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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) ** Obsolete normative reference: RFC 2373 (ref. '4') (Obsoleted by RFC 3513) ** Obsolete normative reference: RFC 2396 (ref. '5') (Obsoleted by RFC 3986) Summary: 4 errors (**), 0 flaws (~~), 7 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group D. New 3 Internet-Draft December 5, 2002 4 Expires: June 5, 2003 6 The TUNNEL Profile 7 draft-ietf-idwg-beep-tunnel-05 9 Status of this Memo 11 This document is an Internet-Draft and is in full conformance with 12 all provisions of Section 10 of RFC2026. 14 Internet-Drafts are working documents of the Internet Engineering 15 Task Force (IETF), its areas, and its working groups. Note that 16 other groups may also distribute working documents as Internet- 17 Drafts. 19 Internet-Drafts are draft documents valid for a maximum of six months 20 and may be updated, replaced, or obsoleted by other documents at any 21 time. It is inappropriate to use Internet-Drafts as reference 22 material or to cite them other than as "work in progress." 24 The list of current Internet-Drafts can be accessed at http:// 25 www.ietf.org/ietf/1id-abstracts.txt. 27 The list of Internet-Draft Shadow Directories can be accessed at 28 http://www.ietf.org/shadow.html. 30 This Internet-Draft will expire on June 5, 2003. 32 Copyright Notice 34 Copyright (C) The Internet Society (2002). All Rights Reserved. 36 Abstract 38 This memo describes a BEEP profile that allows a BEEP peer to serve 39 as an application-layer proxy. It allows authorized users to access 40 services through a firewall. 42 Table of Contents 44 1. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 3 45 2. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 46 2.1 One-Hop Example . . . . . . . . . . . . . . . . . . . . . . . 4 47 2.2 Two-Hop Example . . . . . . . . . . . . . . . . . . . . . . . 5 48 2.3 Failed Set-Up Example . . . . . . . . . . . . . . . . . . . . 6 49 2.4 Non-BEEP Example . . . . . . . . . . . . . . . . . . . . . . . 7 50 2.5 Profile Example . . . . . . . . . . . . . . . . . . . . . . . 8 51 2.6 Endpoint Example . . . . . . . . . . . . . . . . . . . . . . . 9 52 3. Message Syntax . . . . . . . . . . . . . . . . . . . . . . . . 11 53 4. Message Semantics . . . . . . . . . . . . . . . . . . . . . . 13 54 5. Provisioning . . . . . . . . . . . . . . . . . . . . . . . . . 15 55 6. Reply Codes . . . . . . . . . . . . . . . . . . . . . . . . . 16 56 7. Security Considerations . . . . . . . . . . . . . . . . . . . 17 57 Normative References . . . . . . . . . . . . . . . . . . . . . 18 58 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 18 59 A. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 60 A.1 Registration: BEEP Profile . . . . . . . . . . . . . . . . . . 19 61 A.2 Registration: The System (Well-Known) TCP port number for 62 TUNNEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 63 B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21 64 C. Changes from Previous Version . . . . . . . . . . . . . . . . 22 65 C.1 Changes since -04 . . . . . . . . . . . . . . . . . . . . . . 22 66 C.2 Changes since -03 . . . . . . . . . . . . . . . . . . . . . . 22 67 C.3 Changes since -02 . . . . . . . . . . . . . . . . . . . . . . 22 68 C.4 Changes since -01 . . . . . . . . . . . . . . . . . . . . . . 22 69 Full Copyright Statement . . . . . . . . . . . . . . . . . . . 23 71 1. Rationale 73 The TUNNEL profile provides a mechanism for cooperating BEEP peers to 74 form an application-layer tunnel. The peers exchange "tunnel" 75 elements that specify a source route, with the outermost element 76 being stripped off and used to decide the next hop. The innermost, 77 empty "tunnel" element tells the final destination that it is, 78 indeed, the final destination. The term "proxy" is used to refer any 79 of the BEEP peers other than the initiator and the final destination. 81 In one use of this profile, a BEEP peer implementing the TUNNEL 82 profile is co-resident with a firewall. An initiating machine inside 83 the firewall makes a connection to the proxy, then ask that proxy to 84 make a connection to an endpoint outside the firewall. Once this 85 connection is established, the proxy tells the outside endpoint that 86 it will be tunneling. If the outside machine agrees, the proxy "gets 87 out of the way," simply passing octets transparently, and both the 88 initiating and terminating machines perform a "tuning reset," not 89 unlike the way starting a TLS negotiation discards cached session 90 state and starts anew. 92 Another use for this profile is to limit connections to outside 93 servers based on the user identity negotiated via SASL. For example, 94 a manager may connect to a proxy, authenticate herself with SASL, 95 then instruct the proxy to tunnel to an information service 96 restricted to managers. Since each proxy knows the identity of the 97 next proxy being requested, it can refuse to tunnel connections if 98 inadequate levels of authorization have been established. It is also 99 possible to use the TUNNEL profile to anonymize the true source of a 100 BEEP connection, in much the way a NAT translates IP addresses. 101 However, detailed discussion of such uses is beyond the scope of this 102 document. 104 Once both endpoint machines are connected, the tunneling proxy 105 machine does no further interpretation of the data. In particular, 106 it does not look for any BEEP framing. The two endpoint machines may 107 therefore negotiate TLS between them, passing certificates 108 appropriate to the endpoints rather than the proxy, with the 109 assurance that even the proxy cannot access the information 110 exchanged. 112 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 113 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 114 document are to be interpreted as described in RFC 2119 [1]. 116 2. Examples 118 While the semantics described in Section 4 may seem complex, the 119 results are actually relatively simple. A few examples will show the 120 operation and use of this profile. In these examples, the machine 121 attempting to establish the connection is named "initial", while the 122 intermediate proxies are "proxy1" or "proxy2", and the machine with 123 the service that "initial" wishes to access is called "final". The 124 examples also assume that the BEEP framework [2] is implemented on 125 top of TCP [3], or some other mapping where one transport connection 126 carries all channels. 128 2.1 One-Hop Example 130 A simple one-hop connection through a single proxy is illustrated 131 first. 133 initial proxy1 final 134 ----- xport connect -----> 135 <------- greeting --------> 136 --- start TUNNEL [1] ----> 137 ----- xport connect ------> 138 <-------- greeting --------> 139 ---- start TUNNEL [2] ----> 140 <---------- ok ------------ 141 <------- ok -------------- [3] 142 <------------- greeting [4]--------------------------> 144 Notes: 145 [1] The TUNNEL element looks like this: 146 147 148 150 [2] The TUNNEL element looks like this: 151 153 [3] At this point, immediately after sending the 154 element, proxy1 starts passing octets transparently. 155 It continues to do so until either transport connection 156 is closed, after which it closes the other. 158 [4] This greeting may include the TLS profile, allowing 159 initial and final to communicate without proxy1 160 understanding or interfering without being caught. 162 2.2 Two-Hop Example 164 The second example shows the initiator connecting to its proxy, that 165 proxy connecting to another, and finally that second proxy finding a 166 service outside. 168 initial proxy1 proxy2 final 169 --- xport connect --> 170 <---- greeting ------> 171 --start TUNNEL [1]--> 172 -- xport connect ---> 173 <----- greeting -----> 174 --start TUNNEL [2]--> 175 --- xport connect ---> 176 <------- greeting -----> 177 ---start TUNNEL [3]---> 178 <-------- ok ---------- 179 <------- ok --------- [4] 180 <------- ok --------- [5] 181 <-------------------------- greeting ----------------------------> 183 Notes: 184 [1] The TUNNEL element looks like this: 185 186 187 188 189 191 [2] The TUNNEL element looks like this: 192 193 194 196 [3] The TUNNEL element looks like this: 197 199 [4] Proxy2 starts passing octets transparently after 200 sending the . 202 [5] Proxy1 starts passing octets transparently after 203 sending the . 205 2.3 Failed Set-Up Example 207 The third example shows the initiator connecting through two proxys, 208 the second proxy attempting to connect to the specified service and 209 finding the destination is not a BEEP server. (Of course, specifying 210 the telnet service can be expected to lead to this error.) The same 211 would result if the destination did not support the TUNNEL profile. 213 initial proxy1 proxy2 final 214 --- xport connect --> 215 <---- greeting ------> 216 --start TUNNEL [1]--> 217 --- xport connect --> 218 <----- greeting -----> 219 --start TUNNEL [2]--> 220 ---- xport connect ---> 221 <------- login: ------- 222 ----- xport close ----> 223 <---- ------- 224 --- xport close ----> 225 <---- ------ 226 --- xport close ---> [3] 228 Notes: 229 [1] The TUNNEL element looks like this: 230 231 232 233 234 236 [2] The TUNNEL element looks like this: 237 238 239 241 [3] This close is optional. "Initial" may also send another 242 element, attempting to contact a different 243 server, for example. 245 2.4 Non-BEEP Example 247 This example shows the initiator connecting through two proxys, the 248 second proxy attempting to connect to the specified service and 249 accepting that the destination is not a BEEP server. The difference 250 at the protocol level is two-fold: The "initial" machine does not 251 include the innermost "tunnel" element, and the final proxy 252 ("proxy2") therefore does not expect a BEEP greeting. 254 initial proxy1 proxy2 final 255 --- xport connect --> 256 <---- greeting ------> 257 --start TUNNEL [1]--> 258 --- xport connect --> 259 <----- greeting -----> 260 --start TUNNEL [2]--> 261 ---- xport connect ---> 262 <------- login: ------- 263 <------ ------- [3] 264 <----- login: ------ [4] 265 <------ --------- [3] 266 <----- login: -------- [4] [5] 268 Notes: 269 [1] The TUNNEL element looks like this: 270 271 272 273 274 Note the lack of an innermost no-attribute element. 276 [2] The TUNNEL element looks like this: 277 278 279 Note the lack of an innermost no-attribute element. 281 [3] Each proxy starts transparently forwarding octets after this . 283 [4] Each proxy forwards any data it received from the final host, 284 even if that data arrived before the was sent. 286 [5] After receiving the "ok" message, the "initial" peer can expect 287 raw, non-BEEP data to be sent to and received from the "final" 288 machine. 290 2.5 Profile Example 292 This example shows the initiator connecting through two proxys. The 293 initial machine knows there is a server offering the SEP2 profile 294 somewhere beyond proxy1, but it need not know where. Proxy1 has been 295 locally configured to know that all SEP2 servers are beyond proxy2. 296 Proxy2 has been locally configured to chose "final" as the server of 297 choice for SEP2 services. Note that "final" does not necessarily 298 need to offer the requested profile in its initial greeting. 300 initial proxy1 proxy2 final 301 --- xport connect --> 302 <---- greeting ------> 303 --start TUNNEL [1]--> 304 -- xport connect ---> 305 <----- greeting -----> 306 --start TUNNEL [2]--> 307 --- xport connect ---> 308 <------- greeting -----> 309 ---start TUNNEL [3]---> 310 <-------- ok ---------- 311 <------- ok --------- [4] 312 <------- ok --------- [5] 313 <-------------------------- greeting ----------------------------> 315 Notes: 316 [1] The TUNNEL element looks like this: 317 318 Note the lack of an innermost no-attribute element. 320 [2] Proxy1 maps this to 321 322 323 324 based on local configuration, then processes the new 325 element, stripping off the outer element and routing 326 327 to proxy2. 329 [3] Proxy2 receives the TUNNEL element with simply the SEP2 330 URI specified. Local provisioning maps this to 331 332 333 334 Note the presence of an innermost no-attribute element. 335 Proxy2 then strips the outermost element, looking up the 336 appropriate address and port, and forwards the 337 element to the final machine. 339 [4] Proxy2 starts transparently forwarding octets after this . 341 [5] Proxy1 starts transparently forwarding octets after this . 343 2.6 Endpoint Example 345 This example shows the initiator connecting through two proxys. The 346 initial machine knows there is a server known as "operator console" 347 somewhere beyond proxy1, but it need not know where. Proxy1 has been 348 locally configured to know that "operator console" is beyond proxy2. 349 Proxy2 has been locally configured to use "final" as "operator 350 console". This example is almost identical to the previous example, 351 except that "endpoint" is intended to route to a particular server, 352 while "profile" is intended to route to a particular service. 353 Otherwise, these two attributes are very similar. 355 initial proxy1 proxy2 final 356 --- xport connect --> 357 <---- greeting ------> 358 --start TUNNEL [1]--> 359 -- xport connect ---> 360 <----- greeting -----> 361 --start TUNNEL [2]--> 362 --- xport connect ---> 363 <------- greeting -----> 364 ---start TUNNEL [3]---> 365 <-------- ok ---------- 366 <------- ok --------- [4] 367 <------- ok --------- [5] 368 <-------------------------- greeting ----------------------------> 370 Notes: 371 [1] The TUNNEL element looks like this: 372 373 374 Note the lack of an innermost no-attribute element. 376 [2] Proxy1 maps this to 377 378 379 380 381 based on local configuration, then processes the new 382 element, stripping off the outer element and routing 383 384 385 to proxy2. 387 [3] Proxy2 receives the TUNNEL element with simply the endpoint 388 specified. Local provisioning maps this to 389 390 391 392 Note the presence of an innermost no-attribute element. 393 Proxy2 then strips the outermost element, looking up the 394 appropriate address and port, and forwards the 395 element to the final machine. 397 [4] Proxy2 starts transparently forwarding octets after this . 399 [5] Proxy1 starts transparently forwarding octets after this . 401 3. Message Syntax 403 The only element defined in this profile is the "tunnel" element. It 404 is described in the following DTD, with additional limitations as 405 described afterwards. 407 417 426 427 437 The format of the "fqdn" attribute is a fully qualified domain name, 438 such as "proxy.example.com". The format of the "ip4" attribute is 439 four sets of decimal numbers separated by periods, such as 440 "10.23.34.45". The format of the "ip6" attribute is as specified in 441 RFC2373 [4]. The format of the "port" attribute is a decimal number 442 between one and 65535, inclusive. The format of the "srv" attribute 443 is a pair of identifiers each starting with an underline and 444 separated by a period, such as "_sep._tcp". The format of the 445 "profile" attribute is a URI [5]. The format of the "endpoint" 446 attribute is any string that may appear as an attribute value. 448 The only allowable combinations of attributes are as follows: 450 o fqdn + port; 452 o fqdn + srv; 454 o fqdn + srv + port; 456 o ip4 + port; 458 o ip6 + port; 460 o profile, but only on the innermost element; 462 o endpoint, but only on the innermost element; or, 464 o no attributes, but only on the innermost element. 466 4. Message Semantics 468 When a TUNNEL channel is started, the listener expects a "tunnel" 469 element from the initiator, either in the "start" element on channel 470 zero or on the new channel created. As usual, if it arrives on 471 channel zero, it is processed before the reply is returned. 473 In either case, the outermost "tunnel" element is examined. If it 474 has no attributes, then this peer is hosting the BEEP service that 475 the initiator wishes to use. In this case, the listener performs a 476 tuning reset: 478 o All channels, including channel zero, are implicitly closed. 480 o Any previously cached information about the BEEP session is 481 discarded. 483 o A new plaintext greeting is sent. 485 If the outermost element has a "port" attribute and an "fqdn" 486 attribute but no "srv" attribute, then "fqdn" is looked up as an A 487 record via DNS, translated to an IP number. An "ip4" attribute is 488 interpreted as the dotted-quad representation of an IPv4 address. An 489 "ip6" attribute is interpreted as a text representation of an IPv6 490 address. In each of these cases, a transport connection is 491 established to the so-identified server. If the outermost element 492 has a "srv" attribute, the concatenation of the "srv" attribute and 493 the "fqdn" attribute (with a period between) is looked up in the DNS 494 for a SRV record [6], and the appropriate server is contacted; if 495 that lookup fails and a "port" attribute is present, the connection 496 is attempted as if the "srv" attribute were not specified. 498 Alternately, if the outermost element has a "profile" attribute, then 499 it must have no nested elements. The proxy processing this element 500 is responsible for determining the appropriate routing to reach a 501 peer serving the BEEP profile indicated by the URI in the attribute's 502 value. Rather than source routing, this provides a hop-by-hop 503 routing mechanism to a desired service. 505 Similarly, if the outermost element has an "endpoint" attribute, then 506 it must have no nested elements. The proxy processing this element 507 is responsible for determining the appropriate routing to reach a 508 peer indicated by the value of the "endpoint" attribute. Rather than 509 source routing, this provides a hop-by-hop routing mechanism to a 510 desired machine. There are no restrictions on how machines are 511 identified. 513 Then, if the outermost element has no nested elements, but it does 514 have attributes other than "profile" or "endpoint", then this peer is 515 the final BEEP hop. (This corresponds to "proxy2" in the "Non-BEEP" 516 example above.) In this case, as soon as the final underlying 517 transport connection is established, an "ok" element is returned over 518 the listening session, and the tunneling of data starts. No BEEP 519 greeting (or indeed any data) from the final hop is expected. 520 Starting with the octet following the END(CR)(LF) trailer of the 521 frame with the completion flag set (more=".") of the RPY carrying the 522 "ok" element, the proxy begins copying octets directly and without 523 any interpretation between the two underlying transport connections. 525 If the identified server cannot be contacted, an "error" element is 526 returned over the listening channel and any connection established as 527 an initiator is closed. If there is a nested "tunnel" element, and 528 the server that has been contacted does not offer a BEEP greeting, or 529 the BEEP greeting offered does not include the TUNNEL profile, then 530 this too is treated as an error: the initiating transport connection 531 is closed, and an error is returned. 533 If there is a nested "tunnel" element, and the identified server is 534 contacted and offers a BEEP greeting including the TUNNEL profile, 535 then the outermost element from the "tunnel" element received is 536 stripped off, a new TUNNEL channel is started on the initiating 537 session, and the stripped (inner) element is sent to start the next 538 hop. In this case, the peer is considered a "proxy" (meaning that 539 the next paragraph is applicable). 541 Once the proxy has passed the "tunnel" element on the TUNNEL channel, 542 it awaits an "error" or an "ok" element in response. If it receives 543 an "error" element, it closes the initiated session and it's 544 underlying transport connection. It then passes the "error" element 545 unchanged back on the listening session. If, on the other hand, it 546 receives an "ok" element, it passes the "ok" element back on the 547 listening session. Starting with the octet following the END(CR)(LF) 548 trailer of the frame with the completion flag set (more=".") of the 549 RPY carrying the "ok" element, the proxyy begins copying octets 550 directly and without any interpretation between the two underlying 551 transport connections. 553 5. Provisioning 555 While the BEEP Framework [2] is used, the attributes described are 556 sufficient for the TCP mapping [3] of BEEP. The attributes on the 557 "tunnel" element may need to be extended to handle other transport 558 layers. 560 In a mapping where multiple underlying transport connections are 561 used, once the "ok" element is passed, all channels are closed, 562 including channel zero. Thus, only the underlying transport 563 connection initially established remains, and all other underlying 564 transport connections for the session should be closed as well. 566 If a transport security layer (such as TLS) has been negotiated over 567 the session, the semantics for the TUNNEL profile are ill-defined. 568 The TUNNEL profile MUST NOT be advertised in any greetings after 569 transport security has been negotiated. 571 An SRV identifier of "_tunnel" is reserved by IANA for use with this 572 profile. Hence, the "srv" attribute "_tunnel._tcp" MAY be used as a 573 default for finding the appropriate address for tunneling into a 574 particular domain. 576 6. Reply Codes 578 This section lists the three-digit error codes the TUNNEL profile may 579 generate. 581 code meaning 582 ==== ======= 583 421 Service not available 584 (E.g., the proxy does not have sufficient resources.) 586 450 Requested action not taken 587 (E.g., DNS lookup failed or connection could not 588 be established. See too 550.) 590 500 General syntax error (E.g., poorly-formed XML) 592 501 Syntax error in parameters 593 (E.g., non-valid XML, letters in "ip4" attribute, etc.) 595 504 Parameter not implemented 597 530 Authentication required 599 534 Authentication mechanism insufficient 600 (E.g., too weak, sequence exhausted, etc.) 602 537 Action not authorized for user 604 538 Encryption already enabled 605 (E.g., TLS already negotiated, or a SASL that 606 provides encryption already negotiated.) 608 550 Requested action not taken 609 (E.g., next hop could be contacted, but 610 malformed greeting or no TUNNEL profile advertised.) 612 553 Parameter invalid 614 554 Transaction failed (E.g., policy violation) 616 Note that the 450 error code is appropriate when the destination 617 machine could not be contacted, while the 550 error code is 618 appropriate when the destination machine could be contacted but the 619 next phase of the protocol could not be negotiated. It is suggested 620 that the beginning of any reply from the destination machine be 621 included as part of the CDATA text of the error element, for 622 debugging purposes. 624 7. Security Considerations 626 The TUNNEL profile is a profile of BEEP. In BEEP, transport 627 security, user authentication, and data exchange are orthogonal. 628 Refer to Section 8 of [2] for a discussion of this. 630 However, the intent of the TUNNEL profile is to allow bidirectional 631 contact between two machines normally separated by a firewall. Since 632 TUNNEL allows this connection between BEEP peers, and BEEP peers can 633 offer a range of services with appropriate greetings, the TUNNEL 634 profile should be configured with care. It is reasonable to strictly 635 limit the hosts and services that a proxy is allowed to contact. It 636 is also reasonable to limit the use of the TUNNEL profile to 637 authorized users, as identified by a SASL profile. 639 Negotiation of a TLS profile in an end-to-end manner after a TUNNEL 640 has been established will prevent intermediate proxies from observing 641 or modifying the cleartext information exchanged, but only if TLS 642 certificates are properly configured during the negotiation. The 643 proxy could mount a "man in the middle" attack if public key 644 infrastructure is not deployed. 646 In some environments, it is undesirable to expose the names of 647 machines on one side of a firewall in unencrypted messages on the 648 other side of that firewall. In this case, source routing (using the 649 "fqdn", "ip4", "ip6", "port" and "srv" attributes) can route a 650 connection to the firewall proxy, with an innermost "profile" or 651 "endpoint" attribute which the firewall proxy understands. Local 652 provisioning can allow a proxy to translate a particular "profile" 653 or "endpoint" element into a new source route to reach the desired 654 service. This can prevents two attacks: 656 o Attackers sniffing packets on one side of the firewall cannot see 657 IP addresses or FQDNs of machines on the other side of the 658 firewall; and, 660 o Attackers cannot exhaustively attempt to connect to many FQDNs or 661 IP addresses via source routing and use the error messages as an 662 indication of whether the queried machine exists. For this attack 663 to be prevented, the proxy must allow only "profile" or "endpoint" 664 connections, always refusing to even attempt source-routed 665 connections. This latter attack can also be thwarted by requiring 666 a SASL identification before allowing a TUNNEL channel to be 667 started, but this can have higher overhead. 669 Normative References 671 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 672 Levels", BCP 14, RFC 2119, March 1997. 674 [2] Rose, M., "The Blocks Extensible Exchange Protocol Core", RFC 675 3080, March 2001. 677 [3] Rose, M., "Mapping the BEEP Core onto TCP", RFC 3081, March 678 2001. 680 [4] Hinden, R. and S. Deering, "IP Version 6 Addressing 681 Architecture", RFC 2373, July 1998. 683 [5] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource 684 Identifiers (URI): Generic Syntax", RFC 2396, August 1998. 686 [6] Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for 687 specifying the location of services (DNS SRV)", RFC 2782, 688 February 2000. 690 Author's Address 692 Darren New 693 5390 Caminito Exquisito 694 San Diego, CA 92130 695 US 697 Phone: +1 858 350 9733 698 EMail: dnew@san.rr.com 700 Appendix A. IANA Considerations 702 A.1 Registration: BEEP Profile 704 If the IESG approves this memo for publication, then the IANA 705 registers the profiles specified in this section and selects an IANA- 706 specific URI, e.g., "http://iana.org/beep/TUNNEL". 708 Profile identification: http://xml.resource.org/profiles/TUNNEL 710 Message exchanged during channel creation: "tunnel" 712 Messages starting one-to-one exchanges: "tunnel" 714 Messages in positive replies: "ok" 716 Messages in negative replies: "error" 718 Messages in one-to-many exchanges: None. 720 Message syntax: See Section Section 3 of this document. 722 Message semantics: See Section Section 4 of this document. 724 Contact information: See the Author's Address appendix of this 725 document. 727 Any extensions to this protocol MUST be documented in a Standards 728 track RFC." 730 A.2 Registration: The System (Well-Known) TCP port number for TUNNEL 732 A single well-known port is allocated to the TUNNEL profile. Upon 733 allocation, Section 5 will be updated to reflect the correct 734 allocated port. 736 Protocol Number: TCP 738 Message Formats, Types, Opcodes, and Sequences: See Section 3. 740 Functions: See Section 4. 742 Use of Broadcast/Multicast: none 744 Proposed Name: TUNNEL Profile 746 Short name: tunnel 747 Contact Information: See the "Authors' Addresses" section of this 748 memo 750 Appendix B. Acknowledgements 752 The author gratefully acknowledges the contributions of Marshall 753 Rose, Greg Matthews, and Ben Feinstein. 755 Inspiration for this profile comes from the Intrusion Detection 756 Working Group of the IETF. 758 Appendix C. Changes from Previous Version 760 The RFC editor is requested to remove this section and its entry in 761 the table of contents before publication. 763 C.1 Changes since -04 765 Added support for IPv6 address literals. 767 C.2 Changes since -03 769 Added IESG suggested text regarding protocol extensions. 771 C.3 Changes since -02 773 Addition of port number to elements with "srv" since srv is optional. 774 Correction of minor typo's in that area. 776 Renamed "References" section to "Normative References". 778 C.4 Changes since -01 780 Reference to RFC 2119 added. 782 Updated DTD identification headers. 784 Minor typographical changes. 786 Full Copyright Statement 788 Copyright (C) The Internet Society (2002). All Rights Reserved. 790 This document and translations of it may be copied and furnished to 791 others, and derivative works that comment on or otherwise explain it 792 or assist in its implementation may be prepared, copied, published 793 and distributed, in whole or in part, without restriction of any 794 kind, provided that the above copyright notice and this paragraph are 795 included on all such copies and derivative works. However, this 796 document itself may not be modified in any way, such as by removing 797 the copyright notice or references to the Internet Society or other 798 Internet organizations, except as needed for the purpose of 799 developing Internet standards in which case the procedures for 800 copyrights defined in the Internet Standards process must be 801 followed, or as required to translate it into languages other than 802 English. 804 The limited permissions granted above are perpetual and will not be 805 revoked by the Internet Society or its successors or assigns. 807 This document and the information contained herein is provided on an 808 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 809 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 810 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 811 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 812 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 814 Acknowledgement 816 Funding for the RFC Editor function is currently provided by the 817 Internet Society.