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Bush 3 Internet-Draft Internet Initiative Japan 4 Intended status: Best Current Practice January 5, 2017 5 Expires: July 9, 2017 7 BGPsec Operational Considerations 8 draft-ietf-sidr-bgpsec-ops-14 10 Abstract 12 Deployment of the BGPsec architecture and protocols has many 13 operational considerations. This document attempts to collect and 14 present the most critical and universal. It is expected to evolve as 15 BGPsec is formalized and initially deployed. 17 Requirements Language 19 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 20 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to 21 be interpreted as described in RFC 2119 [RFC2119] only when they 22 appear in all upper case. They may also appear in lower or mixed 23 case as English words, without normative meaning. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on July 9, 2017. 42 Copyright Notice 44 Copyright (c) 2017 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 2. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . 3 61 3. RPKI Distribution and Maintenance . . . . . . . . . . . . . . 3 62 4. AS/Router Certificates . . . . . . . . . . . . . . . . . . . 3 63 5. Within a Network . . . . . . . . . . . . . . . . . . . . . . 3 64 6. Considerations for Edge Sites . . . . . . . . . . . . . . . . 4 65 7. Routing Policy . . . . . . . . . . . . . . . . . . . . . . . 4 66 8. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 67 9. Security Considerations . . . . . . . . . . . . . . . . . . . 7 68 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 69 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 70 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 71 12.1. Normative References . . . . . . . . . . . . . . . . . . 7 72 12.2. Informative References . . . . . . . . . . . . . . . . . 8 73 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9 75 1. Introduction 77 BGPsec, [I-D.ietf-sidr-bgpsec-protocol], is a new protocol with many 78 operational considerations. It is expected to be deployed 79 incrementally over a number of years. As core BGPsec-capable routers 80 may require large memory and/or modern CPUs, origin validation based 81 on the Resource Public Key Infrastructure (RPKI), [RFC6811], will 82 occur over some years and BGPsec will start to deploy after that. As 83 with most operational practices, this document will likely evolve. 85 BGPsec relies on widespread propagation of the RPKI [RFC6480]. How 86 the RPKI is distributed and maintained globally and within an 87 operator's infrastructure may be different for BGPsec than for origin 88 validation. 90 BGPsec needs to be spoken only by an AS's eBGP-speaking, AKA border, 91 routers, and is designed so that it can be used to protect 92 announcements which are originated by resource constrained edge 93 routers. This has special operational considerations, see Section 6. 95 Different prefixes may have different timing and replay protection 96 considerations. 98 2. Suggested Reading 100 It is assumed that the reader understands BGP, see [RFC4271], BGPsec, 101 [I-D.ietf-sidr-bgpsec-protocol], the RPKI, see [RFC6480], the RPKI 102 Repository Structure, see [RFC6481], and Route Origin Authorizations 103 (ROAs), see [RFC6482]. 105 3. RPKI Distribution and Maintenance 107 All non-ROA considerations in the section on RPKI Distribution and 108 Maintenance of [RFC7115] apply. 110 4. AS/Router Certificates 112 As described in [I-D.ietf-sidr-rtr-keying] BGPsec-speaking routers 113 are either capable of generating their own public/private key-pairs 114 and having their certificates signed and published in the RPKI by the 115 RPKI CA system, and/or are given public/private key-pairs by the 116 operator. 118 A site/operator may use a single certificate/key in all their 119 routers, one certificate/key per router, or any granularity in 120 between. 122 A large operator, concerned that a compromise of one router's key 123 would make other routers vulnerable, may deploy a more complex 124 certificate/key distribution burden to reduce this exposure. 126 At the other end of the spectrum, an edge site with one or two 127 routers may choose to use a single certificate/key. 129 In anticipation of possible key compromise, a prudent operator should 130 pre-provision each router's 'next' key in the RPKI so there is no 131 propagation delay for provisioning the new key. 133 5. Within a Network 135 BGPsec is spoken by edge routers in a network, those which border 136 other networks/ASs. 138 In an AS where edge routers speak BGPsec and therefore inject BGPsec 139 paths into the iBGP, Route Reflectors MUST have BGPsec enabled if and 140 only if there are eBGP speakers in their client cone, i.e. an RR 141 client or the transitive closure of a client's customers. 143 A BGPsec capable router MAY use the data it receives to influence 144 local policy within its network, see Section 7. In deployment this 145 policy should fit into the AS's existing policy, preferences, etc. 147 This allows a network to incrementally deploy BGPsec enabled border 148 routers. 150 eBGP speakers which face more critical peers or up/downstreams would 151 be candidates for early deployment. Both securing one's own 152 announcements and validating received announcements should be 153 considered in partial deployment. 