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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Bush 3 Internet-Draft IIJ 4 Intended status: Standards Track R. Austein 5 Expires: August 20, 2011 ISC 6 February 16, 2011 8 The RPKI/Router Protocol 9 draft-ietf-sidr-rpki-rtr-08 11 Abstract 13 In order to formally validate the origin ASes of BGP announcements, 14 routers need a simple but reliable mechanism to receive RPKI 15 [I-D.ietf-sidr-arch] or analogous prefix origin data from a trusted 16 cache. This document describes a protocol to deliver validated 17 prefix origin data to routers over ssh. 19 Requirements Language 21 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 22 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 23 document are to be interpreted as described in RFC 2119 [RFC2119]. 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 August 20, 2011. 42 Copyright Notice 44 Copyright (c) 2011 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 2. Deployment Structure . . . . . . . . . . . . . . . . . . . . . 3 61 3. Operational Overview . . . . . . . . . . . . . . . . . . . . . 3 62 4. Protocol Data Units (PDUs) . . . . . . . . . . . . . . . . . . 4 63 4.1. Serial Notify . . . . . . . . . . . . . . . . . . . . . . 5 64 4.2. Serial Query . . . . . . . . . . . . . . . . . . . . . . . 5 65 4.3. Reset Query . . . . . . . . . . . . . . . . . . . . . . . 6 66 4.4. Cache Response . . . . . . . . . . . . . . . . . . . . . . 6 67 4.5. IPv4 Prefix . . . . . . . . . . . . . . . . . . . . . . . 7 68 4.6. IPv6 Prefix . . . . . . . . . . . . . . . . . . . . . . . 8 69 4.7. End of Data . . . . . . . . . . . . . . . . . . . . . . . 9 70 4.8. Cache Reset . . . . . . . . . . . . . . . . . . . . . . . 9 71 4.9. Error Report . . . . . . . . . . . . . . . . . . . . . . . 9 72 4.10. Fields of a PDU . . . . . . . . . . . . . . . . . . . . . 10 73 5. Protocol Sequences . . . . . . . . . . . . . . . . . . . . . . 11 74 5.1. Start or Restart . . . . . . . . . . . . . . . . . . . . . 12 75 5.2. Typical Exchange . . . . . . . . . . . . . . . . . . . . . 13 76 5.3. No Incremental Update Available . . . . . . . . . . . . . 13 77 5.4. Cache has No Data Available . . . . . . . . . . . . . . . 14 78 6. SSH Transport . . . . . . . . . . . . . . . . . . . . . . . . 14 79 7. Router-Cache Set-Up . . . . . . . . . . . . . . . . . . . . . 15 80 8. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 16 81 9. Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . 17 82 10. Security Considerations . . . . . . . . . . . . . . . . . . . 18 83 11. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 84 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 85 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 86 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 87 14.1. Normative References . . . . . . . . . . . . . . . . . . . 20 88 14.2. Informative References . . . . . . . . . . . . . . . . . . 20 89 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 91 1. Introduction 93 In order to formally validate the origin ASes of BGP announcements, 94 routers need a simple but reliable mechanism to receive RPKI 95 [I-D.ietf-sidr-arch] or analogous formally validated prefix origin 96 data from a trusted cache. This document describes a protocol to 97 deliver validated prefix origin data to routers over ssh. 99 Section 2 describes the deployment structure and Section 3 then 100 presents an operational overview. The binary payloads of the 101 protocol are formally described in Section 4, and the expected PDU 102 sequences are described in Section 5. The transport protocol is 103 described in Section 6. Section 7 details how routers and caches are 104 configured to connect and authenticate. Section 8 describes likely 105 deployment scenarios. The traditional security and IANA 106 considerations end the document. 108 The protocol is extensible to support new PDUs with new semantics 109 when and as needed, as indicated by deployment experience. PDUs are 110 versioned should deployment experience call for change. 112 2. Deployment Structure 114 Deployment of the RPKI to reach routers has a three level structure 115 as follows: 117 Global RPKI: The authoritative data of the RPKI are published in a 118 distributed set of servers, RPKI publication repositories, e.g. 119 the IANA, RIRs, NIRs, and ISPs, see [I-D.ietf-sidr-repos-struct]. 