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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-02) exists of draft-acee-ospfv3-lsa-extend-00 ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) == Outdated reference: A later version (-03) exists of draft-baker-ipv6-ospf-dst-src-routing-02 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--).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 OSPFv3 with Token-based Access Control 8 draft-baker-ipv6-ospf-dst-flowlabel-routing-03 10 Abstract 12 This note describes the changes necessary for OSPF 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 OSPF . 4 55 3.1. Authorization Token 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 OSPF for IPv6 [RFC5340] and its 68 extensible LSA, defined in OSPFv3 LSA Extendibility 69 [I-D.acee-ospfv3-lsa-extend]. This note defines the TLV for an IPv6 70 [RFC2460] Flow Label, to define routes from to a destination prefix 71 qualified by an authorization token. 73 The approach may be combined with other qualifying attributes, such 74 as routing "to that destination AND from a specified source". The 75 obvious application is data center inter-tenant routing using a form 76 of token-based access control. If the sender doesn't know the value 77 to insert in the flow label or hop-by-hop option (the receiver's 78 tenant ID), he in effect has no route to that destination. 80 1.1. Requirements Language 82 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 83 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 84 document are to be interpreted as described in [RFC2119]. 86 2. Theory of Routing 88 Both IS-IS and OSPF perform their calculations by building a lattice 89 of routers and links from the router performing the calculation to 90 each router, and then use routes (sequences in the lattice) to get to 91 destinations that those routes advertise connectivity to. Following 92 the SPF algorithm, calculation starts by selecting a starting point 93 (typically the router doing the calculation), and successively adding 94 {link, router} pairs until one has calculated a route to every router 95 in the network. As each router is added, including the original 96 router, destinations that it is directly connected to are turned into 97 routes in the route table: "to get to 2001:db8::/32, route traffic to 98 {interface, list of next hop routers}". For immediate neighbors to 99 the originating router, of course, there is no next hop router; 100 traffic is handled locally. 102 In this context, the route is qualified by an authorization token, 103 carried in the flow label or a hop-by-hop option; It is installed 104 into the FIB with the destination prefix, and the FIB applies the 105 route if and only if the token in the packet matches the token in the 106 route. Of course, there may be multiple LSPs in the RIB with the 107 same destination and differing authorization tokens; these may also 108 have the same or differing next hop lists. The intended forwarding 109 action is to forward matching traffic to one of the next hop routers 110 associated with this destination and authorization tokens, or to 111 discard non-matching traffic as "destination unreachable". 113 LSAs that lack an authorization token TLV match any token that may be 114 present, by definition. 116 2.1. Dealing with ambiguity 118 In any routing protocol, there is the possibility of ambiguity. For 119 example, one router might advertise a fairly general prefix - a 120 default route, a discard prefix (which consumes all traffic that is 121 not directed to an instantiated subnet), or simply an aggregated 122 prefix while another router advertises a more specific one. In 123 source/destination routing, potentially ambiguous cases include cases 124 in which the link state database contains two routes A->B' and A'->B, 125 in which A' is a more specific prefix within the prefix A and B' is a 126 more specific prefix within the prefix B. Traditionally, we have 127 dealt with ambiguous destination routes using a "longest match first" 128 rule. If the same datagram matches more than one destination prefix 129 advertised within an area, we follow the route with the longest 130 matching prefix. 132 In this case, we follow a similar but slightly different rule; the 133 FIB lookup MUST yield the route with the longest matching destination 134 prefix that also matches the authorization token. A FIB route with 135 no such token matches any authorization token. 137 2.2. Interactions with other constraints 139 In the event that there are other constraints on routing, such as 140 proposed in [I-D.baker-ipv6-ospf-dst-src-routing], the effect is a 141 logical AND. The FIB lookup must yield the route with the longest 142 matching destination prefix that also matches each of the 143 constraints. 145 3. Extensions necessary for IPv6 Authenticated Routing in OSPF 147 Section 2 of [RFC5340] defines the "IPv6 Reachability TLV", and 148 carries in it destination prefix advertisements. It has the 149 capability of extension, using TLVs. 151 In this model, the flow label is used to prove that the datagram's 152 sender has specific knowledge of its intended receiver. No proof is 153 requested; this is left for higher layer exchanges such as IPSec or 154 TLS. However, if the information is distributed privately, such as 155 through DHCP/DHCPv6, the network can presume that a system that marks 156 traffic with the right flow label has a good chance of being 157 authorized to communicate with its peer. 159 The key consideration, in this context, is that the flow label is a 160 20 bit number. As such, an advertised route requiring a given flow 161 label value is calling for an exact match of all 20 bits of the label 162 value. 164 3.1. Authorization Token TLV 166 0 1 2 3 167 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 1 168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 169 | Type | Length | MBZ | 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 171 | MBZ | 20 bit Flow Label | 172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 174 Source Prefix Sub-TLV 176 Source Prefix Type: assigned by IANA 178 TLV Length: Length of the TLV in octets 180 Flow Label: Flow Label value (20 bits) 182 4. IANA Considerations 184 The source prefix type mentioned in Section 3 must be defined. 186 5. Security Considerations 188 Network layer Token-based Access Control is part of a security 189 solution. It is not, in itself, a complete solution. It acts as a 190 pervasive network layer firewall, preventing unauthorized traffic 191 from arriving at a destination. However, as in any network, a host 192 is its own last bastion of defense; it needs IPsec or TLS-style 193 authorization and authorization of its peers, and must refuse traffic 194 that contains the authorization token but is in fact malicious. 196 6. Acknowledgements 198 7. References 200 7.1. Normative References 202 [I-D.acee-ospfv3-lsa-extend] 203 Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3 204 LSA Extendibility", draft-acee-ospfv3-lsa-extend-00 (work 205 in progress), May 2013. 207 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 208 Requirement Levels", BCP 14, RFC 2119, March 1997. 210 [RFC2460] Deering, S.E. and R.M. Hinden, "Internet Protocol, Version 211 6 (IPv6) Specification", RFC 2460, December 1998. 213 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 214 for IPv6", RFC 5340, July 2008. 216 7.2. Informative References 218 [I-D.baker-ipv6-ospf-dst-src-routing] 219 Baker, F., "IPv6 Source/Destination Routing using OSPFv3", 220 draft-baker-ipv6-ospf-dst-src-routing-02 (work in 221 progress), May 2013. 223 Appendix A. Change Log 225 Initial Version: February 2013 227 updated Version: August 2013 229 Author's Address 231 Fred Baker 232 Cisco Systems 233 Santa Barbara, California 93117 234 USA 236 Email: fred@cisco.com