155 An operator should be aware that BGPsec, as any other policy change, 156 can cause traffic shifts in their network. And, as with normal 157 policy shift practice, a prudent operator has tools and methods to 158 predict, measure, modify, etc. 160 On the other hand, an operator wanting to monitor router loading, 161 shifts in traffic, etc. might deploy incrementally while watching 162 those and similar effects. 164 BGPsec does not sign over communities, so they are not formally 165 trustable. Additionally, outsourcing verification is not prudent 166 security practice. Therefore an eBGP listener SHOULD NOT strongly 167 trust unsigned security signaling, such as communities, received 168 across a trust boundary. 170 6. Considerations for Edge Sites 172 An edge site which does not provide transit and trusts its 173 upstream(s) may only originate a signed prefix announcement and not 174 validate received announcements. 176 An Operator might need to use hardware with limited resources. In 177 such cases, BGPsec protocol capability negotiation allows for a 178 resource constrained edge router to hold only its own signing key(s) 179 and sign its announcements, but not receive signed announcements. 180 Therefore, the router would not have to deal with the majority of the 181 RPKI, potentially saving the need for additional hardware. 183 As the vast majority of ASs are stubs, and they announce the majority 184 of prefixes, this allows for simpler and less expensive incremental 185 deployment. It may also mean that edge sites concerned with routing 186 security will be attracted to upstreams which support BGPsec. 188 7. Routing Policy 190 Unlike origin validation based on the RPKI, BGPsec marks a received 191 announcement as Valid or Not Valid, there is no explicit NotFound 192 state. In some sense, an unsigned BGP4 path is the equivalent of 193 NotFound. How this is used in routing is up to the operator's local 194 policy, similar to origin validation as in [RFC6811]. 196 As BGPsec will be rolled out over years and does not allow for 197 intermediate non-signing edge routers, coverage will be spotty for a 198 long time. This presents a dilemma; should a router evaluating an 199 inbound BGPsec_Path as Not Valid be very strict and discard it? On 200 the other hand, it might be the only path to that prefix, and a very 201 low local-preference would cause it to be used and propagated only if 202 there was no alternative. Either choice is reasonable, but we 203 recommend dropping because of the next point. 205 Operators should be aware that accepting Not Valid announcements, no 206 matter the local preference, will often be the equivalent of treating 207 them as fully Valid. Local preference affects only routes to the 208 same set of destinations. Consider having a Valid announcement from 209 neighbor V for prefix 10.0.0.0/16 and an Not Valid announcement for 210 10.0.666.0/24 from neighbor I. If local policy on the router is not 211 configured to discard the Not Valid announcement from I, then longest 212 match forwarding will send packets to neighbor I no matter the value 213 of local preference. 215 Validation of signed paths is usually deployed at the eBGP edge. 217 Local policy on the eBGP edge MAY convey the validation state of a 218 BGP signed path through normal local policy mechanisms, e.g. setting 219 a BGP community for internal use, or modifying a metric value such as 220 local-preference or multi-exit discriminator (MED). Some may choose 221 to use the large Local-Pref hammer. Others may choose to let AS-Path 222 rule and set their internal metric, which comes after AS-Path in the 223 BGP decision process. 225 As the mildly stochastic timing of RPKI propagation may cause version 226 skew across routers, an AS Path which does not validate at router R0 227 might validate at R1. Therefore, signed paths that are Not Valid and 228 yet propagated (because they are chosen as best path) should have 229 their signatures left intact and MUST be signed if sent to external 230 BGPsec speakers. 232 This implies that updates which a speaker judges to be Not Valid MAY 233 be propagated to iBGP peers. Therefore, unless local policy ensures 234 otherwise, a signed path learned via iBGP may be Not Valid. If 235 needed, the validation state should be signaled by normal local 236 policy mechanisms such as communities or metrics. 238 On the other hand, local policy on the eBGP edge might preclude iBGP 239 or eBGP announcement of signed AS Paths which are Not Valid. 241 A BGPsec speaker receiving a path SHOULD perform origin validation 242 per [RFC6811] and [RFC7115]. 244 A route server is usually 'transparent', i.e. does not insert an AS 245 into the path so as not to increase the AS hop count and thereby 246 affect downstream path choices. But, with BGPsec, a client router R 247 needs to be able to validate paths which are forward signed to R. 248 But the sending router can not generate signatures to all the 249 possible clients. Therefore a BGPsec-aware route server needs to 250 validate the incoming BGPsec_Path, and to forward updates which can 251 be validated by clients which must therefore know the route server's 252 AS. This implies that the route server creates signatures per client 253 including its own AS in the BGPsec_Path, forward signing to each 254 client AS, see [I-D.ietf-sidr-bgpsec-protocol]. The route server 255 uses pCount of zero to not increase the effective AS hop count, 256 thereby retaining the intent of 'transparency'. 