121 Local Caches: A local set of one or more collected and verified non- 122 authoritative caches. A relying party, e.g. router or other 123 client, MUST have a formally authenticated trust relationship 124 with, and a secure transport channel to, any non-authoritative 125 cache(s) it uses. 127 Routers: A router fetches data from a local cache using the protocol 128 described in this document. It is said to be a client of the 129 cache. There are mechanisms for the router to assure itself of 130 the authenticity of the cache and to authenticate itself to the 131 cache. 133 3. Operational Overview 135 A router establishes and keeps open an authenticated connection to 136 one or more caches with which it has client/server relationships. It 137 is configured with a semi-ordered list of caches, and establishes a 138 connection to the most preferred cache, or set of caches, which 139 accept the connections. 141 The router MUST choose the most preferred, by configuration, cache or 142 set of caches so that the operator may control load on their caches 143 and the Global RPKI. 145 Periodically, the router sends to the cache the serial number of the 146 highest numbered data record it has received from that cache, i.e. 147 the router's current serial number. When a router establishes a new 148 connection to a cache, or wishes to reset a current relationship, it 149 sends a Reset Query. 151 The Cache responds with all data records which have serial numbers 152 greater than that in the router's query. This may be the null set, 153 in which case the End of Data PDU is still sent. Note that 'greater' 154 must take wrap-around into account, see [RFC1982]. 156 When the router has received all data records from the cache, it sets 157 its current serial number to that of the serial number in the End of 158 Data PDU. 160 When the cache updates its database, it sends a Notify message to 161 every currently connected router. This is a hint that now would be a 162 good time for the router to poll for an update, but is only a hint. 163 The protocol requires the router to poll for updates periodically in 164 any case. 166 Strictly speaking, a router could track a cache simply by asking for 167 a complete data set every time it updates, but this would be very 168 inefficient. The serial number based incremental update mechanism 169 allows an efficient transfer of just the data records which have 170 changed since last update. As with any update protocol based on 171 incremental transfers, the router must be prepared to fall back to a 172 full transfer if for any reason the cache is unable to provide the 173 necessary incremental data. Unlike some incremental transfer 174 protocols, this protocol requires the router to make an explicit 175 request to start the fallback process; this is deliberate, as the 176 cache has no way of knowing whether the router has also established 177 sessions with other caches that may be able to provide better 178 service. 180 4. Protocol Data Units (PDUs) 182 The exchanges between the cache and the router are sequences of 183 exchanges of the following PDUs according to the rules described in 184 Section 5. 186 4.1. Serial Notify 188 The cache notifies the router that the cache has new data. 190 The Cache Nonce reassures the router that the serial numbers are 191 comensurate, i.e. the cache session has not been changed. 193 0 8 16 24 31 194 .-------------------------------------------. 195 | Protocol | PDU | | 196 | Version | Type | Cache Nonce | 197 | 0 | 0 | | 198 +-------------------------------------------+ 199 | | 200 | Length=12 | 201 | | 202 +-------------------------------------------+ 203 | | 204 | Serial Number | 205 | | 206 `-------------------------------------------' 208 4.2. Serial Query 210 Serial Query: The router sends Serial Query to ask the cache for all 211 payload PDUs which have serial numbers higher than the serial number 212 in the Serial Query. 214 The cache replies to this query with a Cache Response PDU 215 (Section 4.4) if the cache has a record of the changes since the 216 serial number specified by the router. If there have been no changes 217 since the router last queried, the cache responds with an End Of Data 218 PDU. If the cache does not have the data needed to update the 219 router, perhaps because its records do not go back to the Serial 220 Number in the Serial Query, then it responds with a Cache Reset PDU 221 (Section 4.8). 223 The Cache Nonce tells the cache what instance the router expects to 224 ensure that the serial numbers are comensurate, i.e. the cache 225 session has not been changed. 227 0 8 16 24 31 228 .-------------------------------------------. 