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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 5316 (Obsoleted by RFC 9346) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Networking Working Group S. Previdi, Ed. 3 Internet-Draft Cisco Systems, Inc. 4 Intended status: Standards Track S. Giacalone 5 Expires: December 18, 2015 Unaffiliated 6 D. Ward 7 Cisco Systems, Inc. 8 J. Drake 9 A. Atlas 10 Juniper Networks 11 C. Filsfils 12 Cisco Systems, Inc. 13 Q. Wu 14 Huawei 15 June 16, 2015 17 IS-IS Traffic Engineering (TE) Metric Extensions 18 draft-ietf-isis-te-metric-extensions-07 20 Abstract 22 In certain networks, such as, but not limited to, financial 23 information networks (e.g. stock market data providers), network 24 performance criteria (e.g. latency) are becoming as critical to data 25 path selection as other metrics. 27 This document describes extensions to IS-IS Traffic Engineering 28 Extensions (RFC5305) such that network performance information can be 29 distributed and collected in a scalable fashion. The information 30 distributed using ISIS TE Metric Extensions can then be used to make 31 path selection decisions based on network performance. 33 Note that this document only covers the mechanisms with which network 34 performance information is distributed. The mechanisms for measuring 35 network performance or acting on that information, once distributed, 36 are outside the scope of this document. 38 Requirements Language 40 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 41 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 42 document are to be interpreted as described in RFC 2119 [RFC2119]. 44 In this document, these words will appear with that interpretation 45 only when in ALL CAPS. Lower case uses of these words are not to be 46 interpreted as carrying RFC-2119 significance. 48 Status of This Memo 50 This Internet-Draft is submitted in full conformance with the 51 provisions of BCP 78 and BCP 79. 53 Internet-Drafts are working documents of the Internet Engineering 54 Task Force (IETF). Note that other groups may also distribute 55 working documents as Internet-Drafts. The list of current Internet- 56 Drafts is at http://datatracker.ietf.org/drafts/current/. 58 Internet-Drafts are draft documents valid for a maximum of six months 59 and may be updated, replaced, or obsoleted by other documents at any 60 time. It is inappropriate to use Internet-Drafts as reference 61 material or to cite them other than as "work in progress." 63 This Internet-Draft will expire on December 18, 2015. 65 Copyright Notice 67 Copyright (c) 2015 IETF Trust and the persons identified as the 68 document authors. All rights reserved. 70 This document is subject to BCP 78 and the IETF Trust's Legal 71 Provisions Relating to IETF Documents 72 (http://trustee.ietf.org/license-info) in effect on the date of 73 publication of this document. Please review these documents 74 carefully, as they describe your rights and restrictions with respect 75 to this document. Code Components extracted from this document must 76 include Simplified BSD License text as described in Section 4.e of 77 the Trust Legal Provisions and are provided without warranty as 78 described in the Simplified BSD License. 80 Table of Contents 82 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 83 2. TE Metric Extensions to IS-IS . . . . . . . . . . . . . . . . 4 84 3. Interface and Neighbor Addresses . . . . . . . . . . . . . . 5 85 4. Sub TLV Details . . . . . . . . . . . . . . . . . . . . . . . 6 86 4.1. Unidirectional Link Delay Sub-TLV . . . . . . . . . . . . 6 87 4.2. Min/Max Unidirectional Link Delay Sub-TLV . . . . . . . . 7 88 4.3. Unidirectional Delay Variation Sub-TLV . . . . . . . . . 8 89 4.4. Unidirectional Link Loss Sub-TLV . . . . . . . . . . . . 8 90 4.5. Unidirectional Residual Bandwidth Sub-TLV . . . . . . . . 9 91 4.6. Unidirectional Available Bandwidth Sub-TLV . . . . . . . 10 92 4.7. Unidirectional Utilized Bandwidth Sub-TLV . . . . . . . . 11 93 5. Announcement Thresholds and Filters . . . . . . . . . . . . . 12 94 6. Announcement Suppression . . . . . . . . . . . . . . . . . . 13 95 7. Network Stability and Announcement Periodicity . . . . . . . 13 96 8. Enabling and Disabling Sub-TLVs . . . . . . . . . . . . . . . 14 97 9. Static Metric Override . . . . . . . . . . . . . . . . . . . 14 98 10. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 14 99 11. Security Considerations . . . . . . . . . . . . . . . . . . . 14 100 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 101 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15 102 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 103 14.1. Normative References . . . . . . . . . . . . . . . . . . 15 104 14.2. Informative References . . . . . . . . . . . . . . . . . 16 105 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 107 1. Introduction 109 In certain networks, such as, but not limited to, financial 110 information networks (e.g. stock market data providers), network 111 performance information (e.g. latency) is becoming as critical to 112 data path selection as other metrics. 114 In these networks, extremely large amounts of money rest on the 115 ability to access market data in "real time" and to predictably make 116 trades faster than the competition. Because of this, using metrics 117 such as hop count or cost as routing metrics is becoming only 118 tangentially important. Rather, it would be beneficial to be able to 119 make path selection decisions based on performance data (such as 120 latency) in a cost-effective and scalable way. 122 This document describes extensions to IS-IS Extended Reachability TLV 123 defined in [RFC5305] (hereafter called "IS-IS TE Metric Extensions"), 124 that can be used to distribute network performance information (such 125 as link delay, delay variation, link loss, residual bandwidth, and 126 available bandwidth). 128 The data distributed by the TE Metric Extensions proposed in this 129 document is meant to be used as part of the operation of the routing 130 protocol (e.g. by replacing cost with latency or considering 131 bandwidth as well as cost), by enhancing Constrained-SPF (CSPF), or 132 for other uses such as supplementing the data used by an ALTO server 133 [RFC7285]. With respect to CSPF, the data distributed by ISIS TE 134 Metric Extensions can be used to setup, fail over, and fail back data 135 paths using protocols such as RSVP-TE [RFC3209]. 137 Note that the mechanisms described in this document only disseminate 138 performance information. The methods for initially gathering that 139 performance information, such as [RFC6375], or acting on it once it 140 is distributed are outside the scope of this document. Example 141 mechanisms to measure latency, delay variation, and loss in an MPLS 142 network are given in [RFC6374]. While this document does not specify 143 how the performance information should be obtained, the measurement 144 of delay SHOULD NOT vary significantly based upon the offered traffic 145 load. Thus, queuing delays SHOULD NOT be included in the delay 146 measurement. For links, such as Forwarding Adjacencies, care must be 147 taken that measurement of the associated delay avoids significant 148 queuing delay; that could be accomplished in a variety of ways, 149 including either by measuring with a traffic class that experiences 150 minimal queuing or by summing the measured link delays of the 151 components of the link's path. 153 2. TE Metric Extensions to IS-IS 155 This document proposes new IS-IS TE sub-TLVs that can be announced in 156 TLVs 22, 23, 141, 222, and 223 in order to distribute network 157 performance information. The extensions in this document build on 158 the ones provided in IS-IS TE [RFC5305] and GMPLS [RFC4203]. 160 IS-IS Extended Reachability TLV 22 (defined in [RFC5305]), Inter-AS 161 reachability information TLV 141 (defined in [RFC5316]) and MT-ISIS 162 TLV 222 (defined in [RFC5120]) have nested sub-TLVs which permit the 163 TLVs to be readily extended. This document proposes several 164 additional sub-TLVs: 166 Type Value 167 ---------------------------------------------------- 168 33 (Suggested) Unidirectional Link Delay 170 34 (Suggested) Min/Max Unidirectional Link Delay 172 35 (Suggested) Unidirectional Delay Variation 174 36 (Suggested) Unidirectional Link Loss 176 37 (Suggested) Unidirectional Residual Bandwidth 178 38 (Suggested) Unidirectional Available Bandwidth 180 39 (Suggested) Unidirectional Bandwidth Utilization 182 As can be seen in the list above, the sub-TLVs described in this 183 document carry different types of network performance information. 