258 If it is known that a BGPsec neighbor is not a transparent route 259 server, or is otherwise validly using pCount=0 (e,g, see 260 [I-D.ietf-sidr-as-migration]), and the router provides a knob to 261 disallow a received pCount (of zero, that knob SHOULD be applied. 262 Routers should disallow pCount 0 by default. 264 To prevent exposure of the internals of BGP Confederations [RFC5065], 265 a BGPsec speaker exporting to a non-member removes all intra- 266 confederation Secure_Path segments. Therefore signing within the 267 confederation will not cause external confusion even if non-unique 268 private ASs are used. 270 8. Notes 272 For protection from attacks replaying BGP data on the order of a day 273 or longer old, re-keying routers with new keys (previously) 274 provisioned in the RPKI is sufficient. For one approach, see 275 [I-D.ietf-sidr-bgpsec-rollover] 277 A router that once negotiated (and/or sent) BGPsec should not be 278 expected to always do so. 280 Like the DNS, the global RPKI presents only a loosely consistent 281 view, depending on timing, updating, fetching, etc. Thus, one cache 282 or router may have different data about a particular prefix or router 283 than another cache or router. There is no 'fix' for this, it is the 284 nature of distributed data with distributed caches. 286 Operators who manage certificates SHOULD have RPKI GhostBuster 287 Records (see [RFC6493]), signed indirectly by End Entity 288 certificates, for those certificates on which others' routing depends 289 for certificate and/or ROA validation. 291 Operators should be aware of impending algorithm transitions, which 292 will be rare and slow-paced, see [RFC6916]. They should work with 293 their vendors to ensure support for new algorithms. 295 As a router must evaluate certificates and ROAs which are time 296 dependent, routers' clocks MUST be correct to a tolerance of 297 approximately an hour. The common approach is for operators to 298 deploy servers that provide time service, such as [RFC5905], to 299 client routers. 301 If a router has reason to believe its clock is seriously incorrect, 302 e.g. it has a time earlier than 2011, it SHOULD NOT attempt to 303 validate incoming updates. It SHOULD defer validation until it 304 believes it is within reasonable time tolerance. 306 9. Security Considerations 308 This document describes operational considerations for the deployment 309 of BGPsec. The security considerations for BGPsec are described in 310 [I-D.ietf-sidr-bgpsec-protocol]. 312 10. IANA Considerations 314 This document has no IANA Considerations. 316 11. Acknowledgments 318 The author wishes to thank Thomas King, Arnold Nipper, and Alvaro 319 Retana, and the BGPsec design group. 321 12. References 323 12.1. Normative References 325 [I-D.ietf-sidr-bgpsec-protocol] 326 Lepinski, M., "BGPSEC Protocol Specification", draft-ietf- 327 sidr-bgpsec-protocol-07 (work in progress), February 2013. 329 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 330 Requirement Levels", BCP 14, RFC 2119, March 1997. 332 [RFC6493] Bush, R., "The Resource Public Key Infrastructure (RPKI) 333 Ghostbusters Record", RFC 6493, February 2012. 335 [RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R. 336 Austein, "BGP Prefix Origin Validation", RFC 6811, January 337 2013. 339 [RFC7115] Bush, R., "Origin Validation Operation Based on the 340 Resource Public Key Infrastructure (RPKI)", BCP 185, 341 RFC 7115, DOI 10.17487/RFC7115, January 2014, 342 . 344 12.2. Informative References 346 [I-D.ietf-sidr-as-migration] 347 George, W. and S. Murphy, "BGPSec Considerations for AS 348 Migration", draft-ietf-sidr-as-migration-06 (work in 349 progress), December 2016. 351 [I-D.ietf-sidr-bgpsec-rollover] 352 Gagliano, R., Patel, K., and B. Weis, "BGPSEC router key 353 rollover as an alternative to beaconing", draft-ietf-sidr- 354 bgpsec-rollover-01 (work in progress), October 2012. 356 [I-D.ietf-sidr-rtr-keying] 357 Turner, S., Patel, K., and R. Bush, "Router Keying for 358 BGPsec", draft-ietf-sidr-rtr-keying-01 (work in progress), 359 February 2013. 361 [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway 362 Protocol 4 (BGP-4)", RFC 4271, January 2006. 364 [RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous 365 System Confederations for BGP", RFC 5065, August 2007. 367 [RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network 368 Time Protocol Version 4: Protocol and Algorithms 369 Specification", RFC 5905, June 2010. 371 [RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support 372 Secure Internet Routing", RFC 6480, February 2012. 374 [RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for 375 Resource Certificate Repository Structure", RFC 6481, 376 February 2012. 378 [RFC6482] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route 379 Origin Authorizations (ROAs)", RFC 6482, February 2012. 381 [RFC6916] Gagliano, R., Kent, S., and S. Turner, "Algorithm Agility 382 Procedure for the Resource Public Key Infrastructure 383 (RPKI)", BCP 182, RFC 6916, DOI 10.17487/RFC6916, April 384 2013, . 386 Author's Address 388 Randy Bush 389 Internet Initiative Japan 390 5147 Crystal Springs 391 Bainbridge Island, Washington 98110 392 US 394 Email: randy@psg.com