229 | Protocol | PDU | | 230 | Version | Type | Cache Nonce | 231 | 0 | 1 | | 232 +-------------------------------------------+ 233 | | 234 | Length=12 | 235 | | 236 +-------------------------------------------+ 237 | | 238 | Serial Number | 239 | | 240 `-------------------------------------------' 242 4.3. Reset Query 244 Reset Query: The router tells the cache that it wants to receive the 245 total active, current, non-withdrawn, database. The cache responds 246 with a Cache Response PDU (Section 4.4). 248 0 8 16 24 31 249 .-------------------------------------------. 250 | Protocol | PDU | | 251 | Version | Type | reserved = zero | 252 | 0 | 2 | | 253 +-------------------------------------------+ 254 | | 255 | Length=8 | 256 | | 257 `-------------------------------------------' 259 4.4. Cache Response 261 Cache Response: The cache responds with zero or more payload PDUs. 262 When replying to a Serial Query request (Section 4.2), the cache 263 sends the set of all data records it has with serial numbers greater 264 than that sent by the client router. When replying to a Reset Query, 265 the cache sends the set of all data records it has; in this case the 266 withdraw/announce field in the payload PDUs MUST have the value 1 267 (announce). 269 In response to a Reset Query, the Cache Nonce tells the router the 270 instance of the cache session for future confirmation. In response 271 to a Serial Query, the Cache Nonce reassures the router that the 272 serial numbers are comensurate, i.e. the cache session has not been 273 changed. 275 0 8 16 24 31 276 .-------------------------------------------. 277 | Protocol | PDU | | 278 | Version | Type | Cache Nonce | 279 | 0 | 3 | | 280 +-------------------------------------------+ 281 | | 282 | Length=8 | 283 | | 284 `-------------------------------------------' 286 4.5. IPv4 Prefix 288 0 8 16 24 31 289 .-------------------------------------------. 290 | Protocol | PDU | | 291 | Version | Type | reserved = zero | 292 | 0 | 4 | | 293 +-------------------------------------------+ 294 | | 295 | Length=20 | 296 | | 297 +-------------------------------------------+ 298 | | Prefix | Max | | 299 | Flags | Length | Length | zero | 300 | | 0..32 | 0..32 | | 301 +-------------------------------------------+ 302 | | 303 | IPv4 prefix | 304 | | 305 +-------------------------------------------+ 306 | | 307 | Autonomous System Number | 308 | | 309 `-------------------------------------------' 311 Due to the nature of the RPKI and the IRR, there can be multiple 312 identical IPvX PDUs. A router MUST be prepared to receive multiple 313 identical record announcements and MUST NOT consider a record to have 314 been deleted until it has received a corresponding number of 315 withdrawals or a reset is performed Hence the router will likely keep 316 an internal reference count on each IPvX PDU. 318 In the RPKI, nothing prevents a signing certificate from issuing two 319 identical ROAs, and nothing prohibits the existence of two identical 320 route: or route6: objects in the IRR. In this case there would be no 321 semantic difference between the objects, merely a process redundancy. 323 In the RPKI, there is also an actual need for what will appear to the 324 router as identical IPvX PDUs. This occurs when an upstream 325 certificate is being reissued or a site is changing providers, often 326 a 'make and break' situation. The ROA is identical in the router 327 sense, i.e. has the same {prefix, len, max-len, asn}, but has a 328 different validation path in the RPKI. This is important to the 329 RPKI, but not to the router. 331 The lowest order bit of the Flags field is 1 for an announcement and 332 0 for a withdrawal. 334 4.6. IPv6 Prefix 336 0 8 16 24 31 337 .-------------------------------------------. 338 | Protocol | PDU | | 339 | Version | Type | reserved = zero | 340 | 0 | 6 | | 341 +-------------------------------------------+ 342 | | 343 | Length=32 | 344 | | 345 +-------------------------------------------+ 346 | | Prefix | Max | | 347 | Flags | Length | Length | zero | 348 | | 0..32 | 0..128 | | 349 +-------------------------------------------+ 350 | | 351 +--- ---+ 352 | | 353 +--- IPv6 prefix ---+ 354 | | 355 +--- ---+ 356 | | 357 +-------------------------------------------+ 358 | | 359 | Autonomous System Number | 360 | | 361 `-------------------------------------------' 363 4.7. End of Data 365 End of Data: Cache tells router it has no more data for the request. 367 The Cache Nonce MUST be the same as that of the corresponding Cache 368 Response which began the, possibly null, sequence of data PDUs. 370 0 8 16 24 31 371 .