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Ciavattone 4 Updates: 5357 (if approved) AT&T Labs 5 Intended status: Standards Track February 28, 2010 6 Expires: September 1, 2010 8 TWAMP Reflect Octets and Symmetrical Size Features 9 draft-ietf-ippm-twamp-reflect-octets-04 11 Abstract 13 The IETF has completed its work on the core specification of TWAMP - 14 the Two-Way Active Measurement Protocol. This memo describes two 15 closely-related features for TWAMP: an optional capability where the 16 responder host returns some of the command octets or padding octets 17 to the controller, and an optional sender packet format that ensures 18 equal test packet sizes are used in 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 to IETF 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), its areas, and its working groups. Note that 33 other groups may also distribute working documents as Internet- 34 Drafts. 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 The list of current Internet-Drafts can be accessed at 42 http://www.ietf.org/ietf/1id-abstracts.txt. 44 The list of Internet-Draft Shadow Directories can be accessed at 45 http://www.ietf.org/shadow.html. 47 This Internet-Draft will expire on September 1, 2010. 49 Copyright Notice 51 Copyright (c) 2010 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (http://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the BSD License. 64 This document may contain material from IETF Documents or IETF 65 Contributions published or made publicly available before November 66 10, 2008. The person(s) controlling the copyright in some of this 67 material may not have granted the IETF Trust the right to allow 68 modifications of such material outside the IETF Standards Process. 69 Without obtaining an adequate license from the person(s) controlling 70 the copyright in such materials, this document may not be modified 71 outside the IETF Standards Process, and derivative works of it may 72 not be created outside the IETF Standards Process, except to format 73 it for publication as an RFC or to translate it into languages other 74 than English. 76 Table of Contents 78 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 79 2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 3 80 3. TWAMP Control Extensions . . . . . . . . . . . . . . . . . . . 4 81 3.1. Connection Setup with New Features . . . . . . . . . . . . 4 82 3.2. Reflect Octets: Request-TW-Session Packet Format . . . . . 5 83 3.3. Reflect Octets: Accept Session Packet Format . . . . . . . 7 84 3.4. Additional considerations . . . . . . . . . . . . . . . . 8 85 4. Extended TWAMP Test . . . . . . . . . . . . . . . . . . . . . 9 86 4.1. Sender Behavior . . . . . . . . . . . . . . . . . . . . . 9 87 4.1.1. Packet Timings . . . . . . . . . . . . . . . . . . . . 9 88 4.1.2. Reflect Octets: Packet Formats and Contents . . . . . 9 89 4.1.3. Reflect Octets: Interaction with Padding Truncation . 11 90 4.1.4. Symmetrical Size: Session-Sender Packet Format . . . . 12 91 4.1.5. Symmetrical Size AND Reflect Octets: 92 Session-Sender Packet Format . . . . . . . . . . . . . 12 93 4.2. Reflector Behavior . . . . . . . . . . . . . . . . . . . . 13 94 4.2.1. Reflect Octets: Session-Reflector Packet Format 95 and Contents . . . . . . . . . . . . . . . . . . . . . 14 96 4.2.2. Symmetrical Size: Session-Reflector Packet Format . . 15 97 4.2.3. Symmetrical Size AND Reflect Octets: 98 Session-Sender Packet Format . . . . . . . . . . . . . 15 99 5. Security Considerations . . . . . . . . . . . . . . . . . . . 15 100 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 101 6.1. Registry Specification . . . . . . . . . . . . . . . . . . 16 102 6.2. Registry Management . . . . . . . . . . . . . . . . . . . 16 103 6.3. Experimental Numbers . . . . . . . . . . . . . . . . . . . 16 104 6.4. Registry Contents . . . . . . . . . . . . . . . . . . . . 16 105 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 106 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 107 8.1. Normative References . . . . . . . . . . . . . . . . . . . 17 108 8.2. Informative References . . . . . . . . . . . . . . . . . . 