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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) ** 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reference: RFC 4773 (Obsoleted by RFC 6890) ** Obsolete normative reference: RFC 5736 (Obsoleted by RFC 6890) == Outdated reference: A later version (-14) exists of draft-ietf-pcp-authentication-07 == Outdated reference: A later version (-06) exists of draft-ietf-pcp-optimize-keepalives-05 Summary: 3 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). 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: October 31, 2015 Cisco Systems, Inc. 6 S. Cheshire 7 Apple 8 April 29, 2015 10 Port Control Protocol (PCP) Anycast Addresses 11 draft-ietf-pcp-anycast-05 13 Abstract 15 The Port Control Protocol (PCP) Anycast Addresses enable PCP clients 16 to transmit signaling messages to their closest PCP-aware on-path 17 NAT, Firewall, or other middlebox, without having to learn the IP 18 address 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 Addresses. 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 October 31, 2015. 39 Copyright Notice 41 Copyright (c) 2015 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 5.1. Information Leakage through Anycast . . . . . . . . . . . 9 66 5.2. Hijacking of PCP Messages sent to Anycast Addresses . . . 9 67 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 68 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 69 7.1. Normative References . . . . . . . . . . . . . . . . . . . 11 70 7.2. Informative References . . . . . . . . . . . . . . . . . . 11 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 73 1. Introduction 75 The Port Control Protocol (PCP) [RFC6887] provides a mechanism to 76 control how incoming packets are forwarded by upstream devices such 77 as Network Address Translator IPv6/IPv4 (NAT64), Network Address 78 Translator IPv4/IPv4 (NAT44), and IPv6 and IPv4 firewall devices. 79 Furthermore, it provides a mechanism to reduce application keep alive 80 traffic [I-D.ietf-pcp-optimize-keepalives]. The PCP base protocol 81 document [RFC6887] specifies the message formats used, but the 82 address to which a client sends its request is either assumed to be 83 the default router (which is appropriate in a typical single-link 84 residential network) or has to be configured otherwise via some 85 external mechanism, such as a configuration file or a DHCP option 86 [RFC7291]. 88 This document follows a different approach: it establishes two well- 89 known anycast addresses for the PCP Server, one IPv4 address and one 90 IPv6 address. These well-known addresses may be hard-coded into PCP 91 clients. PCP clients usually send PCP requests to these addresses if 92 no other PCP server addresses are known or after communication 93 attempts to such other addresses have failed. 95 Using an anycast address is particularly useful in larger network 96 topologies. For example, if the PCP-enabled NAT/firewall function is 97 not located on the client's default gateway, but further upstream in 98 a Carrier-grade NAT (CGN), sending PCP requests to the default 99 gateway's IP address will not have the desired effect. When using a 100 configuration file or the DHCP option to learn the PCP server's IP 101 address, this file or the DHCP server configuration must reflect the 102 network topology, and the router and CGN configuration. This may be 103 cumbersome to achieve and maintain. If there is more than one 104 upstream CGN and traffic is routed using a dynamic routing protocol 105 such as OSPF, this approach may not be feasible at all, as it cannot 106 provide timely information on which CGN to interact with. In 107 contrast, when using the PCP anycast address, the PCP request will 108 travel through the network like any other packet, without any special 109 support from DNS, DHCP, other routers, or anything else, until it 110 reaches the PCP-capable device, which receives it, handles it, and 111 sends back a reply. A further advantage of using an anycast address 112 instead of a DHCP option is, that the anycast address can be hard- 113 coded into the application. There is no need for an application 114 programming interface for passing the PCP server's address from the 115 operating system's DHCP client to the application. For further 116 discussion of deployment considerations see Section 3. 