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Uijterwaal 3 Internet-Draft RIPE NCC 4 Intended status: Standards Track December 9, 2008 5 Expires: June 12, 2009 7 A One-Way Packet Duplication Metric 8 draft-ietf-ippm-duplicate-06.txt 10 Status of this Memo 12 By submitting this Internet-Draft, each author represents that any 13 applicable patent or other IPR claims of which he or she is aware 14 have been or will be disclosed, and any of which he or she becomes 15 aware will be disclosed, in accordance with Section 6 of BCP 79. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that 19 other groups may also distribute working documents as Internet- 20 Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 This Internet-Draft will expire on June 12, 2009. 35 Abstract 37 When a packet is sent from one host to the other, one normally 38 expects that exactly one copy of the packet that was sent arrives at 39 the destination. It is, however, possible that a packet is either 40 lost or that multiple copies arrive. 42 In earlier work a metric for packet loss has been defined. This 43 metric quantifies the case where a packet that is sent, does not 44 arrive at its destination within a reasonable time. In this memo, a 45 metric for another case is defined: a packet is sent, but multiple 46 copies arrive. The document also discusses streams and methods to 47 summarize the results of streams. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 52 1.1. Requirements notation . . . . . . . . . . . . . . . . . . 4 53 1.2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 4 54 2. A Singleton Definition for one-way packet arrival count . . . 5 55 2.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 5 56 2.2. Metrics Parameters . . . . . . . . . . . . . . . . . . . . 5 57 2.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 5 58 2.4. Definition . . . . . . . . . . . . . . . . . . . . . . . . 5 59 2.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 6 60 2.6. Methodology . . . . . . . . . . . . . . . . . . . . . . . 7 61 2.7. Errors and uncertainties . . . . . . . . . . . . . . . . . 7 62 2.8. Reporting the metric . . . . . . . . . . . . . . . . . . . 7 63 3. A Singleton Definition for one-way packet duplication . . . . 7 64 3.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 7 65 3.2. Metrics Parameters . . . . . . . . . . . . . . . . . . . . 7 66 3.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 7 67 3.4. Definition . . . . . . . . . . . . . . . . . . . . . . . . 7 68 3.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 8 69 4. Definition for samples for one-way Packet Duplication . . . . 8 70 4.1. Poisson Streams . . . . . . . . . . . . . . . . . . . . . 8 71 4.1.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 8 72 4.1.2. Metric Parameters . . . . . . . . . . . . . . . . . . 8 73 4.1.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 8 74 4.1.4. Definition . . . . . . . . . . . . . . . . . . . . . . 8 75 4.1.5. Methodology . . . . . . . . . . . . . . . . . . . . . 9 76 4.1.6. Errors and uncertainties . . . . . . . . . . . . . . . 9 77 4.1.7. Reporting the metric . . . . . . . . . . . . . . . . . 9 78 4.2. Periodic Streams . . . . . . . . . . . . . . . . . . . . . 9 79 4.2.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 9 80 4.2.2. Metric Parameters . . . . . . . . . . . . . . . . . . 9 81 4.2.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 9 82 4.2.4. Definition . . . . . . . . . . . . . . . . . . . . . . 9 83 4.2.5. Methodology . . . . . . . . . . . . . . . . . . . . . 9 84 4.2.6. Errors and uncertainties . . . . . . . . . . . . . . . 10 85 4.2.7. Reporting the metric . . . . . . . . . . . . . . . . . 10 86 5. Some statistics definitions for one-way Duplication . . . . . 10 87 5.1. Type-P-one-way-packet-duplication-fraction . . . . . . . . 10 88 5.2. Type-P-one-way-replicated-packet-rate . . . . . . . . . . 10 89 5.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 11 90 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 91 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 92 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 93 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 94 9.1. Normative References . . . . . . . . . . . . . . . . . . . 13 95 9.2. Informative References . . . . . . . . . . . . . . . . . . 13 96 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13 97 Intellectual Property and Copyright Statements . . . . . . . . . . 14 99 1. Introduction 101 This document defines a metric for one-way packet duplication across 102 Internet paths. It builds on the IPPM Framework document [RFC2330]; 103 the reader is assumed to be familiar with that document. 