idnits 2.17.1 draft-ietf-pcp-anycast-01.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack a both a reference to RFC 2119 and the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords. RFC 2119 keyword, line 128: '...over PCP servers SHOULD first send a P...' RFC 2119 keyword, line 131: '...nt. The PCP client then SHOULD send a...' Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (February 14, 2014) is 3717 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Downref: Normative reference to an Informational RFC: RFC 1546 ** Obsolete normative reference: RFC 4773 (Obsoleted by RFC 6890) ** Obsolete normative reference: RFC 5736 (Obsoleted by RFC 6890) -- No information found for draft-ietf-ipngwg-dns-discovery - is the name correct? == Outdated reference: A later version (-13) exists of draft-ietf-pcp-dhcp-09 Summary: 4 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCP working group S. Kiesel 3 Internet-Draft University of Stuttgart 4 Intended status: Standards Track R. Penno 5 Expires: August 18, 2014 Cisco Systems, Inc. 6 S. Cheshire 7 Apple 8 February 14, 2014 10 PCP Anycast Address 11 draft-ietf-pcp-anycast-01 13 Abstract 15 The Port Control Protocol (PCP) Anycast Address enables PCP clients 16 to transmit signaling messages to their closest on-path NAT, 17 Firewall, or other middlebox, without having to learn the IP address 18 of that middlebox via some external channel. This document 19 establishes one well-known IPv4 address and one well-known IPv6 20 address to be used as PCP Anycast Address. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on August 18, 2014. 39 Copyright Notice 41 Copyright (c) 2014 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2. PCP Server Discovery based on well-known IP Address . . . . . 4 58 2.1. PCP Discovery Client behavior . . . . . . . . . . . . . . 4 59 2.2. PCP Discovery Server behavior . . . . . . . . . . . . . . 4 60 3. Deployment Considerations . . . . . . . . . . . . . . . . . . 5 61 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 62 4.1. Registration of IPv4 Special Purpose Address . . . . . . . 6 63 4.2. Registration of IPv6 Special Purpose Address . . . . . . . 7 64 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 65 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 66 6.1. Normative References . . . . . . . . . . . . . . . . . . . 10 67 6.2. Informative References . . . . . . . . . . . . . . . . . . 10 68 Appendix A. Discussion of other PCP Discovery methods . . . . . . 11 69 A.1. Default Router . . . . . . . . . . . . . . . . . . . . . . 11 70 A.2. DHCP PCP Options . . . . . . . . . . . . . . . . . . . . . 11 71 A.3. User Input . . . . . . . . . . . . . . . . . . . . . . . . 12 72 A.4. Domain Name System Based . . . . . . . . . . . . . . . . . 12 73 A.5. Addressing only based on Destination Port . . . . . . . . 12 74 Appendix B. Discussion of IP Anycast Address usage for PCP . . . 14 75 B.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 14 76 B.2. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . 14 77 B.3. Historical Objections to Anycast . . . . . . . . . . . . . 14 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 80 1. Introduction 82 The Port Control Protocol (PCP) [RFC6887] provides a mechanism to 83 control how incoming packets are forwarded by upstream devices such 84 as Network Address Translator IPv6/IPv4 (NAT64), Network Address 85 Translator IPv4/IPv4 (NAT44), IPv6 and IPv4 firewall devices, and a 86 mechanism to reduce application keep alive traffic. 88 The PCP document [RFC6887] specifies the message formats used, but 89 the address to which a client sends its request is either assumed to 90 be the default router (which is appropriate in a typical single-link 91 residential network) or has to be configured otherwise via some 92 external mechanism, such as DHCP. The properties and drawbacks of 93 various mechanisms are discussed in Appendix A. 95 This document follows a different approach: it establishes a well- 96 known anycast address for the PCP Server. PCP clients are expected 97 to send requests to this address during the PCP Server discovery 98 process. A PCP Server configured with the anycast address could 99 optionally redirect or return a list of unicast PCP Servers to the 100 client. For a more extensive discussion on anycasting see 101 Appendix B. 103 The benefit of using an anycast address is simplicity and 104 reliability. In an example deployment scenario: 106 1. A network administrator installs a PCP-capable NAT. 108 2. An end user (who may be the same person) runs a PCP-enabled 109 application. This application can implement PCP with purely 110 user-level code -- no operating system support is required. 