-------------------------------------------. 372 | Protocol | PDU | | 373 | Version | Type | Cache Nonce | 374 | 0 | 7 | | 375 +-------------------------------------------+ 376 | | 377 | Length=12 | 378 | | 379 +-------------------------------------------+ 380 | | 381 | Serial Number | 382 | | 383 `-------------------------------------------' 385 4.8. Cache Reset 387 The cache may respond to a Serial Query informing the router that the 388 cache cannot provide an incremental update starting from the serial 389 number specified by the router. The router must decide whether to 390 issue a Reset Query or switch to a different cache. 392 0 8 16 24 31 393 .-------------------------------------------. 394 | Protocol | PDU | | 395 | Version | Type | reserved = zero | 396 | 0 | 8 | | 397 +-------------------------------------------+ 398 | | 399 | Length=8 | 400 | | 401 `-------------------------------------------' 403 4.9. Error Report 405 This PDU is used by either party to report an error to the other. 407 The Error Number is described in Section 9. 409 If the error is not associated with any particular PDU, the Erroneous 410 PDU field should be empty and the Length of Encapsulated PDU field 411 should be zero. 413 The diagnostic text is optional, if not present the Length of Error 414 Text field should be zero. If error text is present, it SHOULD be a 415 string in US-ASCII, for maximum portability; if non-US-ASCII 416 characters are absolutely required, the error text MUST use UTF-8 417 encoding. 419 0 8 16 24 31 420 .-------------------------------------------. 421 | Protocol | PDU | | 422 | Version | Type | Error Number | 423 | 0 | 10 | | 424 +-------------------------------------------+ 425 | | 426 | Length | 427 | | 428 +-------------------------------------------+ 429 | | 430 | Length of Encapsulated PDU | 431 | | 432 +-------------------------------------------+ 433 | | 434 ~ Copy of Erroneous PDU ~ 435 | | 436 +-------------------------------------------+ 437 | | 438 | Length of Error Text | 439 | | 440 +-------------------------------------------+ 441 | | 442 | Arbitrary Text | 443 | of | 444 ~ Error Diagnostic Message ~ 445 | | 446 `-------------------------------------------' 448 4.10. Fields of a PDU 450 PDUs contain the following data elements: 452 Protocol Version: An ordinal, currently 0, denoting the version of 453 this protocol. 455 Serial Number: The serial number of the RPKI Cache when this ROA was 456 received from the cache's up-stream cache server or gathered from 457 the global RPKI. A cache increments its serial number when 458 completing an rigorously validated update from a parent cache, for 459 example via rcynic. See [RFC1982] on DNS Serial Number Arithmetic 460 for too much detail on serial number arithmetic. 462 Cache Nonce: When a cache server is started, it generates a nonce to 463 identify the instance of the cache and to bind it to the sequence 464 of Serial Numbers that cache instance will generate. This allows 465 the router to restart a failed session knowing that the Serial 466 Number it is using is comensurate with that of the cache. If, at 467 any time, either the router or the cache finds the value of the 468 nonces they hold disagree, they MUST completely drop the session 469 and the router MUST flush all data learned from that cache. 471 The nonce might be a pseudo-random, a monotonically increasing 472 value if the cache has reliable storage, etc. An implementation 473 which uses a fine granularity of time for the Serial Number might 474 never change the Cache Nonce. 476 Length: A 32 bit ordinal which has as its value the count of the 477 bytes in the entire PDU, including the eight bytes of header which 478 end with the length field. 480 Flags: The lowest order bit of the Flags field is 1 for an 481 announcement and 0 for a withdrawal, whether this PDU announces a 482 new right to announce the prefix or withdraws a previously 483 announced right. A withdraw effectively deletes one previously 484 announced IPvX Prefix PDU with the exact same Prefix, Length, Max- 485 Len, and ASN. 487 Prefix Length: An ordinal denoting the shortest prefix allowed for 488 the prefix. 490 Max Length: An ordinal denoting the longest prefix allowed by the 491 prefix. This MUST NOT be less than the Prefix Length element. 493 Prefix: The IPv4 or IPv6 prefix of the ROA. 495 Autonomous System Number: ASN allowed to announce this prefix, a 32 496 bit ordinal. 