184 The new sub-TLVs include a bit called the Anomalous (or "A") bit. 185 When the A bit is clear (or when the sub-TLV does not include an A 186 bit), the sub-TLV describes steady state link performance. This 187 information could conceivably be used to construct a steady state 188 performance topology for initial tunnel path computation, or to 189 verify alternative failover paths. 191 When network performance violates configurable link-local thresholds 192 a sub-TLV with the A bit set is advertised. These sub-TLVs could be 193 used by the receiving node to determine whether to fail traffic to a 194 backup path, or whether to calculate an entirely new path. From an 195 MPLS perspective, the intent of the A bit is to permit LSP ingress 196 nodes to: 198 A) Determine whether the link referenced in the sub-TLV affects any 199 of the LSPs for which it is ingress. If there are, then: 201 B) Determine whether those LSPs still meet end-to-end performance 202 objectives. If not, then: 204 C) The node could then conceivably move affected traffic to a pre- 205 established protection LSP or establish a new LSP and place the 206 traffic in it. 208 If link performance then improves beyond a configurable minimum value 209 (reuse threshold), that sub-TLV can be re-advertised with the 210 Anomalous bit cleared. In this case, a receiving node can 211 conceivably do whatever re-optimization (or failback) it wishes to do 212 (including nothing). 214 Note that when a sub-TLV does not include the A bit, that sub-TLV 215 cannot be used for failover purposes. The A bit was intentionally 216 omitted from some sub-TLVs to help mitigate oscillations. See 217 Section 5 for more information. 219 Consistent with existing IS-IS TE specification [RFC5305], the 220 bandwidth advertisements defined in this draft MUST be encoded as 221 IEEE floating point values. The delay and delay variation 222 advertisements defined in this draft MUST be encoded as integer 223 values. Delay values MUST be quantified in units of microseconds, 224 link loss MUST be quantified as a percentage of packets sent, and 225 bandwidth MUST be sent as bytes per second. All values (except 226 residual bandwidth) MUST be calculated as rolling averages where the 227 averaging period MUST be a configurable period of time. See 228 Section 5 for more information. 230 3. Interface and Neighbor Addresses 232 The use of TE Metric Extensions SubTLVs is not confined to the TE 233 context. In other words, IS-IS TE Metric Extensions SubTLVs defined 234 in this document can also be used for computing paths in the absence 235 of a TE subsystem. 237 However, as for the TE case, Interface Address and Neighbor Address 238 SubTLVs (IPv4 or IPv6) MUST be present. The encoding is defined in 239 [RFC5305] for IPv4 and in [RFC6119] for IPv6. 241 4. Sub TLV Details 243 4.1. Unidirectional Link Delay Sub-TLV 245 This sub-TLV advertises the average link delay between two directly 246 connected IS-IS neighbors. The delay advertised by this sub-TLV MUST 247 be the delay from the local neighbor to the remote one (i.e. the 248 forward path latency). The format of this sub-TLV is shown in the 249 following diagram: 251 0 1 2 3 252 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 1 253 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 254 | Type | Length | 255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 256 |A| RESERVED | Delay | 257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 259 where: 261 Figure 1 263 Type: TBA (suggested value: 33). 265 Length: 4. 267 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 268 when the measured value of this parameter exceeds its configured 269 maximum threshold. The A bit is cleared when the measured value 270 falls below its configured reuse threshold. If the A-bit is clear, 271 the sub-TLV represents steady state link performance. 273 RESERVED. This field is reserved for future use. It MUST be set to 274 0 when sent and MUST be ignored when received. 276 Delay. This 24-bit field carries the average link delay over a 277 configurable interval in micro-seconds, encoded as an integer value. 278 When set to the maximum value 16,777,215 (16.777215 sec), then the 279 delay is at least that value and may be larger. 