112 3. This PCP-enabled application sends its PCP request to the PCP 113 anycast address. This packet travels through the network like 114 any other, without any special support from DNS, DHCP, other 115 routers, or anything else, until it reaches the PCP-capable NAT, 116 which receives it, handles it, and sends back a reply. 118 Using the PCP anycast address, the only two things that need to be 119 deployed in the network are the two things that actually use PCP: The 120 PCP-capable NAT, and the PCP-enabled application. Nothing else in 121 the network needs to be changed or upgraded, and nothing needs to be 122 configured, including the PCP client. 124 2. PCP Server Discovery based on well-known IP Address 126 2.1. PCP Discovery Client behavior 128 PCP Clients that need to discover PCP servers SHOULD first send a PCP 129 request to its default router. This is important because in the case 130 of cascaded PCP Servers, all of them need to be discovered in order 131 of hop distance from the client. The PCP client then SHOULD send a 132 PCP request to the anycast address. PCP Clients must be prepared to 133 receive an error and try other discovery methods. 135 2.2. PCP Discovery Server behavior 137 PCP Server can be configured to listen on the anycast address for 138 incoming PCP requests. 140 PCP responses are sent from that same IANA-assigned address (see Page 141 5 of [RFC1546]). 143 3. Deployment Considerations 145 There are known limitations when there is more than one PCP server 146 and asymmetric routing, or similar scenarios. Mechanisms to deal 147 with those situations, such as state synchronization between PCP 148 servers, are beyond the scope of this document. 150 4. IANA Considerations 152 4.1. Registration of IPv4 Special Purpose Address 154 IANA is requested to register a single IPv4 address in the IANA IPv4 155 Special Purpose Address Registry [RFC5736]. 157 [RFC5736] itemizes some information to be recorded for all 158 designations: 160 1. The designated address prefix. 162 Prefix: TBD by IANA. Prefix length: /32 164 2. The RFC that called for the IANA address designation. 166 This document. 168 3. The date the designation was made. 170 TBD. 172 4. The date the use designation is to be terminated (if specified 173 as a limited-use designation). 175 Unlimited. No termination date. 177 5. The nature of the purpose of the designated address (e.g., 178 unicast experiment or protocol service anycast). 180 protocol service anycast. 182 6. For experimental unicast applications and otherwise as 183 appropriate, the registry will also identify the entity and 184 related contact details to whom the address designation has been 185 made. 187 N/A. 189 7. The registry will also note, for each designation, the 190 intended routing scope of the address, indicating whether the 191 address is intended to be routable only in scoped, local, or 192 private contexts, or whether the address prefix is intended to be 193 routed globally. 195 Typically used within a network operator's network domain, but in 196 principle globally routable. 198 8. The date in the IANA registry is the date of the IANA action, 199 i.e., the day IANA records the allocation. 201 TBD. 203 4.2. Registration of IPv6 Special Purpose Address 205 IANA is requested to register a single IPv6 address in the IANA IPv6 206 Special Purpose Address Block [RFC4773]. 208 [RFC4773] itemizes some information to be recorded for all 209 designations: 211 1. The designated address prefix. 213 Prefix: TBD by IANA. Prefix length: /128 215 2. The RFC that called for the IANA address designation. 217 This document. 219 3. The date the designation was made. 221 TBD. 223 4. The date the use designation is to be terminated (if specified 224 as a limited-use designation). 226 Unlimited. No termination date. 228 5. The nature of the purpose of the designated address (e.g., 229 unicast experiment or protocol service anycast). 231 protocol service anycast. 233 6. For experimental unicast applications and otherwise as 234 appropriate, the registry will also identify the entity and 235 related contact details to whom the address designation has been 236 made. 238 N/A. 240 7. The registry will also note, for each designation, the 241 intended routing scope of the address, indicating whether the 242 address is intended to be routable only in scoped, local, or 243 private contexts, or whether the address prefix is intended to be 244 routed globally. 