498 Zero: Fields shown as zero or reserved MUST be zero. The value of 499 such a field MUST be ignored on receipt. 501 5. Protocol Sequences 503 The sequences of PDU transmissions fall into three conversations as 504 follows: 506 5.1. Start or Restart 508 Cache Router 509 ~ ~ 510 | <----- Reset Query -------- | R requests data (or Serial Query) 511 | | 512 | ----- Cache Response -----> | C confirms request 513 | ------- IPvX Prefix ------> | C sends zero or more 514 | ------- IPvX Prefix ------> | IPv4 and IPv6 Prefix 515 | ------- IPvX Prefix ------> | Payload PDUs 516 | ------ End of Data ------> | C sends End of Data 517 | | and sends new serial 518 ~ ~ 520 When a transport session is first established, the router MAY send a 521 Reset Query and the cache responds with a data sequence of all data 522 it contains. 524 Alternatively, if the router has significant unexpired data from a 525 broken session with the same cache, it MAY start with a Serial Query 526 containing the Cache Nonce from the previous session to ensure the 527 serial numbers are comensurate. 529 This Reset Query sequence is also used when the router receives a 530 Cache Reset, chooses a new cache, or fears that it has otherwise lost 531 its way. 533 To limit the length of time a cache must keep the data necessary to 534 generate incremental updates, a router MUST send either a Serial 535 Query or a Reset Query no less frequently than once an hour. This 536 also acts as a keep alive at the application layer. 538 As the cache MAY not keep updates for more than one hour, the router 539 MUST have a polling interval of no greater than half an hour 541 5.2. Typical Exchange 543 Cache Router 544 ~ ~ 545 | -------- Notify ----------> | (optional) 546 | | 547 | <----- Serial Query ------- | R requests data 548 | | 549 | ----- Cache Response -----> | C confirms request 550 | ------- IPvX Prefix ------> | C sends zero or more 551 | ------- IPvX Prefix ------> | IPv4 and IPv6 Prefix 552 | ------- IPvX Prefix ------> | Payload PDUs 553 | ------ End of Data ------> | C sends End of Data 554 | | and sends new serial 555 ~ ~ 557 The cache server SHOULD send a notify PDU with its current serial 558 number when the cache's serial changes, with the expectation that the 559 router MAY then issue a serial query earlier than it otherwise might. 560 This is analogous to DNS NOTIFY in [RFC1996]. The cache SHOULD rate 561 limit Serial Notifies to no more frequently than one per minute. 563 When the transport layer is up and either a timer has gone off in the 564 router, or the cache has sent a Notify, the router queries for new 565 data by sending a Serial Query, and the cache sends all data newer 566 than the serial in the Serial Query. 568 To limit the length of time a cache must keep old withdraws, a router 569 MUST send either a Serial Query or a Reset Query no less frequently 570 than once an hour. 572 5.3. No Incremental Update Available 574 Cache Router 575 ~ ~ 576 | <----- Serial Query ------ | R requests data 577 | ------- Cache Reset ------> | C cannot supply update 578 | | from specified serial 579 | <------ Reset Query ------- | R requests new data 580 | ----- Cache Response -----> | C confirms request 581 | ------- IPvX Prefix ------> | C sends zero or more 582 | ------- IPvX Prefix ------> | IPv4 and IPv6 Prefix 583 | ------- IPvX Prefix ------> | Payload PDUs 584 | ------ End of Data ------> | C sends End of Data 585 | | and sends new serial 586 ~ ~ 588 The cache may respond to a Serial Query with a Cache Reset, informing 589 the router that the cache cannot supply an incremental update from 590 the serial number specified by the router. This might be because the 591 cache has lost state, or because the router has waited too long 592 between polls and the cache has cleaned up old data that it no longer 593 believes it needs, or because the cache has run out of storage space 594 and had to expire some old data early. Regardless of how this state 595 arose, the cache replies with a Cache Reset to tell the router that 596 it cannot honor the request. When a router receives this, the router 597 SHOULD attempt to connect to any more preferred caches in its cache 598 list. If there are no more preferred caches it MUST issue a Reset 599 Query and get an entire new load from the cache. 