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Salgueiro 5 Expires: August 24, 2017 Cisco 6 February 20, 2017 8 Path MTU Discovery Using Session Traversal Utilities for NAT (STUN) 9 draft-ietf-tram-stun-pmtud-05 11 Abstract 13 This document describes a Session Traversal Utilities for NAT (STUN) 14 Usage for Path MTU Discovery (PMTUD) between a client and a server. 16 Status of This Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on August 24, 2017. 33 Copyright Notice 35 Copyright (c) 2017 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 51 2. Overview of Operations . . . . . . . . . . . . . . . . . . . 3 52 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 53 4. Probing Mechanisms . . . . . . . . . . . . . . . . . . . . . 5 54 4.1. Simple Probing Mechanism . . . . . . . . . . . . . . . . 5 55 4.1.1. Sending a Probe Request . . . . . . . . . . . . . . . 5 56 4.1.2. Receiving a Probe Request . . . . . . . . . . . . . . 6 57 4.1.3. Receiving a Probe Response . . . . . . . . . . . . . 6 58 4.2. Complete Probing Mechanism . . . . . . . . . . . . . . . 6 59 4.2.1. Sending the Probe Indications and Report Request . . 7 60 4.2.2. Receiving an ICMP Packet . . . . . . . . . . . . . . 7 61 4.2.3. Receiving a Probe Indication and Report Request . . . 8 62 4.2.4. Receiving a Report Response . . . . . . . . . . . . . 8 63 4.2.5. Using Checksums as Packet Identifiers . . . . . . . . 9 64 4.2.6. Using Sequence Numbers as Packet Identifiers . . . . 9 65 5. Probe Support Signaling Mechanisms . . . . . . . . . . . . . 10 66 5.1. Explicit Probe Support Signaling Mechanism . . . . . . . 10 67 5.2. Implicit Probe Support Signaling Mechanism . . . . . . . 11 68 6. STUN Attributes . . . . . . . . . . . . . . . . . . . . . . . 11 69 6.1. IDENTIFIERS . . . . . . . . . . . . . . . . . . . . . . . 11 70 6.2. PMTUD-SUPPORTED . . . . . . . . . . . . . . . . . . . . . 11 71 7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 72 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 73 8.1. New STUN Methods . . . . . . . . . . . . . . . . . . . . 12 74 8.2. New STUN Attributes . . . . . . . . . . . . . . . . . . . 12 75 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 76 9.1. Normative References . . . . . . . . . . . . . . . . . . 12 77 9.2. Informative References . . . . . . . . . . . . . . . . . 13 78 Appendix A. Release Notes . . . . . . . . . . . . . . . . . . . 13 79 A.1. Modifications between draft-ietf-tram-stun-pmtud-04 and 80 draft-ietf-tram-stun-pmtud-03 . . . . . . . . . . . . . . 13 81 A.2. Modifications between draft-ietf-tram-stun-pmtud-03 and 82 draft-ietf-tram-stun-pmtud-02 . . . . . . . . . . . . . . 13 83 A.3. Modifications between draft-ietf-tram-stun-pmtud-02 and 84 draft-ietf-tram-stun-pmtud-01 . . . . . . . . . . . . . . 14 85 A.4. Modifications between draft-ietf-tram-stun-pmtud-01 and 86 draft-ietf-tram-stun-pmtud-00 . . . . . . . . . . . . . . 14 87 A.5. Modifications between draft-ietf-tram-stun-pmtud-00 and 88 draft-petithuguenin-tram-stun-pmtud-01 . . . . . . . . . 14 89 A.6. Modifications between draft-petithuguenin-tram-stun- 90 pmtud-01 and draft-petithuguenin-tram-stun-pmtud-00 . . . 15 91 A.7. Modifications between draft-petithuguenin-tram-stun- 92 pmtud-00 and draft-petithuguenin-behave-stun-pmtud-03 . . 15 93 A.8. Modifications between draft-petithuguenin-behave-stun- 94 pmtud-03 and draft-petithuguenin-behave-stun-pmtud-02 . . 15 95 A.9. Modifications between draft-petithuguenin-behave-stun- 96 pmtud-02 and draft-petithuguenin-behave-stun-pmtud-01 . . 15 97 A.10. Modifications between draft-petithuguenin-behave-stun- 98 pmtud-01 and draft-petithuguenin-behave-stun-pmtud-00 . . 16 99 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 16 100 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 102 1. Introduction 104 The Packetization Layer Path MTU Discovery (PMTUD) specification 105 [RFC4821] describes a method to discover the Path MTU but does not 106 describe a practical protocol to do so with UDP. 108 Not all UDP-based protocols implement the Path MTU discovery 109 mechanism described in [RFC4821]. These protocols can make use of 110 the probing mechanisms described in this document instead of 111 designing their own adhoc extension. These probing mechanisms are 112 implemented with Session Traversal Utilities for NAT (STUN), but 113 their usage is not limited to STUN-based protocols. 