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Ciavattone 4 Intended status: Standards Track AT&T Labs 5 Expires: April 25, 2010 October 22, 2009 7 TWAMP Reflect Octets and Symmetrical Size Features 8 draft-ietf-ippm-twamp-reflect-octets-03 10 Status of this Memo 12 This Internet-Draft is submitted to IETF in full conformance with the 13 provisions of BCP 78 and BCP 79. This document may contain material 14 from IETF Documents or IETF Contributions published or made publicly 15 available before November 10, 2008. The person(s) controlling the 16 copyright in some of this material may not have granted the IETF 17 Trust the right to allow modifications of such material outside the 18 IETF Standards Process. Without obtaining an adequate license from 19 the person(s) controlling the copyright in such materials, this 20 document may not be modified outside the IETF Standards Process, and 21 derivative works of it may not be created outside the IETF Standards 22 Process, except to format it for publication as an RFC or to 23 translate it into languages other than English. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF), its areas, and its working groups. Note that 27 other groups may also distribute working documents as Internet- 28 Drafts. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 The list of current Internet-Drafts can be accessed at 36 http://www.ietf.org/ietf/1id-abstracts.txt. 38 The list of Internet-Draft Shadow Directories can be accessed at 39 http://www.ietf.org/shadow.html. 41 This Internet-Draft will expire on April 25, 2010. 43 Copyright Notice 45 Copyright (c) 2009 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 in effect on the date of 50 publication of this document (http://trustee.ietf.org/license-info). 51 Please review these documents carefully, as they describe your rights 52 and restrictions with respect to this document. 54 Abstract 56 The IETF has completed its work on the core specification of TWAMP - 57 the Two-Way Active Measurement Protocol. This memo describes two 58 closely-related features for TWAMP: an optional capability where the 59 responder host returns some of the command octets or padding octets 60 to the controller, a new sender packet format that ensures equal test 61 packet sizes are used in both directions. 63 Requirements Language 65 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 66 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 67 document are to be interpreted as described in RFC 2119 [RFC2119]. 69 Table of Contents 71 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 72 2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 4 73 3. TWAMP Control Extensions . . . . . . . . . . . . . . . . . . . 5 74 3.1. Connection Setup with New Features . . . . . . . . . . . . 5 75 3.2. Reflect Octets: Request-TW-Session Packet Format . . . . . 6 76 3.3. Reflect Octets: Accept Session Packet Format . . . . . . . 8 77 3.4. Additional considerations . . . . . . . . . . . . . . . . 9 78 4. Extended TWAMP Test . . . . . . . . . . . . . . . . . . . . . 10 79 4.1. Sender Behavior . . . . . . . . . . . . . . . . . . . . . 10 80 4.1.1. Packet Timings . . . . . . . . . . . . . . . . . . . . 10 81 4.1.2. Reflect Octets: Packet Formats and Contents . . . . . 10 82 4.1.3. Reflect Octets: Interaction with Padding Truncation . 12 83 4.1.4. Symmetrical Size: Session-Sender Packet Format . . . . 13 84 4.1.5. Symmetrical Size AND Reflect Octets: 85 Session-Sender Packet Format . . . . . . . . . . . . . 13 86 4.2. Reflector Behavior . . . . . . . . . . . . . . . . . . . . 14 87 4.2.1. Reflect Octets: Session-Reflector Packet Format 88 and Contents . . . . . . . . . . . . . . . . . . . . . 15 89 4.2.2. Symmetrical Size: Session-Reflector Packet Format . . 16 90 4.2.3. Symmetrical Size AND Reflect Octets: 91 Session-Sender Packet Format . . . . . . . . . . . . . 16 92 5. Security Considerations . . . . . . . . . . . . . . . . . . . 16 93 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 94 6.1. Registry Specification . . . . . . . . . . . . . . . . . . 17 95 6.2. Registry Management . . . . . . . . . . . . . . . . . . . 17 96 6.3. Experimental Numbers . . . . . . . . . . . . . . . . . . . 17 97 6.4. Registry Contents . . . . . . . . . . . . . . . . . . . . 17 98 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18 99 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 100 8.1. Normative References . . . . . . . . . . . . . . . . . . . 