601 5.4. Cache has No Data Available 603 Cache Router 604 ~ ~ 605 | <----- Serial Query ------ | R requests data 606 | ---- Error Report PDU ----> | C cannot supply update 607 ~ ~ 609 Cache Router 610 ~ ~ 611 | <----- Reset Query ------- | R requests data 612 | ---- Error Report PDU ----> | C cannot supply update 613 ~ ~ 615 The cache may respond to either a Serial Query or a Reset Query 616 informing the router that the cache cannot supply any update at all. 617 The most likely cause is that the cache has lost state, perhaps due 618 to a restart, and has not yet recovered. While it is possible that a 619 cache might go into such a state without dropping any of its active 620 sessions, a router is more likely to see this behavior when it 621 initially connects and issues a Reset Query while the cache is still 622 rebuilding its database. 624 When a router receives this kind of error, the router SHOULD attempt 625 to connect to any other caches in its cache list, in preference 626 order. If no other caches are available, the router MUST issue 627 periodic Reset Queries until it gets a new usable load from the 628 cache. 630 6. SSH Transport 632 The transport layer session between a router and a cache carries the 633 binary Protocol Data Units (PDUs) in a persistent SSH session. 635 To run over SSH, the client router first establishes an SSH transport 636 connection using the SSH transport protocol, and the client and 637 server exchange keys for message integrity and encryption. The 638 client then invokes the "ssh-userauth" service to authenticate the 639 application, as described in the SSH authentication protocol RFC 4252 640 [RFC4252]. Once the application has been successfully authenticated, 641 the client invokes the "ssh-connection" service, also known as the 642 SSH connection protocol. 644 After the ssh-connection service is established, the client opens a 645 channel of type "session", which results in an SSH session. 647 Once the SSH session has been established, the application invokes 648 the application transport as an SSH subsystem called "rpki-rtr". 649 Subsystem support is a feature of SSH version 2 (SSHv2) and is not 650 included in SSHv1. Running this protocol as an SSH subsystem avoids 651 the need for the application to recognize shell prompts or skip over 652 extraneous information, such as a system message that is sent at 653 shell start-up. 655 It is assumed that the router and cache have exchanged keys out of 656 band by some reasonably secured means. 658 7. Router-Cache Set-Up 660 A cache has the public authentication data for each router it is 661 configured to support. 663 A router may be configured to peer with a selection of caches, and a 664 cache may be configured to support a selection of routers. Each must 665 have the name of, and authentication data for, each peer. In 666 addition, in a router, this list has a non-unique preference value 667 for each server in order of preference. This preference merely 668 denotes proximity, not trust, preferred belief, etc. The client 669 router attempts to establish a session with each potential serving 670 cache in preference order, and then starts to load data from the most 671 preferred cache to which it can connect and authenticate. The 672 router's list of caches has the following elements: 674 Preference: An ordinal denoting the router's preference to connect 675 to that cache, the lower the value the more preferred. 677 Name: The IP Address or fully qualified domain name of the cache. 679 Key: The public ssh key of the cache. 681 MyKey: The private ssh key of this client. 683 Due to the distributed nature of the RPKI, caches simply can not be 684 rigorously synchronous. A client may hold data from multiple caches, 685 but MUST keep the data marked as to source, as later updates MUST 686 affect the correct data. 688 Just as there may be more than one covering ROA from a single cache, 689 there may be multiple covering ROAs from multiple caches. The 690 results are as described in [I-D.ietf-sidr-pfx-validate]. 692 If data from multiple caches are held, implementations MUST NOT 693 distinguish between data sources when performing validation. 695 When a more preferred cache becomes available, if resources allow, it 696 would be prudent for the client to start fetching from that cache. 698 The client SHOULD attempt to maintain at least one set of data, 699 regardless of whether it has chosen a different cache or established 700 a new connection to the previous cache. 702 A client MAY drop the data from a particular cache when it is fully 703 in synch with one or more other caches. 705 A client SHOULD delete the data from a cache when it has been unable 706 to refresh from that cache for a configurable timer value. The 707 default for that value is twice the polling period for that cache. 