118 2. PCP Server Discovery based on well-known IP Address 120 2.1. PCP Discovery Client behavior 122 The PCP anycast addresses, as defined in Sections 4.1 and 4.2, are 123 added after the default router list (for IPv4 and IPv6) to the list 124 of PCP server(s) (see Section 8.1, step 2. of [RFC6887]). This list 125 is processed as specified in [RFC7488]. 127 Note: If, in some specific scenario, it was desirable to use only the 128 anycast address (and not the default router), this could be achieved 129 by putting the anycast address into the configuration file, or DHCP 130 option, etc. 132 2.2. PCP Discovery Server behavior 134 A PCP Server can be configured to listen on the anycast address for 135 incoming PCP requests. 137 PCP responses are sent from that same IANA-assigned address (see Page 138 5 of [RFC1546]). 140 3. Deployment Considerations 142 There are known limitations when there is more than one PCP-capable 143 NAT/firewall in a cascaded alignment, or in a parallel layout with 144 asymmetric routing, or similar scenarios. Mechanisms to deal with 145 those situations, such as state synchronization between PCP servers, 146 are beyond the scope of this document. 148 For general recommendations regarding operation of anycast services 149 see [RFC4786]. 151 4. IANA Considerations 153 4.1. Registration of IPv4 Special Purpose Address 155 IANA is requested to register a single IPv4 address in the IANA IPv4 156 Special Purpose Address Registry [RFC5736]. 158 [RFC5736] itemizes some information to be recorded for all 159 designations: 161 1. The designated address prefix. 163 Prefix: TBD by IANA. Prefix length: /32 165 2. The RFC that called for the IANA address designation. 167 This document. 169 3. The date the designation was made. 171 TBD. 173 4. The date the use designation is to be terminated (if specified 174 as a limited-use designation). 176 Unlimited. No termination date. 178 5. The nature of the purpose of the designated address (e.g., 179 unicast experiment or protocol service anycast). 181 protocol service anycast. 183 6. For experimental unicast applications and otherwise as 184 appropriate, the registry will also identify the entity and 185 related contact details to whom the address designation has been 186 made. 188 The IETF PCP WG. 190 7. The registry will also note, for each designation, the 191 intended routing scope of the address, indicating whether the 192 address is intended to be routable only in scoped, local, or 193 private contexts, or whether the address prefix is intended to be 194 routed globally. 196 Typically used within a network operator's network domain, but in 197 principle globally routable. 199 8. The date in the IANA registry is the date of the IANA action, 200 i.e., the day IANA records the allocation. 202 TBD. 204 4.2. Registration of IPv6 Special Purpose Address 206 IANA is requested to register a single IPv6 address in the IANA IPv6 207 Special Purpose Address Block [RFC4773]. 209 [RFC4773] itemizes some information to be recorded for all 210 designations: 212 1. The designated address prefix. 214 Prefix: TBD by IANA. Prefix length: /128 216 2. The RFC that called for the IANA address designation. 218 This document. 220 3. The date the designation was made. 222 TBD. 224 4. The date the use designation is to be terminated (if specified 225 as a limited-use designation). 227 Unlimited. No termination date. 229 5. The nature of the purpose of the designated address (e.g., 230 unicast experiment or protocol service anycast). 232 protocol service anycast. 234 6. For experimental unicast applications and otherwise as 235 appropriate, the registry will also identify the entity and 236 related contact details to whom the address designation has been 237 made. 239 The IETF PCP WG. 241 7. The registry will also note, for each designation, the 242 intended routing scope of the address, indicating whether the 243 address is intended to be routable only in scoped, local, or 244 private contexts, or whether the address prefix is intended to be 245 routed globally. 247 Typically used within a network operator's network domain, but in 248 principle globally routable. 250 8. The date in the IANA registry is the date of the IANA action, 251 i.e., the day IANA records the allocation. 