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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'SHOULD not' in this paragraph: It is important to highlight that the definition of the Hop-by-Hop Options in this document SHOULD not affect the throughput on nodes that do not recognize the Option. Indeed, the three high-order bits of the Options Header defined in this draft are 000 and, in theory, as per [RFC8200] and [I-D.hinden-6man-hbh-processing], this means "skip if do not recognize and data do not change en route". [RFC8200] also mentions that the nodes only examine and process the Hop-by-Hop Options header if explicitly configured to do so. For these reasons, this HbH Option should not affect the throughput. Anyway, in practice, it is important to be aware for the implementation that the things may be different and it can happen that packets with Hop-by-Hop are forced onto the slow path, but this is a general issue, as also explained in [I-D.hinden-6man-hbh-processing]. -- The document date (March 8, 2021) is 1145 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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-01) exists of draft-hinden-6man-hbh-processing-00 -- Obsolete informational reference (is this intentional?): RFC 8321 (Obsoleted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 (~~), 4 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: September 9, 2021 M. Cociglio 6 Telecom Italia 7 F. Qin 8 China Mobile 9 R. Pang 10 China Unicom 11 March 8, 2021 13 IPv6 Application of the Alternate Marking Method 14 draft-ietf-6man-ipv6-alt-mark-04 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 Requirements Language 26 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 27 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 28 document are to be interpreted as described in BCP 14 [RFC2119] 29 [RFC8174] when, and only when, they appear in all capitals, as shown 30 here. 32 Status of This Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at https://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 This Internet-Draft will expire on September 9, 2021. 49 Copyright Notice 51 Copyright (c) 2021 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (https://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Table of Contents 66 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 67 2. Alternate Marking application to IPv6 . . . . . . . . . . . . 3 68 2.1. Controlled Domain . . . . . . . . . . . . . . . . . . . . 4 69 3. Definition of the AltMark Option . . . . . . . . . . . . . . 5 70 3.1. Data Fields Format . . . . . . . . . . . . . . . . . . . 5 71 4. Use of the AltMark Option . . . . . . . . . . . . . . . . . . 6 72 5. Alternate Marking Method Operation . . . . . . . . . . . . . 8 73 5.1. Packet Loss Measurement . . . . . . . . . . . . . . . . . 8 74 5.2. Packet Delay Measurement . . . . . . . . . . . . . . . . 9 75 5.3. Flow Monitoring Identification . . . . . . . . . . . . . 10 76 5.3.1. Uniqueness of FlowMonID . . . . . . . . . . . . . . . 11 77 5.4. Multipoint and Clustered Alternate Marking . . . . . . . 12 78 5.5. Data Collection and Calculation . . . . . . . . . . . . . 12 79 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 80 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 81 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 82 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 83 9.1. Normative References . . . . . . . . . . . . . . . . . . 14 84 9.2. Informative References . . . . . . . . . . . . . . . . . 14 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 87 1. Introduction 89 [RFC8321] and [RFC8889] describe a passive performance measurement 90 method, which can be used to measure packet loss, latency and jitter 91 on live traffic. Since this method is based on marking consecutive 92 batches of packets, the method is often referred as the Alternate 93 Marking Method. 95 This document defines how the Alternate Marking Method can be used to 96 measure packet loss and delay metrics in IPv6. 98 The format of IPv6 addresses is defined in [RFC4291] while [RFC8200] 99 defines the IPv6 Header, including a 20-bit Flow Label and the IPv6 100 Extension Headers. 102 [I-D.fioccola-v6ops-ipv6-alt-mark] summarizes the possible 103 implementation options for the application of the Alternate Marking 104 Method in an IPv6 domain. This document, starting from the outcome 105 of [I-D.fioccola-v6ops-ipv6-alt-mark], introduces a new TLV that can 106 be encoded in the Options Headers (Hop-by-Hop or Destination) for the 107 purpose of the Alternate Marking Method application in an IPv6 108 domain. While the case of Segment Routing Header (SRH), defined in 109 [RFC8754], is also discussed, it is valid for all the types of 110 Routing Header (RH). 