idnits 2.17.1 draft-ietf-6man-ipv6-alt-mark-06.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (May 31, 2021) is 1059 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-01) exists of draft-hinden-6man-hbh-processing-00 -- Obsolete informational reference (is this intentional?): RFC 8321 (Obsoleted by RFC 9341) -- Obsolete informational reference (is this intentional?): RFC 8889 (Obsoleted by RFC 9342) Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 6MAN Working Group G. Fioccola 3 Internet-Draft T. Zhou 4 Intended status: Standards Track Huawei 5 Expires: December 2, 2021 M. Cociglio 6 Telecom Italia 7 F. Qin 8 China Mobile 9 R. Pang 10 China Unicom 11 May 31, 2021 13 IPv6 Application of the Alternate Marking Method 14 draft-ietf-6man-ipv6-alt-mark-06 16 Abstract 18 This document describes how the Alternate Marking Method can be used 19 as a passive performance measurement tool in an IPv6 domain. It 20 defines a new Extension Header Option to encode alternate marking 21 information in both the Hop-by-Hop Options Header and Destination 22 Options Header. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at https://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on December 2, 2021. 41 Copyright Notice 43 Copyright (c) 2021 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (https://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 59 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 60 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 61 2. Alternate Marking application to IPv6 . . . . . . . . . . . . 3 62 2.1. Controlled Domain . . . . . . . . . . . . . . . . . . . . 4 63 3. Definition of the AltMark Option . . . . . . . . . . . . . . 5 64 3.1. Data Fields Format . . . . . . . . . . . . . . . . . . . 5 65 4. Use of the AltMark Option . . . . . . . . . . . . . . . . . . 6 66 5. Alternate Marking Method Operation . . . . . . . . . . . . . 8 67 5.1. Packet Loss Measurement . . . . . . . . . . . . . . . . . 8 68 5.2. Packet Delay Measurement . . . . . . . . . . . . . . . . 9 69 5.3. Flow Monitoring Identification . . . . . . . . . . . . . 10 70 5.3.1. Uniqueness of FlowMonID . . . . . . . . . . . . . . . 11 71 5.4. Multipoint and Clustered Alternate Marking . . . . . . . 12 72 5.5. Data Collection and Calculation . . . . . . . . . . . . . 12 73 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 74 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 75 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 76 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 77 9.1. Normative References . . . . . . . . . . . . . . . . . . 14 78 9.2. Informative References . . . . . . . . . . . . . . . . . 14 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 81 1. Introduction 83 [RFC8321] and [RFC8889] describe a passive performance measurement 84 method, which can be used to measure packet loss, latency and jitter 85 on live traffic. Since this method is based on marking consecutive 86 batches of packets, the method is often referred to as the Alternate 87 Marking Method. 89 This document defines how the Alternate Marking Method can be used to 90 measure packet loss and delay metrics in IPv6. 92 The format of IPv6 addresses is defined in [RFC4291] while [RFC8200] 93 defines the IPv6 Header, including a 20-bit Flow Label and the IPv6 94 Extension Headers. 96 [I-D.fioccola-v6ops-ipv6-alt-mark] summarizes the possible 97 implementation options for the application of the Alternate Marking 98 Method in an IPv6 domain. This document, starting from the outcome 99 of [I-D.fioccola-v6ops-ipv6-alt-mark], introduces a new TLV that can 100 be encoded in the Options Headers (Hop-by-Hop or Destination) for the 101 purpose of the Alternate Marking Method application in an IPv6 102 domain. While the case of Segment Routing Header (SRH), defined in 103 [RFC8754], is also discussed, it is valid for all the types of 104 Routing Header (RH). 106 1.1. Terminology 108 This document uses the terms related to the Alternate Marking Method 109 as defined in [RFC8321] and [RFC8889]. 111 1.2. Requirements Language 113 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 114 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 115 "OPTIONAL" in this document are to be interpreted as described in BCP 116 14 [RFC2119] [RFC8174] when, and only when, they appear in all 117 capitals, as shown here. 119 2. Alternate Marking application to IPv6 121 The Alternate Marking Method requires a marking field. As mentioned, 122 several alternatives have been analysed in 123 [I-D.fioccola-v6ops-ipv6-alt-mark] such as IPv6 Extension Headers, 124 IPv6 Address and Flow Label. 