18 101 8.2. Informative References . . . . . . . . . . . . . . . . . . 18 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 104 1. Introduction 106 The IETF has completed its work on the core specification of TWAMP - 107 the Two-Way Active Measurement Protocol [RFC5357]. TWAMP is an 108 extension of the One-way Active Measurement Protocol, OWAMP 109 [RFC4656]. The TWAMP specification gathered wide review as it 110 approached completion, and the by-products were several 111 recommendations for new features in TWAMP. There are a growing 112 number TWAMP implementations at present, and wide-spread usage is 113 expected. There are even devices that are designed to test 114 implementations for protocol compliance. 116 This memo describes two closely-related features for TWAMP. 118 One is the OPTIONAL capability for the responder host to return a 119 limited number of unassigned (padding) octets to the Control-Client 120 or Session-Sender entities. With this capability, the Control-Client 121 or Session-Sender can embed octets of information it deems useful and 122 have the assurance that the corresponding reply/test packet will 123 contain that information when it is reflected and returned (by the 124 Server or Session-Reflector. 126 The memo also adds an OPTIONAL capability to assure that reflected 127 test packets are the same size in both directions of transmission. 128 This is accomplished by specifying a new TWAMP-Test Session-Sender 129 packet format. 131 The relationship between this memo and TWAMP is intended to be an 132 update to [RFC5357] when published. 134 2. Purpose and Scope 136 The purpose of this memo is to define two new closely-related 137 features for TWAMP [RFC5357]. The features enhance the TWAMP 138 responder's capabilities to perform simple operations on control and 139 test packets: the reflection of octets or padding and symmetrical 140 sizes of fields in the TWAMP-Test packets. Motivations include 141 permitting the controller host to tag packets with an index for 142 simplified identification, and/or assert that the same size test 143 packets will be used in each direction. 145 The scope of the memo is currently limited to specifications of the 146 following features: 148 o Reflect Octets: the capability of the Server/Session-Reflector to 149 reflect specific octets back to the Client/Session-Sender. 151 o Symmetrical Size: the capability to ensure that TWAMP-Test 152 protocol uses the same packet size in both directions through 153 support of a new TWAMP-Test Session-Sender test packet format in 154 both the Session-Sender and the Session-Reflector. 156 Extension of the modes of operation through assignment of two new 157 values in the Mode Field (see section 3.1 of[RFC4656] for the format 158 of the Server Greeting message), while retaining backward 159 compatibility with the core TWAMP [RFC5357] implementations. The two 160 new values correspond to the two features defined in this memo. 162 When the Server and Control-Client have agreed to use the Reflect 163 Octets mode during control connection setup, then the Control-Client, 164 the Server, the Session-Sender, and the Session-Reflector MUST all 165 conform to the requirements of that mode, as identified below. 167 When the Server and Control-Client have agreed to use the Symmetrical 168 Size mode during control connection setup, then the Control-Client, 169 the Server, the Session-Sender, and the Session-Reflector MUST all 170 conform to the requirements of that mode, as identified below. 172 3. TWAMP Control Extensions 174 TWAMP-Control protocol [RFC5357] uses the Modes Field to identify and 175 select specific communication capabilities, and this field is a 176 recognized extension mechanism. The following sections describe two 177 such extensions. 179 3.1. Connection Setup with New Features 181 TWAMP connection establishment follows the procedure defined in 182 section 3.1 of [RFC4656] and section 3.1 of [RFC5357]. The new 183 features require two new bit positions (and values) to identify the 184 ability of the Server/Session-Reflector to reflect specific octets 185 back to the Control-Client/Session-Sender, and to support the new 186 Session-Sender packet format in TWAMP-Test Protocol. With this added 187 feature, the complete set of TWAMP Modes Field bit positions and 188 values would be as follows: 190 Value Description Reference/Explanation 191 0 Reserved 192 1 Unauthenticated RFC4656, Section 3.1 193 2 Authenticated RFC4656, Section 3.1 194 4 Encrypted RFC4656, Section 3.1 195 8 Unauth. TEST protocol, RFC5681, Section 3.1 196 Encrypted CONTROL 197 -------------------------------------------------------- 198 xxx Reflect Octets new bit position (X) 199 Capability 200 yyy Symmetrical Size new bit position (Y) 201 Sender Test Packet Format 203 In the original OWAMP Modes Field, setting bit positions 0, 1 or 2 204 indicated the security mode of the Control protocol, and the Test 205 protocol inherited the same mode (see section 4 of [RFC4656]). In 206 [RFC5618], bit position 3 allows unauthenticated TWAMP Test protocol 207 to be used with encryption on the TWAMP-Control protocol in a mixed 208 mode of operation. 210 The Server sets one or both of the new bit positions (X and Y) in the 211 Modes Field of the Server Greeting message to indicate its 212 capabilities and willingness to operate in either of these modes (or 213 both) if desired. 215 >>>IANA: change xxx, yyy, X, and Y to the assigned values <<< 217 If the Control-Client intends to operate all test sessions invoked 218 with this control connection using one or both of the new modes, it 219 MUST set the Modes Field bit corresponding to that function in the 220 Setup Response message. 222 3.2. Reflect Octets: Request-TW-Session Packet Format 224 The bits designated for the Reflect Octets feature in the Request-TW- 225 Session command are as shown in the packet format below. 227 0 1 2 3 228 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 1 229 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 230 | 5 | MBZ | IPVN | Conf-Sender | Conf-Receiver | 231 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 232 | Number of Schedule Slots | 233 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 234 . . 235 . ... Many fields (66 octets) not shown ... . 236 . . 237 . . 238 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 239 | Padding Length (4 octets) | 240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 241 | Start Time, (8 octets) | 242 | | 243 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 244 | Timeout, (8 octets) | 245 | | 246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 247 | Type-P Descriptor | 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 249 | Octets to be reflected | Length of padding to reflect | 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 | MBZ (4 octets) | 252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 | | 254 | HMAC (16 octets) | 255 | | 256 | | 257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 259 The "Padding Length" Field *continues* to specify the number of 260 padding octets that the Session-Sender will append to ALL TWAMP-Test 261 packets associated with this test session. See below for 262 considerations on the minimum length of the padding octets, following 263 the definitions of the two new fields that follow the Type-P 264 Descriptor. 266 Note that the number of padding octets appended to the Session- 267 Reflector's test packet depends on support for the RECOMMENDED 268 truncation process in TWAMP section 4.2.1 [RFC5357]. 270 The "Octets to be reflected" Field SHALL be 2 octets long, as shown 271 and contains the octets that the Server MUST reflect in the Accept 272 Session message as specified below. 274 The "Length of padding to reflect" Field SHALL be 2 octets long, and 275 contain an unsigned binary value in units of octets. This field 276 communicates the length of the padding in the TWAMP-Test Packet that 277 the Session-Sender expects to be reflected, and the length of octets 278 that the Session-Reflector SHALL return in include in its TWAMP-Test 279 packet format (see section 4.2). By including this length field in 280 the Request-TW-Session message, a Server is able to determine if it 281 can comply with a specific request to reflect padding in the TWAMP- 282 Test packets, and to arrange for the Session-Reflector processing in 283 advance. 285 The "Padding Length" SHOULD be >= 27 octets when specifying a test 286 session using the Unauthenticated TWAMP-Test mode, to allow for the 287 RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357]. 289 The "Padding Length" SHOULD be >= 56 octets when specifying a test 290 session using the Authenticated or Encrypted TWAMP-Test modes, to 291 allow for the RECOMMENDED truncation process in TWAMP section 4.2.1 292 [RFC5357]. 294 The "Padding Length" SHALL be > the "Length of padding to reflect" 295 when specifying a test session using the OPTIONAL Reflect Octets 296 mode. 298 The "Padding Length" SHALL be >= 27 + "Length of padding to reflect" 299 octets when specifying a test session using BOTH the OPTIONAL Reflect 300 Octets mode and the RECOMMENDED truncation process in TWAMP section 301 4.2.1 [RFC5357]. 303 The "Padding Length" SHALL be >= 56 + "Length of padding to reflect" 304 octets when specifying a test session using BOTH the OPTIONAL Reflect 305 Octets mode and the RECOMMENDED truncation process in TWAMP section 306 4.2.1 [RFC5357]. 308 3.3. Reflect Octets: Accept Session Packet Format 310 The bits designated for the Reflect Padding feature in the Accept 311 Session command are as shown in the packet format below. 313 0 1 2 3 314 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 1 315 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 316 | Accept | MBZ | Port | 317 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 318 | | 319 | SID (16 octets) | 320 | | 321 | | 322 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 323 | Reflected octets | Server octets | 324 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 325 | MBZ (8 octets) | 326 | | 327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 328 | | 329 | HMAC (16 octets) | 330 | | 331 | | 332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 334 The "Reflected octets" field SHALL contain the octets from the 335 Request-TW-Session "Octets to be reflected" Field, and be 2 octets 336 long, as shown. 338 The "Server octets" field SHALL contain information that the Server 339 intends to be returned in the TWAMP-Test packet padding to-be- 340 reflected Field, OR SHALL be zero, and be 2 octets long, as shown. 341 Although the Server determines the SID, this field is very long (16 342 octets) and does not normally appear in TWAMP-Test packets. 344 When supporting the RECOMMENDED truncation process in TWAMP section 345 4.2.1 [RFC5357], IF calculations on the Padding lengths reveal that 346 there are insufficient octets supplied to produce equal-length 347 Session-Sender and Session-Reflector test packets, then the Accept 348 Field MUST be set to 3 = some aspect of the request is not supported. 350 3.4. Additional considerations 352 The value of the Modes Field sent by the Server in the Server 353 Greeting message is the bit-wise OR of the mode values that it is 354 willing to support during this session. 356 Thus, the last six bits of the Modes 32-bit Field are used. A client 357 conforming to this extension of [RFC5357] MAY ignore the values in 358 the first 24 bits of the Modes Field, or it MAY support other 359 features that are communicated in these bit positions. (The first 24 360 bits are available for future protocol extensions.) 362 4. Extended TWAMP Test 364 The TWAMP test protocol is similar to the OWAMP [RFC4656] test 365 protocol with the exception that the Session-Reflector transmits test 366 packets to the Session-Sender in response to each test packet it 367 receives. TWAMP section 4[RFC5357] defines two additional test 368 packet formats for packets transmitted by the Session-Reflector. The 369 appropriate format depends on the security mode chosen. The new 370 modes specified here utilize some of the padding octets within each 371 test packet format, or require truncation of those octets depending 372 on the security mode in use. 374 4.1. Sender Behavior 376 This section describes extensions to the behavior of the TWAMP 377 Session-Sender. 379 4.1.1. Packet Timings 381 The Send Schedule is not utilized in TWAMP, and this is unchanged in 382 this memo. 384 4.1.2. Reflect Octets: Packet Formats and Contents 386 The Session-Sender packet format and content follow the same 387 procedure and guidelines as defined in section 4.1.2 of [RFC4656] (as 388 indicated in section 4.1.2 of TWAMP [RFC5357]). 390 The Reflect octets mode re-designates the original TWAMP-Test (and 391 OWAMP-Test) Packet Padding Field (see section 4.1.2 of [RFC4656]), as 392 shown below for unauthenticated mode: 394 0 1 2 3 395 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 1 396 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 397 | Sequence Number | 398 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 399 | Timestamp | 400 | | 401 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 402 | Error Estimate | | 403 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 404 | | 405 | Packet Padding (to be reflected) | 406 . (length in octets specified in command) . 407 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 408 . . 409 . Additional Packet Padding . 410 . . 411 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 413 The "Packet Padding (to be reflected)" Field SHALL correspond to the 414 length of octets specified in the Request-TW-Session "Length of 415 padding to reflect" Field to this test session. These are the octets 416 that the Session-Sender expects will be returned by the Session- 417 Reflector. 419 The length of the "Additional Packet Padding" Field is the difference 420 between two fields in the Request-TW-Session command, as follows: 422 "Additional Packet Padding", in octets = 424 "Padding Length" - "Length of padding to reflect" 426 One possible use of the first 4 octets of the "Packet Padding (to be 427 reflected)" Field is 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 | Client octets | | 435 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 436 | Packet Padding (to be reflected) | 437 . (length in octets specified elsewhere) . 438 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 439 In this example, the "Client octets" and the "Server octets" fields 440 contain the same information that the Client and Server exchanged in 441 the Request-TW-Session and Accept-Session messages corresponding to 442 this specific test session. These octets would be reflected the same 443 as the rest of the "Packet Padding (to be reflected)" Field. 445 4.1.3. Reflect Octets: Interaction with Padding Truncation 447 When the Reflect Octets mode is selected, and the RECOMMENDED 448 truncation process in TWAMP section 4.2.1 [RFC5357] is supported, the 449 Session-Sender MUST anticipate a minimum padding required to achieve 450 equal size test packets in both directions. The amount of padding 451 needed to achieve symmetrical packet size depends on BOTH the 452 security mode (Unauthenticated/Authenticated/Encrypted) and whether 453 the Reflect Octets mode is selected simultaneously. 455 When using the RECOMMENDED truncation process in TWAMP section 4.2.1 456 [RFC5357] alone, the Session-Sender MUST append sufficient Packet 457 Padding octets to allow the same IP packet payload lengths to be used 458 in each direction of transmission (this is usually desirable). To 459 compensate for the Session-Reflector's larger test packet format, the 460 Session-Sender MUST append at least 27 octets of padding in 461 Unauthenticated mode, and at least 56 octets in Authenticated and 462 Encrypted modes. The sizes of TWAMP Test protocol packets and the 463 resulting truncated padding to achieve equal packet sizes in both 464 directions are shown in the table below: 466 +-------------------+----------------------+---------------------+ 467 | Octets in: | Unauthenticated Mode | Auth/Encrypted Mode | 468 +-------------------+----------------------+---------------------+ 469 | Reflector Header | 41 | 104 | 470 | Sender Header | 14 | 48 | 471 | Truncated Padding | 27 | 56 | 472 +-------------------+----------------------+---------------------+ 474 TWAMP-Test Padding Trucation 476 When using the Reflect Octets mode simultaneously with the 477 RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357], the 478 Session-Sender MUST append at least 27 octets of padding plus the 479 "Length of the padding to reflect" octets when operating in 480 Unauthenticated mode. The Session-Sender MUST append at least 56 481 octets of padding plus the "Length of the padding to reflect" octets 482 when operating in Authenticated and Encrypted modes. 484 4.1.4. Symmetrical Size: Session-Sender Packet Format 486 When the Symmetrical Size mode is selected, the Session-Sender SHALL 487 use the following TWAMP-Test Packet Format in Unauthenticated mode: 489 Unauthenticated Mode 490 0 1 2 3 491 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 1 492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 493 | Sequence Number | 494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 495 | Timestamp | 496 | | 497 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 498 | Error Estimate | | 499 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 500 | | 501 | | 502 | MBZ (27 octets) | 503 | | 504 | | 505 | | 506 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 507 | | | 508 +-+-+-+-+-+-+-+-+ + 509 . . 510 . Packet Padding . 511 . . 512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 514 4.1.5. Symmetrical Size AND Reflect Octets: Session-Sender Packet 515 Format 517 When BOTH the Symmetrical Size mode and the Reflect Octets mode are 518 selected, the Session-Sender SHALL use the following TWAMP-Test 519 Packet Format in Unauthenticated mode: 521 Unauthenticated Mode 522 0 1 2 3 523 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 1 524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 525 | Sequence Number | 526 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 527 | Timestamp | 528 | | 529 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 530 | Error Estimate | | 531 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 532 | | 533 | | 534 | MBZ (27 octets) | 535 | | 536 | | 537 | | 538 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 539 | | | 540 +-+-+-+-+-+-+-+-+ + 541 | Packet Padding (to be reflected) | 542 . (length in octets specified in command) . 543 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 544 . . 545 . Additional Packet Padding . 546 . . 547 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 549 In this combined mode, the Packet Padding to be reflected follows the 550 27 MBZ octets. In Authenticated or Encrypted modes, the Packet 551 Padding to be reflected follows the 56 MBZ octets. 553 4.2. Reflector Behavior 555 The TWAMP Reflector follows the procedures and guidelines in section 556 4.2 of [RFC5357], with the following additional functions: 558 o Reflect Octets mode: Designated octets in the "Packet Padding (to 559 be reflected)" field of the Session-Sender's test packet MUST be 560 included in the Session-Reflector's test packet. 562 o Symmetrical Size mode: The Session-Reflector MUST operate using 563 the Session_Reflector Packet Format defined in section 4.1.4, 564 where the Padding Octets are separated from the information 565 fields. 567 4.2.1. Reflect Octets: Session-Reflector Packet Format and Contents 569 The Reflect Padding feature re-designates the packet padding field, 570 as shown below. When the Reflect Octets mode is selected, the 571 Session-Sender SHALL use the following TWAMP-Test Packet Format in 572 Unauthenticated mode: 574 0 1 2 3 575 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 1 576 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 577 | Sequence Number | 578 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 579 | Timestamp | 580 | | 581 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 582 | Error Estimate | MBZ | 583 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 584 | Receive Timestamp | 585 | | 586 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 587 | Sender Sequence Number | 588 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 589 | Sender Timestamp | 590 | | 591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 592 | Sender Error Estimate | MBZ | 593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 594 | Sender TTL | Packet Padding (from Session-Sender) | 595 +-+-+-+-+-+-+-+-+ + 596 . . 597 + +-+-+-+-+-+-+-+-+ 598 | Packet Padding (from Session-Sender) | | 599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 600 | | 601 | | 602 . Additional Packet Padding . 603 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 604 The "Packet Padding (from Session-Sender)" field MUST be the same 605 octets as the "Packet Padding (to be reflected)" field in the 606 Session-Sender's test packet, and therefore MUST conform to the 607 length specified in the Request-TW-Session message. 609 When simultaneously using the RECOMMENDED truncation process in TWAMP 610 section 4.2.1 [RFC5357] AND Reflect octets mode, the Session- 611 Reflector MUST reflect the designated octets from the Session- 612 Sender's test packet in the "Packet Padding (from Session-Sender)" 613 Field, and MAY re-use additional Packet Padding from the Session- 614 Sender. The Session-Reflector MUST truncate the padding such that 615 the highest number octets are discarded, and the test packet length 616 equals the Session-Sender's packet length. When using the 617 RECOMMENDED truncation process, the Session-Reflector MUST truncate 618 exactly 27 octets of padding in Unauthenticated mode, and exactly 56 619 octets in Authenticated and Encrypted modes. 621 The Session-Reflector MAY re-use the Sender's Packet Padding (since 622 the requirements for padding generation are the same for each). 624 4.2.2. Symmetrical Size: Session-Reflector Packet Format 626 When Symmetrical Size mode is selected, the Session-Sender packet 627 formats for unauthenticated and authenticated/encrypted modes are 628 identical to the core TWAMP specification, section 4.2.1 of 629 [RFC5357]. 631 The Session-Reflector MUST construct its test packet using the 632 information in the Session-Sender's test packet. The length of the 633 Session-Reflector's test packet SHALL equal the length of the 634 Session-Sender's test packet. 636 4.2.3. Symmetrical Size AND Reflect Octets: Session-Sender Packet 637 Format 639 When BOTH the Symmetrical Size mode and the Reflect Octets mode are 640 selected, the Session-Reflector MUST operate using the 641 Session_Reflector Packet Format defined in section 4.1.5, where the 642 Padding Octets are separated from the information fields, and the 643 Padding to be Reflected field precedes the Additional Padding. 645 The Session-Reflector SHALL use the same TWAMP-Test Packet Format as 646 specified in section 4.2.1 above. 648 5. Security Considerations 650 These extended modes of operation do not appear to permit any new 651 attacks on hosts communicating with core TWAMP [RFC5357]. 653 The security considerations that apply to any active measurement of 654 live networks are relevant here as well. See [RFC4656] and 655 [RFC5357]. 657 6. IANA Considerations 659 This memo adds two modes to the IANA registry for the TWAMP Modes 660 Field, and describes behavior when the new modes are used. This 661 field is a recognized extension mechanism for TWAMP. 663 6.1. Registry Specification 665 IANA has created a TWAMP-Modes registry (as requested in [RFC5618]). 666 TWAMP-Modes are specified in TWAMP Server Greeting messages and 667 Set-up Response messages, as described in section 3.1 of [RFC5357], 668 consistent with section 3.1 of [RFC4656], and extended by this memo. 669 Modes are indicated by setting bits in the 32-bit Modes field. Thus, 670 this registry can contain a total of 32 possible values. 672 6.2. Registry Management 674 This registry must be updated only by "IETF Consensus" as specified 675 in [RFC2434](an RFC documenting registry use that is approved by the 676 IESG). 678 6.3. Experimental Numbers 680 No experimental values are currently assigned for the Modes Registry. 682 6.4. Registry Contents 684 TWAMP Modes Registry is recommended to be augmented as follows: 686 Value Description Semantics Definition 687 0 Reserved 689 1 Unauthenticated RFC4656, Section 3.1 691 2 Authenticated RFC4656, Section 3.1 693 4 Encrypted RFC4656, Section 3.1 695 8 Unauth. TEST protocol, RFC5618, Section 3.1 (3) 696 Auth. CONTROL 697 -------------------------------------------------------- 698 xxx Reflect Octets this memo, section 3.1 699 Capability new bit position (X) 700 yyy Symmetrical Size this memo, section 3.1 701 Sender Test Packet Format new bit position (Y) 703 The suggested values are 705 X=5, xxx=32 707 Y=6, yyy=64 709 7. Acknowledgements 711 The authors would like to thank Walt Steverson for helpful review and 712 comments. 714 8. References 716 8.1. Normative References 718 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 719 Requirement Levels", BCP 14, RFC 2119, March 1997. 721 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 722 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 723 October 1998. 725 [RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. 726 Zekauskas, "A One-way Active Measurement Protocol 727 (OWAMP)", RFC 4656, September 2006. 729 [RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. 730 Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", 731 RFC 5357, October 2008. 733 [RFC5618] Morton, A. and K. Hedayat, "Mixed Security Mode for the 734 Two-Way Active Measurement Protocol (TWAMP)", RFC 5618, 735 August 2009. 737 8.2. Informative References 739 [x] "". 741 Authors' Addresses 743 Al Morton 744 AT&T Labs 745 200 Laurel Avenue South 746 Middletown,, NJ 07748 747 USA 749 Phone: +1 732 420 1571 750 Fax: +1 732 368 1192 751 Email: acmorton@att.com 752 URI: http://home.comcast.net/~acmacm/ 753 Len Ciavattone 754 AT&T Labs 755 200 Laurel Avenue South 756 Middletown,, NJ 07748 757 USA 759 Phone: +1 732 420 1239 760 Fax: 761 Email: lencia@att.com 762 URI: