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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-13) exists of draft-ietf-pcp-dhcp-07 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--).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 M. Boucadair 3 Internet-Draft France Telecom 4 Intended status: Standards Track R. Penno 5 Expires: December 20, 2013 D. Wing 6 Cisco 7 June 18, 2013 9 Port Control Protocol (PCP) Proxy Function 10 draft-ietf-pcp-proxy-03 12 Abstract 14 This document specifies a new PCP functional element denoted as PCP 15 Proxy. The PCP Proxy relays PCP requests received from PCP Clients 16 to upstream PCP Server(s). This function is mandatory when PCP 17 Clients can not be configured with the address of the PCP Server 18 located more than one hop. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on December 20, 2013. 37 Copyright Notice 39 Copyright (c) 2013 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 56 3. PCP Server Discovery and Provisioning . . . . . . . . . . . . 3 57 4. PCP Proxy as a PCP Server . . . . . . . . . . . . . . . . . . 3 58 5. Control of the Firewall . . . . . . . . . . . . . . . . . . . 3 59 6. No NAT is Co-located with the PCP Proxy . . . . . . . . . . . 4 60 7. PCP Proxy Co-located with a NAT Function . . . . . . . . . . 4 61 8. MAP/PEER Handling . . . . . . . . . . . . . . . . . . . . . . 5 62 9. Mapping Repair . . . . . . . . . . . . . . . . . . . . . . . 7 63 10. Advanced Functions . . . . . . . . . . . . . . . . . . . . . 7 64 10.1. Multiple PCP Servers . . . . . . . . . . . . . . . . . . 7 65 10.2. Epoch Handling . . . . . . . . . . . . . . . . . . . . . 8 66 10.3. Request/Response Caching . . . . . . . . . . . . . . . . 9 67 10.4. Retransmission Handling . . . . . . . . . . . . . . . . 9 68 10.5. Full State . . . . . . . . . . . . . . . . . . . . . . . 9 69 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 70 12. Security Considerations . . . . . . . . . . . . . . . . . . . 9 71 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 72 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 73 14.1. Normative References . . . . . . . . . . . . . . . . . . 10 74 14.2. Informative References . . . . . . . . . . . . . . . . . 10 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 77 1. Introduction 79 This document defines a new PCP [RFC6887] function element, called 80 PCP Proxy, which is meant to facilitate the communication between a 81 PCP Client and upstream PCP Server(s). The PCP Proxy acts as a PCP 82 Server receiving PCP requests on internal interfaces, and as a PCP 83 Client forwarding accepted PCP requests on an external interface to a 84 PCP Server. The PCP Server in turn sends PCP responses to the PCP 85 Proxy external interface which are finally forwarded to PCP Clients. 86 A reference architecture is depicted in Figure 1. 88 A PCP Proxy can be for instance embedded in a CP (Customer Premises) 89 router while the PCP Server is located in a network operated by an 90 ISP (Internet Service Provider). It is out of scope of this document 91 to list all deployment scenarios requiring a PCP Proxy to be 92 involved. 94 The PCP Proxy can be simple (i.e., a single-homed entity which 95 implement as transparent/minimal processing as possible) or it can 96 support advanced features (see Section 10). A PCP Proxy can be co- 97 located with UPnP IGD [I-D.ietf-pcp-upnp-igd-interworking] or/and 98 NAT-PMP [I-D.bpw-pcp-nat-pmp-interworking] Interworking Function 99 (IWF). 101 +------------+ 102 | PCP Client |-----+ 103 +--(Host 1)--+ | +-----------+ +----------+ 104 +---| | | | 105 | PCP Proxy |-------|PCP Server| 106 +---| | | | 107 +------------+ | +-----------+ +----------+ 108 | PCP Client |-----+ 109 +--(Host 2)--+ 111 Internal PCP Clients 113 Figure 1: Reference Architecture 115 2. Requirements Language 117 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 118 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 119 document are to be interpreted as described in RFC 2119 [RFC2119]. 121 3. PCP Server Discovery and Provisioning 123 The PCP Proxy MUST follow the procedure defined in Section 8.1 of 124 [RFC6887] to discover its PCP Server. 126 The address of the PCP Proxy is provisioned to internal PCP Clients 127 (see Figure 1) as their default PCP Server: If the PCP DHCP option 128 [RFC6887] is supported by an internal PCP Client, it will retrieve 129 the PCP Server IP address to use from its local DHCP server; 130 otherwise internal PCP Clients will assume their default router being 131 the PCP Server. 133 4. PCP Proxy as a PCP Server 135 The PCP Proxy acts as a PCP Server for internal hosts and accepts PCP 136 requests on the interface(s) facing them. 138 When the topology makes a routing loop possible, the PCP Proxy MAY 139 check it is not the source of a PCP message it received. 141 5. Control of the Firewall 142 A security policy to accept PCP messages from the provisioned PCP 143 Server(s) is to be enabled on the device embedding the PCP Proxy. 144 This policy can be for instance triggered by DHCP configuration or by 145 outbound PCP requests issued from the PCP Proxy to the provisioned 146 PCP Server. 148 In order to accept inbound and outbound traffic associated with PCP 149 mappings instantiated in the upstream PCP Server, appropriate 150 security policies are to be configured on the firewall. 152 For instance if the firewall rules have a lifetime, PCP response can 153 be snooped in order to instantiate the corresponding firewall rules 154 with the same lifetime. If they have no lifetime, an explicit 155 dynamic mapping table can be kept in the PCP Proxy state in order to 156 instantiate and remove corresponding firewall rules. 158 FILTER Options can be installed into the local firewall, forwarded to 159 the PCP Server so installed into the remote NAT/firewall or both. 161 6. No NAT is Co-located with the PCP Proxy 163 When no NAT is co-located with the PCP Proxy, the port numbers 164 included in received PCP messages (from the PCP Server or PCP 165 Client(s)) are not altered by the PCP Proxy. Nevertheless, the PCP 166 Client IP Address MUST be changed to the address of the PCP Proxy and 167 a THIRD_PARTY Option inserted to carry the IP address of the source 168 PCP Client. 170 Because no NAT is invoked, there is no reachability failure risk to 171 relay to the PCP Server unknown Options and OpCodes which carry an IP 172 address. 174 7. PCP Proxy Co-located with a NAT Function 176 When the PCP Proxy is co-located with a NAT function, it MUST update 177 the content of received requests with the mapped port number and the 178 address belonging to the external interface of the PCP Proxy (i.e., 179 after the NAT operation) and not as initially conveyed by the PCP 180 Client. For the reverse path, PCP responses MUST be updated by the 181 PCP Proxy to replace the internal port number to what has been 182 initially positioned by the PCP Client. For this purpose the PCP 183 Proxy MUST have an access to the local NAT state maintained locally. 185 By default, the PCP Proxy MUST relay unknown OpCodes and mandatory- 186 to-process unknown Options. Rejecting unknown Options and OpCodes 187 has the drawback of preventing a PCP Client to make use of new 188 capabilities offered by the PCP Server but not supported by the PCP 189 Proxy even if no IP address and/or port is included in the Option/ 190 OpCode. 192 Because PCP messages with an unknown OpCode or mandatory-to-process 193 unknown Options can carry a hidden internal address or internal port 194 which will not be translated, A PCP Proxy MUST be configurable to 195 disable relaying unknown OpCodes and mandatory-to-process unknown 196 Options. If the PCP Proxy is configured to disable relaying unknown 197 OpCodes and mandatory-to-process unknown Options, the PCP Proxy MUST 198 behave as follows: 200 o a PCP Proxy co-located with a NAT MUST reject by an UNSUPP_OPCODE 201 error response a received request with an unknown OpCode. 203 o a PCP Proxy co-located with a NAT MUST reject by an UNSUPP_OPTION 204 error response a received request with a mandatory-to-process 205 unknown Option. 207 When a PCP request is received and accepted by the PCP Proxy the 208 corresponding mapping (explicit dynamic mapping for a MAP request, 209 implicit dynamic mapping for a PEER request) is looked for in the 210 local NAT state and temporary created if it does not exist. 211 "Temporary" means it is deleted if no SUCCESS response is received, 212 either explicitly or because of its short lifetime at creation. 214 If the local NAT associates explicit dynamic mappings to a lifetime, 215 the requested lifetime in MAP requests SHOULD be adjusted to be in 216 the accepted range of the local NAT, and the assigned lifetime copied 217 from MAP responses to the corresponding mapping in the local NAT. 218 The same processing applies to implicit dynamic mappings and PEER 219 requests/responses. 221 Otherwise explicit dynamic mappings have an undefined lifetime in the 222 local NAT and the PCP Proxy SHOULD maintain an explicit dynamic 223 mapping table and SHOULD delete corresponding explicit dynamic 224 mappings in the local NAT when they expire or are deleted by the MAP 225 request with a zero requested lifetime. 227 8. MAP/PEER Handling 229 A simple PCP Proxy performs minimal modifications to PCP requests and 230 responses, in particular it does not change the Nonce value in 231 requests and the Epoch value in responses. A simple PCP Proxy is 232 assumed to handle only one PCP Server. 234 For handling THIRD_PARTY option, the PCP Proxy MUST follow the PCP 235 Server behavior specified in Section 13.1 of [RFC6887]. 237 The detailed behavior at the reception of a PCP request on an 238 internal interface is as follows: 240 o Check if the source IP address and the PCP Client IP Address are 241 the same. 243 o Apply security controls (e.g., THIRD_PARTY filtering). 245 o If the request is rejected, build a synthetic error response and 246 send it back to the PCP Client. 248 o If the request is accepted, adjust it (e.g., adding a THIRD_PARTY 249 Option, updating the PCP Client IP Address and Internal Port to 250 their translated values as specified in Section 7 and forward it 251 on a fresh UDP socket connected to the PCP Server). 253 o Wait for the response during a reasonable delay. 255 o When the response is received from the PCP Server, adjust it back 256 (e.g., removing the THIRD_PARTY Option added previously, updating 257 the PCP Client IP Address and Internal Port to their initial 258 values as specified in Section 7), forward it to the source PCP 259 Client and close the socket to the PCP Server. 261 o On a hard error on the UDP socket, build a synthetic ICMP error 262 and send it to the source PCP Client. 264 The reasonable delay minimum value is 20 seconds, request 265 retransmission is handled by PCP clients. 267 For each pending request, the proxy MUST maintain in a data record: 269 o the request payload 271 o the interface where the request was received 273 o the source IP address of the request 275 o the source UDP port of the request 277 o the UDP socket connected to the PCP server 279 o an expire timeout 280 Receiving interfaces can be implemented by a set of servicing 281 sockets, each socket bound to an address of an internal interface. 282 Interface, source address and port are used to send back packets to 283 the source PCP Client. The request payload is used to generate 284 synthetic ICMP. Responses are received on the UDP socket. 286 Too large requests SHOULD be forwarded to the PCP Server in order to 287 relay back the error response, i.e., the PCP Proxy is not in charge 288 to enforce the message size limit and in general the PCP Proxy SHOULD 289 NOT generate error response for a reason other than security 290 controls. No behavior is specified in the case the PCP Proxy 291 processing (e.g., adding a THIRD_PARTY Option) makes a valid request 292 too large when it is sent to the PCP Server. 294 9. Mapping Repair 296 ANNOUNCE requests received from PCP Clients are handled locally; as 297 such these requests MUST NOT be relayed to the provisioned PCP 298 Server. 300 Upon receipt of an unsolicited ANNOUNCE response from a PCP Server, 301 the PCP Proxy proceeds to renewing the mappings and checks whether 302 there are changes compared to a local cache if it is maintained by 303 the PCP Proxy. If no change is detected, no unsolicited ANNOUNCE is 304 generated towards PCP Clients. If a change is detected, the PCP 305 Proxy MUST generate unsolicited ANNOUNCE message(s) to appropriate 306 PCP Clients. If the PCP Proxy does not maintain a local cache for 307 the mappings, unsolicited ANNOUNCE messages are relayed to PCP 308 Clients. 310 Unsolicited PCP MAP/PEER responses received from a PCP Server are 311 handled as any normal MAP/PEER response. To handle unsolicited PCP 312 MAP/PEER responses, the PCP Proxy is required to maintain a local 313 cache of instantiated mappings in the PCP Server (Section 10.5). 315 Upon change of its external IP address, the PCP Proxy SHOULD renew 316 the mappings it maintained. If the PCP Server assigns a different 317 external port, the PCP Proxy SHOULD follow the mapping repair 318 procedure defined in [RFC6887]. This can be achieved only if a full 319 state table is maintained by the PCP Proxy. 321 10. Advanced Functions 323 Below are listed a set of advanced features which may be supported by 324 the PCP Proxy. 326 10.1. Multiple PCP Servers 327 A PCP Proxy MAY handle multiple PCP Servers at the same time, each 328 PCP Server is associated to each own handled Epoch value according to 329 Section 10.2. PCP Clients are not aware of the presence of multiple 330 PCP Servers. 332 According to [I-D.ietf-pcp-dhcp], if several PCP Names are configured 333 to the PCP Proxy, it will contact in parallel all these PCP Servers. 335 In some contexts (e.g., PCP-controlled CGNs), the PCP Proxy MAY load 336 balance the PCP Client among available PCP Servers. The PCP Proxy 337 MUST ensure requests of a given PCP Client are relayed to the same 338 PCP Server. 340 In other deployment scenarios (e.g., presence of multiple PCP- 341 controlled firewalls), the PCP Proxy MUST relay PCP requests to all 342 these PCP Servers. 344 The PCP Proxy MAY rely on some fields (e.g., Zone ID 345 [I-D.penno-pcp-zones]) in the PCP request to redirect the request to 346 a given PCP Server. 348 10.2. Epoch Handling 350 A PCP Proxy MAY use its own internal timers and not blindly copy them 351 from PCP responses. There should be no advantages to have more than 352 one managed Epoch per PCP Server. 354 The Epoch MUST be reset when explicit dynamic mappings are lost, 355 i.e.: 357 o at startup if the PCP Proxy can't recover the state. 359 o when the WAN address is changed or any similar events which show 360 any previous state is no longer valid. 362 o when the Epoch value in a PCP response is too small (cf. Epoch 363 value validation rules in [RFC6887]). 365 o when the External IP Address has changed. 367 The last two rules are per PCP Server, a PCP Proxy MAY check these 368 conditions in all received responses for a PCP Server. 370 10.3. Request/Response Caching 372 A PCP Proxy providing request/response caching checks each time it 373 receives a PCP request if it has already seen the same request 374 recently and got the corresponding PCP response. In this case, it 375 sends back directly the cached response with the proper Epoch value 376 and not forward the request to the PCP Server. 378 10.4. Retransmission Handling 380 An extension of the previous service is to manage the retransmission 381 of pending requests to the PCP Server internally, i.e., no longer 382 driven by the PCP Client. A cache entry SHOULD be expired after a 383 delay short enough to keep it easy to distinguish it from a replay. 385 10.5. Full State 387 A PCP Proxy MAY keep the full state, i.e., an image of all active 388 explicit dynamic mappings is kept in memory. When this service is 389 supported the state SHOULD be recovered in case of failures (e.g., 390 according to [I-D.boucadair-pcp-failure]). 392 11. IANA Considerations 394 This document makes no request of IANA. 396 12. Security Considerations 398 The PCP Proxy MUST follow the security considerations elaborated in 399 [RFC6887] for both the client and server side. 401 A received request carrying an unknown OpCode or Option SHOULD be 402 dropped (or in the case of an unknown Option which is not mandatory- 403 to-process the Option be removed) if it is not a priori compatible 404 with security controls or correct processing. 406 The device embedding the PCP Proxy MAY block PCP requests directly 407 sent to the PCP Server. This can be enforced using access control 408 lists (ACLs). 410 13. Acknowledgements 412 Many thanks to C. Zhou and T. Reddy for their review and comments. 414 Special thanks to F. Dupont who contributed to this document. 416 14. References 417 14.1. Normative References 419 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 420 Requirement Levels", BCP 14, RFC 2119, March 1997. 422 [RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. 423 Selkirk, "Port Control Protocol (PCP)", RFC 6887, April 424 2013. 426 14.2. Informative References 428 [I-D.boucadair-pcp-failure] 429 Boucadair, M. and R. Penno, "Analysis of Port Control 430 Protocol (PCP) Failure Scenarios", draft-boucadair-pcp- 431 failure-06 (work in progress), May 2013. 433 [I-D.bpw-pcp-nat-pmp-interworking] 434 Boucadair, M., Penno, R., Wing, D., and F. Dupont, "Port 435 Control Protocol (PCP) NAT-PMP Interworking Function", 436 draft-bpw-pcp-nat-pmp-interworking-00 (work in progress), 437 March 2011. 439 [I-D.ietf-pcp-dhcp] 440 Boucadair, M., Penno, R., and D. Wing, "DHCP Options for 441 the Port Control Protocol (PCP)", draft-ietf-pcp-dhcp-07 442 (work in progress), March 2013. 444 [I-D.ietf-pcp-upnp-igd-interworking] 445 Boucadair, M., Penno, R., and D. Wing, "Universal Plug and 446 Play (UPnP) Internet Gateway Device (IGD)-Port Control 447 Protocol (PCP) Interworking Function", draft-ietf-pcp- 448 upnp-igd-interworking-10 (work in progress), April 2013. 450 [I-D.penno-pcp-zones] 451 Penno, R., "PCP Support for Multi-Zone Environments", 452 draft-penno-pcp-zones-01 (work in progress), October 2011. 454 Authors' Addresses 456 Mohamed Boucadair 457 France Telecom 458 Rennes 35000 459 France 461 Email: mohamed.boucadair@orange.com 462 Reinaldo Penno 463 Cisco 464 USA 466 Email: repenno@cisco.com 468 Dan Wing 469 Cisco Systems, Inc. 470 170 West Tasman Drive 471 San Jose, California 95134 472 USA 474 Email: dwing@cisco.com