idnits 2.17.1 draft-ietf-pcp-anycast-07.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 : ---------------------------------------------------------------------------- == There are 1 instance of lines with non-RFC6890-compliant IPv4 addresses in the document. If these are example addresses, they should be changed. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (August 27, 2015) is 3166 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) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 2 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: February 28, 2016 Cisco Systems, Inc. 6 S. Cheshire 7 Apple 8 August 27, 2015 10 Port Control Protocol (PCP) Anycast Addresses 11 draft-ietf-pcp-anycast-07 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 February 28, 2016. 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 . . . . . . . . . . . . . . . . . . . . . . . 9 68 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 69 7.1. Normative References . . . . . . . . . . . . . . . . . . . 10 70 7.2. Informative References . . . . . . . . . . . . . . . . . . 10 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 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. The anycast addresses 94 are allocated from pools of special-purpose IP addresses (see 95 Section 4), in accordance with Section 3.4 of [RFC4085]. Yet, a 96 means to disable or override these well-known addresses (e. g., a 97 configuration file option) should be available in implementations. 99 Using an anycast address is particularly useful in larger network 100 topologies. For example, if the PCP-enabled NAT/firewall function is 101 not located on the client's default gateway, but further upstream in 102 a Carrier-grade NAT (CGN), sending PCP requests to the default 103 gateway's IP address will not have the desired effect. When using a 104 configuration file or the DHCP option to learn the PCP server's IP 105 address, this file or the DHCP server configuration must reflect the 106 network topology, and the router and CGN configuration. This may be 107 cumbersome to achieve and maintain. If there is more than one 108 upstream CGN and traffic is routed using a dynamic routing protocol 109 such as OSPF, this approach may not be feasible at all, as it cannot 110 provide timely information on which CGN to interact with. In 111 contrast, when using the PCP anycast address, the PCP request will 112 travel through the network like any other packet, without any special 113 support from DNS, DHCP, other routers, or anything else, until it 114 reaches the PCP-capable device, which receives it, handles it, and 115 sends back a reply. A further advantage of using an anycast address 116 instead of a DHCP option is, that the anycast address can be hard- 117 coded into the application. There is no need for an application 118 programming interface for passing the PCP server's address from the 119 operating system's DHCP client to the application. For further 120 discussion of deployment considerations see Section 3. 122 2. PCP Server Discovery based on well-known IP Address 124 2.1. PCP Discovery Client behavior 126 The PCP anycast addresses, as defined in Sections 4.1 and 4.2, are 127 added after the default router list (for IPv4 and IPv6) to the list 128 of PCP server(s) (see Section 8.1, step 2. of [RFC6887]). This list 129 is processed as specified in [RFC7488]. 131 Note: If, in some specific scenario, it was desirable to use only the 132 anycast address (and not the default router), this could be achieved 133 by putting the anycast address into the configuration file, or DHCP 134 option, etc. 136 2.2. PCP Discovery Server behavior 138 A PCP Server can be configured to listen on the anycast address for 139 incoming PCP requests. 141 PCP responses are sent from that same IANA-assigned address (see 142 Page 6 of [RFC1546] for further discussion). 144 3. Deployment Considerations 146 For general recommendations regarding operation of anycast services 147 see [RFC4786]. Architectural considerations of IP anycast are 148 discussed in [RFC7094]. 150 In some deployment scenarios, using PCP anycasting may have certain 151 limitations, which can be overcome by using additional mechanisms or 152 by using other PCP server discovery methods instead, such as DHCP 153 [RFC7291] or a configuration file. 155 One important example is a network topology, in which a network is 156 connected to one or more upstream network(s) via several parallel 157 firewalls, each individually controlled by its own PCP server. Even 158 if all of these PCP servers are configured for anycasting, only one 159 will receive the messages sent by a given client, depending on the 160 state of the routing tables. 