112 2. Alternate Marking application to IPv6 114 The Alternate Marking Method requires a marking field. As mentioned, 115 several alternatives have been analysed in 116 [I-D.fioccola-v6ops-ipv6-alt-mark] such as IPv6 Extension Headers, 117 IPv6 Address and Flow Label. 119 Consequently, a robust choice is to standardize a new Hop-by-Hop or 120 Destination Option. 122 This approach is compliant with [RFC8200]. The Alternate Marking 123 application to IPv6 involves the following operations: 125 o The source node is the only one that writes the Option Header to 126 mark alternately the flow (for both Hop-by-Hop and Destination 127 Option). 129 o In case of Hop-by-Hop Option Header carrying Alternate Marking 130 bits, it is not inserted or deleted, but can be read by any node 131 along the path. The intermediate nodes may be configured to 132 support this Option or not and the measurement can be done only 133 for the nodes configured to read the Option. Anyway this should 134 not affect the traffic throughput on nodes that do not recognize 135 the Option, as further discussed in Section 4. 137 o In case of Destination Option Header carrying Alternate Marking 138 bits, it is not processed, inserted, or deleted by any node along 139 the path until the packet reaches the destination node. Note 140 that, if there is also a Routing Header (RH), any visited 141 destination in the route list can process the Option Header. 143 Hop-by-Hop Option Header is also useful to signal to routers on the 144 path to process the Alternate Marking, anyway it is to be expected 145 that some routers cannot process it unless explicitly configured. 147 The optimization of both implementation and scaling of the Alternate 148 Marking Method is also considered and a way to identify flows is 149 required. The Flow Monitoring Identification field (FlowMonID), as 150 introduced in the next sections, goes in this direction and it is 151 used to identify a monitored flow. 153 Note that the FlowMonID is different from the Flow Label field of the 154 IPv6 Header ([RFC8200]). Flow Label is used for load-balancing/equal 155 cost multi-path (LB/ECMP). Instead, FlowMonID is only used to 156 identify the monitored flow. The reuse of flow label field for 157 identifying monitored flows is not considered since it may change the 158 application intent and forwarding behaviour. Furthermore the flow 159 label may be changed en route and this may also violate the 160 measurement task. Also, since the flow label is pseudo-random, there 161 is always a finite probability of collision. Those reasons make the 162 definition of the FlowMonID necessary for IPv6. Flow Label and 163 FlowMonID within the same packet have different scope, identify 164 different flows, and associate different uses. 166 An important point that will also be discussed in this document is 167 the the uniqueness of the FlowMonID and how to allow disambiguation 168 of the FlowMonID in case of collision. [RFC6437] states that the 169 Flow Label cannot be considered alone to avoid ambiguity since it 170 could be accidentally or intentionally changed en route for 171 compelling operational security reasons and this could also happen to 172 the IP addresses that can change due to NAT. But the Alternate 173 Marking is usually applied in a controlled domain, which would not 174 have NAT and there is no security issue that would necessitate 175 rewriting Flow Labels. So, for the purposes of this document, both 176 IP addresses and Flow Label should not change in flight and, in some 177 cases, they could be considered together with the FlowMonID for 178 disambiguation. 180 2.1. Controlled Domain 182 [RFC8799] introduces the concept of specific limited domain solutions 183 and, in this regard, it is reported the IPv6 Application of the 184 Alternate Marking Method as an example. 186 IPv6 has much more flexibility than IPv4 and innovative applications 187 have been proposed, but for a number of reasons, such as the options 188 supported, the style of network management and security requirements, 189 it is suggested to limit some of these applications to a controlled 190 domain. This is also the case of the Alternate Marking application 191 to IPv6 as assumed hereinafter. 193 3. Definition of the AltMark Option 195 The desired choice is to define a new TLV for the Options Extension 196 Headers, carrying the data fields dedicated to the alternate marking 197 method. 199 3.1. Data Fields Format 201 The following figure shows the data fields format for enhanced 202 alternate marking TLV. This AltMark data is expected to be 203 encapsulated in the IPv6 Options Headers (Hop-by-Hop or Destination 204 Option). 206 0 1 2 3 207 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 1 208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 209 | Option Type | Opt Data Len | 210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 211 | FlowMonID |L|D| Reserved | 212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 214 where: 216 o Option Type: 8 bit identifier of the type of Option that needs to 217 be allocated. Unrecognised Types MUST be ignored on receipt. For 218 Hop-by-Hop Options Header or Destination Options Header, [RFC8200] 219 defines how to encode the three high-order bits of the Option Type 220 field. The two high-order bits specify the action that must be 221 taken if the processing IPv6 node does not recognize the Option 222 Type; for AltMark these two bits MUST be set to 00 (skip over this 223 Option and continue processing the header). The third-highest- 224 order bit specifies whether or not the Option Data can change en 225 route to the packet's final destination; for AltMark the value of 226 this bit MUST be set to 0 (Option Data does not change en route). 228 o Opt Data Len: The length of the Option Data Fields of this Option 229 in bytes. 231 o FlowMonID: 20 bits unsigned integer. The FlowMon identifier is 232 described in Section 5.3. 234 o L: Loss flag for Packet Loss Measurement as described in 235 Section 5.1; 237 o D: Delay flag for Single Packet Delay Measurement as described in 238 Section 5.2; 240 o Reserved: is reserved for future use. These bits MUST be set to 241 zero on transmission and ignored on receipt. 243 4. Use of the AltMark Option 245 The AltMark Option is the best way to implement the Alternate Marking 246 method and can be carried by the Hop-by-Hop Options header and the 247 Destination Options header. In case of Destination Option, it is 248 processed only by the source and destination nodes: the source node 249 inserts and the destination node removes it. While, in case of Hop- 250 by-Hop Option, it may be examined by any node along the path, if 251 explicitly configured to do so. 253 It is important to highlight that the Option Layout can be used both 254 as Destination Option and as Hop-by-Hop Option depending on the Use 255 Cases and it is based on the chosen type of performance measurement. 256 In general, it is needed to perform both end to end and hop by hop 257 measurements, and the alternate marking methodology allows, by 258 definition, both performance measurements. Anyway, in many cases the 259 end-to-end measurement is not enough and it is required also the hop- 260 by-hop measurement, so the most complete choice is the Hop-by-Hop 261 Options Header. 263 IPv6, as specified in [RFC8200], allows nodes to optionally process 264 Hop-by-Hop headers. Specifically the Hop-by-Hop Options header is 265 not inserted or deleted, but may be examined or processed by any node 266 along a packet's delivery path, until the packet reaches the node (or 267 each of the set of nodes, in the case of multicast) identified in the 268 Destination Address field of the IPv6 header. Also, it is expected 269 that nodes along a packet's delivery path only examine and process 270 the Hop-by-Hop Options header if explicitly configured to do so. 272 The Hop-by-Hop Option defined in this document is designed to take 273 advantage of the property of how Hop-by-Hop options are processed. 274 Nodes that do not support this Option SHOULD ignore them. This can 275 mean that, in this case, the performance measurement does not account 276 for all links and nodes along a path. 278 Another application that can be mentioned is the presence of a 279 Routing Header, in particular it is possible to consider SRv6. A new 280 type of Routing Header, referred as SRH, has been defined for SRv6. 281 Like any other use case of IPv6, Hop-by-Hop and Destination Options 282 are useable when SRv6 header is present. Because SRv6 is implemented 283 through a Segment Routing Header (SRH), Destination Options before 284 the Routing Header are processed by each destination in the route 285 list, that means, in case of SRH, by every node that is an identity 286 in the SR path. 288 In summary, it is possible to list the alternative possibilities: 290 o Destination Option not preceding a Routing Header => measurement 291 only by node in Destination Address. 293 o Hop-by-Hop Option => every router on the path with feature 294 enabled. 296 o Destination Option preceding a Routing Header => every destination 297 node in the route list. 299 In general, Hop-by-Hop and Destination Options are the most suitable 300 ways to implement Alternate Marking. 302 It is worth mentioning that new Hop-by-Hop Options are not strongly 303 recommended in [RFC7045] and [RFC8200], unless there is a clear 304 justification to standardize it, because nodes may be configured to 305 ignore the Options Header, drop or assign packets containing an 306 Options Header to a slow processing path. In case of the AltMark 307 data fields described in this document, the motivation to standardize 308 a new Hop-by-Hop Option is that it is needed for OAM. An 309 intermediate node can read it or not but this does not affect the 310 packet behavior. The source node is the only one that writes the 311 Hop-by-Hop Option to mark alternately the flow, so, the performance 312 measurement can be done for those nodes configured to read this 313 Option, while the others are simply not considered for the metrics. 315 It is important to highlight that the definition of the Hop-by-Hop 316 Options in this document SHOULD not affect the throughput on nodes 317 that do not recognize the Option. Indeed, the three high-order bits 318 of the Options Header defined in this draft are 000 and, in theory, 319 as per [RFC8200] and [I-D.hinden-6man-hbh-processing], this means 320 "skip if do not recognize and data do not change en route". 321 [RFC8200] also mentions that the nodes only examine and process the 322 Hop-by-Hop Options header if explicitly configured to do so. For 323 these reasons, this HbH Option should not affect the throughput. 324 Anyway, in practice, it is important to be aware for the 325 implementation that the things may be different and it can happen 326 that packets with Hop-by-Hop are forced onto the slow path, but this 327 is a general issue, as also explained in 328 [I-D.hinden-6man-hbh-processing]. 330 In addition to the previous alternatives, it could be possible to 331 consider a non-conventional application of the Destination Options 332 for hop by hop action, but this would cause worse performance than 333 Hop-by-Hop. The only motivation for the hop by hop usage of 334 Destination Options can be for compatibility reasons but in general 335 it is not recommended. 337 5. Alternate Marking Method Operation 339 This section describes how the method operates. [RFC8321] introduces 340 several alternatives but in this section the most applicable methods 341 are reported and a new field is introduced to facilitate the 342 deployment and improve the scalability. 344 5.1. Packet Loss Measurement 346 The measurement of the packet loss is really straightforward. The 347 packets of the flow are grouped into batches, and all the packets 348 within a batch are marked by setting the L bit (Loss flag) to a same 349 value. The source node can switch the value of the L bit between 0 350 and 1 after a fixed number of packets or according to a fixed timer, 351 and this depends on the implementation. By counting the number of 352 packets in each batch and comparing the values measured by different 353 network nodes along the path, it is possible to measure the packet 354 loss occurred in any single batch between any two nodes. Each batch 355 represents a measurable entity unambiguously recognizable by all 356 network nodes along the path. 358 Packets with different L values may get swapped at batch boundaries, 359 and in this case, it is required that each marked packet can be 360 assigned to the right batch by each router. It is important to 361 mention that for the application of this method there are two 362 elements to consider: the clock error between network nodes and the 363 network delay. These can create offsets between the batches and out- 364 of-order of the packets. There is the condition on timing aspects 365 explained in [RFC8321] that must be satisfied and it takes into 366 considerations the different causes of reordering such as clock 367 error, network delay. The consequence is that it is necessary to 368 define a waiting interval where to get stable counters and to avoid 369 these issues. Usually the counters can be taken in the middle of the 370 batch period to be sure to take still counters. In a few words this 371 implies that the length of the batches MUST be chosen large enough so 372 that the method is not affected by those factors. 374 L bit=1 ----------+ +-----------+ +---------- 375 | | | | 376 L bit=0 +-----------+ +-----------+ 377 Batch n ... Batch 3 Batch 2 Batch 1 378 <---------> <---------> <---------> <---------> <---------> 380 Traffic Flow 381 ===========================================================> 382 L bit ...1111111111 0000000000 11111111111 00000000000 111111111... 383 ===========================================================> 385 Figure 1: Packet Loss Measurement and Single-Marking Methodology 386 using L bit 388 5.2. Packet Delay Measurement 390 The same principle used to measure packet loss can be applied also to 391 one-way delay measurement. Delay metrics MAY be calculated using the 392 two possibilities: 394 1. Single-Marking Methodology: This approach uses only the L bit to 395 calculate both packet loss and delay. In this case, the D flag 396 MUST be set to zero on transmit and ignored by the monitoring 397 points. The alternation of the values of the L bit can be used 398 as a time reference to calculate the delay. Whenever the L bit 399 changes and a new batch starts, a network node can store the 400 timestamp of the first packet of the new batch, that timestamp 401 can be compared with the timestamp of the first packet of the 402 same batch on a second node to compute packet delay. Anyway this 403 measurement is accurate only if no packet loss occurs and if 404 there is no packet reordering at the edges of the batches. A 405 different approach can also be considered and it is based on the 406 concept of the mean delay. The mean delay for each batch is 407 calculated by considering the average arrival time of the packets 408 for the relative batch. There are limitations also in this case 409 indeed, each node needs to collect all the timestamps and 410 calculate the average timestamp for each batch. In addition the 411 information is limited to a mean value. 413 2. Double-Marking Methodology: This approach is more complete and 414 uses the L bit only to calculate packet loss and the D bit (Delay 415 flag) is fully dedicated to delay measurements. The idea is to 416 use the first marking with the L bit to create the alternate flow 417 and, within the batches identified by the L bit, a second marking 418 is used to select the packets for measuring delay. The D bit 419 creates a new set of marked packets that are fully identified 420 over the network, so that a network node can store the timestamps 421 of these packets; these timestamps can be compared with the 422 timestamps of the same packets on a second node to compute packet 423 delay values for each packet. The most efficient and robust mode 424 is to select a single double-marked packet for each batch, in 425 this way there is no time gap to consider between the double- 426 marked packets to avoid their reorder. If a double-marked packet 427 is lost, the delay measurement for the considered batch is simply 428 discarded, but this is not a big problem because it is easy to 429 recognize the problematic batch and skip the measurement just for 430 that one. So in order to have more information about the delay 431 and to overcome out-of-order issues this method is preferred. 433 L bit=1 ----------+ +-----------+ +---------- 434 | | | | 435 L bit=0 +-----------+ +-----------+ 437 D bit=1 + + + + + 438 | | | | | 439 D bit=0 ------+----------+----------+----------+------------+----- 441 Traffic Flow 442 ===========================================================> 443 L bit ...1111111111 0000000000 11111111111 00000000000 111111111... 445 D bit ...0000010000 0000010000 00000100000 00001000000 000001000... 446 ===========================================================> 448 Figure 2: Double-Marking Methodology using L bit and D bit 450 Similar to packet delay measurement (both for Single Marking and 451 Double Marking), the method can also be used to measure the inter- 452 arrival jitter. 454 5.3. Flow Monitoring Identification 456 The Flow Monitoring Identification (FlowMonID) is required for some 457 general reasons: 459 o First, it helps to reduce the per node configuration. Otherwise, 460 each node needs to configure an access-control list (ACL) for each 461 of the monitored flows. Moreover, using a flow identifier allows 462 a flexible granularity for the flow definition. 464 o Second, it simplifies the counters handling. Hardware processing 465 of flow tuples (and ACL matching) is challenging and often incurs 466 into performance issues, especially in tunnel interfaces. 468 o Third, it eases the data export encapsulation and correlation for 469 the collectors. 471 The FlowMon identifier field is to uniquely identify a monitored flow 472 within the measurement domain. The field is set at the source node. 473 The FlowMonID can be uniformly assigned by the central controller or 474 algorithmically generated by the source node. The latter approach 475 cannot guarantee the uniqueness of FlowMonID but it may be preferred 476 for local or private network, where the conflict probability is small 477 due to the large FlowMonID space. 