709 If a client loses connectivity to a cache it is using, or otherwise 710 decides to switch to a new cache, it SHOULD retain the data from the 711 previous cache until it has a full set of data from one or more other 712 caches. Note that this may already be true at the point of 713 connection loss if the client has connections to more than one cache. 715 8. Deployment Scenarios 717 For illustration, we present three likely deployment scenarios. 719 Small End Site: The small multi-homed end site may wish to outsource 720 the RPKI cache to one or more of their upstream ISPs. They would 721 exchange authentication material with the ISP using some out of 722 band mechanism, and their router(s) would connect to one or more 723 up-streams' caches. The ISPs would likely deploy caches intended 724 for customer use separately from the caches with which their own 725 BGP speakers peer. 727 Large End Site: A larger multi-homed end site might run one or more 728 caches, arranging them in a hierarchy of client caches, each 729 fetching from a serving cache which is closer to the global RPKI. 730 They might configure fall-back peerings to up-stream ISP caches. 732 ISP Backbone: A large ISP would likely have one or more redundant 733 caches in each major PoP, and these caches would fetch from each 734 other in an ISP-dependent topology so as not to place undue load 735 on the global RPKI publication infrastructure. 737 Experience with large DNS cache deployments has shown that complex 738 topologies are ill-advised as it is easy to make errors in the graph, 739 e.g. not maintaining a loop-free condition. 741 Of course, these are illustrations and there are other possible 742 deployment strategies. It is expected that minimizing load on the 743 global RPKI servers will be a major consideration. 745 To keep load on global RPKI services from unnecessary peaks, it is 746 recommended that primary caches which load from the distributed 747 global RPKI not do so all at the same times, e.g. on the hour. 748 Choose a random time, perhaps the ISP's AS number modulo 60 and 749 jitter the inter-fetch timing. 751 9. Error Codes 753 This section contains a preliminary list of error codes. The authors 754 expect additions to this section during development of the initial 755 implementations. Eventually, these error codes will probably need to 756 reside in an IANA registry. 758 0: Reserved. 760 1: Internal Error: The party reporting the error experienced some 761 kind of internal error unrelated to protocol operation (ran out of 762 memory, a coding assertion failed, et cetera). 764 2: No Data Available: The cache believes itself to be in good 765 working order, but is unable to answer either a Serial Query or a 766 Reset Query because it has no useful data available at this time. 767 This is likely to be a temporary error, and most likely indicates 768 that the cache has not yet completed pulling down an initial 769 current data set from the global RPKI system after some kind of 770 event that invalidated whatever data it might have previously held 771 (reboot, network partition, etcetera). 773 3: Invalid Request: The cache server believes the client's request 774 to be invalid. 776 10. Security Considerations 778 As this document describes a security protocol, many aspects of 779 security interest are described in the relevant sections. This 780 section points out issues which may not be obvious in other sections. 782 Cache Validation: In order for a collection of caches as described 783 in Section 8 to guarantee a consistent view, they need to be given 784 consistent trust anchors to use in their internal validation 785 process. Distribution of a consistent trust anchor is assumed to 786 be out of band. 788 Cache Peer Identification: The router initiates an ssh transport 789 session to a cache, which it identifies by either IP address or 790 fully qualified domain name. Be aware that a DNS or address 791 spoofing attack could make the correct cache unreachable. No 792 session would be established, as the authorization keys would not 793 match. 795 Transport Security: The RPKI relies on object, not server or 796 transport, trust. I.e. the IANA root trust anchor is distributed 797 to all caches through some out of band means, and can then be used 798 by each cache to validate certificates and ROAs all the way down 799 the tree. The inter-cache relationships are based on this object 800 security model, hence the inter-cache transport can be lightly 801 protected. 