162 As long as routing is always symmetric, i.e., all upstream and 163 downstream packets from/to that client are routed through this very 164 same firewall, communication will be possible as expected. If there 165 is a routing change, a PCP client using PCP anycasting might start 166 interacting with a different PCP server. From the PCP client's point 167 of view this would be the same as a PCP server reboot and the client 168 could detect it by examining the Epoch field during the next PCP 169 response or ANNOUNCE message. The client would re-establish the 170 firewall rules and packet flows could resume. 172 If, however, routing is asymmetric, upstream packets from a client 173 traverse a different firewall than the downstream packets to that 174 client. Establishing policy rules in only one of these two firewalls 175 by means of PCP anycasting will not have the desired result of 176 allowing bi-directional connectivity. One solution approach to 177 overcome this problem is an implementation-specific mechanism to 178 synchronize state between all firewalls at the border of a network, 179 i.e., a PEER message sent to any of these PCP servers would establish 180 rules in all firewalls. Another approach would be to use a different 181 discovery mechanism (e.g., DHCP or a configuration file) that allows 182 a PCP client to acquire a list of all PCP servers controlling the 183 parallel firewalls and configure each of them individually. 185 4. IANA Considerations 187 4.1. Registration of IPv4 Special Purpose Address 189 IANA is requested to assign a single IPv4 address from the 190 192.0.0.0/24 prefix and register it in the IANA IPv4 Special-Purpose 191 Address Registry [RFC6890]. 193 +----------------------+-------------------------------------------+ 194 | Attribute | Value | 195 +----------------------+-------------------------------------------+ 196 | Address Block | 192.0.0.???/32 (??? = TBD by IANA) | 197 | Name | Port Control Protocol Anycast | 198 | RFC | This document, if approved (TBD) | 199 | Allocation Date | Date of approval of this document (TBD) | 200 | Termination Date | N/A | 201 | Source | True | 202 | Destination | True | 203 | Forwardable | True | 204 | Global | True | 205 | Reserved-by-Protocol | False | 206 +----------------------+-------------------------------------------+ 208 4.2. Registration of IPv6 Special Purpose Address 210 IANA is requested to assign a single IPv6 address from the 2001: 211 0000::/23 prefix and register it in the IANA IPv6 Special-Purpose 212 Address Registry [RFC6890]. 214 +----------------------+-------------------------------------------+ 215 | Attribute | Value | 216 +----------------------+-------------------------------------------+ 217 | Address Block | 2001:0????????/128 (??? = TBD by IANA) | 218 | Name | Port Control Protocol Anycast | 219 | RFC | This document, if approved (TBD) | 220 | Allocation Date | Date of approval of this document (TBD) | 221 | Termination Date | N/A | 222 | Source | True | 223 | Destination | True | 224 | Forwardable | True | 225 | Global | True | 226 | Reserved-by-Protocol | False | 227 +----------------------+-------------------------------------------+ 229 5. Security Considerations 231 In addition to the security considerations in [RFC6887], [RFC4786], 232 and [RFC7094], two further security issues are considered here. 234 5.1. Information Leakage through Anycast 236 In a network without any border gateway, NAT or firewall that is 237 aware of the PCP anycast address, outgoing PCP requests could leak 238 out onto the external Internet, possibly revealing information about 239 internal devices. 241 Using an IANA-assigned well-known PCP anycast address enables border 242 gateways to block such outgoing packets. In the default-free zone, 243 routers should be configured to drop such packets. Such 244 configuration can occur naturally via BGP messages advertising that 245 no route exists to said address. 247 Sensitive clients that do not wish to leak information about their 248 presence can set an IP TTL on their PCP requests that limits how far 249 they can travel towards the public Internet. However, methods for 250 choosing an appropriate TTL value, e.g., based on the assumed radius 251 of the trusted network domain, is beyond the scope of this document. 