115 The STUN usage defined in this document for Path MTU Discovery 116 (PMTUD) between a client and a server permits proper operations of 117 UDP-based applications in the network. It also simplifies 118 troubleshooting and has multiple other applications across a wide 119 variety of technologies. 121 Complementary techniques can be used to discover additional network 122 characteristics, such as the network path (using the STUN Traceroute 123 mechanism described in [I-D.martinsen-tram-stuntrace]) and bandwidth 124 availability (using the mechanism described in 125 [I-D.martinsen-tram-turnbandwidthprobe]). 127 2. Overview of Operations 129 This section is meant to be informative only. It is not intended as 130 a replacement for [RFC4821]. 132 A UDP endpoint that uses this specification to discover the Path MTU 133 over UDP and knows that the endpoint it is communicating with also 134 supports this specification can choose to use either the Simple 135 Probing mechanism (as described in Section 4.1) or the Complete 136 Probing mechanism (as described in Section 4.2). The selection of 137 which Probing Mechanism to use is dependent on performance and 138 security and complexity trade-offs. 140 If the Simple Probing mechanism is chosen, then the Client initiates 141 Probe transactions, as shown in Figure 1, which increase in size 142 until transactions timeout, indicating that the Path MTU has been 143 exceeded. It then uses that information to update the Path MTU. 145 Client Server 146 | | 147 | Probe Request | 148 |---------------->| 149 | | 150 | Probe Response | 151 |<----------------| 152 | | 154 Figure 1: Simple Probing Example 156 If the Complete Probing mechanism (as described in Section 4.2) is 157 chosen, then the Client sends Probe Indications of various sizes 158 interleaved with UDP packets sent by the UDP protocol. The Client 159 then sends a Report Request for the ordered list of identifiers for 160 the UDP packets and Probe Indications received by the Server. The 161 Client then compares the list returned in the Report Response with 162 its own list of identifiers for the UDP packets and Probe Indications 163 it sent. The Client then uses that comparison to find which Probe 164 Indications were dropped by the network as a result of their size. 165 It then uses that information to update the Path MTU. 167 Client Server 168 | UDP Packet | 169 |------------------>| 170 | | 171 | UDP Packet | 172 |------------------>| 173 | | 174 | Probe Indication | 175 |------------------>| 176 | | 177 | UDP Packet | 178 |------------------>| 179 | | 180 | Probe Indication | 181 |------------------>| 182 | | 183 | Report Request | 184 |------------------>| 185 | Report Response | 186 |<------------------| 187 | | 189 Figure 2: Complete Probing Example 191 3. Terminology 193 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 194 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 195 document are to be interpreted as described in [RFC2119]. When these 196 words are not in ALL CAPS (such as "must" or "Must"), they have their 197 usual English meanings, and are not to be interpreted as RFC 2119 key 198 words. 200 4. Probing Mechanisms 202 The Probing mechanism is used to discover the Path MTU in one 203 direction only, from the client to the server. 205 Two Probing mechanisms are described, a Simple Probing mechanism and 206 a more complete mechanism that can converge quicker and find an 207 appropriate PMTU in the presence of congestion. Additionally, the 208 Simple Probing mechanism does not require authentication, whereas the 209 complete mechanism does. 211 Implementations supporting this specification MUST implement the 212 server side of both the Simple Probing mechanism (Section 4.1) and 213 the Complete Probing mechanism (Section 4.2). 