105 This document follows the same structure as the document for one-way 106 Packet Loss [RFC2680]; the reader is assumed to be familiar with that 107 document as well. 109 The structure of this memo is as follows: 110 o First, a singleton metric, called Type-P-one-way-packet-arrival- 111 count, is introduced to measure the number of arriving packets for 112 each packet sent. 113 o Then, a singleton metric, called Type-P-one-way-packet- 114 duplication, is defined to describe a single instance of packet 115 duplication. 116 o Next, this singleton metric is used to define samples, Type-P-one- 117 way-Packet-Duplication-Poisson-Stream and Type-P-one-way-Packet- 118 Duplication-Periodic-Stream. These are introduced to measure 119 duplication in a series of packets sent with either Poisson- 120 distributed [RFC2680] or periodic [RFC3432] intervals between the 121 packets. 122 o Finally, statistics that summarize the properties of these samples 123 are introduced. 125 1.1. Requirements notation 127 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 128 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 129 document are to be interpreted as described in [RFC2119]. 131 Although RFC 2119 was written with protocols in mind, the key words 132 are used in this document for similar reasons. They are used to 133 ensure the results of measurements from two different implementations 134 are comparable, and to note instances when an implementation could 135 perturb the network. 137 1.2. Motivation 139 When a packet is sent from one host to the other, one normally 140 expects that exactly one copy of the packet that was sent arrives at 141 the destination. It is, however, possible that a packet is either 142 lost or that multiple copies arrive. 144 In earlier work a metric for packet loss has been defined [RFC2680]. 145 This metric distinguishes between cases where the packet arrives and 146 where the packet does not arrive within a reasonable time. In this 147 memo, a metric for a third outcome is defined: a single packet is 148 sent but multiple copies arrive. 150 As this document describes a case similar to the one discussed in 151 [RFC2680], all considerations from that document on timing and 152 accuracy apply. 154 2. A Singleton Definition for one-way packet arrival count 156 2.1. Metric Name 158 Type-P-one-way-packet-arrival-count 160 2.2. Metrics Parameters 162 o Src, the IP address of a host 163 o Dst, the IP address of a host 164 o T, the wire time of a packet at the source 165 o T0, the maximum waiting time for a packet to arrive at the 166 destination. 168 2.3. Metric Units 170 An integer number 172 2.4. Definition 174 Two packets are considered identical if and only if: 176 o Both contain identical information fields. The recipient thus 177 could take either packet and use the data in an application. The 178 other packet does not contain any additional information. 179 o Both packets appear to have been sent by one and the same host, to 180 one and the same destination. Host are identified by their IP 181 addresses. 182 o Both contain valid, but not necessarily identical IP header 183 fields. 185 The recipient thus could take either packet and use it in an 186 application, the other copy does not contain any additional 187 information. 189 The value of a Type-P-one-way-packet-arrival-count is a positive 190 integer number indicating the number of (uncorrupted and identical) 191 copies received by dst in the interval [T, T+T0] for a packet sent by 192 src at time T. 194 If a packet is sent, but it is lost or does not arrive in the 195 interval [T, T+T0], then the metric is undefined. Applications MAY 196 report an "impossible" value (for example, -1) to indicate this 197 condition instead of undefined. 199 If a packet is fragmented during transport and if, for whatever 200 reason, re-assembly does not occur, then the packet will be deemed 201 lost. It is thus not included in the Type-P-one-way-packet-arrival- 202 count. 204 2.5. Discussion 206 This metric counts the number of packets arriving for each packet 207 sent. The time-out value T0 SHOULD be set to a value when the 208 application could potentially still use the packet and would not 209 discard it automatically. 211 The IP headers do not necessarily have to be identical. This can 212 happen, for example, if two packets take a different route resulting 213 in a different TTL. 215 If this metrics is used in parallel with the Packet Loss Metric 216 [RFC2680], the value of T0 should be the same for both cases in order 217 to keep the results comparable. 219 The metric only counts packets that are not corrupted during 220 transmission and may have been resent automatically by lower layers 221 or intermediate devices. Packets that were corrupted during 222 transmission but nevertheless still arrived at dst are not counted. 224 Clocks do have to be synchronized between src and dst such that it is 225 possible to uniquely and accurately determine the interval [T, T+T0] 226 at both sides. 228 If this metric is used in an active measurement system, the system 229 MUST NOT send multiple packets with identical information fields, in 230 order to avoid that all packets will be declared duplicates. This 231 metric can be used inside a passive measurement system as well, using 232 packets generated by another source. However, if the source can send 233 two identical packets within the interval [T, T+T0], this will be 234 incorrectly labelled as a duplicate, resulting in a false positive. 235 It is up to the implementor to estimate if this scenario is likely to 236 happen and the rate of false positives is acceptable. 238 In IPv4, "information fields" refers to all data following the IPv4 239 header. The equivalent of this in IPv6 is all information following 240 the IPv6 header and the hop-by-hop options header. 242 2.6. Methodology 244 The basic technique to measure this metrics follows the methodology 245 described in [RFC2680], section 2.6, with one exception. 247 [RFC2680] does not specify that the receiving host should be able to 248 receive multiple copies of a single packet, as it only needs one copy 249 to determine the metrics. Implementations for this metric should 250 obviously be capable to receive multiple copies. 252 2.7. Errors and uncertainties 254 Refer to section 2.7 of [RFC2680] 256 2.8. Reporting the metric 258 Refer to section 2.8 of [RFC2680] 260 3. A Singleton Definition for one-way packet duplication 262 3.1. Metric Name 264 Type-P-one-way-packet-duplication 266 3.2. Metrics Parameters 268 o Src, the IP address of a host 269 o Dst, the IP address of a host 270 o T, the wire time of a packet at the source 271 o T0, the maximum waiting time for a packet to arrive at the 272 destination. 274 3.3. Metric Units 276 An integer number. 278 3.4. Definition 280 The value of a Type-P-one-way-packet-duplication is a positive 281 integer number indicating the number of (uncorrupted and identical) 282 additional copies of an individual packet received by dst in the 283 interval [T, T+T0] sent by src at time T. 285 If a packet is sent and only one copy arrives in the interval [T, 286 T+T0], then the metric is 0. If no copy arrives in this interval, 287 then the metric is undefined. Applications MAY report an 288 "impossible" value (for example, -1) to indicate this condition. 290 3.5. Discussion 292 This metric is equal to 294 Type-P-one-way-packet-arrival-count - 1 296 This metric is expected to be used for applications that need to know 297 duplication for an individual packet. All considerations regarding 298 methodology, errors and reporting from the previous section apply. 300 4. Definition for samples for one-way Packet Duplication 302 4.1. Poisson Streams 304 4.1.1. Metric Name 306 Type-P-one-way-Packet-Duplication-Poisson-Stream 308 4.1.2. Metric Parameters 310 o Src, the IP address of a host 311 o Dst, the IP address of a host 312 o Ts, a time 313 o Tf, a time. Ts and Tf specify the time interval when packets can 314 be sent for this stream. 315 o T0, the maximum waiting time for a packet to arrive at the 316 destination. 317 o lambda, a rate in reciprocal seconds 319 4.1.3. Metric Units 321 A sequence of pairs; the elements of each pair are: 322 o T, a time 323 o Type-P-one-way-packet-arrival-count for the packet sent at T. 325 4.1.4. Definition 327 Given Ts, Tf and lambda, we compute a pseudo-random Poisson process 328 beginning at or before Ts, with average rate lambda and ending at or 329 after Tf. Those time values greater than or equal to Ts, and less 330 than or equal to Tf are then selected. At each of the times in this 331 process, we obtain the value of Type-P-one-way-packet-arrival-count. 332 The value of the sample is the sequence made up of the resulting 333 {time, duplication} pairs. If there are no such pairs, the sequence 334 is of length zero and the sample is said to be empty. 336 4.1.5. Methodology 338 Refer to [RFC2680], section 3.6. 340 4.1.6. Errors and uncertainties 342 Refer to [RFC2680], section 3.7. 344 4.1.7. Reporting the metric 346 Refer to [RFC2680], section 3.8. 348 4.2. Periodic Streams 350 4.2.1. Metric Name 352 Type-P-one-way-Packet-Duplication-Periodic-Stream 354 4.2.2. Metric Parameters 356 o Src, the IP address of a host 357 o Dst, the IP address of a host 358 o Ts, a time 359 o Tf, a time. Ts and Tf specify the time interval when packets can 360 be sent for this stream. 361 o T0, the maximum waiting time for a packet to arrive at the 362 destination. 363 o lambda, a rate in reciprocal seconds 365 4.2.3. Metric Units 367 A sequence of pairs; the elements of each pair are: 368 o T, a time 369 o Type-P-one-way-packet-arrival-count for the packet sent at T. 371 4.2.4. Definition 373 At time Ts, we start sending packets with a constant rate lambda, 374 until time Tf. For each packet sent, we obtain the value of Type-P- 375 one-way-packet-arrival-count. The value of the sample is the 376 sequence made up of the resulting {time, duplication} pairs. If 377 there are no such pairs, the sequence is of length zero and the 378 sample is said to be empty. 380 4.2.5. Methodology 382 Refer to [RFC3432], section 4.5. 384 4.2.6. Errors and uncertainties 386 Refer to [RFC3432], section 4.6. 388 4.2.7. Reporting the metric 390 Refer to [RFC3432], section 4.7. 392 5. Some statistics definitions for one-way Duplication 394 Note: the statistics described in this section can be used for both 395 Type-P-one-way-Packet-Duplication-Poisson-Stream and Type-P-one-way- 396 Packet-Duplication-Periodic-Stream. The application SHOULD report 397 which sample was used as input. 399 5.1. Type-P-one-way-packet-duplication-fraction 401 This statistic gives the fraction of additional packets that arrived 402 in a stream. 404 Given a Type-P-one-way-Packet-Duplication-Poisson-Stream, one first 405 removes all values of Type-P-one-way-Packet-Duplication which are 406 undefined. For the remaining pairs in the stream, one calculates: 407 (Sum Type-P-one-Way-packet-arrival-count/Number of pairs left) - 1 408 (In other words, (number of packets received)/(number of packets sent 409 and not lost).) 411 The number can be expressed as a percentage. 413 Note: this statistic is the equivalent of the Y.1540 IPDR [Y1540] 415 5.2. Type-P-one-way-replicated-packet-rate 417 This statistic gives the fraction of packets that was duplicated (one 418 or more times) in a stream. 420 Given a Type-P-one-way-Packet-Duplication-Poisson-Stream, one first 421 removes all values of Type-P-one-way-packet-arrival-count which are 422 undefined. For the remaining pairs in the stream, one counts the 423 number of pairs with Type-P-one-Way-packet-arrival-count greater than 424 1. Then one calculates the fraction of packets that meet this 425 criterion as a fraction of the total. (In other words: (number of 426 duplicated packets)/(number of packets sent and not lost).). 428 The number can be expressed as a percentage. 430 Note: this statistic is the equivalent of the Y.1540 RIPR [Y1540] 432 5.3. Examples 434 Consider a stream of 4 packets, sent as: 436 (1, 2, 3, 4) 438 and arriving as: 439 o Case 1: (1, 2, 3, 4) 440 o Case 2: (1, 1, 2, 2, 3, 3, 4, 4) 441 o Case 3: (1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4) 442 o Case 4: (1, 1, 1, 2, 3, 3, 3, 4) 444 Case 1: No packets are duplicated in a stream and both the Type-P- 445 one-way-packet-duplication-fraction and the type-P-one-way-packet- 446 replicated-packet-rate are 0. 448 Case 2: Every packet is duplicated once and the Type-P-one-way- 449 packet-duplication-fraction is 100%. The type-P-one-way-replicated- 450 packet-rate is 100% too. 452 Case 3: Every packet is duplicated twice, so the Type-P-one-way- 453 packet-duplication-fraction is 200%. The type-P-one-way-replicated- 454 packet-rate is still 100%. 456 Case 4: Half the packets are duplicated twice and the other half are 457 not duplicated. The Type-P-one-way-packet-duplication-fraction is 458 again 100% and this number does not show the difference with case 2. 459 However, the type-P-one-way-packet-replicated-packet-rate is 50% in 460 this case and 100% in case 2. 462 However, the type-P-one-way-packet-duplication-rate will not show the 463 difference between case 2 and 3. For this, one has to look at the 464 Type-P-one-way-packet-duplication-fraction. 466 Finally, note that the order in which the packets arrived, do not 467 affect the results. For example, these variations of case 2: 468 o Case 2a: (1, 1, 2, 2, 3, 3, 4, 4) 469 o Case 2b: (1, 2, 3, 4, 1, 2, 3, 4) 470 o Case 2c: (1, 2, 3, 4, 4, 3, 2, 1) 471 (as well as any other permutation) all yield the same results for 472 Type-P-one-way-packet-duplication-fraction and the type-P-one-way- 473 replicated-packet-rate. 475 6. Security Considerations 477 Conducting Internet measurements raises both security and privacy 478 concerns. This memo does not specify an implementation of the 479 metrics, so it does not directly affect the security of the Internet 480 nor of applications which run on the Internet. However, 481 implementations of these metrics must be mindful of security and 482 privacy concerns. 484 There are two types of security concerns: potential harm caused by 485 the measurements, and potential harm to the measurements. The 486 measurements could cause harm because they are active, and inject 487 packets into the network. The measurement parameters MUST be 488 carefully selected so that the measurements inject trivial amounts of 489 additional traffic into the networks they measure. If they inject 490 "too much" traffic, they can skew the results of the measurement, and 491 in extreme cases cause congestion and denial of service. 493 The measurements themselves could be harmed by routers giving 494 measurement traffic a different priority than "normal" traffic, or by 495 an attacker injecting artificial measurement traffic. If routers can 496 recognize measurement traffic and treat it separately, the 497 measurements will not reflect actual user traffic. If an attacker 498 injects artificial traffic that is accepted as legitimate, the loss 499 rate will be artificially lowered. Therefore, the measurement 500 methodologies SHOULD include appropriate techniques to reduce the 501 probability measurement traffic can be distinguished from "normal" 502 traffic. Authentication techniques, such as digital signatures, may 503 be used where appropriate to guard against injected traffic attacks. 505 The privacy concerns of network measurement are limited by the active 506 measurements described in this memo. Unlike passive measurements, 507 there can be no release of existing user data. 509 7. IANA Considerations 511 IANA is asked to add this metrics to the IANA IP Performance Metrics 512 (IPPM) Metrics Registry, see [RFC4148]. This section can be removed 513 after this has been done and upon publication as a RFC. 515 8. Acknowledgements 517 The idea to write this draft came up in a meeting with Al Morton, 518 Stanislav Shalunov, Emile Stephan and the author, on the IPPM 519 reporting draft. 521 This document relies heavily on [RFC2680] and the author likes to 522 thank the authors of that document for writing it. 524 Finally, thanks are due to Lars Eggert, Al Morton, Martin Swany and 525 Matt Zekauskas for their comments. 527 9. References 529 9.1. Normative References 531 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 532 Requirement Levels", BCP 14, RFC 2119, March 1997. 534 [RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way 535 Packet Loss Metric for IPPM", RFC 2680, September 1999. 537 9.2. Informative References 539 [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, 540 "Framework for IP Performance Metrics", RFC 2330, 541 May 1998. 543 [RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network 544 performance measurement with periodic streams", RFC 3432, 545 November 2002. 547 [RFC4148] Stephan, E., "IP Performance Metrics (IPPM) Metrics 548 Registry", BCP 108, RFC 4148, August 2005. 550 [Y1540] "Y.1540 ITU-T Recommendation Y.1540 (2007), Internet 551 protocol data communication service IP packet transfer 552 and availability performance parameters.", 2007. 554 Author's Address 556 Henk Uijterwaal 557 RIPE NCC 558 Singel 258 559 1016 AB Amsterdam 560 The Netherlands 562 Phone: +31 20 535 4444 563 Email: henk@ripe.net 565 Full Copyright Statement 567 Copyright (C) The IETF Trust (2008). 569 This document is subject to the rights, licenses and restrictions 570 contained in BCP 78, and except as set forth therein, the authors 571 retain all their rights. 573 This document and the information contained herein are provided on an 574 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 575 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 576 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 577 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 578 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 579 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 581 Intellectual Property 583 The IETF takes no position regarding the validity or scope of any 584 Intellectual Property Rights or other rights that might be claimed to 585 pertain to the implementation or use of the technology described in 586 this document or the extent to which any license under such rights 587 might or might not be available; nor does it represent that it has 588 made any independent effort to identify any such rights. Information 589 on the procedures with respect to rights in RFC documents can be 590 found in BCP 78 and BCP 79. 592 Copies of IPR disclosures made to the IETF Secretariat and any 593 assurances of licenses to be made available, or the result of an 594 attempt made to obtain a general license or permission for the use of 595 such proprietary rights by implementers or users of this 596 specification can be obtained from the IETF on-line IPR repository at 597 http://www.ietf.org/ipr. 599 The IETF invites any interested party to bring to its attention any 600 copyrights, patents or patent applications, or other proprietary 601 rights that may cover technology that may be required to implement 602 this standard. Please address the information to the IETF at 603 ietf-ipr@ietf.org.