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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) == Outdated reference: A later version (-07) exists of draft-baker-ipv6-isis-dst-src-routing-00 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group F.J. Baker 3 Internet-Draft Cisco Systems 4 Intended status: Standards Track August 28, 2013 5 Expires: March 01, 2014 7 Using IS-IS with Token-based Access Control 8 draft-baker-ipv6-isis-dst-flowlabel-routing-01 10 Abstract 12 This note describes the changes necessary for IS-IS to route IPv6 13 traffic specified prefix if and only if the packet contains an 14 authorization token. 16 Status of This Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on March 01, 2014. 33 Copyright Notice 35 Copyright (c) 2013 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 49 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 50 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 51 2. Theory of Routing . . . . . . . . . . . . . . . . . . . . . . 2 52 2.1. Dealing with ambiguity . . . . . . . . . . . . . . . . . 3 53 2.2. Interactions with other constraints . . . . . . . . . . . 3 54 3. Extensions necessary for IPv6 Authenticated Routing in IS-IS 4 55 3.1. Authorization Token sub-TLV . . . . . . . . . . . . . . . 4 56 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 57 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 58 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 59 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 60 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 61 7.2. Informative References . . . . . . . . . . . . . . . . . 5 62 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 5 63 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 65 1. Introduction 67 This specification builds on IS-IS for IPv6 [RFC5308] and its 68 extensible TLV. This note defines the sub-TLV for an IPv6 [RFC2460] 69 Flow Label, to define routes from to a destination prefix qualified 70 by an authorization token. 72 The approach may be combined with other qualifying attributes, such 73 as routing "to that destination AND from a specified source". The 74 obvious application is data center inter-tenant routing using a form 75 of token-based access control. If the sender doesn't know the value 76 to insert in the flow label or hop-by-hop option (the receiver's 77 tenant ID), he in effect has no route to that destination. 79 1.1. Requirements Language 81 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 82 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 83 document are to be interpreted as described in [RFC2119]. 85 2. Theory of Routing 87 Both IS-IS and OSPF perform their calculations by building a lattice 88 of routers and links from the router performing the calculation to 89 each router, and then use routes (sequences in the lattice) to get to 90 destinations that those routes advertise connectivity to. Following 91 the SPF algorithm, calculation starts by selecting a starting point 92 (typically the router doing the calculation), and successively adding 93 {link, router} pairs until one has calculated a route to every router 94 in the network. As each router is added, including the original 95 router, destinations that it is directly connected to are turned into 96 routes in the route table: "to get to 2001:db8::/32, route traffic to 97 {interface, list of next hop routers}". For immediate neighbors to 98 the originating router, of course, there is no next hop router; 99 traffic is handled locally. 101 In this context, the route is qualified by an authorization token, 102 carried in the flow label or a hop-by-hop option; It is installed 103 into the FIB with the destination prefix, and the FIB applies the 104 route if and only if the token in the packet matches the token in the 105 route. Of course, there may be multiple LSPs in the RIB with the 106 same destination and differing authorization tokens; these may also 107 have the same or differing next hop lists. The intended forwarding 108 action is to forward matching traffic to one of the next hop routers 109 associated with this destination and authorization tokens, or to 110 discard non-matching traffic as "destination unreachable". 112 LSAs that lack an authorization tokens sub-TLV match any token that 113 may be present, by definition. 115 2.1. Dealing with ambiguity 117 In any routing protocol, there is the possibility of ambiguity. For 118 example, one router might advertise a fairly general prefix - a 119 default route, a discard prefix (which consumes all traffic that is 120 not directed to an instantiated subnet), or simply an aggregated 121 prefix while another router advertises a more specific one. In 122 source/destination routing, potentially ambiguous cases include cases 123 in which the link state database contains two routes A->B' and A'->B, 124 in which A' is a more specific prefix within the prefix A and B' is a 125 more specific prefix within the prefix B. Traditionally, we have 126 dealt with ambiguous destination routes using a "longest match first" 127 rule. If the same datagram matches more than one destination prefix 128 advertised within an area, we follow the route with the longest 129 matching prefix. 131 In this case, we follow a similar but slightly different rule; the 132 FIB lookup MUST yield the route with the longest matching destination 133 prefix that also matches the authorization token. A FIB route with 134 no such token matches any authorization token. 136 2.2. Interactions with other constraints 138 In the event that there are other constraints on routing, such as 139 proposed in [I-D.baker-ipv6-isis-dst-src-routing], the effect is a 140 logical AND. The FIB lookup must yield the route with the longest 141 matching destination prefix that also matches each of the 142 constraints. 144 3. Extensions necessary for IPv6 Authenticated Routing in IS-IS 146 Section 2 of [RFC5308] defines the "IPv6 Reachability TLV", and 147 carries in it destination prefix advertisements. It has the 148 capability of extension, using sub-TLVs. 150 In this model, the flow label is used to prove that the datagram's 151 sender has specific knowledge of its intended receiver. No proof is 152 requested; this is left for higher layer exchanges such as IPSec or 153 TLS. However, if the information is distributed privately, such as 154 through DHCP/DHCPv6, the network can presume that a system that marks 155 traffic with the right flow label has a good chance of being 156 authorized to communicate with its peer. 158 The key consideration, in this context, is that the flow label is a 159 20 bit number. As such, an advertised route requiring a given flow 160 label value is calling for an exact match of all 20 bits of the label 161 value. 163 3.1. Authorization Token sub-TLV 165 0 1 2 3 166 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 167 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 168 | Type | Length | MBZ | 20 bit Flow Label 169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 170 | 171 +-+-+-+-+-+-+-+-+ 173 Source Prefix Sub-TLV 175 Source Prefix Type: assigned by IANA 177 TLV Length: Length of the sub-TLV in octets 179 Flow Label: Flow Label value (20 bits) 181 4. IANA Considerations 183 The source prefix type mentioned in Section 3 must be defined. 185 5. Security Considerations 187 Network layer Token-based Access Control is part of a security 188 solution. It is not, in itself, a complete solution. It acts as a 189 pervasive network layer firewall, preventing unauthorized traffic 190 from arriving at a destination. However, as in any network, a host 191 is its own last bastion of defense; it needs IPsec or TLS-style 192 authorization and authorization of its peers, and must refuse traffic 193 that contains the authorization token but is in fact malicious. 195 6. Acknowledgements 197 7. References 199 7.1. Normative References 201 [ISO.10589.1992] 202 International Organization for Standardization, 203 "Intermediate system to intermediate system intra-domain- 204 routing routine information exchange protocol for use in 205 conjunction with the protocol for providing the 206 connectionless-mode Network Service (ISO 8473)", ISO 207 Standard 10589, 1992. 209 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 210 Requirement Levels", BCP 14, RFC 2119, March 1997. 212 [RFC2460] Deering, S.E. and R.M. Hinden, "Internet Protocol, Version 213 6 (IPv6) Specification", RFC 2460, December 1998. 215 [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, October 216 2008. 218 7.2. Informative References 220 [I-D.baker-ipv6-isis-dst-src-routing] 221 Baker, F., "IPv6 Source/Destination Routing using IS-IS", 222 draft-baker-ipv6-isis-dst-src-routing-00 (work in 223 progress), February 2013. 225 Appendix A. Change Log 227 Initial Version: February 2013 229 updated Version: August 2013 231 Author's Address 233 Fred Baker 234 Cisco Systems 235 Santa Barbara, California 93117 236 USA 238 Email: fred@cisco.com