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Ciavattone 4 Updates: 5357 (if approved) AT&T Labs 5 Intended status: Standards Track April 19, 2010 6 Expires: October 21, 2010 8 TWAMP Reflect Octets and Symmetrical Size Features 9 draft-ietf-ippm-twamp-reflect-octets-05 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 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 October 21, 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 . . . . . . . . . . . . . . . . . . . . . 10 80 4.1. Sender Behavior . . . . . . . . . . . . . . . . . . . . . 10 81 4.1.1. Packet Timings . . . . . . . . . . . . . . . . . . . . 10 82 4.1.2. Reflect Octets: Packet Formats and Contents . . . . . 10 83 4.1.3. Reflect Octets: Interaction with Padding Truncation . 12 84 4.1.4. Symmetrical Size: Session-Sender Packet Format . . . . 13 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 . . . . . . . . . . . . . . . . . . . . . 16 95 6.1. Registry Specification . . . . . . . . . . . . . . . . . . 17 96 6.2. Registry Management . . . . . . . . . . . . . . . . . . . 17 97 6.3. Experimental Numbers . . . . . . . . . . . . . . . . . . . 17 98 6.4. Registry Contents . . . . . . . . . . . . . . . . . . . . 17 99 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18 100 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 101 8.1. Normative References . . . . . . . . . . . . . . . . . . . 18 102 8.2. Informative References . . . . . . . . . . . . . . . . . . 19 103 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 105 1. Introduction 107 The IETF has completed its work on the core specification of TWAMP - 108 the Two-Way Active Measurement Protocol [RFC5357]. TWAMP is an 109 extension of the One-way Active Measurement Protocol, OWAMP 110 [RFC4656]. The TWAMP specification gathered wide review as it 111 approached completion, and the by-products were several 112 recommendations for new features in TWAMP. There are a growing 113 number TWAMP implementations at present, and wide-spread usage is 114 expected. There are even devices that are designed to test 115 implementations for protocol compliance. 117 This memo describes two closely-related features for TWAMP. 119 One is the OPTIONAL capability for the responder host to return a 120 limited number of unassigned (padding) octets to the Control-Client 121 or Session-Sender entities. With this capability, the Control-Client 122 or Session-Sender can embed octets of information it deems useful and 123 have the assurance that the corresponding reply/test packet will 124 contain that information when it is reflected and returned (by the 125 Server or Session-Reflector. 127 The memo also adds an OPTIONAL capability to assure that reflected 128 test packets are the same size in both directions of transmission. 129 This is accomplished by specifying a new TWAMP-Test Session-Sender 130 packet format. 132 This memo is an update to the TWAMP core protocol specified in 133 [RFC5357]. Measurement systems are not required to implement the 134 features described in this memo to claim compliance with [RFC5357]. 136 Throughout this memo, the bits marked MBZ (Must Be Zero) MUST be set 137 to zero by senders and MUST be ignored by receivers. Also, the HMAC 138 (Hashed Message Authentication Code) MUST be calculated as defined in 139 Section 3.2 of [RFC4656]. 141 2. Purpose and Scope 143 The purpose of this memo is to define two OPTIONAL closely-related 144 features for TWAMP [RFC5357]. The features enhance the TWAMP 145 responder's capabilities to perform simple operations on control and 146 test packets: the reflection of octets or padding and symmetrical 147 sizes of fields in the TWAMP-Test packets. Motivations include 148 permitting the controller host to tag packets with an index for 149 simplified identification, and/or assert that the same size test 150 packets will be used in each direction. 152 The scope of the memo is limited to specifications of the following 153 features: 155 o Reflect Octets: the capability of the Server/Session-Reflector to 156 reflect specific octets back to the Client/Session-Sender. 158 o Symmetrical Size: the capability to ensure that TWAMP-Test 159 protocol uses the same packet size in both directions through 160 support of a new TWAMP-Test Session-Sender test packet format in 161 both the Session-Sender and the Session-Reflector. Only the 162 Session-Sender test packet format is new. 164 This memo extends the modes of operation through assignment of two 165 new values in the Modes Field (see section 3.1 of[RFC4656] for the 166 format of the Server Greeting message), while retaining backward 167 compatibility with the core TWAMP [RFC5357] implementations. The two 168 new values correspond to the two features defined in this memo. 170 When the Server and Control-Client have agreed to use the Reflect 171 Octets mode during control connection setup, then the Control-Client, 172 the Server, the Session-Sender, and the Session-Reflector MUST all 173 conform to the requirements of that mode, as identified below. 175 When the Server and Control-Client have agreed to use the Symmetrical 176 Size mode during control connection setup, then the Control-Client, 177 the Server, the Session-Sender, and the Session-Reflector MUST all 178 conform to the requirements of that mode, as identified below. 180 3. TWAMP Control Extensions 182 TWAMP-Control protocol [RFC5357] uses the Modes Field to identify and 183 select specific communication capabilities, and this field is a 184 recognized extension mechanism. The following sections describe two 185 such extensions. 187 3.1. Connection Setup with New Features 189 TWAMP connection establishment follows the procedure defined in 190 section 3.1 of [RFC4656] and section 3.1 of [RFC5357]. The new 191 features require two new bit positions (and values) to identify the 192 ability of the Server/Session-Reflector to reflect specific octets 193 back to the Control-Client/Session-Sender, and to support the new 194 Session-Sender packet format in TWAMP-Test Protocol. With this added 195 feature, the complete set of TWAMP Modes Field bit positions and 196 values would be as follows: 198 Value Description Reference/Explanation 199 0 Reserved 200 1 Unauthenticated RFC4656, Section 3.1 201 2 Authenticated RFC4656, Section 3.1 202 4 Encrypted RFC4656, Section 3.1 203 8 Unauth. TEST protocol, RFC5681, Section 3.1 204 Encrypted CONTROL 205 16 Individual Session RFC????, Section 3.1 206 Control 207 -------------------------------------------------------- 208 xxx Reflect Octets new bit position (X) 209 Capability 210 yyy Symmetrical Size new bit position (Y) 211 Sender Test Packet Format 213 In the original OWAMP Modes Field, setting bit positions 0, 1 or 2 214 indicated the security mode of the Control protocol, and the Test 215 protocol inherited the same mode (see section 4 of [RFC4656]). In 216 [RFC5618], bit position 3 allows unauthenticated TWAMP Test protocol 217 to be used with encryption on the TWAMP-Control protocol in a mixed 218 mode of operation. 220 The Server sets one or both of the new bit positions (X and Y) in the 221 Modes Field of the Server Greeting message to indicate its 222 capabilities and willingness to operate in either of these modes (or 223 both) if desired. 225 >>>IANA: change xxx, yyy, X, Y, and RFC???? to the assigned values 226 <<< 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 Mode Field bit corresponding to each function in the 231 Setup Response message. With this and other extensions, the Control- 232 Client MAY set multiple Mode Field bits in the Setup Response 233 message. 235 3.2. Reflect Octets: Request-TW-Session Packet Format 237 The bits designated for the Reflect Octets feature in the Request-TW- 238 Session command are as shown in the packet format below. 240 0 1 2 3 241 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 1 242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 243 | 5 | MBZ | IPVN | Conf-Sender | Conf-Receiver | 244 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 245 | Number of Schedule Slots | 246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 247 . . 248 . ... Many fields (66 octets) not shown ... . 249 . . 250 . . 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 252 | Padding Length (4 octets) | 253 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 254 | Start Time, (8 octets) | 255 | | 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 | Timeout, (8 octets) | 258 | | 259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 260 | Type-P Descriptor | 261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 262 | Octets to be reflected | Length of padding to reflect | 263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 264 | MBZ (4 octets) | 265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 266 | | 267 | HMAC (16 octets) | 268 | | 269 | | 270 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 272 The "Padding Length" Field *continues* to specify the number of 273 padding octets that the Session-Sender will append to ALL TWAMP-Test 274 packets associated with this test session. See below for 275 considerations on the minimum length of the padding octets, following 276 the definitions of the two new fields that follow the Type-P 277 Descriptor. 279 Note that the number of padding octets appended to the Session- 280 Reflector's test packet depends on support for the RECOMMENDED 281 truncation process in TWAMP section 4.2.1 [RFC5357]. 283 The "Octets to be reflected" Field SHALL be 2 octets long, as shown 284 and contains the octets that the Server MUST reflect in the Accept 285 Session message as specified below. 287 The "Length of padding to reflect" Field SHALL be 2 octets long, and 288 contain an unsigned binary value in units of octets. This field 289 communicates the length of the padding in the TWAMP-Test Packet that 290 the Session-Sender expects to be reflected, and the length of octets 291 that the Session-Reflector SHALL return in include in its TWAMP-Test 292 packet format (see section 4.2). By including this length field in 293 the Request-TW-Session message, a Server is able to determine if it 294 can comply with a specific request to reflect padding in the TWAMP- 295 Test packets, and to arrange for the Session-Reflector processing in 296 advance. 298 The "Padding Length" SHOULD be >= 27 octets when specifying a test 299 session using the Unauthenticated TWAMP-Test mode, to allow for the 300 RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357]. 302 The "Padding Length" SHOULD be >= 56 octets when specifying a test 303 session using the Authenticated or Encrypted TWAMP-Test modes, to 304 allow for the RECOMMENDED truncation process in TWAMP section 4.2.1 305 [RFC5357]. 307 The "Padding Length" SHALL be > the "Length of padding to reflect" 308 when specifying a test session using the OPTIONAL Reflect Octets 309 mode. 311 In Unauthenticated TWAMP-Test mode, the "Padding Length" SHALL be >= 312 27 + "Length of padding to reflect" octets when specifying a test 313 session using BOTH the OPTIONAL Reflect Octets mode and the 314 RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357]. 316 In Authenticated or Encrypted TWAMP-Test modes, the "Padding Length" 317 SHALL be >= 56 + "Length of padding to reflect" octets when 318 specifying a test session using BOTH the OPTIONAL Reflect Octets mode 319 and the RECOMMENDED truncation process in TWAMP section 4.2.1 320 [RFC5357]. 322 3.3. Reflect Octets: Accept Session Packet Format 324 The bits designated for the Reflect Padding feature in the Accept 325 Session command are as shown in the packet format below. 327 0 1 2 3 328 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 1 329 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 330 | Accept | MBZ | Port | 331 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 332 | | 333 | SID (16 octets) | 334 | | 335 | | 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 | Reflected octets | Server octets | 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 339 | MBZ (8 octets) | 340 | | 341 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 342 | | 343 | HMAC (16 octets) | 344 | | 345 | | 346 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 348 The "Reflected octets" field SHALL contain the octets from the 349 Request-TW-Session "Octets to be reflected" Field, and be 2 octets 350 long, as shown. 352 The "Server octets" field SHALL contain information that the Server 353 intends to be returned in the TWAMP-Test packet padding to-be- 354 reflected Field, OR SHALL be zero, and be 2 octets long, as shown. 355 Although the Server determines the SID, this field is very long (16 356 octets) and does not normally appear in TWAMP-Test packets. 358 When supporting the RECOMMENDED truncation process in TWAMP section 359 4.2.1 [RFC5357], IF calculations on the Padding lengths reveal that 360 there are insufficient octets supplied to produce equal-length 361 Session-Sender and Session-Reflector test packets, then the Accept 362 Field MUST be set to 3 = some aspect of the request is not supported. 364 3.4. Additional considerations 366 The value of the Modes Field sent by the Server in the Server 367 Greeting message is the bit-wise OR of the mode values that it is 368 willing to support during this session. 370 With the publication of this memo as an RFC, the last 7 bit positions 371 of the Modes 32-bit Field are used. A Control-Client conforming to 372 this extension of [RFC5357] MAY ignore the values in the higher bits 373 of the Modes Field, or it MAY support other features that are 374 communicated in those bit positions. The other bits are available 375 for future protocol extensions. 377 4. Extended TWAMP Test 379 The TWAMP test protocol is similar to the OWAMP [RFC4656] test 380 protocol with the exception that the Session-Reflector transmits test 381 packets to the Session-Sender in response to each test packet it 382 receives. TWAMP section 4[RFC5357] defines two additional test 383 packet formats for packets transmitted by the Session-Reflector. The 384 appropriate format depends on the security mode chosen. The new 385 modes specified here utilize some of the padding octets within each 386 test packet format, or require truncation of those octets depending 387 on the security mode in use. 389 4.1. Sender Behavior 391 This section describes extensions to the behavior of the TWAMP 392 Session-Sender. 