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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: April 25, 2015 Thomson Reuters 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 October 22, 2014 17 IS-IS Traffic Engineering (TE) Metric Extensions 18 draft-ietf-isis-te-metric-extensions-04 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 April 25, 2015. 65 Copyright Notice 67 Copyright (c) 2014 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 . . . . . . . . . . . . 9 90 4.5. Unidirectional Residual Bandwidth Sub-TLV . . . . . . . . 10 91 4.6. Unidirectional Available Bandwidth Sub-TLV . . . . . . . 11 92 4.7. Unidirectional Utilized Bandwidth Sub-TLV . . . . . . . . 12 93 5. Announcement Thresholds and Filters . . . . . . . . . . . . . 13 94 6. Announcement Suppression . . . . . . . . . . . . . . . . . . 14 95 7. Network Stability and Announcement Periodicity . . . . . . . 14 96 8. Enabling and Disabling Sub-TLVs . . . . . . . . . . . . . . . 14 97 9. Static Metric Override . . . . . . . . . . . . . . . . . . . 14 98 10. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 15 99 11. Security Considerations . . . . . . . . . . . . . . . . . . . 15 100 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 101 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, packet 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]; 136 [I-D.atlas-mpls-te-express-path] describes some methods for using 137 this information to compute Label Switched Paths (LSPs) at the LSP 138 ingress. 140 Note that the mechanisms described in this document only disseminate 141 performance information. The methods for initially gathering that 142 performance information, such as [RFC6375], or acting on it once it 143 is distributed are outside the scope of this document. Example 144 mechanisms to measure latency, delay variation, and loss in an MPLS 145 network are given in [RFC6374]. While this document does not specify 146 how the performance information should be obtained, the measurement 147 of delay SHOULD NOT vary significantly based upon the offered traffic 148 load. Thus, queuing delays SHOULD NOT be included in the delay 149 measurement. For links, such as Forwarding Adjacencies, care must be 150 taken that measurement of the associated delay avoids significant 151 queuing delay; that could be accomplished in a variety of ways, 152 including either by measuring with a traffic class that experiences 153 minimal queuing or by summing the measured link delays of the 154 components of the link's path. 156 2. TE Metric Extensions to IS-IS 158 This document proposes new IS-IS TE sub-TLVs that can be announced in 159 ISIS Extended Reachability TLV (TLV-22) to distribute network 160 performance information. The extensions in this document build on 161 the ones provided in IS-IS TE [RFC5305] and GMPLS [RFC4203]. 163 IS-IS Extended Reachability TLV 22 (defined in [RFC5305]), Inter-AS 164 reachability information TLV 141 (defined in [RFC5316]) and MT-ISN 165 TLV 222 (defined in [RFC5120]) have nested sub-TLVs which permit the 166 TLVs to be readily extended. This document proposes several 167 additional sub-TLVs: 169 Type Value 170 ----------------------------------------------- 171 TBA Unidirectional Link Delay 173 TBA Low/High Unidirectional Link Delay 175 TBA Unidirectional Delay Variation 177 TBA Unidirectional Packet Loss 179 TBA Unidirectional Residual Bandwidth 181 TBA Unidirectional Available Bandwidth 183 TBA Unidirectional Bandwidth Utilization 185 As can be seen in the list above, the sub-TLVs described in this 186 document carry different types of network performance information. 187 The new sub-TLVs include a bit called the Anomalous (or "A") bit. 188 When the A bit is clear (or when the sub-TLV does not include an A 189 bit), the sub-TLV describes steady state link performance. This 190 information could conceivably be used to construct a steady state 191 performance topology for initial tunnel path computation, or to 192 verify alternative failover paths. 194 When network performance violates configurable link-local thresholds 195 a sub-TLV with the A bit set is advertised. These sub-TLVs could be 196 used by the receiving node to determine whether to fail traffic to a 197 backup path, or whether to calculate an entirely new path. From an 198 MPLS perspective, the intent of the A bit is to permit LSP ingress 199 nodes to: 201 A) Determine whether the link referenced in the sub-TLV affects any 202 of the LSPs for which it is ingress. If there are, then: 204 B) Determine whether those LSPs still meet end-to-end performance 205 objectives. If not, then: 207 C) The node could then conceivably move affected traffic to a pre- 208 established protection LSP or establish a new LSP and place the 209 traffic in it. 211 If link performance then improves beyond a configurable minimum value 212 (reuse threshold), that sub-TLV can be re-advertised with the 213 Anomalous bit cleared. In this case, a receiving node can 214 conceivably do whatever re-optimization (or failback) it wishes to do 215 (including nothing). 