246 Typically used within a network operator's network domain, but in 247 principle globally routable. 249 8. The date in the IANA registry is the date of the IANA action, 250 i.e., the day IANA records the allocation. 252 TBD. 254 5. Security Considerations 256 In a network without any border gateway, NAT or firewall that is 257 aware of the PCP anycast address, outgoing PCP requests could leak 258 out onto the external Internet, possibly revealing information about 259 internal devices. 261 Using an IANA-assigned well-known PCP anycast address enables border 262 gateways to block such outgoing packets. In the default-free zone, 263 routers should be configured to drop such packets. Such 264 configuration can occur naturally via BGP messages advertising that 265 no route exists to said address. 267 Sensitive clients that do not wish to leak information about their 268 presesence can set an IP TTL on their PCP requests that limits how 269 far they can travel into the public Internet. 271 6. References 273 6.1. Normative References 275 [RFC1546] Partridge, C., Mendez, T., and W. Milliken, "Host 276 Anycasting Service", RFC 1546, November 1993. 278 [RFC3958] Daigle, L. and A. Newton, "Domain-Based Application 279 Service Location Using SRV RRs and the Dynamic Delegation 280 Discovery Service (DDDS)", RFC 3958, January 2005. 282 [RFC4773] Huston, G., "Administration of the IANA Special Purpose 283 IPv6 Address Block", RFC 4773, December 2006. 285 [RFC5736] Huston, G., Cotton, M., and L. Vegoda, "IANA IPv4 Special 286 Purpose Address Registry", RFC 5736, January 2010. 288 [RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. 289 Selkirk, "Port Control Protocol (PCP)", RFC 6887, 290 April 2013. 292 6.2. Informative References 294 [DNSDisc] Hagino, J. and D. Thaler, "Analysis of DNS Server 295 Discovery Mechanisms for IPv6", 296 draft-ietf-ipngwg-dns-discovery-01 (work in progress), 297 November 2001. 299 [DhcpRequestParams] 300 OpenFlow, "OpenFlow Switch Specification", February 2011, 301 . 304 [I-D.chen-pcp-mobile-deployment] 305 Chen, G., Cao, Z., Boucadair, M., Ales, V., and L. 306 Thiebaut, "Analysis of Port Control Protocol in Mobile 307 Network", draft-chen-pcp-mobile-deployment-04 (work in 308 progress), July 2013. 310 [I-D.ietf-dhc-container-opt] 311 Droms, R. and R. Penno, "Container Option for Server 312 Configuration", draft-ietf-dhc-container-opt-07 (work in 313 progress), April 2013. 315 [I-D.ietf-pcp-dhcp] 316 Boucadair, M., Penno, R., and D. Wing, "DHCP Options for 317 the Port Control Protocol (PCP)", draft-ietf-pcp-dhcp-09 318 (work in progress), November 2013. 320 Appendix A. Discussion of other PCP Discovery methods 322 Several algorithms have been specified that allows PCP Client to 323 discover the PCP Servers on a network . However, each of this 324 approaches has technical or operational issues that will hinder the 325 fast deployment of PCP. 327 A.1. Default Router 329 The PCP specification allows one mode of operation in which the PCP 330 client sends its requests to the default router. This approach is 331 appropriate in a typical single-link residential network but has 332 limitations in more complex network topologies. 334 If PCP server does not reside in first hop router, whether because 335 subscriber has a existing home router or in the case of Wireless 336 Networks (3G, LTE) [I-D.chen-pcp-mobile-deployment], trying to send a 337 request to default router will not work. 339 A.2. DHCP PCP Options 341 One general drawback of relying on external configuration mechanisms, 342 such as DHCP [I-D.ietf-pcp-dhcp], is that it creates an external 343 dependency on another piece of network infrastructure which must be 344 configured with the right address for PCP to work. In some 345 environments the staff managing the DHCP servers may not be the same 346 staff managing the NAT gateways, and in any case, constantly keeping 347 the DHCP server address information up to date as NAT gateways are 348 added, removed, or reconfigured, is burdensome. 