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Ciavattone 4 Updates: 5357 (if approved) AT&T Labs 5 Intended status: Standards Track June 28, 2010 6 Expires: December 30, 2010 8 TWAMP Reflect Octets and Symmetrical Size Features 9 draft-ietf-ippm-twamp-reflect-octets-07 11 Abstract 13 This memo describes two closely-related features for the core 14 specification of TWAMP - the Two-Way Active Measurement Protocol: an 15 optional capability where the responding host returns some of the 16 command octets or padding octets to the sender, and an optional 17 sender packet format that ensures equal test packet sizes are used in 18 both directions. 20 Requirements Language 22 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 23 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 24 document are to be interpreted as described in RFC 2119 [RFC2119]. 26 Status of this Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at http://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on December 30, 2010. 43 Copyright Notice 45 Copyright (c) 2010 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (http://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 This document may contain material from IETF Documents or IETF 59 Contributions published or made publicly available before November 60 10, 2008. The person(s) controlling the copyright in some of this 61 material may not have granted the IETF Trust the right to allow 62 modifications of such material outside the IETF Standards Process. 63 Without obtaining an adequate license from the person(s) controlling 64 the copyright in such materials, this document may not be modified 65 outside the IETF Standards Process, and derivative works of it may 66 not be created outside the IETF Standards Process, except to format 67 it for publication as an RFC or to translate it into languages other 68 than English. 70 Table of Contents 72 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 73 2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 4 74 3. TWAMP Control Extensions . . . . . . . . . . . . . . . . . . . 5 75 3.1. Connection Setup with New Features . . . . . . . . . . . . 5 76 3.2. Reflect Octets: Request-TW-Session Packet Format . . . . . 6 77 3.3. Reflect Octets: Accept Session Packet Format . . . . . . . 8 78 3.4. Additional considerations . . . . . . . . . . . . . . . . 9 79 4. Extended TWAMP Test . . . . . . . . . . . . . . . . . . . . . 9 80 4.1. Sender Behavior . . . . . . . . . . . . . . . . . . . . . 9 81 4.1.1. Packet Timings . . . . . . . . . . . . . . . . . . . . 9 82 4.1.2. Reflect Octets: Packet Formats and Contents . . . . . 10 83 4.1.3. Reflect Octets: Interaction with Padding Truncation . 11 84 4.1.4. Symmetrical Size: Session-Sender Packet Format . . . . 12 85 4.1.5. Symmetrical Size AND Reflect Octets: 86 Session-Sender Packet Format . . . . . . . . . . . . . 13 87 4.2. Reflector Behavior . . . . . . . . . . . . . . . . . . . . 14 88 4.2.1. Reflect Octets: Session-Reflector Packet Format 89 and Contents . . . . . . . . . . . . . . . . . . . . . 15 90 4.2.2. Symmetrical Size: Session-Reflector Packet Format . . 16 91 4.2.3. Symmetrical Size AND Reflect Octets: 92 Session-Sender Packet Format . . . . . . . . . . . . . 16 93 5. Security Considerations . . . . . . . . . . . . . . . . . . . 16 94 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 95 6.1. Registry Specification . . . . . . . . . . . . . . . . . . 17 96 6.2. Registry Contents . . . . . . . . . . . . . . . . . . . . 17 97 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18 98 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 99 8.1. Normative References . . . . . . . . . . . . . . . . . . . 18 100 8.2. Informative References . . . . . . . . . . . . . . . . . . 18 101 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 103 1. Introduction 105 TWAMP - the Two-Way Active Measurement Protocol [RFC5357] is an 106 extension of the One-way Active Measurement Protocol, OWAMP 107 [RFC4656]. The TWAMP specification gathered wide review as it 108 approached completion, and the by-products were several 109 recommendations for new features in TWAMP. 111 This memo describes two closely-related features for TWAMP. 113 One is the OPTIONAL capability for the responder host to return a 114 limited number of unassigned (padding) octets to the Control-Client 115 or Session-Sender entities in both the TWAMP-Control and TWAMP-Test 116 protocols. With this capability, the Control-Client or Session- 117 Sender can embed octets of information it deems useful and have the 118 assurance that the corresponding reply/test packet will contain that 119 information when it is reflected and returned (by the Server or 120 Session-Reflector. 