803 But this protocol document assumes that the routers can not do the 804 validation cryptography. Hence the last link, from cache to 805 router, is secured by server authentication and transport level 806 security. This is dangerous, as server authentication and 807 transport have very different threat models than object security. 809 So the strength of the trust relationship and the transport 810 between the router(s) and the cache(s) are critical. You're 811 betting your routing on this. 813 While we can not say the cache must be on the same LAN, if only 814 due to the issue of an enterprise wanting to off-load the cache 815 task to their upstream ISP(s), locality, trust, and control are 816 very critical issues here. The cache(s) really SHOULD be as 817 close, in the sense of controlled and protected (against DDoS, 818 MITM) transport, to the router(s) as possible. It also SHOULD be 819 topologically close so that a minimum of validated routing data 820 are needed to bootstrap a router's access to a cache. 822 11. Glossary 824 The following terms are used with special meaning: 826 Global RPKI: The authoritative data of the RPKI are published in a 827 distributed set of servers at the IANA, RIRs, NIRs, and ISPs, see 828 [I-D.ietf-sidr-repos-struct]. 830 Non-authorative Cache: A coalesced copy of the RPKI which is 831 periodically fetched/refreshed directly or indirectly from the 832 global RPKI using the [RFC5781] protocol/tools 834 Cache: Relying party update sofcware such as rcynic is used to 835 gather and validate the distributed data of the RPKI into a cache. 836 Trusting this cache further is a matter between the provider of 837 the cache and a relying party. 839 Serial Number: A 32-bit monotonically increasing ordinal which wraps 840 from 2^32-1 to 0. It denotes the logical version of a cache. A 841 cache increments the value by one when it successfully updates its 842 data from a parent cache or from primary RPKI data. As a cache is 843 receiving, new incoming data, and implicit deletes, are marked 844 with the new serial but MUST NOT be sent until the fetch is 845 complete. A serial number is not commensurate between caches, nor 846 need it be maintained across resets of the cache server. See 847 [RFC1982] on DNS Serial Number Arithmetic for too much detail on 848 serial number arithmetic. 850 12. IANA Considerations 852 This document requests the IANA to create a registry for PDU types. 854 This document requests the IANA to create a registry for Error Codes. 856 In addition, a registry for Version Numbers would be needed if new 857 Version Number is defined in a new RFC. 859 Note to RFC Editor: this section may be replaced on publication as an 860 RFC. 862 13. Acknowledgments 864 The authors wish to thank Steve Bellovin, Rex Fernando, Russ Housley, 865 Pradosh Mohapatra, Keyur Patel, Sandy Murphy, Robert Raszuk, John 866 Scudder, Ruediger Volk, and David Ward. Particular thanks go to 867 Hannes Gredler for showing us the dangers of unnecessary fields. 869 14. References 871 14.1. Normative References 873 [I-D.ietf-sidr-pfx-validate] 874 Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R. 875 Austein, "BGP Prefix Origin Validation", 876 draft-ietf-sidr-pfx-validate-01 (work in progress), 877 February 2011. 879 [RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982, 880 August 1996. 882 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 883 Requirement Levels", BCP 14, RFC 2119, March 1997. 885 [RFC4252] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) 886 Authentication Protocol", RFC 4252, January 2006. 888 14.2. Informative References 890 [I-D.ietf-sidr-arch] 891 Lepinski, M. and S. Kent, "An Infrastructure to Support 892 Secure Internet Routing", draft-ietf-sidr-arch-11 (work in 893 progress), September 2010. 895 [I-D.ietf-sidr-repos-struct] 896 Huston, G., Loomans, R., and G. Michaelson, "A Profile for 897 Resource Certificate Repository Structure", 898 draft-ietf-sidr-repos-struct-06 (work in progress), 899 November 2010. 901 [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone 902 Changes (DNS NOTIFY)", RFC 1996, August 1996. 904 [RFC5781] Weiler, S., Ward, D., and R. Housley, "The rsync URI 905 Scheme", RFC 5781, February 2010. 907 Authors' Addresses 909 Randy Bush 910 Internet Initiative Japan, Inc. 911 5147 Crystal Springs 912 Bainbridge Island, Washington 98110 913 US 915 Phone: +1 206 780 0431 x1 916 Email: randy@psg.com 918 Rob Austein 919 Internet Systems Consortium 920 950 Charter Street 921 Redwood City, CA 94063 922 USA 924 Email: sra@isc.org