215 Implementations supporting this specification MUST implement the 216 client side of the Complete Probing mechanism. They MAY implement 217 the client side of the Simple Probing mechanism. 219 4.1. Simple Probing Mechanism 221 The Simple Probing mechanism is implemented by sending a Probe 222 Request with a PADDING [RFC5780] attribute and the DF bit set over 223 UDP. A router on the path to the server can reject this request with 224 an ICMP message or drop it. 226 4.1.1. Sending a Probe Request 228 A client forms a Probe Request by using the Probe Method and 229 following the rules in Section 7.1 of [RFC5389]. 231 The Probe transaction MUST be authenticated if the Simple Probing 232 mechanism is used in conjunction with the Implicit Probing Support 233 mechanism described in Section 5.2 If not, the Probe transaction MAY 234 be authenticated. 236 The client adds a PADDING [RFC5780] attribute with a length that, 237 when added to the IP and UDP headers and the other STUN components, 238 is equal to the Selected Probe Size, as defined in [RFC4821] 239 Section 7.3. The client MUST add the FINGERPRINT attribute so the 240 STUN messages are disambiguated from the other protocol packets. 242 Then the client sends the Probe Request to the server over UDP with 243 the DF bit set. For the purpose of this transaction, the Rc 244 parameter specified in Section 7.2.1 of [RFC5389] is set to 3. The 245 initial value for RTO stays at 500 ms. 247 A client MUST NOT send a probe if it does not have knowledge that the 248 server supports this specification. This is done either by external 249 signalling or by a mechanism specific to the UDP protocol to which 250 PMTUD capabilities are added or by one of the mechanisms specified in 251 Section 5. 253 4.1.2. Receiving a Probe Request 255 A server receiving a Probe Request MUST process it as specified in 256 [RFC5389]. 258 The server then creates a Probe Response. The server MUST add the 259 FINGERPRINT attribute so the STUN messages are disambiguated from the 260 other protocol packets. The server then sends the response to the 261 client. 263 4.1.3. Receiving a Probe Response 265 A client receiving a Probe Response MUST process it as specified in 266 [RFC5389]. If a response is received this is interpreted as a Probe 267 Success, as defined in [RFC4821] Section 7.6.1. If an ICMP packet 268 "Fragmentation needed" is received then this is interpreted as a 269 Probe Failure, as defined in [RFC4821] Section 7.6.2. If the Probe 270 transaction times out, then this is interpreted as a Probe 271 Inconclusive, as defined in [RFC4821] Section 7.6.4. 273 4.2. Complete Probing Mechanism 275 The Complete Probing mechanism is implemented by sending one or more 276 Probe Indications with a PADDING attribute and the DF bit set over 277 UDP followed by a Report Request to the same server. A router on the 278 path to the server can reject this Indication with an ICMP message or 279 drop it. The server keeps a chronologically ordered list of 280 identifiers for all packets received (including retransmitted 281 packets) and sends this list back to the client in the Report 282 Response. The client analyzes this list to find which packets were 283 not received. Because UDP packets do not contain an identifier, the 284 Complete Probing mechanism needs a way to identify each packet 285 received. 287 Some protocols may already have a way of identifying each individual 288 UDP packet, in which case these identifiers SHOULD be used in the 289 IDENTIFIERS attribute of the Report Response. While there are other 290 possible packet identification schemes, this document describes two 291 different ways to identify a specific packet. 293 In the first packet identification mechanism, the server computes a 294 checksum over each packet received and sends back to the sender the 295 list of checksums ordered chronologically. The client compares this 296 list to its own list of checksums. 298 In the second packet identification mechanism, the client prepends 299 the UDP data with a header that provides a sequence number. The 300 server sends back the chronologically ordered list of sequence 301 numbers received that the client then compares with its own list. 303 4.2.1. Sending the Probe Indications and Report Request 305 A client forms a Probe Indication by using the Probe Method and 306 following the rules in [RFC5389] Section 7.1. The client adds to the 307 Probe Indication a PADDING attribute with a size that, when added to 308 the IP and UDP headers and the other STUN components, is equal to the 309 Selected Probe Size, as defined in [RFC4821] Section 7.3. If the 310 authentication mechanism permits it, then the Indication MUST be 311 authenticated. The client MUST add the FINGERPRINT attribute so the 312 STUN messages are disambiguated from the other protocol packets. 314 Then the client sends the Probe Indication to the server over UDP 315 with the DF bit set. 317 Then the client forms a Report Request by following the rules in 318 [RFC5389] Section 7.1. The Report transaction MUST be authenticated 319 to prevent amplification attacks. The client MUST add the 320 FINGERPRINT attribute so the STUN messages are disambiguated from the 321 other protocol packets. 323 Then the client waits half the RTO, if it is known, or 250 ms after 324 sending the last Probe Indication and then sends the Report Request 325 to the server over UDP. 327 4.2.2. Receiving an ICMP Packet 329 If an ICMP packet "Fragmentation needed" is received then this is 330 interpreted as a Probe Failure, as defined in [RFC4821] Section 7.5. 332 4.2.3. Receiving a Probe Indication and Report Request 334 A server supporting this specification will keep the identifiers of 335 all packets received in a chronologically ordered list. The packets 336 that are to be associated to a list are selected according to 337 Section 5.2 of [RFC4821]. The same identifier can appear multiple 338 times in the list because of retransmissions. The maximum size of 339 this list is calculated such that when the list is added to the 340 Report Response, the total size of the packet does not exceed the 341 unknown Path MTU, as defined in [RFC5389] Section 7.1. Older 342 identifiers are removed when new identifiers are added to a list that 343 is already full. 345 A server receiving a Report Request MUST process it as specified in 346 [RFC5389]. 348 The server creates a Report Response and adds an IDENTIFIERS 349 attribute that contains the chronologically ordered list of all 350 identifiers received so far. The server MUST add the FINGERPRINT 351 attribute. The server then sends the response to the client. 353 The exact content of the IDENTIFIERS attribute depends on what type 354 of identifiers have been chosen for the protocol. Each protocol 355 adding PMTUD capabilities as specified by this specification MUST 356 describe the format of the contents of the IDENTIFIERS attribute, 357 unless it is using one of the formats described in this 358 specification. See Section 6.1 for details about the IDENTIFIERS 359 attribute. 361 4.2.4. Receiving a Report Response 363 A client receiving a Report Response processes it as specified in 364 [RFC5389]. If the response IDENTIFIERS attribute contains the 365 identifier of the Probe Indication, then this is interpreted as a 366 Probe Success for this probe, as defined in [RFC4821] Section 7.5. 367 If the Probe Indication identifier cannot be found in the Report 368 Response, this is interpreted as a Probe Failure, as defined in 369 [RFC4821] Section 7.5. If the Probe Indication identifier cannot be 370 found in the Report Response but identifiers for other packets sent 371 before or after the Probe Indication can all be found, this is 372 interpreted as a Probe Failure as defined in [RFC4821] Section 7.5. 373 If the Report Transaction times out, this is interpreted as a Full- 374 Stop Timeout, as defined in [RFC4821] Section 3. 