217 Note that when a sub-TLV does not include the A bit, that sub-TLV 218 cannot be used for failover purposes. The A bit was intentionally 219 omitted from some sub-TLVs to help mitigate oscillations. See 220 Section 5 for more information. 222 Consistent with existing IS-IS TE specifications [RFC5305], the 223 bandwidth advertisements defined in this draft MUST be encoded as 224 IEEE floating point values. The delay and delay variation 225 advertisements defined in this draft MUST be encoded as integer 226 values. Delay values MUST be quantified in units of microseconds, 227 packet loss MUST be quantified as a percentage of packets sent, and 228 bandwidth MUST be sent as bytes per second. All values (except 229 residual bandwidth) MUST be calculated as rolling averages where the 230 averaging period MUST be a configurable period of time. See 231 Section 5 for more information. 233 3. Interface and Neighbor Addresses 235 The use of TE Metric Extensions SubTLVs is not confined to the TE 236 context. In other words, IS-IS TE Metric Extensions SubTLVs defined 237 in this document can also be used for computing paths in the absence 238 of a TE subsystem. 240 However, as for the TE case, Interface Address and Neighbor Address 241 SubTLVs (IPv4 or IPv6) MUST be present. The encoding is defined in 242 [RFC5305] for IPv4 and in [RFC6119] for IPv6. 244 4. Sub TLV Details 246 4.1. Unidirectional Link Delay Sub-TLV 248 This sub-TLV advertises the average link delay between two directly 249 connected IS-IS neighbors. The delay advertised by this sub-TLV MUST 250 be the delay from the local neighbor to the remote one (i.e. the 251 forward path latency). The format of this sub-TLV is shown in the 252 following diagram: 254 0 1 2 3 255 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 1 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 | Type | Length | 258 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 259 |A| RESERVED | Delay | 260 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 262 where: 264 Figure 1 266 Type: TBA 268 Length: 4 270 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 271 when the measured value of this parameter exceeds its configured 272 maximum threshold. The A bit is cleared when the measured value 273 falls below its configured reuse threshold. If the A-bit is clear, 274 the sub-TLV represents steady state link performance. 276 RESERVED. This field is reserved for future use. It MUST be set to 277 0 when sent and MUST be ignored when received. 279 Delay. This 24-bit field carries the average link delay over a 280 configurable interval in micro-seconds, encoded as an integer value. 281 When set to the maximum value 16,777,215 (16.777215 sec), then the 282 delay is at least that value and may be larger. If there is no value 283 to send (unmeasured and not statically specified), then the sub-TLV 284 should not be sent or be withdrawn. 286 4.2. Min/Max Unidirectional Link Delay Sub-TLV 288 This sub-TLV advertises the minimum and maximum delay values between 289 two directly connected IS-IS neighbors. The delay advertised by this 290 sub-TLV MUST be the delay from the local neighbor to the remote one 291 (i.e. the forward path latency). The format of this sub-TLV is shown 292 in the following diagram: 294 0 1 2 3 295 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 1 296 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 297 | Type | Length | 298 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 299 |A| RESERVED | Low Delay | 300 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 301 | RESERVED | High Delay | 302 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 304 where: 306 Figure 2 308 Type: TBA 310 Length: 8 312 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 313 when the measured value of this parameter exceeds its configured 314 maximum threshold. The A bit is cleared when the measured value 315 falls below its configured reuse threshold. If the A-bit is clear, 316 the sub-TLV represents steady state link performance. 318 RESERVED. This field is reserved for future use. It MUST be set to 319 0 when sent and MUST be ignored when received. 321 Low Delay. This 24-bit field carries minimum measured link delay 322 value (in microseconds) over a configurable interval, encoded as an 323 integer value. 325 High Delay. This 24-bit field carries the maximum measured link 326 delay value (in microseconds) over a configurable interval, encoded 327 as an integer value. 329 Implementations MAY also permit the configuration of a static (non 330 dynamic) offset value (in microseconds) to be added to the measured 331 delay value, to facilitate the communication of operator specific 332 delay constraints. 334 It is possible for the high delay and low delay to be the same value. 336 When the delay value (Low or High) is set to maximum value 16,777,215 337 (16.777215 sec), then the delay is at least that value and may be 338 larger. 340 4.3. Unidirectional Delay Variation Sub-TLV 342 This sub-TLV advertises the average link delay variation between two 343 directly connected IS-IS neighbors. The delay variation advertised 344 by this sub-TLV MUST be the delay from the local neighbor to the 345 remote one (i.e. the forward path latency). The format of this sub- 346 TLV is shown in the following diagram: 348 0 1 2 3 349 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 1 350 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 351 | Type | Length | 352 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 353 |A| RESERVED | Delay Variation | 354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 356 where: 358 Figure 3 360 Type: TBA. 362 Lenght: 4. 364 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 365 when the measured value of this parameter exceeds its configured 366 maximum threshold. The A bit is cleared when the measured value 367 falls below its configured reuse threshold. If the A-bit is clear, 368 the sub-TLV represents steady state link performance. 370 RESERVED. This field is reserved for future use. It MUST be set to 371 0 when sent and MUST be ignored when received. 373 Delay Variation. This 24-bit field carries the average link delay 374 variation over a configurable interval in micro-seconds, encoded as 375 an integer value. When set to 0, it has not been measured. When set 376 to the maximum value 16,777,215 (16.777215 sec), then the delay is at 377 least that value and may be larger. 379 4.4. Unidirectional Link Loss Sub-TLV 381 This sub-TLV advertises the loss (as a packet percentage) between two 382 directly connected IS-IS neighbors. The link loss advertised by this 383 sub-TLV MUST be the packet loss from the local neighbor to the remote 384 one (i.e. the forward path loss). The format of this sub-TLV is 385 shown in the following diagram: 387 0 1 2 3 388 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 1 389 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 390 | Type | Length | 391 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 392 |A| RESERVED | Link Loss | 393 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 395 This sub-TLV has a type of TBD3. 396 The length is 4. 398 where: 400 Type: TBA. 402 Length: 4. 404 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 405 when the measured value of this parameter exceeds its configured 406 maximum threshold. The A bit is cleared when the measured value 407 falls below its configured reuse threshold. If the A-bit is clear, 408 the sub-TLV represents steady state link performance. 410 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 411 when the measured value of this parameter exceeds its configured 412 maximum threshold. The A bit is cleared when the measured value 413 falls below its configured reuse threshold. If the A-bit is clear, 414 the sub-TLV represents steady state link performance. 416 RESERVED. This field is reserved for future use. It MUST be set to 417 0 when sent and MUST be ignored when received. 419 Link Loss. This 24-bit field carries link packet loss as a 420 percentage of the total traffic sent over a configurable interval. 421 The basic unit is 0.000003%, where (2^24 - 2) is 50.331642%. This 422 value is the highest packet loss percentage that can be expressed 423 (the assumption being that precision is more important on high speed 424 links than the ability to advertise loss rates greater than this, and 425 that high speed links with over 50% loss are unusable). Therefore, 426 measured values that are larger than the field maximum SHOULD be 427 encoded as the maximum value. When set to a value of all 1s (2^24 - 428 1), the link packet loss has not been measured. 430 4.5. Unidirectional Residual Bandwidth Sub-TLV 432 This TLV advertises the residual bandwidth between two directly 433 connected IS-IS neighbors. The residual bandwidth advertised by this 434 sub-TLV MUST be the residual bandwidth from the system originating 435 the LSA to its neighbor. 437 0 1 2 3 438 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 1 439 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 440 | Type | Length |A| RESERVED | 441 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 442 | Residual Bandwidth | 443 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 445 where: 447 Type: TBA. 449 Length: 4. 451 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 452 when the measured value of this parameter exceeds its configured 453 maximum threshold. The A bit is cleared when the measured value 454 falls below its configured reuse threshold. If the A-bit is clear, 455 the sub-TLV represents steady state link performance. 457 RESERVED. This field is reserved for future use. It MUST be set to 458 0 when sent and MUST be ignored when received. 460 Residual Bandwidth. This field carries the residual bandwidth on a 461 link, forwarding adjacency [RFC4206], or bundled link in IEEE 462 floating point format with units of bytes per second. For a link or 463 forwarding adjacency, residual bandwidth is defined to be Maximum 464 Bandwidth [RFC3630] minus the bandwidth currently allocated to RSVP- 465 TE LSPs. For a bundled link, residual bandwidth is defined to be the 466 sum of the component link residual bandwidths. 468 The calculation of Residual Bandwidth is different than that of 469 Unreserved Bandwidth [RFC3630]. Residual Bandwidth subtracts tunnel 470 reservations from Maximum Bandwidth (i.e. the link capacity) 471 [RFC3630] and provides an aggregated remainder across QoS classes. 472 Unreserved Bandwidth [RFC3630], on the other hand, is subtracted from 473 the Maximum Reservable Bandwidth (the bandwidth that can 474 theoretically be reserved) [RFC3630] and provides per-QoS-class 475 remainders. Residual Bandwidth and Unreserved Bandwidth [RFC3630] 476 can be used concurrently, and each has a separate use case (e.g. the 477 former can be used for applications like Weighted ECMP while the 478 latter can be used for call admission control). 480 4.6. Unidirectional Available Bandwidth Sub-TLV 482 This Sub-TLV advertises the available bandwidth between two directly 483 connected IS-IS neighbors. The available bandwidth advertised by 484 this sub-TLV MUST be the available bandwidth from the system 485 originating this Sub-TLV. The format of this Sub-TLV is shown in the 486 following diagram: 488 0 1 2 3 489 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 1 490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 491 | Type | Length |A| RESERVED | 492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 493 | Available Bandwidth | 494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 496 where: 498 Figure 4 500 Type: TBA. 502 Length: 4. 504 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 505 when the measured value of this parameter exceeds its configured 506 maximum threshold. The A bit is cleared when the measured value 507 falls below its configured reuse threshold. If the A-bit is clear, 508 the sub-TLV represents steady state link performance. 510 RESERVED. This field is reserved for future use. It MUST be set to 511 0 when sent and MUST be ignored when received. 513 Available Bandwidth. This field carries the available bandwidth on a 514 link, forwarding adjacency, or bundled link in IEEE floating point 515 format with units of bytes per second. For a link or forwarding 516 adjacency, available bandwidth is defined to be residual bandwidth 517 minus the measured bandwidth used for the actual forwarding of non- 518 RSVP-TE LSP packets. For a bundled link, available bandwidth is 519 defined to be the sum of the component link available bandwidths 520 minus the measured bandwidth used for the actual forwarding of non- 521 RSVP-TE Label Switched Paths packets. For a bundled link, available 522 bandwidth is defined to be the sum of the component link available 523 bandwidths. 525 4.7. Unidirectional Utilized Bandwidth Sub-TLV 527 This Sub-TLV advertises the bandwidth utilization between two 528 directly connected IS-IS neighbors. The bandwidth utilization 529 advertised by this sub-TLV MUST be the bandwidth from the system 530 originating this Sub-TLV. The format of this Sub-TLV is shown in the 531 following diagram: 533 0 1 2 3 534 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 1 535 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 536 | Type | Length |A| RESERVED | 537 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 538 | Bandwidth Utilization | 539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 541 where: 543 Figure 5 545 Type: TBA. 547 Length: 4. 549 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 550 when the measured value of this parameter exceeds its configured 551 maximum threshold. The A bit is cleared when the measured value 552 falls below its configured reuse threshold. If the A-bit is clear, 553 the sub-TLV represents steady state link performance. 555 RESERVED. This field is reserved for future use. It MUST be set to 556 0 when sent and MUST be ignored when received. 558 Bandwidth Utilization. This field carries the bandwidth utilization 559 on a link, forwarding adjacency, or bundled link in IEEE floating 560 point format with units of bytes per second. For a link or 561 forwarding adjacency, bandwidth utilization represent the actual 562 utilization of the link (i.e.: as measured in the router). For a 563 bundled link, bandwidth utilization is defined to be the sum of the 564 component link bandwidth utilization. 566 5. Announcement Thresholds and Filters 568 The values advertised in all sub-TLVs (except Low/High delay and 569 residual bandwidth) MUST represent an average over a period or be 570 obtained by a filter that is reasonably representative of an average. 571 For example, a rolling average is one such filter. 573 Low or High delay MAY be the lowest and/or highest measured value 574 over a measurement interval or MAY make use of a filter, or other 575 technique to obtain a reasonable representation of a low and high 576 value representative of the interval with compensation for outliers. 578 The measurement interval, any filter coefficients, and any 579 advertisement intervals MUST be configurable per sub-TLV. 581 In addition to the measurement intervals governing re-advertisement, 582 implementations SHOULD provide per sub-TLV configurable accelerated 583 advertisement thresholds, such that: 585 1. If the measured parameter falls outside a configured upper 586 bound for all but the low delay metric (or lower bound for 587 low-delay metric only) and the advertised sub-TLV is not 588 already outside that bound or, 590 2. If the difference between the last advertised value and 591 current measured value exceed a configured threshold then, 593 3. The advertisement is made immediately. 595 4. For sub-TLVs which include an A-bit (except low/high 596 delay), an additional threshold SHOULD be included 597 corresponding to the threshold for which the performance 598 is considered anomalous (and sub-TLVs with the A-bit are 599 sent). The A-bit is cleared when the sub-TLV's performance 600 has been below (or re-crosses) this threshold for an 601 advertisement interval(s) to permit fail back. 603 To prevent oscillations, only the high threshold or the low threshold 604 (but not both) may be used to trigger any given sub-TLV that supports 605 both. 607 Additionally, once outside of the bounds of the threshold, any 608 readvertisement of a measurement within the bounds would remain 609 governed solely by the measurement interval for that sub-TLV. 611 6. Announcement Suppression 613 When link performance values change by small amounts that fall under 614 thresholds that would cause the announcement of a sub-TLV, 615 implementations SHOULD suppress sub-TLV readvertisement and/or 616 lengthen the period within which they are refreshed. 618 Only the accelerated advertisement threshold mechanism may shorten 619 the re-advertisement interval. All suppression and re-advertisement 620 interval backoff timer features SHOULD be configurable. 622 7. Network Stability and Announcement Periodicity 624 Section 5 and Section 6 provide configurable mechanisms to bound the 625 number of re-advertisements. Instability might occur in very large 626 networks if measurement intervals are set low enough to overwhelm the 627 processing of flooded information at some of the routers in the 628 topology. Therefore care SHOULD be taken in setting these values. 630 Additionally, the default measurement interval for all sub-TLVs 631 SHOULD be 30 seconds. 633 Announcements MUST also be able to be throttled using configurable 634 inter-update throttle timers. The minimum announcement periodicity 635 is 1 announcement per second. The default value SHOULD be set to 120 636 seconds. 638 Implementations SHOULD NOT permit the inter-update timer to be lower 639 than the measurement interval. 641 Furthermore, it is RECOMMENDED that any underlying performance 642 measurement mechanisms not include any significant buffer delay, any 643 significant buffer induced delay variation, or any significant loss 644 due to buffer overflow or due to active queue management. 646 8. Enabling and Disabling Sub-TLVs 648 Implementations MUST make it possible to individually enable or 649 disable each sub-TLV based on configuration. 651 9. Static Metric Override 653 Implementations SHOULD permit the static configuration and/or manual 654 override of dynamic measurements data on a per sub-TLV, per metric 655 basis in order to simplify migrations and to mitigate scenarios where 656 measurements are not possible across an entire network. 658 10. Compatibility 660 As per [RFC5305], unrecognized Sub-TLVs should be silently ignored 662 11. Security Considerations 664 This document does not introduce security issues beyond those 665 discussed in [RFC3630] and [RFC5329]. 667 12. IANA Considerations 669 IANA maintains the registry for the sub-TLVs. IS-IS TE Metric 670 Extensions will require one new type code per sub-TLV defined in this 671 document. 673 13. Acknowledgements 675 The authors would like to recognize Ayman Soliman, Nabil Bitar, David 676 McDysan, Les Ginsberg, Edward Crabbe, Don Fedyk and Hannes Gredler 677 for their contributions. 679 The authors also recognize Curtis Villamizar for significant comments 680 and direct content collaboration. 682 14. References 684 14.1. Normative References 686 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 687 Requirement Levels", BCP 14, RFC 2119, March 1997. 689 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 690 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 691 Tunnels", RFC 3209, December 2001. 693 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 694 (TE) Extensions to OSPF Version 2", RFC 3630, September 695 2003. 697 [RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support 698 of Generalized Multi-Protocol Label Switching (GMPLS)", 699 RFC 4203, October 2005. 701 [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) 702 Hierarchy with Generalized Multi-Protocol Label Switching 703 (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005. 705 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 706 Topology (MT) Routing in Intermediate System to 707 Intermediate Systems (IS-ISs)", RFC 5120, February 2008. 709 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 710 Engineering", RFC 5305, October 2008. 712 [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in 713 Support of Inter-Autonomous System (AS) MPLS and GMPLS 714 Traffic Engineering", RFC 5316, December 2008. 716 [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, 717 "Traffic Engineering Extensions to OSPF Version 3", RFC 718 5329, September 2008. 720 [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic 721 Engineering in IS-IS", RFC 6119, February 2011. 723 [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay 724 Measurement for MPLS Networks", RFC 6374, September 2011. 726 14.2. Informative References 728 [I-D.atlas-mpls-te-express-path] 729 Atlas, A., Drake, J., Giacalone, S., Ward, D., Previdi, 730 S., and C. Filsfils, "Performance-based Path Selection for 731 Explicitly Routed LSPs using TE Metric Extensions", draft- 732 atlas-mpls-te-express-path-04 (work in progress), 733 September 2013. 735 [RFC6375] Frost, D. and S. Bryant, "A Packet Loss and Delay 736 Measurement Profile for MPLS-Based Transport Networks", 737 RFC 6375, September 2011. 739 [RFC7285] Alimi, R., Penno, R., Yang, Y., Kiesel, S., Previdi, S., 740 Roome, W., Shalunov, S., and R. Woundy, "Application-Layer 741 Traffic Optimization (ALTO) Protocol", RFC 7285, September 742 2014. 744 Authors' Addresses 746 Stefano Previdi (editor) 747 Cisco Systems, Inc. 748 Via Del Serafico 200 749 Rome 00191 750 IT 752 Email: sprevidi@cisco.com 753 Spencer Giacalone 754 Thomson Reuters 755 195 Broadway 756 New York, NY 10007 757 USA 759 Email: Spencer.giacalone@thomsonreuters.com 761 Dave Ward 762 Cisco Systems, Inc. 763 3700 Cisco Way 764 SAN JOSE, CA 95134 765 US 767 Email: wardd@cisco.com 769 John Drake 770 Juniper Networks 771 1194 N. Mathilda Ave. 772 Sunnyvale, CA 94089 773 USA 775 Email: jdrake@juniper.net 777 Alia Atlas 778 Juniper Networks 779 1194 N. Mathilda Ave. 780 Sunnyvale, CA 94089 781 USA 783 Email: akatlas@juniper.net 785 Clarence Filsfils 786 Cisco Systems, Inc. 787 Brussels 788 Belgium 790 Email: cfilsfil@cisco.com 791 Qin Wu 792 Huawei 793 101 Software Avenue, Yuhua District 794 Nanjing, Jiangsu 210012 795 China 797 Email: sunseawq@huawei.com