126 Consequently, a robust choice is to standardize a new Hop-by-Hop or 127 Destination Option. 129 This approach is compliant with [RFC8200]. The Alternate Marking 130 application to IPv6 involves the following operations: 132 o The source node is the only one that writes the Option Header to 133 mark alternately the flow (for both Hop-by-Hop and Destination 134 Option). 136 o In case of Hop-by-Hop Option Header carrying Alternate Marking 137 bits, it is not inserted or deleted, but can be read by any node 138 along the path. The intermediate nodes may be configured to 139 support this Option or not and the measurement can be done only 140 for the nodes configured to read the Option. Anyway this should 141 not affect the traffic throughput on nodes that do not recognize 142 the Option, as further discussed in Section 4. 144 o In case of Destination Option Header carrying Alternate Marking 145 bits, it is not processed, inserted, or deleted by any node along 146 the path until the packet reaches the destination node. Note 147 that, if there is also a Routing Header (RH), any visited 148 destination in the route list can process the Option Header. 150 Hop-by-Hop Option Header is also useful to signal to routers on the 151 path to process the Alternate Marking. However, as said, routers 152 will examine this option if properly configured. 154 The optimization of both implementation and scaling of the Alternate 155 Marking Method is also considered and a way to identify flows is 156 required. The Flow Monitoring Identification field (FlowMonID), as 157 introduced in the next sections, goes in this direction and it is 158 used to identify a monitored flow. 160 Note that the FlowMonID is different from the Flow Label field of the 161 IPv6 Header ([RFC8200]). Flow Label is used for load-balancing/equal 162 cost multi-path (LB/ECMP). Instead, FlowMonID is only used to 163 identify the monitored flow. The reuse of flow label field for 164 identifying monitored flows is not considered since it may change the 165 application intent and forwarding behaviour. Furthermore the flow 166 label may be changed en route and this may also violate the 167 measurement task. Also, since the flow label is pseudo-random, there 168 is always a finite probability of collision. Those reasons make the 169 definition of the FlowMonID necessary for IPv6. Flow Label and 170 FlowMonID within the same packet have different scope, identify 171 different flows, and are intended for different use cases. 173 An important point that will also be discussed in this document is 174 the uniqueness of the FlowMonID and how to allow disambiguation of 175 the FlowMonID in case of collision. [RFC6437] states that the Flow 176 Label cannot be considered alone to avoid ambiguity since it could be 177 accidentally or intentionally changed en route for compelling 178 operational security reasons. But the Alternate Marking is usually 179 applied in a controlled domain and there is no security issue that 180 would necessitate rewriting Flow Labels. So, for the purposes of 181 this document, both IP addresses and Flow Label should not change in 182 flight and, in some cases, they could be considered together with the 183 FlowMonID for disambiguation. 185 2.1. Controlled Domain 187 [RFC8799] introduces the concept of specific limited domain solutions 188 and, in this regard, it is reported the IPv6 Application of the 189 Alternate Marking Method as an example. 191 IPv6 has much more flexibility than IPv4 and innovative applications 192 have been proposed, but for a number of reasons, such as the options 193 supported, the style of network management and security requirements, 194 it is suggested to limit some of these applications to a controlled 195 domain. This is also the case of the Alternate Marking application 196 to IPv6 as assumed hereinafter. 198 3. Definition of the AltMark Option 200 The desired choice is to define a new TLV for the Options Extension 201 Headers, carrying the data fields dedicated to the alternate marking 202 method. 204 3.1. Data Fields Format 206 The following figure shows the data fields format for enhanced 207 alternate marking TLV. This AltMark data is expected to be 208 encapsulated in the IPv6 Options Headers (Hop-by-Hop or Destination 209 Option). 211 0 1 2 3 212 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 1 213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 214 | Option Type | Opt Data Len | 215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 216 | FlowMonID |L|D| Reserved | 217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 219 where: 221 o Option Type: 8 bit identifier of the type of Option that needs to 222 be allocated. Unrecognised Types MUST be ignored on receipt. For 223 Hop-by-Hop Options Header or Destination Options Header, [RFC8200] 224 defines how to encode the three high-order bits of the Option Type 225 field. The two high-order bits specify the action that must be 226 taken if the processing IPv6 node does not recognize the Option 227 Type; for AltMark these two bits MUST be set to 00 (skip over this 228 Option and continue processing the header). The third-highest- 229 order bit specifies whether or not the Option Data can change en 230 route to the packet's final destination; for AltMark the value of 231 this bit MUST be set to 0 (Option Data does not change en route). 233 o Opt Data Len: The length of the Option Data Fields of this Option 234 in bytes. 236 o FlowMonID: 20 bits unsigned integer. The FlowMon identifier is 237 described in Section 5.3. 239 o L: Loss flag for Packet Loss Measurement as described in 240 Section 5.1; 242 o D: Delay flag for Single Packet Delay Measurement as described in 243 Section 5.2; 245 o Reserved: is reserved for future use. These bits MUST be set to 246 zero on transmission and ignored on receipt. 248 4. Use of the AltMark Option 250 The AltMark Option is the best way to implement the Alternate Marking 251 method and can be carried by the Hop-by-Hop Options header and the 252 Destination Options header. In case of Destination Option, it is 253 processed only by the source and destination nodes: the source node 254 inserts and the destination node removes it. While, in case of Hop- 255 by-Hop Option, it may be examined by any node along the path, if 256 explicitly configured to do so. 258 It is important to highlight that the Option Layout can be used both 259 as Destination Option and as Hop-by-Hop Option depending on the Use 260 Cases and it is based on the chosen type of performance measurement. 261 In general, it is needed to perform both end to end and hop by hop 262 measurements, and the alternate marking methodology allows, by 263 definition, both performance measurements. Anyway, in many cases the 264 end-to-end measurement is not enough and it is required also the hop- 265 by-hop measurement, so the most complete choice is the Hop-by-Hop 266 Options Header. 268 IPv6, as specified in [RFC8200], allows nodes to optionally process 269 Hop-by-Hop headers. Specifically the Hop-by-Hop Options header is 270 not inserted or deleted, but may be examined or processed by any node 271 along a packet's delivery path, until the packet reaches the node (or 272 each of the set of nodes, in the case of multicast) identified in the 273 Destination Address field of the IPv6 header. Also, it is expected 274 that nodes along a packet's delivery path only examine and process 275 the Hop-by-Hop Options header if explicitly configured to do so. 277 The Hop-by-Hop Option defined in this document is designed to take 278 advantage of the property of how Hop-by-Hop options are processed. 279 Nodes that do not support this Option SHOULD ignore them. This can 280 mean that, in this case, the performance measurement does not account 281 for all links and nodes along a path. 283 Another application that can be mentioned is the presence of a 284 Routing Header, in particular it is possible to consider SRv6. A new 285 type of Routing Header, referred as SRH, has been defined for SRv6. 286 Like any other use case of IPv6, Hop-by-Hop and Destination Options 287 are useable when SRv6 header is present. Because SRv6 is implemented 288 through a Segment Routing Header (SRH), Destination Options before 289 the Routing Header are processed by each destination in the route 290 list, that means, in case of SRH, by every SR node that is identified 291 by the SR path. 293 In summary, it is possible to list the alternative possibilities: 295 o Destination Option not preceding a Routing Header => measurement 296 only by node in Destination Address. 298 o Hop-by-Hop Option => every router on the path with feature 299 enabled. 301 o Destination Option preceding a Routing Header => every destination 302 node in the route list. 304 In general, Hop-by-Hop and Destination Options are the most suitable 305 ways to implement Alternate Marking. 307 It is worth mentioning that new Hop-by-Hop Options are not strongly 308 recommended in [RFC7045] and [RFC8200], unless there is a clear 309 justification to standardize it, because nodes may be configured to 310 ignore the Options Header, drop or assign packets containing an 311 Options Header to a slow processing path. In case of the AltMark 312 data fields described in this document, the motivation to standardize 313 a new Hop-by-Hop Option is that it is needed for OAM. An 314 intermediate node can read it or not but this does not affect the 315 packet behavior. The source node is the only one that writes the 316 Hop-by-Hop Option to mark alternately the flow, so, the performance 317 measurement can be done for those nodes configured to read this 318 Option, while the others are simply not considered for the metrics. 320 It is important to highlight that the definition of the Hop-by-Hop 321 Options in this document SHOULD NOT affect the throughput on nodes 322 that do not recognize the Option. Indeed, the three high-order bits 323 of the Options Header defined in this draft are 000 and, in theory, 324 as per [RFC8200] and [I-D.hinden-6man-hbh-processing], this means 325 "skip if do not recognize and data do not change en route". 326 [RFC8200] also mentions that the nodes only examine and process the 327 Hop-by-Hop Options header if explicitly configured to do so. For 328 these reasons, this HbH Option should not affect the throughput. 329 Anyway, in practice, it is important to be aware for the 330 implementation that the things may be different and it can happen 331 that packets with Hop-by-Hop are forced onto the slow path, but this 332 is a general issue, as also explained in 333 [I-D.hinden-6man-hbh-processing]. 335 5. Alternate Marking Method Operation 337 This section describes how the method operates. [RFC8321] introduces 338 several alternatives but in this section the most applicable methods 339 are reported and a new field is introduced to facilitate the 340 deployment and improve the scalability. 342 5.1. Packet Loss Measurement 344 The measurement of the packet loss is really straightforward. The 345 packets of the flow are grouped into batches, and all the packets 346 within a batch are marked by setting the L bit (Loss flag) to a same 347 value. The source node can switch the value of the L bit between 0 348 and 1 after a fixed number of packets or according to a fixed timer, 349 and this depends on the implementation. By counting the number of 350 packets in each batch and comparing the values measured by different 351 network nodes along the path, it is possible to measure the packet 352 loss occurred in any single batch between any two nodes. Each batch 353 represents a measurable entity unambiguously recognizable by all 354 network nodes along the path. 356 Packets with different L values may get swapped at batch boundaries, 357 and in this case, it is required that each marked packet can be 358 assigned to the right batch by each router. It is important to 359 mention that for the application of this method there are two 360 elements to consider: the clock error between network nodes and the 361 network delay. These can create offsets between the batches and out- 362 of-order of the packets. There is the condition on timing aspects 363 explained in [RFC8321] that must be satisfied and it takes into 364 considerations the different causes of reordering such as clock 365 error, network delay. The consequence is that it is necessary to 366 define a waiting interval where to get stable counters and to avoid 367 these issues. Usually the counters can be taken in the middle of the 368 batch period to be sure to take still counters. In a few words this 369 implies that the length of the batches MUST be chosen large enough so 370 that the method is not affected by those factors. 372 L bit=1 ----------+ +-----------+ +---------- 373 | | | | 374 L bit=0 +-----------+ +-----------+ 375 Batch n ... Batch 3 Batch 2 Batch 1 376 <---------> <---------> <---------> <---------> <---------> 378 Traffic Flow 379 ===========================================================> 380 L bit ...1111111111 0000000000 11111111111 00000000000 111111111... 381 ===========================================================> 383 Figure 1: Packet Loss Measurement and Single-Marking Methodology 384 using L bit 386 5.2. Packet Delay Measurement 388 The same principle used to measure packet loss can be applied also to 389 one-way delay measurement. Delay metrics MAY be calculated using the 390 two possibilities: 392 1. Single-Marking Methodology: This approach uses only the L bit to 393 calculate both packet loss and delay. In this case, the D flag 394 MUST be set to zero on transmit and ignored by the monitoring 395 points. The alternation of the values of the L bit can be used 396 as a time reference to calculate the delay. Whenever the L bit 397 changes and a new batch starts, a network node can store the 398 timestamp of the first packet of the new batch, that timestamp 399 can be compared with the timestamp of the first packet of the 400 same batch on a second node to compute packet delay. Anyway this 401 measurement is accurate only if no packet loss occurs and if 402 there is no packet reordering at the edges of the batches. A 403 different approach can also be considered and it is based on the 404 concept of the mean delay. The mean delay for each batch is 405 calculated by considering the average arrival time of the packets 406 for the relative batch. There are limitations also in this case 407 indeed, each node needs to collect all the timestamps and 408 calculate the average timestamp for each batch. In addition the 409 information is limited to a mean value. 411 2. Double-Marking Methodology: This approach is more complete and 412 uses the L bit only to calculate packet loss and the D bit (Delay 413 flag) is fully dedicated to delay measurements. The idea is to 414 use the first marking with the L bit to create the alternate flow 415 and, within the batches identified by the L bit, a second marking 416 is used to select the packets for measuring delay. The D bit 417 creates a new set of marked packets that are fully identified 418 over the network, so that a network node can store the timestamps 419 of these packets; these timestamps can be compared with the 420 timestamps of the same packets on a second node to compute packet 421 delay values for each packet. The most efficient and robust mode 422 is to select a single double-marked packet for each batch, in 423 this way there is no time gap to consider between the double- 424 marked packets to avoid their reorder. If a double-marked packet 425 is lost, the delay measurement for the considered batch is simply 426 discarded, but this is not a big problem because it is easy to 427 recognize the problematic batch and skip the measurement just for 428 that one. So in order to have more information about the delay 429 and to overcome out-of-order issues this method is preferred. 431 L bit=1 ----------+ +-----------+ +---------- 432 | | | | 433 L bit=0 +-----------+ +-----------+ 435 D bit=1 + + + + + 436 | | | | | 437 D bit=0 ------+----------+----------+----------+------------+----- 439 Traffic Flow 440 ===========================================================> 441 L bit ...1111111111 0000000000 11111111111 00000000000 111111111... 443 D bit ...0000010000 0000010000 00000100000 00001000000 000001000... 444 ===========================================================> 446 Figure 2: Double-Marking Methodology using L bit and D bit 448 Similar to packet delay measurement (both for Single Marking and 449 Double Marking), the method can also be used to measure the inter- 450 arrival jitter. 452 5.3. Flow Monitoring Identification 454 The Flow Monitoring Identification (FlowMonID) is required for some 455 general reasons: 457 o First, it helps to reduce the per node configuration. Otherwise, 458 each node needs to configure an access-control list (ACL) for each 459 of the monitored flows. Moreover, using a flow identifier allows 460 a flexible granularity for the flow definition. 462 o Second, it simplifies the counters handling. Hardware processing 463 of flow tuples (and ACL matching) is challenging and often incurs 464 into performance issues, especially in tunnel interfaces. 466 o Third, it eases the data export encapsulation and correlation for 467 the collectors. 469 The FlowMon identifier field is to uniquely identify a monitored flow 470 within the measurement domain. The field is set at the source node. 471 The FlowMonID can be uniformly assigned by the central controller or 472 algorithmically generated by the source node. The latter approach 473 cannot guarantee the uniqueness of FlowMonID but it may be preferred 474 for local or private network, where the conflict probability is small 475 due to the large FlowMonID space. 477 5.3.1. Uniqueness of FlowMonID 479 It is important to note that if the 20 bit FlowMonID is set 480 independently and pseudo randomly there is a chance of collision. 481 So, in some cases, FlowMonID could not be sufficient for uniqueness. 483 In general the probability of a flow identifier uniqueness correlates 484 to the amount of entropy of the inputs. For instance, using the 485 well-known birthday problem in probability theory, if the 20 bit 486 FlowMonID is set independently and pseudo randomly without any 487 additional input entropy, there is a 50% chance of collision for just 488 1206 flows. For a 32 bit identifier the 50% threshold jumps to 489 77,163 flows and so on. So, for more entropy, FlowMonID can either 490 be combined with other identifying flow information in a packet (e.g. 491 it is possible to consider the hashed 3-tuple Flow Label, Source and 492 Destination addresses) or the FlowMonID size could be increased. 494 This issue is more visible when the FlowMonID is pseudo randomly 495 generated by the source node and there needs to tag it with 496 additional flow information to allow disambiguation. While, in case 497 of a centralized controller, the controller should set FlowMonID by 498 considering these aspects and instruct the nodes properly in order to 499 guarantee its uniqueness. 501 Anyway, it is worth highlighting that the uniqueness of FlowMonID may 502 not be a problem and a low rate of ambiguous FlowMonIDs can be 503 acceptable, since this does not cause significant harm to the 504 operators or their clients and this harm may not justify the 505 complications of avoiding it. But, for large scale measurements 506 where it is possible to monitor a big number of flows, the 507 disambiguation of the Flow Monitoring Identification field is 508 something to take into account. 510 5.4. Multipoint and Clustered Alternate Marking 512 The Alternate Marking method can also be extended to any kind of 513 multipoint to multipoint paths, and the network clustering approach 514 allows a flexible and optimized performance measurement, as described 515 in [RFC8889]. 517 The Cluster is the smallest identifiable subnetwork of the entire 518 Network graph that still satisfies the condition that the number of 519 packets that goes in is the same that goes out. With network 520 clustering, it is possible to use the partition of the network into 521 clusters at different levels in order to perform the needed degree of 522 detail. So, for Multipoint Alternate Marking, FlowMonID can identify 523 in general a multipoint-to-multipoint flow and not only a point-to- 524 point flow. 526 5.5. Data Collection and Calculation 528 The nodes enabled to perform performance monitoring collect the value 529 of the packet counters and timestamps. There are several 530 alternatives to implement Data Collection and Calculation, but this 531 is not specified in this document. 533 6. Security Considerations 535 This document aims to apply a method to perform measurements that 536 does not directly affect Internet security nor applications that run 537 on the Internet. However, implementation of this method must be 538 mindful of security and privacy concerns. 540 There are two types of security concerns: potential harm caused by 541 the measurements and potential harm to the measurements. 543 Harm caused by the measurement: Alternate Marking implies 544 modifications on the fly to an Option Header of IPv6 packets by the 545 source node but this must be performed in a way that does not alter 546 the quality of service experienced by the packets and that preserves 547 stability and performance of routers doing the measurements. The 548 advantage of the Alternate Marking method is that the marking bits 549 are the only small information that is exchanged between the network 550 nodes. Therefore, due to this intrinsic characteristic, network 551 reconnaissance through passive eavesdropping on data-plane traffic is 552 difficult. Indeed the only way for an attacker can be to eavesdrop 553 on multiple nodes at the same time, apply the methodology and finally 554 gain information about the network performance, but this is not 555 immediate. Moreover, Alternate Marking should usually be applied in 556 a controlled domain and this also helps to limit the problem. 558 Harm to the Measurement: Alternate Marking measurements could be 559 harmed by routers altering the marking of the packets or by an 560 attacker injecting artificial traffic. Since the measurement itself 561 may be affected by network nodes along the path intentionally 562 altering the value of the marking bits of IPv6 packets, the Alternate 563 Marking should be applied in the context of a controlled domain, 564 where the network nodes are locally administered and this type of 565 attack can be avoided. Indeed the source and destination addresses 566 are within the controlled domain and therefore it is unlikely subject 567 to hijacking of packets, because it is possible to filter external 568 packets at the domain boundaries. In addition, an attacker cannot 569 gain information about network performance from a single monitoring 570 point; it must use synchronized monitoring points at multiple points 571 on the path, because they have to do the same kind of measurement and 572 aggregation as Alternate Marking requires. 574 Additionally, it is to be noted that Alternate Marking bits are 575 carried by the Options Header and it may have some impact on the 576 packet sizes for the monitored flow and on the path MTU, since some 577 packets might exceed the MTU. Anyway the relative small size (48 bit 578 in total) of these Option Headers and its application to a controlled 579 domain help to mitigate the problem. 581 The privacy concerns of network measurement are limited because the 582 method only relies on information contained in the Option Header 583 without any release of user data. Although information in the Option 584 Header is metadata that can be used to compromise the privacy of 585 users, the limited marking technique seems unlikely to substantially 586 increase the existing privacy risks from header or encapsulation 587 metadata. 589 The Alternate Marking application described in this document relies 590 on an time synchronization protocol. Thus, by attacking the time 591 protocol, an attacker can potentially compromise the integrity of the 592 measurement. A detailed discussion about the threats against time 593 protocols and how to mitigate them is presented in [RFC7384]. 595 7. IANA Considerations 597 The Option Type should be assigned in IANA's "Destination Options and 598 Hop-by-Hop Options" registry. 600 This draft requests the following IPv6 Option Type assignment from 601 the Destination Options and Hop-by-Hop Options sub-registry of 602 Internet Protocol Version 6 (IPv6) Parameters 603 (https://www.iana.org/assignments/ipv6-parameters/). 605 Hex Value Binary Value Description Reference 606 act chg rest 607 ---------------------------------------------------------------- 608 TBD 00 0 tbd AltMark [This draft] 610 8. Acknowledgements 612 The authors would like to thank Bob Hinden, Ole Troan, Tom Herbert, 613 Stefano Previdi, Brian Carpenter, Eric Vyncke, Ron Bonica, Greg 614 Mirsky for the precious comments and suggestions. 616 9. References 618 9.1. Normative References 620 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 621 Requirement Levels", BCP 14, RFC 2119, 622 DOI 10.17487/RFC2119, March 1997, 623 . 625 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 626 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 627 May 2017, . 629 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 630 (IPv6) Specification", STD 86, RFC 8200, 631 DOI 10.17487/RFC8200, July 2017, 632 . 634 9.2. Informative References 636 [I-D.fioccola-v6ops-ipv6-alt-mark] 637 Fioccola, G., Velde, G. V. D., Cociglio, M., and P. Muley, 638 "IPv6 Performance Measurement with Alternate Marking 639 Method", draft-fioccola-v6ops-ipv6-alt-mark-01 (work in 640 progress), June 2018. 642 [I-D.hinden-6man-hbh-processing] 643 Hinden, R. M. and G. Fairhurst, "IPv6 Hop-by-Hop Options 644 Processing Procedures", draft-hinden-6man-hbh- 645 processing-00 (work in progress), December 2020. 647 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 648 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 649 2006, . 651 [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, 652 "IPv6 Flow Label Specification", RFC 6437, 653 DOI 10.17487/RFC6437, November 2011, 654 . 656 [RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing 657 of IPv6 Extension Headers", RFC 7045, 658 DOI 10.17487/RFC7045, December 2013, 659 . 661 [RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in 662 Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384, 663 October 2014, . 665 [RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli, 666 L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi, 667 "Alternate-Marking Method for Passive and Hybrid 668 Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321, 669 January 2018, . 671 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 672 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 673 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 674 . 676 [RFC8799] Carpenter, B. and B. Liu, "Limited Domains and Internet 677 Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020, 678 . 680 [RFC8889] Fioccola, G., Ed., Cociglio, M., Sapio, A., and R. Sisto, 681 "Multipoint Alternate-Marking Method for Passive and 682 Hybrid Performance Monitoring", RFC 8889, 683 DOI 10.17487/RFC8889, August 2020, 684 . 686 Authors' Addresses 688 Giuseppe Fioccola 689 Huawei 690 Riesstrasse, 25 691 Munich 80992 692 Germany 694 Email: giuseppe.fioccola@huawei.com 695 Tianran Zhou 696 Huawei 697 156 Beiqing Rd. 698 Beijing 100095 699 China 701 Email: zhoutianran@huawei.com 703 Mauro Cociglio 704 Telecom Italia 705 Via Reiss Romoli, 274 706 Torino 10148 707 Italy 709 Email: mauro.cociglio@telecomitalia.it 711 Fengwei Qin 712 China Mobile 713 32 Xuanwumenxi Ave. 714 Beijing 100032 715 China 717 Email: qinfengwei@chinamobile.com 719 Ran Pang 720 China Unicom 721 9 Shouti South Rd. 722 Beijing 100089 723 China 725 Email: pangran@chinaunicom.cn