253 TBD. 255 5. Security Considerations 257 In addition to the security considerations in [RFC6887], two 258 additional issues are considered here. 260 5.1. Information Leakage through Anycast 262 In a network without any border gateway, NAT or firewall that is 263 aware of the PCP anycast address, outgoing PCP requests could leak 264 out onto the external Internet, possibly revealing information about 265 internal devices. 267 Using an IANA-assigned well-known PCP anycast address enables border 268 gateways to block such outgoing packets. In the default-free zone, 269 routers should be configured to drop such packets. Such 270 configuration can occur naturally via BGP messages advertising that 271 no route exists to said address. 273 Sensitive clients that do not wish to leak information about their 274 presence can set an IP TTL on their PCP requests that limits how far 275 they can travel into the public Internet. 277 5.2. Hijacking of PCP Messages sent to Anycast Addresses 279 The anycast addresses are treated by normal host operating systems 280 just as normal unicast addresses, i.e., packets destined for an 281 anycast address are sent to the default router for processing and 282 forwarding. Hijacking such packets in the first network segment 283 would effectively require to impersonate the default router, e.g., by 284 means of ARP spoofing in an Ethernet network. If such attacks are a 285 serious concern in a given scenario, much more severe consequences to 286 other protocols have to be feared as well. Therefore, adequate 287 measures have to be taken to prevent spoofing attacks targeted at the 288 default router. 290 Once an anycast message is forwarded closer to the core network, 291 routing will likely become subject to dynamic routing protocols such 292 as OSPF or BGP. Anycast messages could be hijacked by announcing 293 counterfeited messages in these routing protocols. But again, an 294 attacker capable of performing these attacks could cause 295 significantly more damage to other protocols and therefore adequate 296 means should be taken to prevent these attacks. 298 In addition to following best current practices in first hop security 299 and routing protocol security, PCP authentication 300 [I-D.ietf-pcp-authentication] may be useful in some scenarios, 301 although it might thwart the goal of fully automatic configuration in 302 other scenarios. 304 6. Acknowledgments 306 The authors would like to thank the members of the PCP working group 307 for contributions and feedback, in particular Mohamed Boucadair, 308 Charles Eckel, Simon Perreault, Tirumaleswar Reddy, Markus Stenberg, 309 Dave Thaler, and Dan Wing. 311 7. References 313 7.1. Normative References 315 [RFC1546] Partridge, C., Mendez, T., and W. Milliken, "Host 316 Anycasting Service", RFC 1546, November 1993. 318 [RFC4773] Huston, G., "Administration of the IANA Special Purpose 319 IPv6 Address Block", RFC 4773, December 2006. 321 [RFC5736] Huston, G., Cotton, M., and L. Vegoda, "IANA IPv4 Special 322 Purpose Address Registry", RFC 5736, January 2010. 324 [RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. 325 Selkirk, "Port Control Protocol (PCP)", RFC 6887, 326 April 2013. 328 [RFC7488] Boucadair, M., Penno, R., Wing, D., Patil, P., and T. 329 Reddy, "Port Control Protocol (PCP) Server Selection", 330 RFC 7488, March 2015. 332 7.2. Informative References 334 [I-D.ietf-pcp-authentication] 335 Wasserman, M., Hartman, S., Zhang, D., and T. Reddy, "Port 336 Control Protocol (PCP) Authentication Mechanism", 337 draft-ietf-pcp-authentication-07 (work in progress), 338 December 2014. 340 [I-D.ietf-pcp-optimize-keepalives] 341 Reddy, T., Patil, P., Isomaki, M., and D. Wing, 342 "Optimizing NAT and Firewall Keepalives Using Port Control 343 Protocol (PCP)", draft-ietf-pcp-optimize-keepalives-05 344 (work in progress), November 2014. 346 [RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast 347 Services", BCP 126, RFC 4786, December 2006. 349 [RFC7291] Boucadair, M., Penno, R., and D. Wing, "DHCP Options for 350 the Port Control Protocol (PCP)", RFC 7291, July 2014. 352 Authors' Addresses 354 Sebastian Kiesel 355 University of Stuttgart Information Center 356 Networks and Communication Systems Department 357 Allmandring 30 358 Stuttgart 70550 359 Germany 361 Email: ietf-pcp@skiesel.de 363 Reinaldo Penno 364 Cisco Systems, Inc. 365 170 West Tasman Drive 366 San Jose, California 95134 367 USA 369 Email: repenno@cisco.com 371 Stuart Cheshire 372 Apple Inc. 373 1 Infinite Loop 374 Cupertino, California 95014 375 USA 377 Phone: +1 408 974 3207 378 Email: cheshire@apple.com