394 4.1.1. Packet Timings 396 The Send Schedule is not utilized in TWAMP, and this is unchanged in 397 this memo. 399 4.1.2. Reflect Octets: Packet Formats and Contents 401 The Session-Sender packet format and content follow the same 402 procedure and guidelines as defined in section 4.1.2 of [RFC4656] (as 403 indicated in section 4.1.2 of TWAMP [RFC5357]). 405 The Reflect octets mode re-designates the original TWAMP-Test (and 406 OWAMP-Test) Packet Padding Field (see section 4.1.2 of [RFC4656]), as 407 shown below for unauthenticated mode: 409 0 1 2 3 410 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 1 411 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 412 | Sequence Number | 413 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 414 | Timestamp | 415 | | 416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 417 | Error Estimate | | 418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 419 | | 420 | Packet Padding (to be reflected) | 421 . (length in octets specified in command) . 422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 423 . . 424 . Additional Packet Padding . 425 . . 426 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 428 The "Packet Padding (to be reflected)" Field SHALL correspond to the 429 length of octets specified in the Request-TW-Session "Length of 430 padding to reflect" Field to this test session. These are the octets 431 that the Session-Sender expects will be returned by the Session- 432 Reflector. 434 The length of the "Additional Packet Padding" Field is the difference 435 between two fields in the Request-TW-Session command, as follows: 437 "Additional Packet Padding", in octets = 439 "Padding Length" - "Length of padding to reflect" 441 One possible use of the first 4 octets of the "Packet Padding (to be 442 reflected)" Field is shown below: 444 0 1 2 3 445 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 1 446 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 447 | Server octets | 448 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 449 | Client octets | | 450 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 451 | Packet Padding (to be reflected) | 452 . (length in octets specified elsewhere) . 453 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 454 In this example, the "Client octets" and the "Server octets" fields 455 contain the same information that the Client and Server exchanged in 456 the Request-TW-Session and Accept-Session messages corresponding to 457 this specific test session. These octets would be reflected the same 458 as the rest of the "Packet Padding (to be reflected)" Field. 460 4.1.3. Reflect Octets: Interaction with Padding Truncation 462 When the Reflect Octets mode is selected, and the RECOMMENDED 463 truncation process in TWAMP section 4.2.1 [RFC5357] is supported, the 464 Session-Sender MUST anticipate a minimum padding required to achieve 465 equal size test packets in both directions. The amount of padding 466 needed to achieve symmetrical packet size depends on BOTH the 467 security mode (Unauthenticated/Authenticated/Encrypted) and whether 468 the Reflect Octets mode is selected simultaneously. 470 When using the RECOMMENDED truncation process in TWAMP section 4.2.1 471 [RFC5357] alone, the Session-Sender MUST append sufficient Packet 472 Padding octets to allow the same IP packet payload lengths to be used 473 in each direction of transmission (this is usually desirable). To 474 compensate for the Session-Reflector's larger test packet format, the 475 Session-Sender MUST append at least 27 octets of padding in 476 Unauthenticated mode, and at least 56 octets in Authenticated and 477 Encrypted modes. The sizes of TWAMP Test protocol packets and the 478 resulting truncated padding to achieve equal packet sizes in both 479 directions are shown in the table below: 481 +-------------------+----------------------+---------------------+ 482 | Octets in: | Unauthenticated Mode | Auth/Encrypted Mode | 483 +-------------------+----------------------+---------------------+ 484 | Reflector Header | 41 | 104 | 485 | Sender Header | 14 | 48 | 486 | Truncated Padding | 27 | 56 | 487 +-------------------+----------------------+---------------------+ 489 TWAMP-Test Padding Trucation 491 When using the Reflect Octets mode simultaneously with the 492 RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357], the 493 Session-Sender MUST append at least 27 octets of padding plus the 494 "Length of the padding to reflect" octets when operating in 495 Unauthenticated mode. The Session-Sender MUST append at least 56 496 octets of padding plus the "Length of the padding to reflect" octets 497 when operating in Authenticated and Encrypted modes. 499 4.1.4. Symmetrical Size: Session-Sender Packet Format 501 When the Symmetrical Size mode is selected, the Session-Sender SHALL 502 use the following TWAMP-Test Packet Format in Unauthenticated mode: 504 Unauthenticated Mode 505 0 1 2 3 506 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 1 507 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 508 | Sequence Number | 509 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 510 | Timestamp | 511 | | 512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 513 | Error Estimate | | 514 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 515 | | 516 | | 517 | MBZ (27 octets) | 518 | | 519 | | 520 | | 521 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 522 | | | 523 +-+-+-+-+-+-+-+-+ + 524 . . 525 . Packet Padding . 526 . . 527 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 529 This feature REQUIRES only a new Session-Sender test packet format, 530 the Session-Reflector test packet format is unchanged. 532 4.1.5. Symmetrical Size AND Reflect Octets: Session-Sender Packet 533 Format 535 When BOTH the Symmetrical Size mode and the Reflect Octets mode are 536 selected, the Session-Sender SHALL use the following TWAMP-Test 537 Packet Format in Unauthenticated mode: 539 Unauthenticated Mode 540 0 1 2 3 541 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 1 542 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 543 | Sequence Number | 544 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 545 | Timestamp | 546 | | 547 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 548 | Error Estimate | | 549 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 550 | | 551 | | 552 | MBZ (27 octets) | 553 | | 554 | | 555 | | 556 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 557 | | | 558 +-+-+-+-+-+-+-+-+ + 559 | Packet Padding (to be reflected) | 560 . (length in octets specified in command) . 561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 562 . . 563 . Additional Packet Padding . 564 . . 565 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 567 In this combined mode, the Packet Padding to be reflected follows the 568 27 MBZ octets. In Authenticated or Encrypted modes, the Packet 569 Padding to be reflected follows the 56 MBZ octets. 571 4.2. Reflector Behavior 573 The TWAMP Reflector follows the procedures and guidelines in section 574 4.2 of [RFC5357], with the following additional functions: 576 o Reflect Octets mode: Designated octets in the "Packet Padding (to 577 be reflected)" field of the Session-Sender's test packet MUST be 578 included in the Session-Reflector's test packet. 580 o Symmetrical Size mode: The Session-Reflector MUST operate using 581 the Session_Reflector Packet Format defined in section 4.1.4, 582 where the Padding Octets are separated from the information 583 fields. 585 4.2.1. Reflect Octets: Session-Reflector Packet Format and Contents 587 The Reflect Padding feature re-designates the packet padding field, 588 as shown below. When the Reflect Octets mode is selected, the 589 Session-Sender SHALL use the following TWAMP-Test Packet Format in 590 Unauthenticated mode: 592 0 1 2 3 593 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 1 594 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 595 | Sequence Number | 596 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 | Timestamp | 598 | | 599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 600 | Error Estimate | MBZ | 601 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 602 | Receive Timestamp | 603 | | 604 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 605 | Sender Sequence Number | 606 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 607 | Sender Timestamp | 608 | | 609 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 610 | Sender Error Estimate | MBZ | 611 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 612 | Sender TTL | Packet Padding (from Session-Sender) | 613 +-+-+-+-+-+-+-+-+ + 614 . . 615 + +-+-+-+-+-+-+-+-+ 616 | Packet Padding (from Session-Sender) | | 617 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 618 | | 619 | | 620 . Additional Packet Padding . 621 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 622 The "Packet Padding (from Session-Sender)" field MUST be the same 623 octets as the "Packet Padding (to be reflected)" field in the 624 Session-Sender's test packet, and therefore MUST conform to the 625 length specified in the Request-TW-Session message. 627 When simultaneously using the RECOMMENDED truncation process in TWAMP 628 section 4.2.1 [RFC5357] AND Reflect octets mode, the Session- 629 Reflector MUST reflect the designated octets from the Session- 630 Sender's test packet in the "Packet Padding (from Session-Sender)" 631 Field, and MAY re-use additional Packet Padding from the Session- 632 Sender. The Session-Reflector MUST truncate the padding such that 633 the highest number octets are discarded, and the test packet length 634 equals the Session-Sender's packet length. When using the 635 RECOMMENDED truncation process, the Session-Reflector MUST truncate 636 exactly 27 octets of padding in Unauthenticated mode, and exactly 56 637 octets in Authenticated and Encrypted modes. 639 The Session-Reflector MAY re-use the Sender's Packet Padding (since 640 the requirements for padding generation are the same for each). 642 4.2.2. Symmetrical Size: Session-Reflector Packet Format 644 When Symmetrical Size mode is selected, the Session-Sender packet 645 formats for unauthenticated and authenticated/encrypted modes are 646 identical to the core TWAMP specification, section 4.2.1 of 647 [RFC5357]. Thus, the Session-Reflector test packet format is 648 unchanged. 650 The Session-Reflector MUST construct its test packet using the 651 information in the Session-Sender's test packet. The length of the 652 Session-Reflector's test packet SHALL equal the length of the 653 Session-Sender's test packet. 655 4.2.3. Symmetrical Size AND Reflect Octets: Session-Sender Packet 656 Format 658 When BOTH the Symmetrical Size mode and the Reflect Octets mode are 659 selected, the Session-Reflector MUST operate using the 660 Session_Reflector Packet Format defined in section 4.1.5, where the 661 Padding Octets are separated from the information fields, and the 662 Padding to be Reflected field precedes the Additional Padding. 664 The Session-Reflector SHALL use the same TWAMP-Test Packet Format as 665 specified in section 4.2.1 above. 667 5. Security Considerations 669 These extended modes of operation do not appear to permit any new 670 attacks on hosts communicating with core TWAMP [RFC5357]. 672 The security considerations that apply to any active measurement of 673 live networks are relevant here as well. See [RFC4656] and 674 [RFC5357]. 676 6. IANA Considerations 678 This memo adds two modes to the IANA registry for the TWAMP Modes 679 Field, and describes behavior when the new modes are used. This 680 field is a recognized extension mechanism for TWAMP. 682 6.1. Registry Specification 684 IANA has created a TWAMP-Modes registry (as requested in [RFC5618]). 685 TWAMP-Modes are specified in TWAMP Server Greeting messages and 686 Set-up Response messages, as described in section 3.1 of [RFC5357], 687 consistent with section 3.1 of [RFC4656], and extended by this memo. 688 Modes are indicated by setting bits in the 32-bit Modes field that 689 correspond to values in the Modes registry. For the TWAMP-Modes 690 registry, we expect that new features will be assigned increasing 691 registry values that correspond to single bit positions, unless there 692 is a good reason to do otherwise (more complex encoding than single 693 bit positions may be used in the future, to access the 2^32 value 694 space). 696 6.2. Registry Management 698 This registry must be updated only by "IETF Consensus" as specified 699 in [RFC5226](an RFC documenting registry use that is approved by the 700 IESG). 702 6.3. Experimental Numbers 704 No experimental values are currently assigned for the Modes Registry. 706 6.4. Registry Contents 708 TWAMP Modes Registry is recommended to be augmented as follows: 710 Value Description Semantics Definition 711 0 Reserved 713 1 Unauthenticated RFC4656, Section 3.1 715 2 Authenticated RFC4656, Section 3.1 717 4 Encrypted RFC4656, Section 3.1 719 8 Unauth. TEST protocol, RFC5618, Section 3.1 (3) 720 Auth. CONTROL 721 16 Individual Session RFC????, Section 3.1 722 Control bit position (4) 723 -------------------------------------------------------- 724 xxx Reflect Octets this memo, section 3.1 725 Capability new bit position (X) 726 yyy Symmetrical Size this memo, section 3.1 727 Sender Test Packet Format new bit position (Y) 729 The suggested values are 731 X=5, xxx=32 733 Y=6, yyy=64 735 7. Acknowledgements 737 The authors thank Steve Baillargeon, Walt Steverson, and Stina Ross 738 for helpful review and comments. 740 8. References 742 8.1. Normative References 744 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 745 Requirement Levels", BCP 14, RFC 2119, March 1997. 747 [RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. 748 Zekauskas, "A One-way Active Measurement Protocol 749 (OWAMP)", RFC 4656, September 2006. 751 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 752 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 753 May 2008. 755 [RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. 756 Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", 757 RFC 5357, October 2008. 759 [RFC5618] Morton, A. and K. Hedayat, "Mixed Security Mode for the 760 Two-Way Active Measurement Protocol (TWAMP)", RFC 5618, 761 August 2009. 763 8.2. Informative References 765 Authors' Addresses 767 Al Morton 768 AT&T Labs 769 200 Laurel Avenue South 770 Middletown,, NJ 07748 771 USA 773 Phone: +1 732 420 1571 774 Fax: +1 732 368 1192 775 Email: acmorton@att.com 776 URI: http://home.comcast.net/~acmacm/ 778 Len Ciavattone 779 AT&T Labs 780 200 Laurel Avenue South 781 Middletown,, NJ 07748 782 USA 784 Phone: +1 732 420 1239 785 Fax: 786 Email: lencia@att.com 787 URI: