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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-29) exists of draft-ietf-pcp-base-26 == Outdated reference: A later version (-13) exists of draft-ietf-pcp-dhcp-04 == Outdated reference: A later version (-06) exists of draft-boucadair-pcp-failure-03 == Outdated reference: A later version (-10) exists of draft-ietf-pcp-upnp-igd-interworking-02 Summary: 0 errors (**), 0 flaws (~~), 5 warnings (==), 1 comment (--).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. Dupont 5 Expires: February 18, 2013 Internet Systems Consortium 6 R. Penno 7 D. Wing 8 Cisco 9 August 17, 2012 11 Port Control Protocol (PCP) Proxy Function 12 draft-ietf-pcp-proxy-01 14 Abstract 16 This document specifies a new PCP functional element denoted as PCP 17 Proxy. The PCP Proxy relays PCP requests received from PCP Clients 18 to upstream PCP Server(s). This function is mandatory when PCP 19 Clients can not be configured with the address of the PCP Server 20 located more than one hop. 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 18, 2013. 39 Copyright Notice 41 Copyright (c) 2012 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. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 58 3. PCP Server Discovery and Provisioning . . . . . . . . . . . . 3 59 4. PCP Proxy as a PCP Server . . . . . . . . . . . . . . . . . . 4 60 5. Control of the Firewall . . . . . . . . . . . . . . . . . . . 4 61 6. No NAT is Co-located with the PCP Proxy . . . . . . . . . . . 4 62 7. PCP Proxy Co-located with a NAT Function . . . . . . . . . . . 5 63 8. MAP/PEER Handling . . . . . . . . . . . . . . . . . . . . . . 6 64 9. Mapping Repair . . . . . . . . . . . . . . . . . . . . . . . . 7 65 10. Advanced Functions . . . . . . . . . . . . . . . . . . . . . . 8 66 10.1. Multiple PCP Servers . . . . . . . . . . . . . . . . . . 8 67 10.2. Epoch Handling . . . . . . . . . . . . . . . . . . . . . 8 68 10.3. Request/Response Caching . . . . . . . . . . . . . . . . 9 69 10.4. Retransmission Handling . . . . . . . . . . . . . . . . . 9 70 10.5. Full State . . . . . . . . . . . . . . . . . . . . . . . 9 71 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 72 12. Security Considerations . . . . . . . . . . . . . . . . . . . 9 73 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 74 13.1. Normative References . . . . . . . . . . . . . . . . . . 10 75 13.2. Informative References . . . . . . . . . . . . . . . . . 10 76 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 78 1. Introduction 80 This document defines a new PCP [I-D.ietf-pcp-base] function element, 81 called PCP Proxy, which is meant to facilitate the communication 82 between a PCP Client and upstream PCP Server(s). The PCP Proxy acts 83 as a PCP Server receiving PCP requests on internal interfaces, and as 84 a PCP Client forwarding accepted PCP requests on an external 85 interface to a PCP Server. The PCP Server in turn send PCP responses 86 to the PCP Proxy external interface which are finally forwarded to 87 PCP Clients. A reference architecture is depicted in Figure 1. 89 A PCP Proxy can be for instance embedded in a CP (Customer Premises) 90 router while the PCP Server is located in a network operated by an 91 ISP (Internet Service Provider). It is out of scope of this document 92 to list all deployment scenarios requiring a PCP Proxy to be 93 involved. 95 The PCP Proxy can be simple, i.e., implement as transparent/minimal 96 processing as possible, or it can support advanced features (see 97 Section 10). A Proxy can be co-located with UPnP IGD 98 [I-D.ietf-pcp-upnp-igd-interworking] or/and NAT-PMP 99 [I-D.bpw-pcp-nat-pmp-interworking] Interworking Function (IWF). 101 +------------+ 102 | PCP Client |-----+ 103 +--(Host 1)--+ | +-----------+ +----------+ 104 +---| | | | 105 | PCP Proxy |-------|PCP Server| 106 +---| | | | 107 +------------+ | +-----------+ +----------+ 108 | PCP Client |-----+ 109 +--(Host 2)--+ 111 Figure 1: Reference Architecture 113 2. Requirements Language 115 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 116 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 117 document are to be interpreted as described in RFC 2119 [RFC2119]. 119 3. PCP Server Discovery and Provisioning 121 The PCP Proxy MUST implement one of the discovery methods listed in 123 [I-D.ietf-pcp-base] (e.g., DHCP [I-D.ietf-pcp-dhcp]). 125 The address of the PCP Proxy is provisioned to local PCP Clients as 126 their default PCP Server: If the PCP DHCP option [I-D.ietf-pcp-dhcp] 127 is supported by an internal PCP Client, it will retrieve the PCP 128 Server IP address to use from its local DHCP server; otherwise 129 internal PCP Clients will assume their default router being the PCP 130 Server. 132 4. PCP Proxy as a PCP Server 134 The PCP Proxy acts as a PCP Server for internal hosts and accepts PCP 135 requests on the interface(s) facing them, e.g., it creates servicing 136 socket(s) and bound them to each address of this (these) interface(s) 137 on UDP port 5350. 139 When the topology makes a routing loop possible, the PCP Proxy MAY 140 check it is not the source of a PCP message it received. 142 5. Control of the Firewall 144 A security policy to accept PCP messages from the provisioned PCP 145 Server(s) is to be enabled on the device embedding the PCP Proxy. 146 This policy can be for instance triggered by DHCP configuration or by 147 outbound PCP requests issued from the PCP Proxy to the provisioned 148 PCP Server. 150 In order to accept inbound and outbound traffic associated with PCP 151 mappings instantiated in the upstream PCP Server, appropriate 152 security policies are to be configured on the firewall. 154 For instance if the firewall rules have a lifetime, PCP response can 155 be snooped in order to instantiate the corresponding firewall rules 156 with the same lifetime. If they have no lifetime, an explicit 157 dynamic mapping table can be kept in the PCP Proxy state in order to 158 instantiate and remove corresponding firewall rules. 160 REMOTE_PEER_FILTER Options can be installed into the local firewall, 161 forwarded to the PCP Server so installed into the remote NAT/firewall 162 or both. 164 6. No NAT is Co-located with the PCP Proxy 166 When no NAT is co-located with the PCP Proxy, the port numbers 167 included in received PCP messages (from the PCP Server or PCP 168 Client(s)) are not altered by the PCP Proxy. Nevertheless, the PCP 169 Client IP Address MUST be changed to the address of the PCP Proxy and 170 a THIRD_PARTY Option inserted to carry the IP address of the source 171 PCP Client. 173 Because no NAT is invoked, there is no reachability failure risk to 174 relay to the PCP Server unknown Options and OpCodes which carry an IP 175 address. 177 7. PCP Proxy Co-located with a NAT Function 179 When the PCP Proxy is co-located with a NAT function, it MUST update 180 the content of received requests with the mapped port number and the 181 address belonging to the external interface of the PCP Proxy (i.e., 182 after the NAT operation) and not as initially positioned by the PCP 183 Client. For the reverse path, PCP responses MUST be updated by the 184 PCP Proxy to replace the internal port number to what has been 185 initially positioned by the PCP Client. For this purpose the PCP 186 Proxy MUST have an access to the local NAT state maintained locally. 187 Because PCP messages with an unknown OpCode or Option can carry a 188 hidden internal address or internal port which will not be 189 translated: 191 o a PCP Proxy co-located with a NAT SHOULD reject by an 192 UNSUPP_OPCODE error response a received request with an unknown 193 OpCode; 195 o a PCP Proxy co-located with a NAT SHOULD reject by an 196 UNSUPP_OPTION error response a received request with a mandatory- 197 to-process unknown Option; 199 o a PCP Proxy co-located with a NAT MAY remove any optional-to- 200 process unknown Options from received requests before forwarding 201 them. 203 Rejecting unknown Options and OpCodes has the drawback of preventing 204 a PCP Client to make use of new capabilities offered by the PCP 205 Server but not supported by the PCP Proxy even if no IP address 206 and/or port is included in the Option/OpCode. 208 When a PCP request is received and accepted by the PCP Proxy the 209 corresponding mapping (explicit dynamic mapping for a MAP request, 210 implicit dynamic mapping for a PEER request) is looked for in the 211 local NAT state and temporary created if it does not exist. 212 Temporary means it is deleted if no SUCCESS response is received, 213 either explicitly or because of its short lifetime at creation. 215 If the local NAT associates explicit dynamic mappings to a lifetime, 216 the requested lifetime in MAP requests SHOULD be adjusted to be in 217 the accepted range of the local NAT, and the assigned lifetime copied 218 from MAP responses to the corresponding mapping in the local NAT. 219 The same processing applies to implicit dynamic mappings and PEER 220 requests/responses. 222 Otherwise explicit dynamic mappings have an undefined lifetime in the 223 local NAT and the PCP Proxy SHOULD maintain an explicit dynamic 224 mapping table and SHOULD delete corresponding explicit dynamic 225 mappings in the local NAT when they expire or are deleted by the MAP 226 request with a zero requested lifetime. 228 8. MAP/PEER Handling 230 A simple PCP Proxy performs minimal modifications to PCP requests and 231 responses, in particular it does not change the Nonce value in 232 requests and the Epoch value in responses. A simple PCP Proxy is 233 assumed to handle only one PCP Server. 235 The detailed behavior at the reception of a PCP request on an 236 internal interface is as follows: 238 o Check if the source IP address and the PCP Client IP Address are 239 the same. 241 o Apply security controls, including with the result of the previous 242 item. 244 o If the request is rejected, build a synthetic error response and 245 send it back to the PCP Client. 247 o If the request is accepted, adjust it (e.g., adding a THIRD_PARTY 248 Option, updating the PCP Client IP Address and Internal Port to 249 their translated values as specified in Section 7 and forward it 250 on a fresh UDP socket connected to the PCP Server). 252 o Wait for the response during a reasonable delay. 254 o When the response is received from the PCP Server, adjust it back 255 (e.g., removing the THIRD_PARTY Option added previously, updating 256 the PCP Client IP Address and Internal Port to their initial 257 values as specified in Section 7), forward it to the source PCP 258 Client and close the socket to the PCP Server. 260 o On a hard error on the UDP socket, build a synthetic ICMP error 261 and send it to the source PCP Client. 263 The reasonable delay minimum value is 20 seconds, request 264 retransmission is handled by PCP clients. 266 For each pending request, the proxy MUST maintain in a data record: 268 o the request payload 270 o the interface where the request was received 272 o the source IP address of the request 274 o the source UDP port of the request 276 o the UDP socket connected to the PCP server 278 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 [I-D.ietf-pcp-base]. This can be achieved only 319 if a full 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 328 A PCP Proxy MAY offer to handle multiple PCP Servers at the same 329 time, each PCP Server is associated to each own handled Epoch value 330 according to Section 10.2. PCP Clients are not aware of the presence 331 of multiple PCP Servers. 333 According to [I-D.ietf-pcp-dhcp], if several PCP Names are configured 334 to the PCP Proxy, it will contact in parallel all these PCP Servers. 336 In some contexts (e.g., PCP-controlled CGNs), the PCP Proxy MAY load 337 balance the PCP Client among available PCP Servers. The PCP Proxy 338 MUST ensure requests of a given PCP Client are relayed to the same 339 PCP Server. 341 In other deployment scenarios (e.g., presence of multiple PCP- 342 controlled firewalls), the PCP Proxy MUST relay PCP requests to all 343 these PCP Servers. 345 10.2. Epoch Handling 347 A PCP Proxy MAY use its own internal timers and not blindly copy them 348 from PCP responses. There should be no advantages to have more than 349 one managed Epoch per PCP Server. 351 The Epoch MUST be reset when explicit dynamic mappings are lost, 352 i.e.: 354 o at startup if the PCP Proxy can't recover the state. 356 o when the WAN address is changed or any similar events which show 357 any previous state is no longer valid. 359 o when the Epoch value in a PCP response is too small (cf. Epoch 360 value validation rules in [I-D.ietf-pcp-base]). 362 o when the External IP Address has changed. 364 The last two rules are per PCP Server, a PCP Proxy MAY check these 365 conditions in all received responses for a PCP Server. 367 10.3. Request/Response Caching 369 A PCP Proxy providing request/response caching checks each time it 370 receives a PCP request if it has already seen the same request 371 recently and got the corresponding PCP response. In this case, it 372 sends back directly the cached response with the proper Epoch value 373 and not forward the request to the PCP Server. 375 10.4. Retransmission Handling 377 An extension of the previous service is to manage the retransmission 378 of pending requests to the PCP Server internally, i.e., no longer 379 driven by the PCP Client. A cache entry SHOULD be expired after a 380 delay short enough to keep it easy to distinguish it from a replay. 382 10.5. Full State 384 A PCP Proxy MAY keep the full state, i.e., an image of all active 385 explicit dynamic mappings is kept in memory. When this service is 386 supported the state SHOULD be recovered in case of failures (e.g., 387 according to [I-D.boucadair-pcp-failure]). 389 11. IANA Considerations 391 This document makes no request of IANA. 393 12. Security Considerations 395 The PCP Proxy MUST follow the security considerations elaborated in 396 [I-D.ietf-pcp-base] for both the client and server side. 398 A received request carrying an unknown OpCode or Option SHOULD be 399 dropped (or in the case of an unknown Option which is not mandatory- 400 to-process the Option be removed) if it is not a priori compatible 401 with security controls or correct processing. 403 13. References 405 13.1. Normative References 407 [I-D.ietf-pcp-base] 408 Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. 409 Selkirk, "Port Control Protocol (PCP)", 410 draft-ietf-pcp-base-26 (work in progress), June 2012. 412 [I-D.ietf-pcp-dhcp] 413 Boucadair, M., Penno, R., and D. Wing, "DHCP Options for 414 the Port Control Protocol (PCP)", draft-ietf-pcp-dhcp-04 415 (work in progress), August 2012. 417 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 418 Requirement Levels", BCP 14, RFC 2119, March 1997. 420 13.2. Informative References 422 [I-D.boucadair-pcp-failure] 423 Boucadair, M., Dupont, F., and R. Penno, "Port Control 424 Protocol (PCP) Failure Scenarios", 425 draft-boucadair-pcp-failure-03 (work in progress), 426 May 2012. 428 [I-D.bpw-pcp-nat-pmp-interworking] 429 Boucadair, M., Penno, R., Wing, D., and F. Dupont, "Port 430 Control Protocol (PCP) NAT-PMP Interworking Function", 431 draft-bpw-pcp-nat-pmp-interworking-00 (work in progress), 432 March 2011. 434 [I-D.ietf-pcp-upnp-igd-interworking] 435 Boucadair, M., Dupont, F., Penno, R., and D. Wing, 436 "Universal Plug and Play (UPnP) Internet Gateway Device 437 (IGD)-Port Control Protocol (PCP) Interworking Function", 438 draft-ietf-pcp-upnp-igd-interworking-02 (work in 439 progress), August 2012. 441 Authors' Addresses 443 Mohamed Boucadair 444 France Telecom 445 Rennes 35000 446 France 448 Email: mohamed.boucadair@orange.com 449 Francis Dupont 450 Internet Systems Consortium 452 Email: fdupont@isc.org 454 Reinaldo Penno 455 Cisco 456 USA 458 Email: repenno@cisco.com 460 Dan Wing 461 Cisco Systems, Inc. 462 170 West Tasman Drive 463 San Jose, California 95134 464 USA 466 Email: dwing@cisco.com