479 5.3.1. Uniqueness of FlowMonID 481 It is important to note that if the 20 bit FlowMonID is set 482 independently and pseudo randomly there is a chance of collision. 483 So, in some cases, FlowMonID could not be sufficient for uniqueness. 485 In general the probability of a flow identifier uniqueness correlates 486 to the amount of entropy of the inputs. For instance, using the 487 well-known birthday problem in probability theory, if the 20 bit 488 FlowMonID is set independently and pseudo randomly without any 489 additional input entropy, there is a 50% chance of collision for just 490 1206 flows. For a 32 bit identifier the 50% threshold jumps to 491 77,163 flows and so on. So, for more entropy, FlowMonID can either 492 be combined with other identifying flow information in a packet (e.g. 493 it is possible to consider the hashed 3-tuple Flow Label, Source and 494 Destination addresses) or the FlowMonID size could be increased. 496 This issue is more visible when the FlowMonID is pseudo randomly 497 generated by the source node and there needs to tag it with 498 additional flow information to allow disambiguation. While, in case 499 of a centralized controller, the controller should set FlowMonID by 500 considering these aspects and instruct the nodes properly in order to 501 guarantee its uniqueness. 503 Anyway, it is worth highlighting that the uniqueness of FlowMonID may 504 not be a problem and a low rate of ambiguous FlowMonIDs can be 505 acceptable, since this does not cause significant harm to the 506 operators or their clients and this harm may not justify the 507 complications of avoiding it. But, for large scale measurements 508 where it is possible to monitor a big number of flows, the 509 disambiguation of the Flow Monitoring Identification field is 510 something to take into account. 512 5.4. Multipoint and Clustered Alternate Marking 514 The Alternate Marking method can also be extended to any kind of 515 multipoint to multipoint paths, and the network clustering approach 516 allows a flexible and optimized performance measurement, as described 517 in [RFC8889]. 519 The Cluster is the smallest identifiable subnetwork of the entire 520 Network graph that still satisfies the condition that the number of 521 packets that goes in is the same that goes out. With network 522 clustering, it is possible to use the partition of the network into 523 clusters at different levels in order to perform the needed degree of 524 detail. So, for Multipoint Alternate Marking, FlowMonID can identify 525 in general a multipoint-to-multipoint flow and not only a point-to- 526 point flow. 528 5.5. Data Collection and Calculation 530 The nodes enabled to perform performance monitoring collect the value 531 of the packet counters and timestamps. There are several 532 alternatives to implement Data Collection and Calculation, but this 533 is not specified in this document. 535 6. Security Considerations 537 This document aims to apply a method to perform measurements that 538 does not directly affect Internet security nor applications that run 539 on the Internet. However, implementation of this method must be 540 mindful of security and privacy concerns. 542 There are two types of security concerns: potential harm caused by 543 the measurements and potential harm to the measurements. 545 Harm caused by the measurement: Alternate Marking implies 546 modifications on the fly to an Option Header of IPv6 packets by the 547 source node but this must be performed in a way that does not alter 548 the quality of service experienced by the packets and that preserves 549 stability and performance of routers doing the measurements. The 550 advantage of the Alternate Marking method is that the marking bits 551 are the only information that is exchanged between the network nodes. 552 Therefore, network reconnaissance through passive eavesdropping on 553 data-plane traffic does not allow attackers to gain information about 554 the network performance. Moreover, Alternate Marking should usually 555 be applied in a controlled domain and this also helps to limit the 556 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 assignments 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., Cociglio, M., and P. Muley, "IPv6 638 Performance Measurement with Alternate Marking Method", 639 draft-fioccola-v6ops-ipv6-alt-mark-01 (work in progress), 640 June 2018. 642 [I-D.hinden-6man-hbh-processing] 643 Hinden, R. 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