376 4.2.5. Using Checksums as Packet Identifiers 378 When using a checksum as a packet identifier, the client calculates 379 the checksum for each packet sent over UDP that is not a STUN Probe 380 Indication or Request and keeps this checksum in a chronologically 381 ordered list. The client also keeps the checksum of the STUN Probe 382 Indication or Request sent in that same chronologically ordered list. 383 The algorithm used to calculate the checksum is similar to the 384 algorithm used for the FINGERPRINT attribute (i.e., the CRC-32 of the 385 payload XOR'ed with the 32-bit value 0x5354554e). 387 For each STUN Probe Indication or Request, the server retrieves the 388 STUN FINGERPRINT value. For all other packets, the server calculates 389 the checksum as described above. It puts these FINGERPRINT and 390 checksum values in a chronologically ordered list that is sent back 391 in the Report Response. 393 The contents of the IDENTIFIERS attribute is a list of 4 byte 394 numbers, each using the same encoding that is used for the contents 395 of the FINGERPRINT attribute. 397 It could have been possible to use the checksum generated in the UDP 398 checksum for this, but this value is generally not accessible to 399 applications. Also, sometimes the checksum is not calculated or is 400 off-loaded to network hardware. 402 4.2.6. Using Sequence Numbers as Packet Identifiers 404 When using sequence numbers, a small header similar to the TURN 405 ChannelData header is added in front of all packets that are not a 406 STUN Probe Indication or Request. The sequence number is 407 monotonically incremented by one for each packet sent. The most 408 significant bit of the sequence number is always 0. The server 409 collects the sequence number of the packets sent, or the 4 first 410 bytes of the transaction ID if a STUN Probe Indication or Request is 411 sent. In that case, the most significant bit of the 4 first bytes is 412 set to 1. 414 0 1 2 3 415 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 417 | Channel Number | Length | 418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 419 |0| Sequence number | 420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 421 | | 422 / Application Data / 423 / / 424 | | 425 | +-------------------------------+ 426 | | 427 +-------------------------------+ 429 The Channel Number is always 0xFFFF. The header values are encoded 430 using network order. 432 The contents of the IDENTIFIERS attribute is a chronologically 433 ordered list of 4 byte numbers, each containing either a sequence 434 number, if the packet was not a STUN Probe Indication or Request, or 435 the 4 first bytes of the transaction ID, with the most significant 436 bit forced to 1, if the packet is a STUN Probe Indication or Request. 438 5. Probe Support Signaling Mechanisms 440 The PMTUD mechanism described in this document is intended to be used 441 by any UDP-based protocols that do not have built-in PMTUD 442 capabilities, irrespective of whether those UDP-based protocols are 443 STUN-based or not. So the manner in which a specific protocol 444 discovers that it is safe to send PMTUD probes is largely dependent 445 on the details of that specific protocol, with the exception of the 446 Implicit Mechanism described below, which applies to any protocol. 448 5.1. Explicit Probe Support Signaling Mechanism 450 Some of these mechanisms can use a separate signalling mechanism (for 451 instance, an SDP attribute in an Offer/Answer exchange [RFC3264]), or 452 an optional flag that can be set in the protocol that is augmented 453 with PMTUD capabilities. STUN Usages that can benefit from PMTUD 454 capabilities can signal in-band that they support probing by 455 inserting a PMTUD-SUPPORTED attribute in some STUN methods. The 456 decision of which methods support this attribute is left to each 457 specific STUN Usage. 459 UDP-based protocols that want to use any of these mechanisms, 460 including the PMTUD-SUPPORTED attribute, to signal PMTUD capabilities 461 MUST ensure that it cannot be used to launch an amplification attack. 462 For example, using authentication can ensure this. 464 5.2. Implicit Probe Support Signaling Mechanism 466 As a result of the fact that all endpoints implementing this 467 specification are both clients and servers, a Probe Request or 468 Indication received by an endpoint acting as a server implicitly 469 signals that this server can now act as a client and MAY send a Probe 470 Request or Indication to probe the Path MTU in the reverse direction 471 toward the former client, that will now be acting as a server. 