350 Another drawback of relying on DHCP for configuration is that at 351 least one significant target deployment environments for PCP -- 352 namely 3GPP for mobile telephones -- does not use DHCP. 354 There are two problems with DHCP Options: DHCP Server on Home 355 Gateways (HGW) and Operating Systems DHCP clients 357 Currently what the HGW does with the options it receives from the ISP 358 is not standardized in any general way. As a matter of practice, the 359 HGW is most likely to use its own customer-LAN-facing IP address for 360 the DNS server address. As for other options, it's free to offer the 361 same values to the client, offer no value at all, or offer its own IP 362 address if that makes sense, as it does (sort of) for DNS. 364 In scenarios where PCP Server resides on ISP network and is intended 365 to work with arbitrary home gateways that don't know they are being 366 used in a PCP context, that won't work, because there's no reason to 367 think that the HGW will even request the option from the DHCP server, 368 much less offer the value it gets from the server on the customer- 369 facing LAN. There is work on the DHC WG to overcome some of these 370 limitations [I-D.ietf-dhc-container-opt] but in terms of deployment 371 it also needs HGW to be upgraded. 373 The problems with Operating Systems is that even if DHCP PCP Option 374 were made available to customer-facing LAN, host stack DHCP 375 enhancements are required to process or request new DHCP PCP option. 376 One exception is Windows [DhcpRequestParams] 378 Finally, in the case of IPv6 there are networks where there is DHCPv6 379 infrastructure at all or some hosts do not have a DHCPv6 client. 381 A.3. User Input 383 A regular subscriber can not be expected to input IP address of PCP 384 Server or network domain name. Moreover, user can be at a Wi-Fi 385 hotspot, Hotel or related. Therefore relying on user input is not 386 reliable. 388 A.4. Domain Name System Based 390 There are three separate category of problems with NAPTR [RFC3958] 392 1. End Points: It relies on PCP client determining the domain name 393 and supporting certain DNS queries 395 2. DNS Servers: DNS server need to be provisioned with the necessary 396 records 398 3. CPEs: CPEs might interfere with DNS queries and the DHCP domain 399 name option conveyed by ISP that could be used to bootstrap NAPTR 400 might not be relayed to home network. 402 A.5. Addressing only based on Destination Port 404 One design option that was considered for Apple's NAT gateways was to 405 have the NAT gateway simply handle and respond to all packets 406 addressed to UDP port 5351, regardless of the destination address in 407 the packet. Since the device is a NAT gateway, it already examines 408 every packet in order to rewrite port numbers, so also detecting 409 packets addressed to UDP port 5351 is not a significant additional 410 burden. Also, since this device is a NAT gateway which rewrites port 411 numbers, any attempt by a client to talk *though* this first NAT 412 gateway to create mappings in some second upstream NAT gateway is 413 futile and pointless. Any mappings created in the second NAT gateway 414 are useful to the client only if there are also corresponding 415 mappings created in the first NAT gateway. Consequently, there is no 416 case where it is useful for PCP requests to pass transparently 417 through the first PCP-aware NAT gateway on their way to the second 418 PCP-aware NAT gateway. In all cases, for useful connectivity to be 419 established, the PCP request must be handled by the first NAT 420 gateway, and then the first NAT gateway generates a corresponding new 421 upstream request to establish a mapping in the second NAT gateway. 422 (This process can be repeated recursively for as many times as 423 necessary for the depth of nesting of NAT gateways; this is 424 transparent to the client device.) 426 Appendix B. Discussion of IP Anycast Address usage for PCP 428 B.1. Motivation 430 The two issues identified in Appendix A.5 result in the following 431 related observations: the PCP client may not *know* what destination 432 address to use in its PCP request packets; the PCP server doesn't 433 *care* what destination address is in the PCP request packets. 435 Given that the devices neither need to know nor care what destination 436 address goes in the packet, all we need to do is pick one and use it. 437 It's little more than a placeholder in the IP header. Any globally 438 routable unicast address will do. Since this address is one that 439 automatically routes its packet to the closest on-path device that 440 implements the desired functionality, it is an anycast address. 442 B.2. Scenarios 444 In the simple case where the first-hop router is also the NAT gateway 445 (as is common in a typical single-link residential network), sending 446 to the PCP anycast address is equivalent to sending to the client's 447 default router, as specified in the PCP base document [RFC6887]. 