122 The memo also adds an OPTIONAL capability to assure that reflected 123 test packets are the same size in both directions of transmission. 124 This is accomplished by specifying a new TWAMP-Test Session-Sender 125 packet format. 127 This memo is an update to the TWAMP core protocol specified in 128 [RFC5357]. Measurement systems are not required to implement the 129 features described in this memo to claim compliance with [RFC5357]. 131 Throughout this memo, the bits marked MBZ (Must Be Zero) MUST be set 132 to zero by senders and MUST be ignored by receivers. Also, the HMAC 133 (Hashed Message Authentication Code) MUST be calculated as defined in 134 Section 3.2 of [RFC4656]. 136 2. Purpose and Scope 138 The purpose of this memo is to define two OPTIONAL closely-related 139 features for TWAMP [RFC5357]. The features enhance the TWAMP host's 140 capabilities to perform a simple operation on control and test 141 packets: the reflection of octets or padding, and the capability to 142 ensure symmetrical size TWAMP-Test packets. Motivations include 143 permitting the controller host to tag packets with an index for 144 simplified identification, and/or assert that the same size test 145 packets will be used in each direction. 147 The scope of the memo is limited to specifications of the following 148 features: 150 o Reflect Octets: the capability of the Server/Session-Reflector to 151 reflect specific octets back to the Client/Session-Sender, and a 152 similar service provided by the Client and Session-Sender. 154 o Symmetrical Size: the capability to ensure that TWAMP-Test 155 protocol uses the same packet size in both directions through 156 support of a new TWAMP-Test Session-Sender test packet format in 157 both the Session-Sender and the Session-Reflector. Only the 158 Session-Sender test packet format is new. 160 This memo extends the modes of operation through assignment of two 161 new values in the Modes Field (see section 3.1 of[RFC4656] for the 162 format of the Server Greeting message), while retaining backward 163 compatibility with the core TWAMP [RFC5357] implementations. The two 164 new values correspond to the two features defined in this memo. 166 When the Server and Control-Client have agreed to use the Reflect 167 Octets mode during control connection setup, then the Control-Client, 168 the Server, the Session-Sender, and the Session-Reflector MUST all 169 conform to the requirements of that mode, as identified below. 171 When the Server and Control-Client have agreed to use the Symmetrical 172 Size mode during control connection setup, then the Control-Client, 173 the Server, the Session-Sender, and the Session-Reflector MUST all 174 conform to the requirements of that mode, as identified below. 176 3. TWAMP Control Extensions 178 TWAMP-Control protocol [RFC5357] uses the Modes Field to identify and 179 select specific communication capabilities, and this field is a 180 recognized extension mechanism. The following sections describe two 181 such extensions. 183 3.1. Connection Setup with New Features 185 TWAMP connection establishment follows the procedure defined in 186 section 3.1 of [RFC4656] and section 3.1 of [RFC5357]. The new 187 features require two new bit positions (and values) to identify the 188 ability of the Server/Session-Reflector to reflect specific octets 189 back to the Control-Client/Session-Sender, and to support the new 190 Session-Sender packet format in TWAMP-Test Protocol. See the IANA 191 section for details on the assigned values and bit positions. 193 The Server sets one or both of the new bit positions in the Modes 194 Field of the Server Greeting message to indicate its capabilities and 195 willingness to operate in either of these modes (or both) if desired. 197 If the Control-Client intends to operate all test sessions invoked 198 with this control connection using one or both of the new modes, it 199 MUST set the Mode Field bit corresponding to each function in the 200 Setup Response message. With this and other extensions, the Control- 201 Client MAY set multiple Mode Field bits in the Setup Response 202 message. 204 3.2. Reflect Octets: Request-TW-Session Packet Format 206 The bits designated for the Reflect Octets feature in the Request-TW- 207 Session command are as shown in the packet format below. 209 0 1 2 3 210 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 1 211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 | 5 | MBZ | IPVN | Conf-Sender | Conf-Receiver | 213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 214 | Number of Schedule Slots | 215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 216 . . 217 . ... Many fields (66 octets) not shown ... . 218 . . 219 . . 220 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 221 | Padding Length (4 octets) | 222 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 223 | Start Time, (8 octets) | 224 | | 225 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 226 | Timeout, (8 octets) | 227 | | 228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 229 | Type-P Descriptor | 230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 231 | Octets to be reflected | Length of padding to reflect | 232 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 233 | MBZ (4 octets) | 234 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 235 | | 236 | HMAC (16 octets) | 237 | | 238 | | 239 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 241 The "Padding Length" Field *continues* to specify the number of 242 padding octets that the Session-Sender will append to ALL TWAMP-Test 243 packets associated with this test session. See below for 244 considerations on the minimum length of the padding octets, following 245 the definitions of the two new fields that follow the Type-P 246 Descriptor. 248 Note that the number of padding octets appended to the Session- 249 Reflector's test packet depends on support for the RECOMMENDED 250 truncation process in TWAMP section 4.2.1 [RFC5357]. 252 The "Octets to be reflected" Field SHALL be 2 octets long, as shown 253 and contains the octets that the Server MUST reflect in the Accept 254 Session message as specified below. 256 The "Length of padding to reflect" Field SHALL be 2 octets long, and 257 contain an unsigned binary value in units of octets. This field 258 communicates the length of the padding in the TWAMP-Test Packet that 259 the Session-Sender expects to be reflected, and the length of octets 260 that the Session-Reflector SHALL return in include in its TWAMP-Test 261 packet format (see section 4.2). By including this length field in 262 the Request-TW-Session message, a Server is able to determine if it 263 can comply with a specific request to reflect padding in the TWAMP- 264 Test packets, and to arrange for the Session-Reflector processing in 265 advance. 267 The "Padding Length" SHOULD be >= 27 octets when specifying a test 268 session using the Unauthenticated TWAMP-Test mode, to allow for the 269 RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357]. 271 The "Padding Length" SHOULD be >= 56 octets when specifying a test 272 session using the Authenticated or Encrypted TWAMP-Test modes, to 273 allow for the RECOMMENDED truncation process in TWAMP section 4.2.1 274 [RFC5357]. 276 The "Padding Length" SHALL be > the "Length of padding to reflect" 277 when specifying a test session using the OPTIONAL Reflect Octets 278 mode. 280 In Unauthenticated TWAMP-Test mode, the "Padding Length" SHALL be >= 281 27 + "Length of padding to reflect" octets when specifying a test 282 session using BOTH the OPTIONAL Reflect Octets mode and the 283 RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357]. 285 In Authenticated or Encrypted TWAMP-Test modes, the "Padding Length" 286 SHALL be >= 56 + "Length of padding to reflect" octets when 287 specifying a test session using BOTH the OPTIONAL Reflect Octets mode 288 and the RECOMMENDED truncation process in TWAMP section 4.2.1 289 [RFC5357]. 291 3.3. Reflect Octets: Accept Session Packet Format 293 The bits designated for the Reflect Padding feature in the Accept 294 Session command are as shown in the packet format below. 296 0 1 2 3 297 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 1 298 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 299 | Accept | MBZ | Port | 300 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 301 | | 302 | SID (16 octets) | 303 | | 304 | | 305 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 306 | Reflected octets | Server octets | 307 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 308 | MBZ (8 octets) | 309 | | 310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 311 | | 312 | HMAC (16 octets) | 313 | | 314 | | 315 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 317 The "Reflected octets" field SHALL contain the octets from the 318 Request-TW-Session "Octets to be reflected" Field, and be 2 octets 319 long, as shown. 