473 The Probe Request or Indication that are used to implicitly signal 474 probing support in the reverse direction MUST be authenticated to 475 prevent amplification attacks. 477 6. STUN Attributes 479 6.1. IDENTIFIERS 481 The IDENTIFIERS attribute carries a chronologically ordered list of 482 UDP packet identifiers. 484 While Sections Section 4.2.5 and Section 4.2.6 describe two possible 485 methods for acquiring and formatting the identifiers used for this 486 purpose, ultimately each protocol has to define how these identifiers 487 are acquired and formatted. Therefore, the contents of the 488 IDENTIFIERS attribute is opaque. 490 6.2. PMTUD-SUPPORTED 492 The PMTUD-SUPPORTED attribute indicates that its sender supports this 493 specification. This attribute has no value part and thus the 494 attribute length field is 0. 496 7. Security Considerations 498 The PMTUD mechanism described in this document does not introduce any 499 specific security considerations beyond those described in [RFC4821]. 501 The attacks described in Section 11 of [RFC4821] apply equally to the 502 mechanism described in this document. 504 The Simple Probing mechanism may be used without authentication 505 because this usage by itself cannot trigger an amplification attack 506 because the Probe Response is smaller than the Probe Request. An 507 unauthenticated Simple Probing mechanism cannot be used in 508 conjunction with the Implicit Probing Support Signaling mechanism in 509 order to prevent amplification attacks. 511 8. IANA Considerations 513 This specification defines two new STUN methods and two new STUN 514 attributes. IANA added these new protocol elements to the "STUN 515 Parameters Registry" created by [RFC5389]. 517 8.1. New STUN Methods 519 This section lists the codepoints for the new STUN methods defined in 520 this specification. See Sections Section 4.1 and Section 4.2 for the 521 semantics of these new methods. 523 0xXXX : Probe 525 0xXXX : Report 527 8.2. New STUN Attributes 529 This document defines the IDENTIFIERS STUN attribute, described in 530 Section 6.1. IANA has allocated the comprehension-required codepoint 531 0xXXXX for this attribute. 533 This document also defines the PMTUD-SUPPORTED STUN attribute, 534 described in Section 6.2. IANA has allocated the comprehension- 535 optional codepoint 0xXXXX for this attribute. 537 9. References 539 9.1. Normative References 541 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 542 Requirement Levels", BCP 14, RFC 2119, 543 DOI 10.17487/RFC2119, March 1997, 544 . 546 [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 547 Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, 548 . 550 [RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, 551 "Session Traversal Utilities for NAT (STUN)", RFC 5389, 552 DOI 10.17487/RFC5389, October 2008, 553 . 555 9.2. Informative References 557 [I-D.martinsen-tram-stuntrace] 558 Martinsen, P. and D. Wing, "STUN Traceroute", draft- 559 martinsen-tram-stuntrace-01 (work in progress), June 2015. 561 [I-D.martinsen-tram-turnbandwidthprobe] 562 Martinsen, P., Andersen, T., Salgueiro, G., and M. Petit- 563 Huguenin, "Traversal Using Relays around NAT (TURN) 564 Bandwidth Probe", draft-martinsen-tram- 565 turnbandwidthprobe-00 (work in progress), May 2015. 567 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 568 with Session Description Protocol (SDP)", RFC 3264, 569 DOI 10.17487/RFC3264, June 2002, 570 . 572 [RFC5780] MacDonald, D. and B. Lowekamp, "NAT Behavior Discovery 573 Using Session Traversal Utilities for NAT (STUN)", 574 RFC 5780, DOI 10.17487/RFC5780, May 2010, 575 . 577 Appendix A. Release Notes 579 This section must be removed before publication as an RFC. 581 A.1. Modifications between draft-ietf-tram-stun-pmtud-04 and draft- 582 ietf-tram-stun-pmtud-03 584 o Modifications following Simon Perreault and Brandon Williams 585 reviews. 587 A.2. Modifications between draft-ietf-tram-stun-pmtud-03 and draft- 588 ietf-tram-stun-pmtud-02 590 o Add new Overview of Operations section with ladder diagrams. 592 o Authentication is mandatory for the Complete Probing mechanism, 593 optional for the Simple Probing mechanism. 595 o All the ICE specific text moves to a separate draft to be 596 discussed in the ICE WG. 598 o The TURN usage is removed because probing between a TURN server 599 and TURN client is not useful. 601 o Any usage of PMTUD-SUPPORTED or other signaling mechanisms 602 (formerly knows as discovery mechanisms) must now be 603 authenticated. 605 o Both probing mechanisms are MTI in the server, the complete 606 probing mechanism is MTI in the client. 608 o Make clear that stopping after 3 retransmission is done by 609 changing the STUN parameter. 611 o Define the format of the attributes. 613 o Make clear that the specification is for any UDP protocol that 614 does not already have PMTUD capabilities, not just STUN based 615 protocols. 617 o Change the default delay to send the Report Request to 250 ms 618 after the last Indication if the RTO is unknown. 620 o Each usage of this specification must the format of the 621 IDENTIFIERS attribute contents. 623 o Better define the implicit signaling mechanism. 625 o Extend the Security Consideration section. 627 o Tons of nits. 629 A.3. Modifications between draft-ietf-tram-stun-pmtud-02 and draft- 630 ietf-tram-stun-pmtud-01 632 o Cleaned up references. 634 A.4. Modifications between draft-ietf-tram-stun-pmtud-01 and draft- 635 ietf-tram-stun-pmtud-00 637 o Added Security Considerations Section. 639 o Added IANA Considerations Section. 641 A.5. Modifications between draft-ietf-tram-stun-pmtud-00 and draft- 642 petithuguenin-tram-stun-pmtud-01 644 o Adopted by WG - Text unchanged. 646 A.6. Modifications between draft-petithuguenin-tram-stun-pmtud-01 and 647 draft-petithuguenin-tram-stun-pmtud-00 649 o Moved some Introduction text to the Probing Mechanism section. 651 o Added cross-reference to the other two STUN troubleshooting 652 mechanism drafts. 654 o Updated references. 656 o Added Gonzalo Salgueiro as co-author. 658 A.7. Modifications between draft-petithuguenin-tram-stun-pmtud-00 and 659 draft-petithuguenin-behave-stun-pmtud-03 661 o General refresh for republication. 663 A.8. Modifications between draft-petithuguenin-behave-stun-pmtud-03 and 664 draft-petithuguenin-behave-stun-pmtud-02 666 o Changed author address. 668 o Changed the IPR to trust200902. 670 A.9. Modifications between draft-petithuguenin-behave-stun-pmtud-02 and 671 draft-petithuguenin-behave-stun-pmtud-01 673 o Defined checksum and sequential numbers as possible packet 674 identifiers. 676 o Updated the reference to RFC 5389 678 o The FINGERPRINT attribute is now mandatory. 680 o Changed the delay between Probe indication and Report request to 681 be RTO/2 or 50 milliseconds. 683 o Added ICMP packet processing. 685 o Added Full-Stop Timeout detection. 687 o Stated that Binding request with PMTUD-SUPPORTED does not start 688 the PMTUD process if already started. 690 A.10. Modifications between draft-petithuguenin-behave-stun-pmtud-01 691 and draft-petithuguenin-behave-stun-pmtud-00 693 o Removed the use of modified STUN transaction but shorten the 694 retransmission for the simple probing mechanism. 696 o Added a complete probing mechanism. 698 o Removed the PADDING-RECEIVED attribute. 700 o Added release notes. 702 Acknowledgements 704 Thanks to Eilon Yardeni, Geir Sandbakken, Paal-Erik Martinsen, 705 Tirumaleswar Reddy, Ram Mohan R, Simon Perreault, and Brandon 706 Williams for their review comments, suggestions and questions that 707 helped to improve this document. 709 Special thanks to Dan Wing, who supported this document since its 710 first publication back in 2008. 712 Authors' Addresses 714 Marc Petit-Huguenin 715 Impedance Mismatch 717 Email: marc@petit-huguenin.org 719 Gonzalo Salgueiro 720 Cisco Systems, Inc. 721 7200-12 Kit Creek Road 722 Research Triangle Park, NC 27709 723 United States 725 Email: gsalguei@cisco.com