449 In the case of a larger corporate network, where there may be several 450 internal routed subnets and one or more border NAT gateway(s) 451 connecting to the rest of the Internet, sending to the PCP anycast 452 address has the interesting property that it magically finds the 453 right border NAT gateway for that client. Since we posit that other 454 network infrastructure does not need (and should not have) any 455 special knowledge of PCP (or its anycast address) this means that to 456 other non-NAT routers, the PCP anycast address will look like any 457 other unicast destination address on the public Internet, and 458 consequently the packet will be forwarded as for any other packet 459 destined to the public Internet, until it reaches a NAT or firewall 460 device that is aware of the PCP anycast address. This will result in 461 the packet naturally arriving the NAT gateway that handles this 462 client's outbound traffic destined to the public Internet, which is 463 exactly the NAT gateway that the client wishes to communicate with 464 when managing its port mappings. 466 B.3. Historical Objections to Anycast 468 In March 2001 a draft document entitled "Analysis of DNS Server 469 Discovery Mechanisms for IPv6" [DNSDisc] proposed using anycast to 470 discover DNS servers, a proposal that was subsequently abandoned in 471 later revisions of that draft document. 473 There are legitimate reasons why using anycast to discover DNS 474 servers is not compelling, mainly because it requires explicit 475 configuration of routing tables to direct those anycast packets to 476 the desired DNS server. However, DNS server discovery is very 477 different to NAT gateway discovery. A DNS server is something a 478 client explicitly talks to, via IP address. The DNS server may be 479 literally anywhere on the Internet. Various reasons make anycast an 480 uncompelling technique for DNS server discovery: 482 o DNS is a pure application-layer protocol, running over UDP. 484 o On an operating system without appropriate support for configuring 485 anycast addresses, a DNS server would have to use something like 486 Berkeley Packet Filter (BPF) to snoop on received packets to 487 intercept DNS requests, which is inelegant and inefficient. 489 o Without appropriate routing changes elsewhere in the network, 490 there's no reason to assume that packets sent to that anycast 491 address would even make it to the desired DNS server machine. 492 This places an addition configuration burden on the network 493 administrators, to install appropriate routing table entries to 494 direct packets to the desired DNS server machine. 496 In contrast, a NAT gateway is something a client's packets stumble 497 across as they try to leave the local network and head out onto the 498 public Internet. The NAT gateway has to be on the path those packets 499 naturally take or it can't perform its NAT functions. As a result, 500 the objections to using anycast for DNS server discovery do not apply 501 to PCP: 503 o No routing changes are needed (or desired) elsewhere in the local 504 network, because the whole *point* of using anycast is that we 505 want the client's PCP request packet to take the same forwarding 506 path through the network as a TCP SYN to any other remote 507 destination address, because we want the *same* NAT gateway that 508 would have made a mapping in response to receiving an outbound TCP 509 SYN packet from the client to be the the one that makes a mapping 510 in response to receiving a PCP request packet from the client. 512 o A NAT engine is already snooping on (and rewriting) every packet 513 it forwards. As part of that snooping it could trivially look for 514 packets addressed to the PCP UDP port and process them locally 515 (just like the local processing it already does when it sees an 516 outbound TCP SYN packet). 518 Authors' Addresses 520 Sebastian Kiesel 521 University of Stuttgart Computing Center 522 Allmandring 30 523 Stuttgart 70550 524 Germany 526 Email: ietf-pcp@skiesel.de 527 URI: http://www.rus.uni-stuttgart.de/nks/ 529 Reinaldo Penno 530 Cisco Systems, Inc. 531 San Jose, CA 532 US 534 Phone: 535 Fax: 536 Email: repenno@cisco.com 537 URI: 539 Stuart Cheshire 540 Apple Inc. 541 1 Infinite Loop 542 Cupertino, California 95014 543 USA 545 Phone: +1 408 974 3207 546 Email: cheshire@apple.com