253 5.2. Hijacking of PCP Messages sent to Anycast Addresses 255 The anycast addresses are treated by normal host operating systems 256 just as normal unicast addresses, i.e., packets destined for an 257 anycast address are sent to the default router for processing and 258 forwarding. Hijacking such packets in the first network segment 259 would effectively require to impersonate the default router, e.g., by 260 means of ARP spoofing in an Ethernet network. If such attacks are a 261 serious concern in a given scenario, much more severe consequences to 262 other protocols have to be feared as well. Therefore, adequate 263 measures have to be taken to prevent spoofing attacks targeted at the 264 default router. 266 Once an anycast message is forwarded closer to the core network, 267 routing will likely become subject to dynamic routing protocols such 268 as OSPF or BGP. Anycast messages could be hijacked by announcing 269 counterfeited messages in these routing protocols. But again, an 270 attacker capable of performing these attacks could cause 271 significantly more damage to other protocols and therefore adequate 272 means should be taken to prevent these attacks. 274 In addition to following best current practices in first hop security 275 and routing protocol security, PCP authentication 276 [I-D.ietf-pcp-authentication] may be useful in some scenarios. 278 However, the effort needed for a proper setup of this authentication 279 mechanism (e.g., installing the right shared secrets or cryptograpic 280 keys on all involved systems) may thwart the goal of fully automatic 281 configuration by using PCP anycast. Therefore, this approach may be 282 less suitable for scenarios with high trust between the operator of 283 the PCP-controlled middlebox and all users (e.g., a residential 284 gateway used only by family members) or if there is anyway rather 285 limited trust that the middlebox will behave correctly (e.g., the 286 Wifi in an airport lounge). In contrast, this scheme may be highly 287 useful in scenarios with many users and a trusted network operator, 288 such as a large corporate network or a university campus network, 289 which uses several parallel NATs or firewalls to connect to the 290 Internet. Therefore, a thorough analysis of the benefits and costs 291 of using PCP authentication in a given network scenario is 292 recommended. 294 6. Acknowledgments 296 The authors would like to thank the members of the PCP working group 297 for contributions and feedback, in particular Mohamed Boucadair, 298 Charles Eckel, Simon Perreault, Tirumaleswar Reddy, Markus Stenberg, 299 Dave Thaler, and Dan Wing. 301 7. References 303 7.1. Normative References 305 [RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. 306 Selkirk, "Port Control Protocol (PCP)", RFC 6887, 307 April 2013. 309 [RFC6890] Cotton, M., Vegoda, L., Bonica, R., and B. Haberman, 310 "Special-Purpose IP Address Registries", BCP 153, 311 RFC 6890, April 2013. 313 [RFC7488] Boucadair, M., Penno, R., Wing, D., Patil, P., and T. 314 Reddy, "Port Control Protocol (PCP) Server Selection", 315 RFC 7488, March 2015. 317 7.2. Informative References 319 [I-D.ietf-pcp-authentication] 320 Wasserman, M., Hartman, S., Zhang, D., and T. Reddy, "Port 321 Control Protocol (PCP) Authentication Mechanism", 322 draft-ietf-pcp-authentication-14 (work in progress), 323 July 2015. 325 [I-D.ietf-pcp-optimize-keepalives] 326 Reddy, T., Patil, P., Isomaki, M., and D. Wing, 327 "Optimizing NAT and Firewall Keepalives Using Port Control 328 Protocol (PCP)", draft-ietf-pcp-optimize-keepalives-06 329 (work in progress), May 2015. 331 [RFC1546] Partridge, C., Mendez, T., and W. Milliken, "Host 332 Anycasting Service", RFC 1546, November 1993. 334 [RFC4085] Plonka, D., "Embedding Globally-Routable Internet 335 Addresses Considered Harmful", BCP 105, RFC 4085, 336 DOI 10.17487/RFC4085, June 2005, 337 . 339 [RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast 340 Services", BCP 126, RFC 4786, December 2006. 342 [RFC7094] McPherson, D., Oran, D., Thaler, D., and E. Osterweil, 343 "Architectural Considerations of IP Anycast", RFC 7094, 344 DOI 10.17487/RFC7094, January 2014, 345 . 347 [RFC7291] Boucadair, M., Penno, R., and D. Wing, "DHCP Options for 348 the Port Control Protocol (PCP)", RFC 7291, July 2014. 350 Authors' Addresses 352 Sebastian Kiesel 353 University of Stuttgart Information Center 354 Networks and Communication Systems Department 355 Allmandring 30 356 Stuttgart 70550 357 Germany 359 Email: ietf-pcp@skiesel.de 361 Reinaldo Penno 362 Cisco Systems, Inc. 363 170 West Tasman Drive 364 San Jose, California 95134 365 USA 367 Email: repenno@cisco.com 369 Stuart Cheshire 370 Apple Inc. 371 1 Infinite Loop 372 Cupertino, California 95014 373 USA 375 Phone: +1 408 974 3207 376 Email: cheshire@apple.com