17 109 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 111 1. Introduction 113 The IETF has completed its work on the core specification of TWAMP - 114 the Two-Way Active Measurement Protocol [RFC5357]. TWAMP is an 115 extension of the One-way Active Measurement Protocol, OWAMP 116 [RFC4656]. The TWAMP specification gathered wide review as it 117 approached completion, and the by-products were several 118 recommendations for new features in TWAMP. There are a growing 119 number TWAMP implementations at present, and wide-spread usage is 120 expected. There are even devices that are designed to test 121 implementations for protocol compliance. 123 This memo describes two closely-related features for TWAMP. 125 One is the OPTIONAL capability for the responder host to return a 126 limited number of unassigned (padding) octets to the Control-Client 127 or Session-Sender entities. With this capability, the Control-Client 128 or Session-Sender can embed octets of information it deems useful and 129 have the assurance that the corresponding reply/test packet will 130 contain that information when it is reflected and returned (by the 131 Server or Session-Reflector. 133 The memo also adds an OPTIONAL capability to assure that reflected 134 test packets are the same size in both directions of transmission. 135 This is accomplished by specifying a new TWAMP-Test Session-Sender 136 packet format. 138 This memo and TWAMP is intended to be an update to [RFC5357] when 139 published. It is not required to implement the features described in 140 this memo to claim compliance with [RFC5357]. 142 2. Purpose and Scope 144 The purpose of this memo is to define two OPTIONAL closely-related 145 features for TWAMP [RFC5357]. The features enhance the TWAMP 146 responder's capabilities to perform simple operations on control and 147 test packets: the reflection of octets or padding and symmetrical 148 sizes of fields in the TWAMP-Test packets. Motivations include 149 permitting the controller host to tag packets with an index for 150 simplified identification, and/or assert that the same size test 151 packets will be used in each direction. 153 The scope of the memo is currently limited to specifications of the 154 following features: 156 o Reflect Octets: the capability of the Server/Session-Reflector to 157 reflect specific octets back to the Client/Session-Sender. 159 o Symmetrical Size: the capability to ensure that TWAMP-Test 160 protocol uses the same packet size in both directions through 161 support of a new TWAMP-Test Session-Sender test packet format in 162 both the Session-Sender and the Session-Reflector. Only the 163 Session-Sender test packet format is new. 165 Extension of the modes of operation through assignment of two new 166 values in the Mode Field (see section 3.1 of[RFC4656] for the format 167 of the Server Greeting message), while retaining backward 168 compatibility with the core TWAMP [RFC5357] implementations. The two 169 new values correspond to the two features defined in this memo. 171 When the Server and Control-Client have agreed to use the Reflect 172 Octets 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 When the Server and Control-Client have agreed to use the Symmetrical 177 Size mode during control connection setup, then the Control-Client, 178 the Server, the Session-Sender, and the Session-Reflector MUST all 179 conform to the requirements of that mode, as identified below. 181 3. TWAMP Control Extensions 183 TWAMP-Control protocol [RFC5357] uses the Modes Field to identify and 184 select specific communication capabilities, and this field is a 185 recognized extension mechanism. The following sections describe two 186 such extensions. 188 3.1. Connection Setup with New Features 190 TWAMP connection establishment follows the procedure defined in 191 section 3.1 of [RFC4656] and section 3.1 of [RFC5357]. The new 192 features require two new bit positions (and values) to identify the 193 ability of the Server/Session-Reflector to reflect specific octets 194 back to the Control-Client/Session-Sender, and to support the new 195 Session-Sender packet format in TWAMP-Test Protocol. With this added 196 feature, the complete set of TWAMP Modes Field bit positions and 197 values would be as follows: 199 Value Description Reference/Explanation 200 0 Reserved 201 1 Unauthenticated RFC4656, Section 3.1 202 2 Authenticated RFC4656, Section 3.1 203 4 Encrypted RFC4656, Section 3.1 204 8 Unauth. TEST protocol, RFC5681, Section 3.1 205 Encrypted CONTROL 206 zzz Individual Session RFC????, Section 3.1 207 Control 208 -------------------------------------------------------- 209 xxx Reflect Octets new bit position (X) 210 Capability 211 yyy Symmetrical Size new bit position (Y) 212 Sender Test Packet Format 214 In the original OWAMP Modes Field, setting bit positions 0, 1 or 2 215 indicated the security mode of the Control protocol, and the Test 216 protocol inherited the same mode (see section 4 of [RFC4656]). In 217 [RFC5618], bit position 3 allows unauthenticated TWAMP Test protocol 218 to be used with encryption on the TWAMP-Control protocol in a mixed 219 mode of operation. 