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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-14) exists of draft-ietf-pcp-authentication-07 Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--).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: November 21, 2015 Cisco Systems, Inc. 6 S. Cheshire 7 Apple 8 May 20, 2015 10 Port Control Protocol (PCP) Anycast Addresses 11 draft-ietf-pcp-anycast-06 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 November 21, 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 . . . . . . . 6 64 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 65 5.1. Information Leakage through Anycast . . . . . . . . . . . 7 66 5.2. Hijacking of PCP Messages sent to Anycast Addresses . . . 7 67 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 68 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 69 7.1. Normative References . . . . . . . . . . . . . . . . . . . 9 70 7.2. Informative References . . . . . . . . . . . . . . . . . . 9 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 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 138 Page 6 of [RFC1546] for further discussion). 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 assign a single IPv4 address from the 156 192.0.0.0/24 prefix and register it in the IANA IPv4 Special-Purpose 157 Address Registry [RFC6890]. 159 +----------------------+-------------------------------------------+ 160 | Attribute | Value | 161 +----------------------+-------------------------------------------+ 162 | Address Block | 192.0.0.???/32 (??? = TBD by IANA) | 163 | Name | Port Control Protocol Anycast | 164 | RFC | This document, if approved (TBD) | 165 | Allocation Date | Date of approval of this document (TBD) | 166 | Termination Date | N/A | 167 | Source | True | 168 | Destination | True | 169 | Forwardable | True | 170 | Global | True | 171 | Reserved-by-Protocol | False | 172 +----------------------+-------------------------------------------+ 174 4.2. Registration of IPv6 Special Purpose Address 176 IANA is requested to assign a single IPv6 address from the 2001: 177 0000::/23 prefix and register it in the IANA IPv6 Special-Purpose 178 Address Registry [RFC6890]. 180 +----------------------+-------------------------------------------+ 181 | Attribute | Value | 182 +----------------------+-------------------------------------------+ 183 | Address Block | 2001:0????????/128 (??? = TBD by IANA) | 184 | Name | Port Control Protocol Anycast | 185 | RFC | This document, if approved (TBD) | 186 | Allocation Date | Date of approval of this document (TBD) | 187 | Termination Date | N/A | 188 | Source | True | 189 | Destination | True | 190 | Forwardable | True | 191 | Global | True | 192 | Reserved-by-Protocol | False | 193 +----------------------+-------------------------------------------+ 195 5. Security Considerations 197 In addition to the security considerations in [RFC6887], two 198 additional issues are considered here. 200 5.1. Information Leakage through Anycast 202 In a network without any border gateway, NAT or firewall that is 203 aware of the PCP anycast address, outgoing PCP requests could leak 204 out onto the external Internet, possibly revealing information about 205 internal devices. 207 Using an IANA-assigned well-known PCP anycast address enables border 208 gateways to block such outgoing packets. In the default-free zone, 209 routers should be configured to drop such packets. Such 210 configuration can occur naturally via BGP messages advertising that 211 no route exists to said address. 213 Sensitive clients that do not wish to leak information about their 214 presence can set an IP TTL on their PCP requests that limits how far 215 they can travel into the public Internet. 217 5.2. Hijacking of PCP Messages sent to Anycast Addresses 219 The anycast addresses are treated by normal host operating systems 220 just as normal unicast addresses, i.e., packets destined for an 221 anycast address are sent to the default router for processing and 222 forwarding. Hijacking such packets in the first network segment 223 would effectively require to impersonate the default router, e.g., by 224 means of ARP spoofing in an Ethernet network. If such attacks are a 225 serious concern in a given scenario, much more severe consequences to 226 other protocols have to be feared as well. Therefore, adequate 227 measures have to be taken to prevent spoofing attacks targeted at the 228 default router. 230 Once an anycast message is forwarded closer to the core network, 231 routing will likely become subject to dynamic routing protocols such 232 as OSPF or BGP. Anycast messages could be hijacked by announcing 233 counterfeited messages in these routing protocols. But again, an 234 attacker capable of performing these attacks could cause 235 significantly more damage to other protocols and therefore adequate 236 means should be taken to prevent these attacks. 238 In addition to following best current practices in first hop security 239 and routing protocol security, PCP authentication 240 [I-D.ietf-pcp-authentication] may be useful in some scenarios, 241 although it might thwart the goal of fully automatic configuration in 242 other scenarios. 244 6. Acknowledgments 246 The authors would like to thank the members of the PCP working group 247 for contributions and feedback, in particular Mohamed Boucadair, 248 Charles Eckel, Simon Perreault, Tirumaleswar Reddy, Markus Stenberg, 249 Dave Thaler, and Dan Wing. 251 7. References 253 7.1. Normative References 255 [RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. 256 Selkirk, "Port Control Protocol (PCP)", RFC 6887, 257 April 2013. 259 [RFC6890] Cotton, M., Vegoda, L., Bonica, R., and B. Haberman, 260 "Special-Purpose IP Address Registries", BCP 153, 261 RFC 6890, April 2013. 263 [RFC7488] Boucadair, M., Penno, R., Wing, D., Patil, P., and T. 264 Reddy, "Port Control Protocol (PCP) Server Selection", 265 RFC 7488, March 2015. 267 7.2. Informative References 269 [I-D.ietf-pcp-authentication] 270 Wasserman, M., Hartman, S., Zhang, D., and T. Reddy, "Port 271 Control Protocol (PCP) Authentication Mechanism", 272 draft-ietf-pcp-authentication-07 (work in progress), 273 December 2014. 275 [I-D.ietf-pcp-optimize-keepalives] 276 Reddy, T., Patil, P., Isomaki, M., and D. Wing, 277 "Optimizing NAT and Firewall Keepalives Using Port Control 278 Protocol (PCP)", draft-ietf-pcp-optimize-keepalives-06 279 (work in progress), May 2015. 281 [RFC1546] Partridge, C., Mendez, T., and W. Milliken, "Host 282 Anycasting Service", RFC 1546, November 1993. 284 [RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast 285 Services", BCP 126, RFC 4786, December 2006. 287 [RFC7291] Boucadair, M., Penno, R., and D. Wing, "DHCP Options for 288 the Port Control Protocol (PCP)", RFC 7291, July 2014. 290 Authors' Addresses 292 Sebastian Kiesel 293 University of Stuttgart Information Center 294 Networks and Communication Systems Department 295 Allmandring 30 296 Stuttgart 70550 297 Germany 299 Email: ietf-pcp@skiesel.de 301 Reinaldo Penno 302 Cisco Systems, Inc. 303 170 West Tasman Drive 304 San Jose, California 95134 305 USA 307 Email: repenno@cisco.com 309 Stuart Cheshire 310 Apple Inc. 311 1 Infinite Loop 312 Cupertino, California 95014 313 USA 315 Phone: +1 408 974 3207 316 Email: cheshire@apple.com