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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 7 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Mobile Ad hoc Networking (MANET) T. Clausen 3 Internet-Draft LIX, Ecole Polytechnique, France 4 Intended status: Standards Track C. Dearlove 5 Expires: February 2, 2009 BAE Systems Advanced Technology 6 Centre 7 August 1, 2008 9 Representing multi-value time in MANETs 10 draft-ietf-manet-timetlv-06 12 Status of This Memo 14 By submitting this Internet-Draft, each author represents that any 15 applicable patent or other IPR claims of which he or she is aware 16 have been or will be disclosed, and any of which he or she becomes 17 aware will be disclosed, in accordance with Section 6 of BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt. 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html. 35 This Internet-Draft will expire on February 2, 2009. 37 Abstract 39 This document describes a general and flexible TLV (type-length-value 40 structure) for representing time using the generalized MANET packet/ 41 message format. It defines two message and two address block TLVs 42 for representing validity and interval times for MANET routing 43 protocols. 45 Table of Contents 47 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 48 1.1. Motivation and Rationale . . . . . . . . . . . . . . . . . 3 49 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 50 3. Applicability Statement . . . . . . . . . . . . . . . . . . . 5 51 4. Protocol Overview and Functioning . . . . . . . . . . . . . . 5 52 5. Representing Time . . . . . . . . . . . . . . . . . . . . . . 5 53 6. General Time TLV Structure . . . . . . . . . . . . . . . . . . 6 54 6.1. Single-value Time TLVs . . . . . . . . . . . . . . . . . . 7 55 6.2. Multi-value Time TLVs . . . . . . . . . . . . . . . . . . 8 56 7. Message TLVs . . . . . . . . . . . . . . . . . . . . . . . . . 9 57 7.1. INTERVAL_TIME TLV . . . . . . . . . . . . . . . . . . . . 9 58 7.2. VALIDITY_TIME TLV . . . . . . . . . . . . . . . . . . . . 9 59 8. Address Block TLVs . . . . . . . . . . . . . . . . . . . . . . 9 60 8.1. INTERVAL_TIME TLV . . . . . . . . . . . . . . . . . . . . 9 61 8.2. VALIDITY_TIME TLV . . . . . . . . . . . . . . . . . . . . 10 62 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 63 9.1. Expert Review: Evaluation Guidelines . . . . . . . . . . . 10 64 9.2. Message TLV Types . . . . . . . . . . . . . . . . . . . . 11 65 9.3. Address Block TLV Types . . . . . . . . . . . . . . . . . 11 66 10. Security Considerations . . . . . . . . . . . . . . . . . . . 12 67 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 68 11.1. Normative References . . . . . . . . . . . . . . . . . . . 12 69 11.2. Informative References . . . . . . . . . . . . . . . . . . 12 70 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 12 72 1. Introduction 74 The generalized packet/message format [packetbb] specifies a 75 signaling format which MANET routing protocols can employ for 76 exchanging protocol information. This format presents the ability to 77 express and associate attributes to packets, messages or addresses, 78 by way of a general TLV (type-length-value) mechanism. 80 This document specifies a general Time TLV structure, which can be 81 used by any MANET routing protocol that needs to express either 82 single time-values or a set of time-values with each time-value 83 associated with a range of hop counts, as provided by the message 84 header of [packetbb]. This allows a receiving node to determine a 85 single time-value if either it knows its hop count from the 86 originator node, or the Time TLV specifies a single time-value. 88 This document also specifies two message TLV types, which use the TLV 89 structure proposed. These TLV types are INTERVAL_TIME and 90 VALIDITY_TIME, specifying respectively the maximum time before 91 another message of the same type as this message from the same 92 originator should be received, and the duration for which the 93 information in this message is valid after receipt. Note that, if 94 both are present, then the latter will usually be greater than the 95 former in order to allow for possible message loss. 97 This document also specifies two address block TLV types, which use 98 the TLV structure proposed. These TLV types are INTERVAL_TIME and 99 VALIDITY_TIME, defined equivalently to the two message TLVs with the 100 same names. 102 1.1. Motivation and Rationale 104 The TLV mechanism as specified in [packetbb] allows associating a 105 "value" to either a packet, a message or to addresses. The data 106 structure for doing so - the TLV - is identical in each of the three 107 cases, however the TLV's position in a received packet allows 108 determining if that TLV is a "packet TLV" (it appears in the packet 109 header, before any messages), a "message TLV" (it appears in the TLV 110 block immediately following a message header) or an "address block 111 TLV" (it appears in the TLV block immediately following an address 112 block). 114 While TLVs may be structurally identical, that which they express may 115 be different. This is determined from the kind (packet, message or 116 address block) and type of the TLV. For example one TLV might 117 associate a lifetime to an address, another a content sequence number 118 to a message, and another a cryptographic signature to a packet. For 119 this reason, [packetbb] specifies separate registries for packet, 120 message and address block TLV types, and does not specify any 121 structure in the TLV value field. 123 The TLVs defined in this document express, essentially, that "this 124 information will be refreshed within X seconds" and that "this 125 information is valid for X seconds after being received", each 126 allowing the "X seconds" to be specified as a function of the number 127 of hops from the originator of the information. This document 128 specifies a general format allowing expressing and encoding this as 129 the value field of a TLV. This representation uses a compact (8 bit) 130 representation of time, as message size is an issue in many MANETs, 131 and the offered precision and range is appropriate for MANET routing 132 protocols. 134 A TLV of this format may be used for packets, messages or addresses. 135 For example, a proactive MANET routing protocol periodically 136 reporting link state information could include a TLV of this format 137 as a message TLV. This may indicate a different periodicity in 138 different scopes (possibly frequently up to a few hops, less 139 frequently beyond that) because some messages may be sent with 140 limited scope, as specified in [packetbb]. A reactive MANET routing 141 protocol could include a TLV of this format as an address block TLV 142 for reporting the lifetime of routes to individual addresses. 144 In addition to defining the general format as outlined above, this 145 document requests IANA assignments for INTERVAL_TIME and 146 VALIDITY_TIME TLVs. These IANA assignments are requested in this 147 document in order to avoid interdependencies between otherwise 148 unrelated MANET protocols and in order to not exhaust the TLV type 149 spaces by having different protocols request types for essentially 150 identical data structures. Only message and address block TLVs are 151 requested, as these are those for which a need has been demonstrated. 153 2. Terminology 155 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 156 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 157 "OPTIONAL" in this document are to be interpreted as described in 158 [RFC2119]. 160 Additionally, this document uses terminology from [packetbb], and 161 introduces the following terminology: 163 hop count - the number of hops from the message originator to the 164 message recipient. This is defined to equal the 165 field in the element defined in [packetbb], if 166 present, after it is incremented on reception. If the field is not present, or in a packet TLV, then hop count is 168 defined to equal 255. 170 time-value - a time, measured in seconds. 172 time-code - an 8 bit field, representing a time-value. 174 3. Applicability Statement 176 The TLV structure described in this document is applicable whenever a 177 single time-value, or a time-value that varies with the number of 178 hops from the originator of a message, is required in a protocol 179 using the generalized MANET packet/message format [packetbb]. 181 Examples of time-values that may be included in a protocol message 182 are: 184 o The maximum time interval until the next message of the same type 185 is to be generated by the message's originator node. 187 o The validity time of the information with which the time-value is 188 associated. 190 Either of these may vary with the hop count between the originating 191 and receiving nodes, e.g. if messages of the same type are sent with 192 different hop limits as defined in [packetbb]. 194 Parts of this document have been generalized from material in the 195 proactive MANET routing protocol OLSR (The Optimized Link State 196 Routing Protocol) [RFC3626]. 198 4. Protocol Overview and Functioning 200 This document does not specify a protocol nor does it mandate 201 specific node or protocol behavior. Rather, it outlines mechanisms 202 for encoding time-values using the TLV mechanism of [packetbb]. 204 5. Representing Time 206 This document specifies a TLV structure in which time-values are each 207 represented in an 8 bit time-code, one or more of which may be used 208 in a TLV's field. Of these 8 bits, the least significant 3 209 bits represent the mantissa (a), and the most significant 5 bits 210 represent the exponent (b), so that: 212 o time-value = (1 + a/8) * 2^b * C 214 o time-code = 8 * b + a 215 All nodes in the MANET MUST use the same value of the constant C, 216 which will be specified in seconds, hence so will be all time-values. 217 C MUST be greater than 0 seconds. Note that ascending values of the 218 time-code represent ascending time-values, time-values may thus be 219 compared by comparison of time-codes. 221 An algorithm for computing the time-code representing the smallest 222 representable time-value not less than the time-value t is: 224 1. find the largest integer b such that t/C >= 2^b; 226 2. set a = 8 * (t / (C * 2^b) - 1), rounded up to the nearest 227 integer; 229 3. if a == 8 then set b = b + 1 and set a = 0; 231 4. if 0 <= a <= 7, and 0 <= b <= 31, then the required time-value 232 can be represented by the time-code 8 * b + a, otherwise it can 233 not. 235 The minimum time-value that can be represented in this manner is C. 236 The maximum time-value that can be represented in this manner is 15 * 237 2^28 * C, or about 4.0 * 10^9 * C. If, for example, C = 1/1024 238 second, then this is about 45 days. 240 A protocol using this time representation MUST define the value of C. 241 A protocol using this specification MAY specify that the all bits 242 zero time-value (0) represents a time-value of zero and/or that the 243 all bits one time-value (255) represents an indefinitely large time- 244 value. 246 6. General Time TLV Structure 248 The following data structure allows the representation of a single 249 time-value, or of a default time-value plus pairs of (time-values, 250 hop counts) for when hop count dependent time-values are required. 251 The time-values are represented as time-codes as defined in 252 Section 5. This data structure is specified, using the 253 regular expression syntax of [packetbb], by: 255 = ()* 257 where: 259 is an 8 bit unsigned integer field containing a time- 260 code as defined in Section 5. 262 is an 8 bit unsigned integer field specifying a hop 263 count from the message originator. 265 A structure thus consists of an odd number of octets; 266 with a repetition factor of n for the (time, hop count) pairs in the 267 regular expression syntax, it contains 2n+1 octets. On reception, n 268 is determined from the length. 270 A field may be thus represented by: 272 ... ... 274 , ... , if present, MUST be a strictly increasing sequence, 275 with < 255. Then, at the receiving node's hop count from the 276 originator node, the time-value indicated is that represented by the 277 time-code: 279 o , if n > 0 and hop count <= ; 281 o , if n > 1 and < hop count <= for some i such 282 that 1 <= i < n; 284 o otherwise, i.e. if n == 0 or hop count > . 286 If included in a message without a field in its 287 message header, or in a packet TLV, then the form of this data 288 structure with a single time-code in (i.e. n == 0) SHOULD 289 be used. 291 6.1. Single-value Time TLVs 293 The purpose of a single value Time TLV is to allow a single time- 294 value to be determined by a node receiving an entity containing the 295 Time TLV, based on its hop count from the entity's originator. The 296 Time TLV may contain information that allows that time-value to be a 297 function of the hop count, and thus different receiving nodes may 298 determine different time-values. 300 A single-value Time TLV may be a packet TLVs, a message TLV or an 301 address block TLV. 303 A Time TLV which has the tismultivalue flag cleared ('0') in its 304 field, as defined in [packetbb], contains a single , as defined above, in its field. For such a Time TLV: 307 o The field in the TLV MUST contain the value 2n+1, with n 308 being the number of (time-value, hop count) pairs in the Time TLV. 310 o The number of (time-value, hop count) pairs MUST be identified by 311 inspecting the field in the TLV. The number of such 312 pairs, n, is: 314 * n = ( - 1) / 2 316 This MUST be an integer value. 318 6.2. Multi-value Time TLVs 320 The purpose of a multi-value Time TLV is to associate a set of structures to an identically sized set of addresses, as 322 described in [packetbb]. For each of these structures, a 323 single time-value can be determined by a node receiving an entity 324 containing the Time TLV, based on its hop count from the entity's 325 originator. The Time TLV may contain information that allows that 326 time-value to be a function of the hop count, and thus different 327 receiving nodes may determine different time-values. 329 Multi-value Time TLVs MUST be address block TLVs. A multi-value Time 330 TLV MUST NOT be a packet or message TLV. 332 A Time TLV which has the tismultivalue flag set ('1') in its field, as defined in [packetbb], contains a sequence of structures, as defined above, in its field. For such a 335 Time TLV: 337 o The field in the TLV MUST contain the value m * (2n+1), 338 with n being the number of (time-value, hop count) pairs in the 339 Time TLV, and m being number-values as defined in [packetbb]. 341 o The number of structures included in the field 342 is equal to number-values as defined in [packetbb]. 344 o The number of (time-value, hop count) pairs in each 345 structure MUST be the same, and MUST be identified by inspecting 346 the field in the TLV and using number-values as defined 347 in [packetbb]. The number of such pairs in each 348 structure, n, is: 350 * n = (( / number-values) - 1) / 2 352 This MUST be an integer value. The lists of hop count values MAY 353 be different. 355 7. Message TLVs 357 Two message TLVs are defined, for signaling message interval 358 (INTERVAL_TIME) and message validity time (VALIDITY_TIME). 360 7.1. INTERVAL_TIME TLV 362 An INTERVAL_TIME TLV is a message TLV that defines the maximum time 363 before another message of the same type as this message from the same 364 originator should be received. This interval time MAY be specified 365 to depend on the hop count from the originator. (This is appropriate 366 if messages are sent with different hop limits, so that receiving 367 nodes at greater hop counts have an increased interval time.) 369 A message MUST NOT include more than one INTERVAL_TIME TLV. 371 An INTERVAL_TIME TLV is an example of a Time TLV specified as in 372 Section 5. 374 7.2. VALIDITY_TIME TLV 376 A VALIDITY_TIME TLV is a message TLV that defines the validity time 377 of the information carried in the message in which the TLV is 378 contained. After this time the receiving node MUST consider the 379 message content to no longer be valid (unless repeated in a later 380 message). The validity time of a message MAY be specified to depend 381 on the hop count from its originator. (This is appropriate if 382 messages are sent with different hop limits, so that receiving nodes 383 at greater hop counts receive information less frequently and must 384 treat is as valid for longer.) 386 A message MUST NOT include more than one VALIDITY_TIME TLV. 388 A VALIDITY_TIME TLV is an example of a Time TLV specified as in 389 Section 5. 391 8. Address Block TLVs 393 Two address block TLVs are defined, for signaling address 394 advertisement interval (INTERVAL_TIME) and address validity time 395 (VALIDITY_TIME). 397 8.1. INTERVAL_TIME TLV 399 An INTERVAL_TIME TLV is an address block TLV that defines the maximum 400 time before this address from the same originator should be received 401 again. This interval time MAY be specified to depend on the hop 402 count from the originator. (This is appropriate if addresses are 403 contained in messages sent with different hop limits, so that 404 receiving nodes at greater hop counts have an increased interval 405 time.) 407 A protocol using this TLV and the similarly named message TLV MUST 408 specify how to interpret the case when both are present (typically 409 that the former over-rides the latter for those addresses which are 410 covered by the former). 412 An INTERVAL_TIME TLV is an example of a Time TLV specified as in 413 Section 5. 415 8.2. VALIDITY_TIME TLV 417 A VALIDITY_TIME TLV is an address block TLV that defines the validity 418 time of the addresses to which the TLV is associated. After this 419 time the receiving node MUST consider the addresses to no longer be 420 valid (unless these are repeated in a later message). The validity 421 time of an address MAY be specified to depend on the hop count from 422 its originator. (This is appropriate if addresses are contained in 423 messages sent with different hop limits, so that receiving nodes at 424 greater hop counts receive information less frequently and must treat 425 is as valid for longer.) 427 A protocol using this TLV and the similarly named message TLV MUST 428 specify how to interpret the case when both are present (typically 429 that the former over-rides the latter for those addresses which are 430 covered by the former). 432 A VALIDITY_TIME TLV is an example of a Time TLV specified as in 433 Section 5. 435 9. IANA Considerations 437 This specification defines two message TLV types, which must be 438 allocated from the "Assigned Message TLV Types" repository of 439 [packetbb] as specified in Table 1 and two address block TLV types, 440 which must be allocated from the "Assigned Address Block TLV Types" 441 repository of [packetbb] as specified in Table 2. 443 IANA is requested to assign the same numerical value to the message 444 TLV and address block TLV types with the same name. 446 9.1. Expert Review: Evaluation Guidelines 448 For the registries for TLV type extensions where an Expert Review is 449 required, the designated expert SHOULD take the same general 450 recommendations into consideration as are specified by [packetbb]. 452 9.2. Message TLV Types 454 +---------------+------+-----------+--------------------------------+ 455 | Name | Type | Type | Description | 456 | | | Extension | | 457 +---------------+------+-----------+--------------------------------+ 458 | INTERVAL_TIME | TBD1 | 0 | The maximum time before | 459 | | | | another message of the same | 460 | | | | type as this message from the | 461 | | | | same originator should be | 462 | | | | received | 463 | | | 1-223 | Expert Review | 464 | | | 224-255 | Experimental Use | 465 | VALIDITY_TIME | TBD2 | 0 | The time from receipt of the | 466 | | | | message during which the | 467 | | | | information contained in the | 468 | | | | message is to be considered | 469 | | | | valid | 470 | | | 1-223 | Expert Review | 471 | | | 224-255 | Experimental Use | 472 +---------------+------+-----------+--------------------------------+ 474 Table 1 476 9.3. Address Block TLV Types 478 +---------------+------+-----------+--------------------------------+ 479 | Name | Type | Type | Description | 480 | | | extension | | 481 +---------------+------+-----------+--------------------------------+ 482 | INTERVAL_TIME | TBD1 | 0 | The maximum time before | 483 | | | | another message of the same | 484 | | | | type as this message from the | 485 | | | | same originator and containing | 486 | | | | this address should be | 487 | | | | received | 488 | | | 1-223 | Expert Review | 489 | | | 224-255 | Experimental Use | 490 | VALIDITY_TIME | TBD2 | 0 | The time from receipt of the | 491 | | | | address during which the | 492 | | | | information regarding this | 493 | | | | address is to be considered | 494 | | | | valid | 495 | | | 1-223 | Expert Review | 496 | | | 224-255 | Experimental Use | 497 +---------------+------+-----------+--------------------------------+ 499 Table 2 501 10. Security Considerations 503 This document specifies how to add data structures (TLVs) which 504 provide timing information to packets and messages specified using 505 [packetbb]. In particular, information validity durations and 506 reporting intervals may be added. 508 The general security threats that apply are those general to 509 [packetbb] and described therein, problems of integrity and 510 confidentiality. With regard to the former, modification of a time 511 TLV can cause information to have an invalid validity time, or 512 expected interval time. This may cause incorrect protocol 513 performance. Modification or addition of timed information can add 514 to a protocol's workload (especially if a short validity time is 515 specified) and storage requirements (especially if a long validity 516 time is specified). 518 To counter these threats, the security suggestions in [packetbb], for 519 the use of authentication and encryption, are appropriate. 521 11. References 523 11.1. Normative References 525 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 526 Requirement Levels", RFC 2119, BCP 14, March 1997. 528 [packetbb] Clausen, T., Dearlove, C., Dean, J., and C. Adjih, 529 "Generalized MANET Packet/Message Format", 530 draft-ietf-manet-packetbb-14.txt (work in progress), 531 August 2008. 533 11.2. Informative References 535 [RFC3626] Clausen, T. and P. Jacquet, "The Optimized Link State 536 Routing Protocol", RFC 3626, October 2003. 538 Appendix A. Acknowledgements 540 The authors would like to thank Brian Adamson and Justin Dean (both 541 NRL) and Ian Chakeres (Motorola) for their contributions, and Alan 542 Cullen (BAE Systems) for his careful review of this specification. 544 Authors' Addresses 546 Thomas Heide Clausen 547 LIX, Ecole Polytechnique, France 549 Phone: +33 6 6058 9349 550 EMail: T.Clausen@computer.org 551 URI: http://www.ThomasClausen.org/ 553 Christopher Dearlove 554 BAE Systems Advanced Technology Centre 556 Phone: +44 1245 242194 557 EMail: chris.dearlove@baesystems.com 558 URI: http://www.baesystems.com/ 560 Full Copyright Statement 562 Copyright (C) The IETF Trust (2008). 564 This document is subject to the rights, licenses and restrictions 565 contained in BCP 78, and except as set forth therein, the authors 566 retain all their rights. 568 This document and the information contained herein are provided on an 569 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 570 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 571 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 572 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 573 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 574 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 576 Intellectual Property 578 The IETF takes no position regarding the validity or scope of any 579 Intellectual Property Rights or other rights that might be claimed to 580 pertain to the implementation or use of the technology described in 581 this document or the extent to which any license under such rights 582 might or might not be available; nor does it represent that it has 583 made any independent effort to identify any such rights. 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