221 The Server sets one or both of the new bit positions (X and Y) in the 222 Modes Field of the Server Greeting message to indicate its 223 capabilities and willingness to operate in either of these modes (or 224 both) if desired. 226 >>>IANA: change xxx, yyy, X, and Y to the assigned values <<< 228 If the Control-Client intends to operate all test sessions invoked 229 with this control connection using one or both of the new modes, it 230 MUST set the Modes Field bit corresponding to that function in the 231 Setup Response message. 233 3.2. Reflect Octets: Request-TW-Session Packet Format 235 The bits designated for the Reflect Octets feature in the Request-TW- 236 Session command are as shown in the packet format below. 238 0 1 2 3 239 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 1 240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 241 | 5 | MBZ | IPVN | Conf-Sender | Conf-Receiver | 242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 243 | Number of Schedule Slots | 244 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 245 . . 246 . ... Many fields (66 octets) not shown ... . 247 . . 248 . . 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 | Padding Length (4 octets) | 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 252 | Start Time, (8 octets) | 253 | | 254 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 255 | Timeout, (8 octets) | 256 | | 257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 | Type-P Descriptor | 259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 260 | Octets to be reflected | Length of padding to reflect | 261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 262 | MBZ (4 octets) | 263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 264 | | 265 | HMAC (16 octets) | 266 | | 267 | | 268 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 270 The "Padding Length" Field *continues* to specify the number of 271 padding octets that the Session-Sender will append to ALL TWAMP-Test 272 packets associated with this test session. See below for 273 considerations on the minimum length of the padding octets, following 274 the definitions of the two new fields that follow the Type-P 275 Descriptor. 277 Note that the number of padding octets appended to the Session- 278 Reflector's test packet depends on support for the RECOMMENDED 279 truncation process in TWAMP section 4.2.1 [RFC5357]. 281 The "Octets to be reflected" Field SHALL be 2 octets long, as shown 282 and contains the octets that the Server MUST reflect in the Accept 283 Session message as specified below. 285 The "Length of padding to reflect" Field SHALL be 2 octets long, and 286 contain an unsigned binary value in units of octets. This field 287 communicates the length of the padding in the TWAMP-Test Packet that 288 the Session-Sender expects to be reflected, and the length of octets 289 that the Session-Reflector SHALL return in include in its TWAMP-Test 290 packet format (see section 4.2). By including this length field in 291 the Request-TW-Session message, a Server is able to determine if it 292 can comply with a specific request to reflect padding in the TWAMP- 293 Test packets, and to arrange for the Session-Reflector processing in 294 advance. 296 The "Padding Length" SHOULD be >= 27 octets when specifying a test 297 session using the Unauthenticated TWAMP-Test mode, to allow for the 298 RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357]. 300 The "Padding Length" SHOULD be >= 56 octets when specifying a test 301 session using the Authenticated or Encrypted TWAMP-Test modes, to 302 allow for the RECOMMENDED truncation process in TWAMP section 4.2.1 303 [RFC5357]. 305 The "Padding Length" SHALL be > the "Length of padding to reflect" 306 when specifying a test session using the OPTIONAL Reflect Octets 307 mode. 309 The "Padding Length" SHALL be >= 27 + "Length of padding to reflect" 310 octets when specifying a test session using BOTH the OPTIONAL Reflect 311 Octets mode and the RECOMMENDED truncation process in TWAMP section 312 4.2.1 [RFC5357]. 314 The "Padding Length" SHALL be >= 56 + "Length of padding to reflect" 315 octets when specifying a test session using BOTH the OPTIONAL Reflect 316 Octets mode and the RECOMMENDED truncation process in TWAMP section 317 4.2.1 [RFC5357]. 319 3.3. Reflect Octets: Accept Session Packet Format 321 The bits designated for the Reflect Padding feature in the Accept 322 Session command are as shown in the packet format below. 324 0 1 2 3 325 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 1 326 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 327 | Accept | MBZ | Port | 328 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 329 | | 330 | SID (16 octets) | 331 | | 332 | | 333 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 334 | Reflected octets | Server octets | 335 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 336 | MBZ (8 octets) | 337 | | 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 339 | | 340 | HMAC (16 octets) | 341 | | 342 | | 343 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 345 The "Reflected octets" field SHALL contain the octets from the 346 Request-TW-Session "Octets to be reflected" Field, and be 2 octets 347 long, as shown. 349 The "Server octets" field SHALL contain information that the Server 350 intends to be returned in the TWAMP-Test packet padding to-be- 351 reflected Field, OR SHALL be zero, and be 2 octets long, as shown. 352 Although the Server determines the SID, this field is very long (16 353 octets) and does not normally appear in TWAMP-Test packets. 355 When supporting the RECOMMENDED truncation process in TWAMP section 356 4.2.1 [RFC5357], IF calculations on the Padding lengths reveal that 357 there are insufficient octets supplied to produce equal-length 358 Session-Sender and Session-Reflector test packets, then the Accept 359 Field MUST be set to 3 = some aspect of the request is not supported. 361 3.4. Additional considerations 363 The value of the Modes Field sent by the Server in the Server 364 Greeting message is the bit-wise OR of the mode values that it is 365 willing to support during this session. 367 With the publication of this memo as an RFC, the last 7 bit positions 368 of the Modes 32-bit Field are used. A Control-Client conforming to 369 this extension of [RFC5357] MAY ignore the values in the higher bits 370 of the Modes Field, or it MAY support other features that are 371 communicated in those bit positions. The other bits are available 372 for future protocol extensions. 374 4. Extended TWAMP Test 376 The TWAMP test protocol is similar to the OWAMP [RFC4656] test 377 protocol with the exception that the Session-Reflector transmits test 378 packets to the Session-Sender in response to each test packet it 379 receives. TWAMP section 4[RFC5357] defines two additional test 380 packet formats for packets transmitted by the Session-Reflector. The 381 appropriate format depends on the security mode chosen. The new 382 modes specified here utilize some of the padding octets within each 383 test packet format, or require truncation of those octets depending 384 on the security mode in use. 386 4.1. Sender Behavior 388 This section describes extensions to the behavior of the TWAMP 389 Session-Sender. 391 4.1.1. Packet Timings 393 The Send Schedule is not utilized in TWAMP, and this is unchanged in 394 this memo. 396 4.1.2. Reflect Octets: Packet Formats and Contents 398 The Session-Sender packet format and content follow the same 399 procedure and guidelines as defined in section 4.1.2 of [RFC4656] (as 400 indicated in section 4.1.2 of TWAMP [RFC5357]). 402 The Reflect octets mode re-designates the original TWAMP-Test (and 403 OWAMP-Test) Packet Padding Field (see section 4.1.2 of [RFC4656]), as 404 shown below for unauthenticated mode: 406 0 1 2 3 407 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 1 408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 409 | Sequence Number | 410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 411 | Timestamp | 412 | | 413 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 414 | Error Estimate | | 415 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 416 | | 417 | Packet Padding (to be reflected) | 418 . (length in octets specified in command) . 419 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 420 . . 421 . Additional Packet Padding . 422 . . 423 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 425 The "Packet Padding (to be reflected)" Field SHALL correspond to the 426 length of octets specified in the Request-TW-Session "Length of 427 padding to reflect" Field to this test session. These are the octets 428 that the Session-Sender expects will be returned by the Session- 429 Reflector. 431 The length of the "Additional Packet Padding" Field is the difference 432 between two fields in the Request-TW-Session command, as follows: 434 "Additional Packet Padding", in octets = 436 "Padding Length" - "Length of padding to reflect" 438 One possible use of the first 4 octets of the "Packet Padding (to be 439 reflected)" Field is shown below: 441 0 1 2 3 442 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 1 443 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 444 | Server octets | 445 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 446 | Client octets | | 447 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 448 | Packet Padding (to be reflected) | 449 . (length in octets specified elsewhere) . 450 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 451 In this example, the "Client octets" and the "Server octets" fields 452 contain the same information that the Client and Server exchanged in 453 the Request-TW-Session and Accept-Session messages corresponding to 454 this specific test session. These octets would be reflected the same 455 as the rest of the "Packet Padding (to be reflected)" Field. 457 4.1.3. Reflect Octets: Interaction with Padding Truncation 459 When the Reflect Octets mode is selected, and the RECOMMENDED 460 truncation process in TWAMP section 4.2.1 [RFC5357] is supported, the 461 Session-Sender MUST anticipate a minimum padding required to achieve 462 equal size test packets in both directions. The amount of padding 463 needed to achieve symmetrical packet size depends on BOTH the 464 security mode (Unauthenticated/Authenticated/Encrypted) and whether 465 the Reflect Octets mode is selected simultaneously. 467 When using the RECOMMENDED truncation process in TWAMP section 4.2.1 468 [RFC5357] alone, the Session-Sender MUST append sufficient Packet 469 Padding octets to allow the same IP packet payload lengths to be used 470 in each direction of transmission (this is usually desirable). To 471 compensate for the Session-Reflector's larger test packet format, the 472 Session-Sender MUST append at least 27 octets of padding in 473 Unauthenticated mode, and at least 56 octets in Authenticated and 474 Encrypted modes. The sizes of TWAMP Test protocol packets and the 475 resulting truncated padding to achieve equal packet sizes in both 476 directions are shown in the table below: 478 +-------------------+----------------------+---------------------+ 479 | Octets in: | Unauthenticated Mode | Auth/Encrypted Mode | 480 +-------------------+----------------------+---------------------+ 481 | Reflector Header | 41 | 104 | 482 | Sender Header | 14 | 48 | 483 | Truncated Padding | 27 | 56 | 484 +-------------------+----------------------+---------------------+ 486 TWAMP-Test Padding Trucation 488 When using the Reflect Octets mode simultaneously with the 489 RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357], the 490 Session-Sender MUST append at least 27 octets of padding plus the 491 "Length of the padding to reflect" octets when operating in 492 Unauthenticated mode. The Session-Sender MUST append at least 56 493 octets of padding plus the "Length of the padding to reflect" octets 494 when operating in Authenticated and Encrypted modes. 496 4.1.4. Symmetrical Size: Session-Sender Packet Format 498 When the Symmetrical Size mode is selected, the Session-Sender SHALL 499 use the following TWAMP-Test Packet Format in Unauthenticated mode: 501 Unauthenticated Mode 502 0 1 2 3 503 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 1 504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 | Sequence Number | 506 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 507 | Timestamp | 508 | | 509 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 510 | Error Estimate | | 511 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 512 | | 513 | | 514 | MBZ (27 octets) | 515 | | 516 | | 517 | | 518 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 519 | | | 520 +-+-+-+-+-+-+-+-+ + 521 . . 522 . Packet Padding . 523 . . 524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 526 This feature REQUIRES only a new Session-Sender test packet format, 527 the Session-Reflector test packet format is unchanged. 529 4.1.5. Symmetrical Size AND Reflect Octets: Session-Sender Packet 530 Format 532 When BOTH the Symmetrical Size mode and the Reflect Octets mode are 533 selected, the Session-Sender SHALL use the following TWAMP-Test 534 Packet Format in Unauthenticated mode: 536 Unauthenticated Mode 537 0 1 2 3 538 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 1 539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 540 | Sequence Number | 541 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 542 | Timestamp | 543 | | 544 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 545 | Error Estimate | | 546 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 547 | | 548 | | 549 | MBZ (27 octets) | 550 | | 551 | | 552 | | 553 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 554 | | | 555 +-+-+-+-+-+-+-+-+ + 556 | Packet Padding (to be reflected) | 557 . (length in octets specified in command) . 558 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 559 . . 560 . Additional Packet Padding . 561 . . 562 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 564 In this combined mode, the Packet Padding to be reflected follows the 565 27 MBZ octets. In Authenticated or Encrypted modes, the Packet 566 Padding to be reflected follows the 56 MBZ octets. 568 4.2. Reflector Behavior 570 The TWAMP Reflector follows the procedures and guidelines in section 571 4.2 of [RFC5357], with the following additional functions: 573 o Reflect Octets mode: Designated octets in the "Packet Padding (to 574 be reflected)" field of the Session-Sender's test packet MUST be 575 included in the Session-Reflector's test packet. 577 o Symmetrical Size mode: The Session-Reflector MUST operate using 578 the Session_Reflector Packet Format defined in section 4.1.4, 579 where the Padding Octets are separated from the information 580 fields. 582 4.2.1. Reflect Octets: Session-Reflector Packet Format and Contents 584 The Reflect Padding feature re-designates the packet padding field, 585 as shown below. When the Reflect Octets mode is selected, the 586 Session-Sender SHALL use the following TWAMP-Test Packet Format in 587 Unauthenticated mode: 589 0 1 2 3 590 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 1 591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 592 | Sequence Number | 593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 594 | Timestamp | 595 | | 596 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 | Error Estimate | MBZ | 598 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 599 | Receive Timestamp | 600 | | 601 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 602 | Sender Sequence Number | 603 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 604 | Sender Timestamp | 605 | | 606 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 607 | Sender Error Estimate | MBZ | 608 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 609 | Sender TTL | Packet Padding (from Session-Sender) | 610 +-+-+-+-+-+-+-+-+ + 611 . . 612 + +-+-+-+-+-+-+-+-+ 613 | Packet Padding (from Session-Sender) | | 614 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 615 | | 616 | | 617 . Additional Packet Padding . 618 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 619 The "Packet Padding (from Session-Sender)" field MUST be the same 620 octets as the "Packet Padding (to be reflected)" field in the 621 Session-Sender's test packet, and therefore MUST conform to the 622 length specified in the Request-TW-Session message. 624 When simultaneously using the RECOMMENDED truncation process in TWAMP 625 section 4.2.1 [RFC5357] AND Reflect octets mode, the Session- 626 Reflector MUST reflect the designated octets from the Session- 627 Sender's test packet in the "Packet Padding (from Session-Sender)" 628 Field, and MAY re-use additional Packet Padding from the Session- 629 Sender. The Session-Reflector MUST truncate the padding such that 630 the highest number octets are discarded, and the test packet length 631 equals the Session-Sender's packet length. When using the 632 RECOMMENDED truncation process, the Session-Reflector MUST truncate 633 exactly 27 octets of padding in Unauthenticated mode, and exactly 56 634 octets in Authenticated and Encrypted modes. 636 The Session-Reflector MAY re-use the Sender's Packet Padding (since 637 the requirements for padding generation are the same for each). 639 4.2.2. Symmetrical Size: Session-Reflector Packet Format 641 When Symmetrical Size mode is selected, the Session-Sender packet 642 formats for unauthenticated and authenticated/encrypted modes are 643 identical to the core TWAMP specification, section 4.2.1 of 644 [RFC5357]. Thus, the Session-Reflector test packet format is 645 unchanged. 647 The Session-Reflector MUST construct its test packet using the 648 information in the Session-Sender's test packet. The length of the 649 Session-Reflector's test packet SHALL equal the length of the 650 Session-Sender's test packet. 652 4.2.3. Symmetrical Size AND Reflect Octets: Session-Sender Packet 653 Format 655 When BOTH the Symmetrical Size mode and the Reflect Octets mode are 656 selected, the Session-Reflector MUST operate using the 657 Session_Reflector Packet Format defined in section 4.1.5, where the 658 Padding Octets are separated from the information fields, and the 659 Padding to be Reflected field precedes the Additional Padding. 661 The Session-Reflector SHALL use the same TWAMP-Test Packet Format as 662 specified in section 4.2.1 above. 664 5. Security Considerations 666 These extended modes of operation do not appear to permit any new 667 attacks on hosts communicating with core TWAMP [RFC5357]. 669 The security considerations that apply to any active measurement of 670 live networks are relevant here as well. See [RFC4656] and 671 [RFC5357]. 673 6. IANA Considerations 675 This memo adds two modes to the IANA registry for the TWAMP Modes 676 Field, and describes behavior when the new modes are used. This 677 field is a recognized extension mechanism for TWAMP. 679 6.1. Registry Specification 681 IANA has created a TWAMP-Modes registry (as requested in [RFC5618]). 682 TWAMP-Modes are specified in TWAMP Server Greeting messages and 683 Set-up Response messages, as described in section 3.1 of [RFC5357], 684 consistent with section 3.1 of [RFC4656], and extended by this memo. 685 Modes are indicated by setting bits in the 32-bit Modes field. Thus, 686 this registry can contain a total of 32 possible values. 688 6.2. Registry Management 690 This registry must be updated only by "IETF Consensus" as specified 691 in [RFC5226](an RFC documenting registry use that is approved by the 692 IESG). 694 6.3. Experimental Numbers 696 No experimental values are currently assigned for the Modes Registry. 698 6.4. Registry Contents 700 TWAMP Modes Registry is recommended to be augmented as follows: 702 Value Description Semantics Definition 703 0 Reserved 705 1 Unauthenticated RFC4656, Section 3.1 707 2 Authenticated RFC4656, Section 3.1 709 4 Encrypted RFC4656, Section 3.1 711 8 Unauth. TEST protocol, RFC5618, Section 3.1 (3) 712 Auth. CONTROL 713 -------------------------------------------------------- 714 xxx Reflect Octets this memo, section 3.1 715 Capability new bit position (X) 716 yyy Symmetrical Size this memo, section 3.1 717 Sender Test Packet Format new bit position (Y) 719 The suggested values are 721 X=5, xxx=32 722 Y=6, yyy=64 724 7. Acknowledgements 726 The authors would like to thank Walt Steverson and Stina Ross for 727 helpful review and comments. 729 8. References 731 8.1. Normative References 733 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 734 Requirement Levels", BCP 14, RFC 2119, March 1997. 736 [RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. 737 Zekauskas, "A One-way Active Measurement Protocol 738 (OWAMP)", RFC 4656, September 2006. 740 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 741 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 742 May 2008. 744 [RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. 745 Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", 746 RFC 5357, October 2008. 748 [RFC5618] Morton, A. and K. Hedayat, "Mixed Security Mode for the 749 Two-Way Active Measurement Protocol (TWAMP)", RFC 5618, 750 August 2009. 752 8.2. Informative References 754 Authors' Addresses 756 Al Morton 757 AT&T Labs 758 200 Laurel Avenue South 759 Middletown,, NJ 07748 760 USA 762 Phone: +1 732 420 1571 763 Fax: +1 732 368 1192 764 Email: acmorton@att.com 765 URI: http://home.comcast.net/~acmacm/ 766 Len Ciavattone 767 AT&T Labs 768 200 Laurel Avenue South 769 Middletown,, NJ 07748 770 USA 772 Phone: +1 732 420 1239 773 Fax: 774 Email: lencia@att.com 775 URI: