sub-TLV(s) is discussed in the following 84 subsections. 86 5.1. 32-bit Administrative Tag Sub-TLV 1 88 The Administrative Tag shall be encoded as one or more 4 octet 89 unsigned integers using Sub-TLV 1 in TLV-135 [3] and TLV 235 [6]. The 90 Administrative Tag Sub-TLV has following structure: 92 1 octet of type (value: 1) 93 1 octet of length (value: multiple of 4) 94 one or more instances of 4 octets of administrative tag 96 An implementation may consider only one of the encoded tags, in which 97 case the first encoded tag must be considered. A tag value of zero 98 is reserved and should be treated as "no tag". 100 5.2. 64-bit Administrative Tag Sub-TLV 2 102 The Administrative Tag shall be encoded as one or more 8 octet 103 unsigned integers using Sub-TLV 2 in TLV-135 [3] and TLV 235 [6]. The 104 64-bit Administrative Tag Sub-TLV has following structure: 106 1 octet of type (value: 1) 107 1 octet of length (value: multiple of 8) 108 one or more instances of 8 octets of administrative tag 110 An implementation may consider only one of the encoded tags, in which 111 case the first encoded tag must be considered. A tag value of zero 112 is reserved and should be treated as "no tag". 114 6. Ordering of Tags 116 The semantics of the tag order are implementation-dependent. That 117 is, there is no implied meaning to the ordering of the tags that 118 indicates a certain operation or set of operations need be performed, 119 based on the order of the tags. Each tag SHOULD be treated as an 120 autonomous identifier that MAY be used in policy to perform a policy 121 action. Whether or not tag A preceeds or succeeds tag B SHOULD not 122 change the meaning of the tag set. However, an implementation MAY 123 wish to preserve tag ordering such that an ordered set of tags has 124 meaning to the local policy. 126 Each IS that receives an LSP with TLV(s) 135 and/or 235, that have 127 associated SubTLV(s) 1 and/or 2, MAY operate on the tag values as 128 warranted by the implementation. If an implementation needs to 129 change tag values, for example, at an area boundary, then the TLV(s) 130 SHOULD be copied to the newly generated Level-1 or Level-2 LSP at 131 which point, the contents of the SubTLV(s) MAY change as dictated by 132 the policy action. In the event that no change is required, the 133 SubTLV(s) SHOULD be copied in order into the new LSP, such that 134 ordering is preserved. 136 7. A compliant IS-IS implementation: 138 MUST be able to assign one tag to any IP prefix in TLV(s) 135 and/or 139 235. 141 MAY be able to assign more than one tag to any IP prefix in TLV(s) 142 135 and/or 235. 144 MAY be able to rewrite or remove one or more tags associated with a 145 prefix in TLV(s) 135 and/or 235 upon LSP generation at an area 146 boundary. 148 8. Operation 150 An administrator associates an Administrative Tag value with some 151 interesting property. When IS-IS advertises reachability for some IP 152 prefix that has that property, it adds the Administrative Tag to the 153 IP reachability information TLV for that prefix, and the tag "sticks" 154 to the prefix as it is flooded throughout the routing domian. 156 Consider the network in figure 1. We wish to "leak" L1 prefixes [5] 157 with some property, A, from L2 to the L1 router R1. Without policy- 158 groups, there is no way for R2 to know property A prefixes from 159 property B prefixes. 161 R2--------R3--------R4 162 L2 / \ 163 - - - /- - - - - - - - - - - - - - 164 L1 / \ 165 R1----1.1.1.0/24 (A) R5 166 | 167 | 168 1.1.2.0/24 (B) 170 Figure 1 172 We associate Administrative Tag 100 with property A, and have R5 173 attach that value to the IP extended reachability information TLV for 174 prefix 1.1.2.0/24. R2 has a policy in place to "match prefixes with 175 Administrative Tag 100, and leak to L1." 177 The previous example is rather simplistic; it seems that it would be 178 just as easy for R2 simply to match the prefix 1.1.2.0/24. However, 179 if there are a large number of routers that need to apply some policy 180 according to property A and large number of "A" prefixes, this 181 mechanism can be quite helpful. 183 9. Security Considerations 185 This document raises no new security issues for IS-IS, as any 186 annotations to IP prefixes should not pass outside the administrative 187 control of the network operator of the IS-IS domain. Such an 188 allowance would violate the spirit of Interior Gateway Protocols in 189 general and IS-IS in particular. 191 10. IANA Considerations 193 The authors have chosen "1" as the typecode of the 32-bit 194 Administrative Tag sub-TLV and "2" as the typecode of the 64-bt 195 Administrative Tag SubTLV. These values must be allocated by IANA. 197 11. Acknowledgments 199 The authors would like to thank Henk Smit for clarifying the best 200 place to describe this new information, Tony Li and Tony Przygienda 201 for useful comments on this draft, Danny McPherson for some much 202 needed formatting assistance, and Mike Shand for useful discussions 203 on encoding structure of the sub-TLV. 205 12. References 207 [1] "Intermediate System to Intermediate System Intra-Domain Routeing 208 Exchange Protocol for use in Conjunction with the Protocol for 209 Providing the Connectionless-mode Network Service (ISO 8473)", 210 ISO 10589. 212 [2] Callon, R., RFC 1195, "Use of OSI IS-IS for routing in TCP/IP and 213 dual environments", RFC 1195, December 1990. 215 [3] Li, T., and Smit, H., "IS-IS extensions for Traffic Engineering", 216 Internet Draft, "Work in Progress", September 2000. 218 [4] Adwuche, D., Malcolm, J., Agogbua, M., O'Dell, M. and McManus, 219 J., "Requirements for Traffic Engineering Over MPLS," RFC 2702, 220 September 1999. 222 [5] Li,T., Przygienda, T., Smit, H., "Domain-wide Prefix Distribution 223 with Two-Level IS-IS" RFC 2966, October 2000 225 [6] Przygienda, T., Shen, N., Sheth, N., "M-ISIS: Multi Topology 226 Routing in IS-IS", draft-ietf-isis-wg-multi-topology-03.txt, April 227 2002. 229 13. Authors' Address 231 Christian Martin 232 Verizon 233 1880 Campus Commons Dr 234 Reston, VA 20191 235 Email: cmartin@verizon.com 237 Brad Neal 238 Broadwing Communications 239 1835 Kramer Lane - Suite 100 240 Austin, TX 78758 241 USA 242 Email: bneal@broadwing.com 244 Stefano Previdi 245 Cisco Systems, Inc. 246 De Kleetlaan 6A 247 1831 Diegem - Belgium 248 email: sprevidi@cisco.com