281 4.2. Min/Max Unidirectional Link Delay Sub-TLV 283 This sub-TLV advertises the minimum and maximum delay values between 284 two directly connected IS-IS neighbors. The delay advertised by this 285 sub-TLV MUST be the delay from the local neighbor to the remote one 286 (i.e. the forward path latency). The format of this sub-TLV is shown 287 in the following diagram: 289 0 1 2 3 290 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 1 291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 292 | Type | Length | 293 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 294 |A| RESERVED | Min Delay | 295 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 296 | RESERVED | Max Delay | 297 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 299 where: 301 Figure 2 303 Type: TBA (suggested value: 34). 305 Length: 8. 307 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 308 when the measured value of this parameter exceeds its configured 309 maximum threshold. The A bit is cleared when the measured value 310 falls below its configured reuse threshold. If the A-bit is clear, 311 the sub-TLV represents steady state link performance. 313 RESERVED. This field is reserved for future use. It MUST be set to 314 0 when sent and MUST be ignored when received. 316 Min Delay. This 24-bit field carries minimum measured link delay 317 value (in microseconds) over a configurable interval, encoded as an 318 integer value. 320 Max Delay. This 24-bit field carries the maximum measured link delay 321 value (in microseconds) over a configurable interval, encoded as an 322 integer value. 324 Implementations MAY also permit the configuration of an offset value 325 (in microseconds) to be added to the measured delay value, to 326 facilitate the communication of operator specific delay constraints. 328 It is possible for the Min and Max delay to be the same value. 330 When the delay value (Min or Max) is set to maximum value 16,777,215 331 (16.777215 sec), then the delay is at least that value and may be 332 larger. 334 4.3. Unidirectional Delay Variation Sub-TLV 336 This sub-TLV advertises the average link delay variation between two 337 directly connected IS-IS neighbors. The delay variation advertised 338 by this sub-TLV MUST be the delay from the local neighbor to the 339 remote one (i.e. the forward path latency). The format of this sub- 340 TLV is shown in the following diagram: 342 0 1 2 3 343 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 1 344 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 345 | Type | Length | 346 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 347 | RESERVED | Delay Variation | 348 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 350 where: 352 Figure 3 354 Type: TBA (suggested value: 35). 356 Length: 4. 358 RESERVED. This field is reserved for future use. It MUST be set to 359 0 when sent and MUST be ignored when received. 361 Delay Variation. This 24-bit field carries the average link delay 362 variation over a configurable interval in microseconds, encoded as an 363 integer value. When set to 0, it has not been measured. When set to 364 the maximum value 16,777,215 (16.777215 sec), then the delay is at 365 least that value and may be larger. 367 4.4. Unidirectional Link Loss Sub-TLV 369 This sub-TLV advertises the loss (as a packet percentage) between two 370 directly connected IS-IS neighbors. The link loss advertised by this 371 sub-TLV MUST be the packet loss from the advertising node to its 372 neighbor (i.e. the forward path loss). The format of this sub-TLV is 373 shown in the following diagram: 375 0 1 2 3 376 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 1 377 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 378 | Type | Length | 379 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 380 |A| RESERVED | Link Loss | 381 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 383 This sub-TLV has a type of TBD3. 384 The length is 4. 386 where: 388 Type: TBA (suggested value: 36). 390 Length: 4. 392 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 393 when the measured value of this parameter exceeds its configured 394 maximum threshold. The A bit is cleared when the measured value 395 falls below its configured reuse threshold. If the A-bit is clear, 396 the sub-TLV represents steady state link performance. 398 RESERVED. This field is reserved for future use. It MUST be set to 399 0 when sent and MUST be ignored when received. 401 Link Loss. This 24-bit field carries link packet loss as a 402 percentage of the total traffic sent over a configurable interval. 403 The basic unit is 0.000003%, where (2^24 - 2) is 50.331642%. This 404 value is the highest packet loss percentage that can be expressed 405 (the assumption being that precision is more important on high speed 406 links than the ability to advertise loss rates greater than this, and 407 that high speed links with over 50% loss are unusable). Therefore, 408 measured values that are larger than the field maximum SHOULD be 409 encoded as the maximum value. 411 4.5. Unidirectional Residual Bandwidth Sub-TLV 413 This TLV advertises the residual bandwidth between two directly 414 connected IS-IS neighbors. The residual bandwidth advertised by this 415 sub-TLV MUST be the residual bandwidth from the system originating 416 the LSA to its neighbor. 418 0 1 2 3 419 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 1 420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 421 | Type | Length | RESERVED | 422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 423 | Residual Bandwidth | 424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 426 where: 428 Type: TBA (suggested value: 37). 430 Length: 4. 432 RESERVED. This field is reserved for future use. It MUST be set to 433 0 when sent and MUST be ignored when received. 435 Residual Bandwidth. This field carries the residual bandwidth on a 436 link, forwarding adjacency [RFC4206], or bundled link in IEEE 437 floating point format with units of bytes per second. For a link or 438 forwarding adjacency, residual bandwidth is defined to be Maximum 439 Bandwidth [RFC5305] minus the bandwidth currently allocated to RSVP- 440 TE LSPs. For a bundled link, residual bandwidth is defined to be the 441 sum of the component link residual bandwidths. 443 The calculation of Residual Bandwidth is different than that of 444 Unreserved Bandwidth [RFC5305]. Residual Bandwidth subtracts tunnel 445 reservations from Maximum Bandwidth (i.e. the link capacity) 446 [RFC5305] and provides an aggregated remainder across priorities. 447 Unreserved Bandwidth, on the other hand, is subtracted from the 448 Maximum Reservable Bandwidth (the bandwidth that can theoretically be 449 reserved) and provides per priority remainders. Residual Bandwidth 450 and Unreserved Bandwidth [RFC5305] can be used concurrently, and each 451 has a separate use case (e.g. the former can be used for applications 452 like Weighted ECMP while the latter can be used for call admission 453 control). 455 4.6. Unidirectional Available Bandwidth Sub-TLV 457 This Sub-TLV advertises the available bandwidth between two directly 458 connected IS-IS neighbors. The available bandwidth advertised by 459 this sub-TLV MUST be the available bandwidth from the system 460 originating this Sub-TLV. The format of this Sub-TLV is shown in the 461 following diagram: 463 0 1 2 3 464 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 1 465 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 466 | Type | Length | RESERVED | 467 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 468 | Available Bandwidth | 469 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 471 where: 473 Figure 4 475 Type: TBA (suggested value: 38). 477 Length: 4. 479 RESERVED. This field is reserved for future use. It MUST be set to 480 0 when sent and MUST be ignored when received. 482 Available Bandwidth. This field carries the available bandwidth on a 483 link, forwarding adjacency, or bundled link in IEEE floating point 484 format with units of bytes per second. For a link or forwarding 485 adjacency, available bandwidth is defined to be residual bandwidth 486 (see Section 4.5 minus the measured bandwidth used for the actual 487 forwarding of non-RSVP-TE LSP packets. For a bundled link, available 488 bandwidth is defined to be the sum of the component link available 489 bandwidths minus the measured bandwidth used for the actual 490 forwarding of non-RSVP-TE Label Switched Paths packets. For a 491 bundled link, available bandwidth is defined to be the sum of the 492 component link available bandwidths. 494 4.7. Unidirectional Utilized Bandwidth Sub-TLV 496 This Sub-TLV advertises the bandwidth utilization between two 497 directly connected IS-IS neighbors. The bandwidth utilization 498 advertised by this sub-TLV MUST be the bandwidth from the system 499 originating this Sub-TLV. The format of this Sub-TLV is shown in the 500 following diagram: 502 0 1 2 3 503 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 1 504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 | Type | Length | RESERVED | 506 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 507 | Bandwidth Utilization | 508 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 510 where: 512 Figure 5 514 Type: TBA (suggested value: 39). 516 Length: 4. 518 RESERVED. This field is reserved for future use. It MUST be set to 519 0 when sent and MUST be ignored when received. 521 This field carries the bandwidth utilization on a link, forwarding 522 adjacency, or bundled link in IEEE floating-point format with units 523 of bytes per second. For a link or forwarding adjacency, bandwidth 524 utilization represents the actual utilization of the link (i.e., as 525 measured by the advertising node). For a bundled link, bandwidth 526 utilization is defined to be the sum of the component link bandwidth 527 utilizations. 529 5. Announcement Thresholds and Filters 531 The values advertised in all sub-TLVs (except Min/Max delay and 532 residual bandwidth) MUST represent an average over a period or be 533 obtained by a filter that is reasonably representative of an average. 534 For example, a rolling average is one such filter. 536 Min and max delay MAY be the lowest and/or highest measured value 537 over a measurement interval or MAY make use of a filter, or other 538 technique, to obtain a reasonable representation of a min and max 539 value representative of the interval with compensation for outliers. 541 The measurement interval, any filter coefficients, and any 542 advertisement intervals MUST be configurable per sub-TLV. 544 In addition to the measurement intervals governing re-advertisement, 545 implementations SHOULD provide per sub-TLV configurable accelerated 546 advertisement thresholds, such that: 548 1. If the measured parameter falls outside a configured upper 549 bound for all but the min delay metric (or lower bound for 550 min delay metric only) and the advertised sub-TLV is not 551 already outside that bound or, 553 2. If the difference between the last advertised value and 554 current measured value exceed a configured threshold then, 556 3. The advertisement is made immediately. 558 4. For sub-TLVs which include an A-bit (except min/max 559 delay), an additional threshold SHOULD be included 560 corresponding to the threshold for which the performance 561 is considered anomalous (and sub-TLVs with the A-bit are 562 sent). The A-bit is cleared when the sub-TLV's performance 563 has been below (or re-crosses) this threshold for an 564 advertisement interval(s) to permit fail back. 566 To prevent oscillations, only the high threshold or the low threshold 567 (but not both) may be used to trigger any given sub-TLV that supports 568 both. 570 Additionally, once outside of the bounds of the threshold, any 571 readvertisement of a measurement within the bounds would remain 572 governed solely by the measurement interval for that sub-TLV. 574 6. Announcement Suppression 576 When link performance values change by small amounts that fall under 577 thresholds that would cause the announcement of a sub-TLV, 578 implementations SHOULD suppress sub-TLV readvertisement and/or 579 lengthen the period within which they are refreshed. 581 Only the accelerated advertisement threshold mechanism described in 582 Section 5 may shorten the re-advertisement interval. All suppression 583 and re-advertisement interval backoff timer features SHOULD be 584 configurable. 586 7. Network Stability and Announcement Periodicity 588 Section 5 and Section 6 provide configurable mechanisms to bound the 589 number of re-advertisements. Instability might occur in very large 590 networks if measurement intervals are set low enough to overwhelm the 591 processing of flooded information at some of the routers in the 592 topology. Therefore care should be taken in setting these values. 594 Additionally, the default measurement interval for all sub-TLVs 595 SHOULD be 30 seconds. 597 Announcements MUST also be able to be throttled using configurable 598 inter-update throttle timers. The minimum announcement periodicity 599 is 1 announcement per second. The default value SHOULD be set to 120 600 seconds. 602 Implementations SHOULD NOT permit the inter-update timer to be lower 603 than the measurement interval. 605 Furthermore, it is RECOMMENDED that any underlying performance 606 measurement mechanisms not include any significant buffer delay, any 607 significant buffer induced delay variation, or any significant loss 608 due to buffer overflow or due to active queue management. 610 8. Enabling and Disabling Sub-TLVs 612 Implementations MUST make it possible to individually enable or 613 disable each sub-TLV based on configuration. 615 9. Static Metric Override 617 Implementations SHOULD permit the static configuration and/or manual 618 override of dynamic measurements for each sub-TLV in order to 619 simplify migration and to mitigate scenarios where dynamic 620 measurements are not possible. 622 10. Compatibility 624 As per [RFC5305], unrecognized Sub-TLVs should be silently ignored. 626 11. Security Considerations 628 This document does not introduce security issues beyond those 629 discussed in [RFC5305] and [RFC5329]. 631 12. IANA Considerations 633 IANA maintains the registry for the sub-TLVs. IS-IS TE Metric 634 Extensions will require one new type code per sub-TLV defined in this 635 document in the following sub-TLV registry: TLVs 22, 23, 141, 222, 636 and 223: 638 Type Value 639 ---------------------------------------------------- 640 33 (Suggested) Unidirectional Link Delay 642 34 (Suggested) Min/Max Unidirectional Link Delay 644 35 (Suggested) Unidirectional Delay Variation 646 36 (Suggested) Unidirectional Link Loss 648 37 (Suggested) Unidirectional Residual Bandwidth 650 38 (Suggested) Unidirectional Available Bandwidth 652 39 (Suggested) Unidirectional Bandwidth Utilization 654 13. Acknowledgements 656 The authors would like to recognize Ayman Soliman, Nabil Bitar, David 657 McDysan, Les Ginsberg, Edward Crabbe, Don Fedyk, Hannes Gredler and 658 Uma Chunduri for their contributions. 660 The authors also recognize Curtis Villamizar for significant comments 661 and direct content collaboration. 663 14. References 665 14.1. Normative References 667 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 668 Requirement Levels", BCP 14, RFC 2119, March 1997. 670 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 671 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 672 Tunnels", RFC 3209, December 2001. 674 [RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support 675 of Generalized Multi-Protocol Label Switching (GMPLS)", 676 RFC 4203, October 2005. 678 [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) 679 Hierarchy with Generalized Multi-Protocol Label Switching 680 (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005. 682 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 683 Topology (MT) Routing in Intermediate System to 684 Intermediate Systems (IS-ISs)", RFC 5120, February 2008. 686 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 687 Engineering", RFC 5305, October 2008. 689 [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in 690 Support of Inter-Autonomous System (AS) MPLS and GMPLS 691 Traffic Engineering", RFC 5316, December 2008. 693 [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, 694 "Traffic Engineering Extensions to OSPF Version 3", RFC 695 5329, September 2008. 697 [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic 698 Engineering in IS-IS", RFC 6119, February 2011. 700 [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay 701 Measurement for MPLS Networks", RFC 6374, September 2011. 703 14.2. Informative References 705 [RFC6375] Frost, D. and S. Bryant, "A Packet Loss and Delay 706 Measurement Profile for MPLS-Based Transport Networks", 707 RFC 6375, September 2011. 709 [RFC7285] Alimi, R., Penno, R., Yang, Y., Kiesel, S., Previdi, S., 710 Roome, W., Shalunov, S., and R. Woundy, "Application-Layer 711 Traffic Optimization (ALTO) Protocol", RFC 7285, September 712 2014. 714 Authors' Addresses 716 Stefano Previdi (editor) 717 Cisco Systems, Inc. 718 Via Del Serafico 200 719 Rome 00191 720 IT 722 Email: sprevidi@cisco.com 724 Spencer Giacalone 725 Unaffiliated 727 Email: spencer.giacalone@gmail.com 728 Dave Ward 729 Cisco Systems, Inc. 730 3700 Cisco Way 731 SAN JOSE, CA 95134 732 US 734 Email: wardd@cisco.com 736 John Drake 737 Juniper Networks 738 1194 N. Mathilda Ave. 739 Sunnyvale, CA 94089 740 USA 742 Email: jdrake@juniper.net 744 Alia Atlas 745 Juniper Networks 746 1194 N. Mathilda Ave. 747 Sunnyvale, CA 94089 748 USA 750 Email: akatlas@juniper.net 752 Clarence Filsfils 753 Cisco Systems, Inc. 754 Brussels 755 Belgium 757 Email: cfilsfil@cisco.com 759 Qin Wu 760 Huawei 761 101 Software Avenue, Yuhua District 762 Nanjing, Jiangsu 210012 763 China 765 Email: sunseawq@huawei.com