321 The "Server octets" field SHALL contain information that the Server 322 intends to be returned in the TWAMP-Test packet padding to-be- 323 reflected Field, OR SHALL be zero, and be 2 octets long, as shown. 324 Although the Server determines the SID, this field is very long (16 325 octets) and does not normally appear in TWAMP-Test packets. The 326 following items MUST be part of compliant implementations using the 327 Reflect Octets feature: 329 o When a Server does not require octets to be returned in TWAMP-Test 330 packets, it MUST send all zeros in the Server octets field 332 o When a Server intends octets to be returned in TWAMP-Test packets, 333 it MUST send a non-zero value in the Server octets field, and the 334 TWAMP-Test Sender MUST include those octets at the beginning of 335 the "Packet Padding (to be reflected)" field 337 o Section 4.1.2 defines how Server octets MUST be included in the 338 TWAMP-Test packet padding when this service is desired by the 339 Server (indicated in the second of two figures in the section) 341 When supporting the RECOMMENDED truncation process in TWAMP section 342 4.2.1 [RFC5357], IF calculations on the Padding lengths reveal that 343 there are insufficient octets supplied to produce equal-length 344 Session-Sender and Session-Reflector test packets, then the Accept 345 Field MUST be set to 3 = some aspect of the request is not supported. 347 3.4. Additional considerations 349 The value of the Modes Field sent by the Server in the Server 350 Greeting message is the bit-wise OR of the mode values that it is 351 willing to support during this session. 353 With the publication of this memo as an RFC, the last 7 bit positions 354 of the Modes 32-bit Field are used. A Control-Client conforming to 355 this extension of [RFC5357] MAY ignore the values in the higher bits 356 of the Modes Field, or it MAY support other features that are 357 communicated in those bit positions. The other bits are available 358 for future protocol extensions. 360 4. Extended TWAMP Test 362 The TWAMP test protocol is similar to the OWAMP [RFC4656] test 363 protocol with the exception that the Session-Reflector transmits test 364 packets to the Session-Sender in response to each test packet it 365 receives. TWAMP section 4[RFC5357] defines two additional test 366 packet formats for packets transmitted by the Session-Reflector. The 367 appropriate format depends on the security mode chosen. The new 368 modes specified here utilize some of the padding octets within each 369 test packet format, or require truncation of those octets depending 370 on the security mode in use. 372 4.1. Sender Behavior 374 This section describes extensions to the behavior of the TWAMP 375 Session-Sender. 377 4.1.1. Packet Timings 379 The Send Schedule is not utilized in TWAMP, and this is unchanged in 380 this memo. 382 4.1.2. Reflect Octets: Packet Formats and Contents 384 The Session-Sender packet format and content follow the same 385 procedure and guidelines as defined in section 4.1.2 of [RFC4656] (as 386 indicated in section 4.1.2 of TWAMP [RFC5357]). 388 The Reflect octets mode re-designates the original TWAMP-Test (and 389 OWAMP-Test) Packet Padding Field (see section 4.1.2 of [RFC4656]), as 390 shown below for unauthenticated mode: 392 0 1 2 3 393 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 1 394 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 395 | Sequence Number | 396 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 397 | Timestamp | 398 | | 399 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 400 | Error Estimate | | 401 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 402 | | 403 | Packet Padding (to be reflected) | 404 . (length in octets specified in command) . 405 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 406 . . 407 . Additional Packet Padding . 408 . . 409 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 411 The "Packet Padding (to be reflected)" Field SHALL correspond to the 412 length of octets specified in the Request-TW-Session "Length of 413 padding to reflect" Field to this test session. These are the octets 414 that the Session-Sender expects will be returned by the Session- 415 Reflector. 417 The length of the "Additional Packet Padding" Field is the difference 418 between two fields in the Request-TW-Session command, as follows: 420 "Additional Packet Padding", in octets = 422 "Padding Length" - "Length of padding to reflect" 424 When a Server intends octets to be returned in TWAMP-Test packets, it 425 MUST send a non-zero value in the Server octets field, and the TWAMP- 426 Test Session-Sender MUST include those octets in the first 2 octets 427 of the "Packet Padding (to be reflected)" Field as shown below: 429 0 1 2 3 430 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 1 431 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 432 | Server octets | 433 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 434 | | 435 | Packet Padding (to be reflected) | 436 . (length in octets specified elsewhere) . 437 . . 438 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 440 The "Server octets" field contains the same information that the 441 Server returned to the Control-Client in the Accept-Session message 442 corresponding to this specific test session (see section 3.3). At 443 the Session-Reflector, these octets MUST be reflected the same as the 444 rest of the "Packet Padding (to be reflected)" field. 446 Note that it is permissible for the Session-Sender to insert the same 447 octets used in the "Octets to be reflected" field of the Request-TW- 448 Session command elsewhere in the "Packet Padding (to be reflected)" 449 field. 451 4.1.3. Reflect Octets: Interaction with Padding Truncation 453 When the Reflect Octets mode is selected, and the RECOMMENDED 454 truncation process in TWAMP section 4.2.1 [RFC5357] is supported, the 455 Session-Sender MUST anticipate a minimum padding required to achieve 456 equal size test packets in both directions. The amount of padding 457 needed to achieve symmetrical packet size depends on BOTH the 458 security mode (Unauthenticated/Authenticated/Encrypted) and whether 459 the Reflect Octets mode is selected simultaneously. 461 When using the RECOMMENDED truncation process in TWAMP section 4.2.1 462 [RFC5357] alone, the Session-Sender MUST append sufficient Packet 463 Padding octets to allow the same IP packet payload lengths to be used 464 in each direction of transmission (this is usually desirable). To 465 compensate for the Session-Reflector's larger test packet format, the 466 Session-Sender MUST append at least 27 octets of padding in 467 Unauthenticated mode, and at least 56 octets in Authenticated and 468 Encrypted modes. The sizes of TWAMP Test protocol packets and the 469 resulting truncated padding to achieve equal packet sizes in both 470 directions are shown in the table below: 472 +-------------------+----------------------+---------------------+ 473 | Octets in: | Unauthenticated Mode | Auth/Encrypted Mode | 474 +-------------------+----------------------+---------------------+ 475 | Reflector Header | 41 | 104 | 476 | Sender Header | 14 | 48 | 477 | Truncated Padding | 27 | 56 | 478 +-------------------+----------------------+---------------------+ 480 TWAMP-Test Padding Truncation 482 When using the Reflect Octets mode simultaneously with the 483 RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357], the 484 Session-Sender MUST append at least 27 octets of padding plus the 485 "Length of the padding to reflect" octets when operating in 486 Unauthenticated mode. The Session-Sender MUST append at least 56 487 octets of padding plus the "Length of the padding to reflect" octets 488 when operating in Authenticated and Encrypted modes. 490 4.1.4. Symmetrical Size: Session-Sender Packet Format 492 When the Symmetrical Size mode is selected, the Session-Sender SHALL 493 use the following TWAMP-Test Packet Format in Unauthenticated mode: 495 Unauthenticated Mode 496 0 1 2 3 497 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 1 498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 499 | Sequence Number | 500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 501 | Timestamp | 502 | | 503 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 504 | Error Estimate | | 505 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 506 | | 507 | | 508 | MBZ (27 octets) | 509 | | 510 | | 511 | | 512 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 513 | | | 514 +-+-+-+-+-+-+-+-+ + 515 . . 516 . Packet Padding . 517 . . 518 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 520 This feature REQUIRES only a new Session-Sender test packet format, 521 the Session-Reflector test packet format is unchanged. 523 4.1.5. Symmetrical Size AND Reflect Octets: Session-Sender Packet 524 Format 526 When BOTH the Symmetrical Size mode and the Reflect Octets mode are 527 selected, the Session-Sender SHALL use the following TWAMP-Test 528 Packet Format in Unauthenticated mode: 530 Unauthenticated Mode 531 0 1 2 3 532 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 1 533 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 534 | Sequence Number | 535 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 536 | Timestamp | 537 | | 538 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 539 | Error Estimate | | 540 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 541 | | 542 | | 543 | MBZ (27 octets) | 544 | | 545 | | 546 | | 547 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 548 | | | 549 +-+-+-+-+-+-+-+-+ + 550 | Packet Padding (to be reflected) | 551 . (length in octets specified in command) . 552 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 553 . . 554 . Additional Packet Padding . 555 . . 556 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 558 In this combined mode, the Packet Padding to be reflected follows the 559 27 MBZ octets. In Authenticated or Encrypted modes, the Packet 560 Padding to be reflected follows the 56 MBZ octets. 562 4.2. Reflector Behavior 564 The TWAMP Reflector follows the procedures and guidelines in section 565 4.2 of [RFC5357], with the following additional functions: 567 o Reflect Octets mode: Designated octets in the "Packet Padding (to 568 be reflected)" field of the Session-Sender's test packet MUST be 569 included in the Session-Reflector's test packet. 571 o Symmetrical Size mode: The Session-Reflector MUST operate using 572 the Session_Reflector Packet Format defined in section 4.1.4, 573 where the Padding Octets are separated from the information 574 fields. 576 4.2.1. Reflect Octets: Session-Reflector Packet Format and Contents 578 The Reflect Padding feature re-designates the packet padding field, 579 as shown below. When the Reflect Octets mode is selected, the 580 Session-Sender SHALL use the following TWAMP-Test Packet Format in 581 Unauthenticated mode: 583 0 1 2 3 584 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 1 585 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 586 | Sequence Number | 587 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 588 | Timestamp | 589 | | 590 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 591 | Error Estimate | MBZ | 592 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 593 | Receive Timestamp | 594 | | 595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 596 | Sender Sequence Number | 597 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 598 | Sender Timestamp | 599 | | 600 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 601 | Sender Error Estimate | MBZ | 602 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 603 | Sender TTL | Packet Padding (from Session-Sender) | 604 +-+-+-+-+-+-+-+-+ + 605 . . 606 + +-+-+-+-+-+-+-+-+ 607 | Packet Padding (from Session-Sender) | | 608 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 609 | | 610 | | 611 . Additional Packet Padding . 612 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 613 The "Packet Padding (from Session-Sender)" field MUST be the same 614 octets as the "Packet Padding (to be reflected)" field in the 615 Session-Sender's test packet, and therefore MUST conform to the 616 length specified in the Request-TW-Session message. 618 When the Server has returned a non-zero value in the "Server octets" 619 field of the Accept Session message (as described in section 3.3), 620 then the Session-Reflector SHALL reflect these octets the same as the 621 rest of the "Packet Padding (to be reflected)" Field. 623 When simultaneously using the RECOMMENDED truncation process in TWAMP 624 section 4.2.1 [RFC5357] AND Reflect octets mode, the Session- 625 Reflector MUST reflect the designated octets from the Session- 626 Sender's test packet in the "Packet Padding (from Session-Sender)" 627 Field, and MAY re-use additional Packet Padding from the Session- 628 Sender. The Session-Reflector MUST truncate the padding such that 629 the highest number octets are discarded, and the test packet length 630 equals the Session-Sender's packet length. When using the 631 RECOMMENDED truncation process, the Session-Reflector MUST truncate 632 exactly 27 octets of padding in Unauthenticated mode, and exactly 56 633 octets in Authenticated and Encrypted modes. 635 The Session-Reflector MAY re-use the Sender's Packet Padding (since 636 the requirements for padding generation are the same for each). 638 4.2.2. Symmetrical Size: Session-Reflector Packet Format 640 When Symmetrical Size mode is selected, the Session-Sender packet 641 formats for unauthenticated and authenticated/encrypted modes are 642 identical to the core TWAMP specification, section 4.2.1 of 643 [RFC5357]. Thus, the Session-Reflector test packet format is 644 unchanged. 646 The Session-Reflector MUST construct its test packet using the 647 information in the Session-Sender's test packet. The length of the 648 Session-Reflector's test packet SHALL equal the length of the 649 Session-Sender's test packet. 651 4.2.3. Symmetrical Size AND Reflect Octets: Session-Sender Packet 652 Format 654 When BOTH the Symmetrical Size mode and the Reflect Octets mode are 655 selected, the Session-Reflector MUST operate using the 656 Session_Reflector Packet Format defined in section 4.1.5, where the 657 Padding Octets are separated from the information fields, and the 658 Padding to be Reflected field precedes the Additional Padding. 660 The Session-Reflector SHALL use the same TWAMP-Test Packet Format as 661 specified in section 4.2.1 above. 663 5. Security Considerations 665 These extended modes of operation do not appear to permit any new 666 attacks on hosts communicating with core TWAMP [RFC5357]. 668 The security considerations that apply to any active measurement of 669 live networks are relevant here as well. See [RFC4656] and 670 [RFC5357]. 672 6. IANA Considerations 674 This memo adds two modes to the IANA registry for the TWAMP Modes 675 Field, and describes behavior when the new modes are used. This 676 field is a recognized extension mechanism for TWAMP. 678 6.1. Registry Specification 680 IANA has created a TWAMP-Modes registry (as requested in [RFC5618]). 681 TWAMP-Modes are specified in TWAMP Server Greeting messages and 682 Set-up Response messages, as described in section 3.1 of [RFC5357], 683 consistent with section 3.1 of [RFC4656], and extended by this memo. 684 Modes are indicated by setting bits in the 32-bit Modes field that 685 correspond to values in the Modes registry. For the TWAMP-Modes 686 registry, we expect that new features will be assigned increasing 687 registry values that correspond to single bit positions, unless there 688 is a good reason to do otherwise (more complex encoding than single 689 bit positions may be used in the future, to access the 2^32 value 690 space). 692 6.2. Registry Contents 694 TWAMP Modes Registry is recommended to be augmented as follows: 696 Value Description Semantics Definition 697 0 Reserved 699 1 Unauthenticated RFC4656, Section 3.1 701 2 Authenticated RFC4656, Section 3.1 703 4 Encrypted RFC4656, Section 3.1 705 8 Unauth. TEST protocol, RFC5618, Section 3.1 (3) 706 Auth. CONTROL 707 16 Individual Session RFC????, Section 3.1 708 Control bit position (4) 709 -------------------------------------------------------- 710 xxx Reflect Octets this memo, section 3.1 711 Capability new bit position (X) 712 yyy Symmetrical Size this memo, section 3.1 713 Sender Test Packet Format new bit position (Y) 715 >>>IANA: change xxx, yyy, X, Y, and RFC???? to the assigned values 717 The suggested values are 718 X=5, xxx=32 720 Y=6, yyy=64 <<<< 722 7. Acknowledgements 724 The authors thank Steve Baillargeon, Walt Steverson, and Stina Ross 725 for helpful review and comments. 727 8. References 729 8.1. Normative References 731 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 732 Requirement Levels", BCP 14, RFC 2119, March 1997. 734 [RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. 735 Zekauskas, "A One-way Active Measurement Protocol 736 (OWAMP)", RFC 4656, September 2006. 738 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 739 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 740 May 2008. 742 [RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. 743 Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", 744 RFC 5357, October 2008. 746 [RFC5618] Morton, A. and K. Hedayat, "Mixed Security Mode for the 747 Two-Way Active Measurement Protocol (TWAMP)", RFC 5618, 748 August 2009. 750 8.2. Informative References 751 Authors' Addresses 753 Al Morton 754 AT&T Labs 755 200 Laurel Avenue South 756 Middletown,, NJ 07748 757 USA 759 Phone: +1 732 420 1571 760 Fax: +1 732 368 1192 761 Email: acmorton@att.com 762 URI: http://home.comcast.net/~acmacm/ 764 Len Ciavattone 765 AT&T Labs 766 200 Laurel Avenue South 767 Middletown,, NJ 07748 768 USA 770 Phone: +1 732 420 1239 771 Fax: 772 Email: lencia@att.com 773 URI: