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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (October 10, 2013) is 3850 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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 5316 (Obsoleted by RFC 9346) == Outdated reference: A later version (-27) exists of draft-ietf-alto-protocol-20 Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--).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 13, 2014 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 10, 2013 17 IS-IS Traffic Engineering (TE) Metric Extensions 18 draft-ietf-isis-te-metric-extensions-01 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 TE [RFC5305] such that 28 network performance information can be distributed and collected in a 29 scalable fashion. The information distributed using ISIS TE Metric 30 Extensions can then be used to make path selection decisions based on 31 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 49 This Internet-Draft is submitted in full conformance with the 50 provisions of BCP 78 and BCP 79. 52 Internet-Drafts are working documents of the Internet Engineering 53 Task Force (IETF). Note that other groups may also distribute 54 working documents as Internet-Drafts. The list of current Internet- 55 Drafts is at http://datatracker.ietf.org/drafts/current/. 57 Internet-Drafts are draft documents valid for a maximum of six months 58 and may be updated, replaced, or obsoleted by other documents at any 59 time. It is inappropriate to use Internet-Drafts as reference 60 material or to cite them other than as "work in progress." 62 This Internet-Draft will expire on April 13, 2014. 64 Copyright Notice 66 Copyright (c) 2013 IETF Trust and the persons identified as the 67 document authors. All rights reserved. 69 This document is subject to BCP 78 and the IETF Trust's Legal 70 Provisions Relating to IETF Documents 71 (http://trustee.ietf.org/license-info) in effect on the date of 72 publication of this document. Please review these documents 73 carefully, as they describe your rights and restrictions with respect 74 to this document. Code Components extracted from this document must 75 include Simplified BSD License text as described in Section 4.e of 76 the Trust Legal Provisions and are provided without warranty as 77 described in the Simplified BSD License. 79 Table of Contents 81 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 82 2. TE Metric Extensions to IS-IS . . . . . . . . . . . . . . . . 5 83 3. Interface and Neighbor Addresses . . . . . . . . . . . . . . . 6 84 4. Sub TLV Details . . . . . . . . . . . . . . . . . . . . . . . 6 85 4.1. Unidirectional Link Delay Sub-TLV . . . . . . . . . . . . 7 86 4.2. Min/Max Unidirectional Link Delay Sub-TLV . . . . . . . . 7 87 4.3. Unidirectional Delay Variation Sub-TLV . . . . . . . . . . 9 88 4.4. Unidirectional Link Loss Sub-TLV . . . . . . . . . . . . . 9 89 4.5. Unidirectional Residual Bandwidth Sub-TLV . . . . . . . . 10 90 4.6. Unidirectional Available Bandwidth Sub-TLV . . . . . . . . 11 91 4.7. Unidirectional Utilized Bandwidth Sub-TLV . . . . . . . . 12 92 5. Announcement Thresholds and Filters . . . . . . . . . . . . . 13 93 6. Announcement Suppression . . . . . . . . . . . . . . . . . . . 14 94 7. Network Stability and Announcement Periodicity . . . . . . . . 14 95 8. Enabling and Disabling Sub-TLVs . . . . . . . . . . . . . . . 15 96 9. Static Metric Override . . . . . . . . . . . . . . . . . . . . 15 97 10. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 15 98 11. Security Considerations . . . . . . . . . . . . . . . . . . . 15 99 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 100 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16 101 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 102 14.1. Normative References . . . . . . . . . . . . . . . . . . . 16 103 14.2. Informative References . . . . . . . . . . . . . . . . . . 17 104 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 106 1. Introduction 108 In certain networks, such as, but not limited to, financial 109 information networks (e.g. stock market data providers), network 110 performance information (e.g. latency) is becoming as critical to 111 data path selection as other metrics. 113 In these networks, extremely large amounts of money rest on the 114 ability to access market data in "real time" and to predictably make 115 trades faster than the competition. Because of this, using metrics 116 such as hop count or cost as routing metrics is becoming only 117 tangentially important. Rather, it would be beneficial to be able to 118 make path selection decisions based on performance data (such as 119 latency) in a cost-effective and scalable way. 121 This document describes extensions to IS-IS Extended Reachability TLV 122 defined in [RFC5305] (hereafter called "IS-IS TE Metric Extensions"), 123 that can be used to distribute network performance information (such 124 as link delay, delay variation, packet loss, residual bandwidth, and 125 available bandwidth). 127 The data distributed by the TE Metric Extensions proposed in this 128 document is meant to be used as part of the operation of the routing 129 protocol (e.g. by replacing cost with latency or considering 130 bandwidth as well as cost), by enhancing Constrained-SPF (CSPF), or 131 for other uses such as supplementing the data used by an ALTO server 132 [I-D.ietf-alto-protocol]. With respect to CSPF, the data distributed 133 by ISIS TE Metric Extensions can be used to setup, fail over, and 134 fail back data paths using protocols such as RSVP-TE [RFC3209]; 135 [I-D.atlas-mpls-te-express-path] describes some methods for using 136 this information to compute Label Switched Paths (LSPs) at the LSP 137 ingress. 139 Note that the mechanisms described in this document only disseminate 140 performance information. The methods for initially gathering that 141 performance information, such as [RFC6375], or acting on it once it 142 is distributed are outside the scope of this document. Example 143 mechanisms to measure latency, delay variation, and loss in an MPLS 144 network are given in [RFC6374]. While this document does not specify 145 how the performance information should be obtained, the measurement 146 of delay SHOULD NOT vary significantly based upon the offered traffic 147 load. Thus, queuing delays SHOULD NOT be included in the delay 148 measurement. For links, such as Forwarding Adjacencies, care must be 149 taken that measurement of the associated delay avoids significant 150 queuing delay; that could be accomplished in a variety of ways, 151 including either by measuring with a traffic class that experiences 152 minimal queuing or by summing the measured link delays of the 153 components of the link's path. 155 2. TE Metric Extensions to IS-IS 157 This document proposes new IS-IS TE sub-TLVs that can be announced in 158 ISIS Extended Reachability TLV (TLV-22) to distribute network 159 performance information. The extensions in this document build on 160 the ones provided in IS-IS TE [RFC5305] and GMPLS [RFC4203]. 162 IS-IS Extended Reachability TLV 22 (defined in [RFC5305]), Inter-AS 163 reachability information TLV 141 (defined in [RFC5316]) and MT-ISN 164 TLV 222 (defined in [RFC5120]) have nested sub-TLVs which permit the 165 TLVs to be readily extended. This document proposes several 166 additional sub-TLVs: 167 Type Value 168 ----------------------------------------------- 169 TBA Unidirectional Link Delay 171 TBA Low/High Unidirectional Link Delay 173 TBA Unidirectional Delay Variation 175 TBA Unidirectional Packet Loss 177 TBA Unidirectional Residual Bandwidth 179 TBA Unidirectional Available Bandwidth 181 TBA Unidirectional Bandwidth Utilization 183 As can be seen in the list above, the sub-TLVs described in this 184 document carry different types of network performance information. 185 The new sub-TLVs include a bit called the Anomalous (or "A") bit. 186 When the A bit is clear (or when the sub-TLV does not include an A 187 bit), the sub-TLV describes steady state link performance. This 188 information could conceivably be used to construct a steady state 189 performance topology for initial tunnel path computation, or to 190 verify alternative failover paths. 192 When network performance violates configurable link-local thresholds 193 a sub-TLV with the A bit set is advertised. These sub-TLVs could be 194 used by the receiving node to determine whether to fail traffic to a 195 backup path, or whether to calculate an entirely new path. From an 196 MPLS perspective, the intent of the A bit is to permit LSP ingress 197 nodes to: 199 A) Determine whether the link referenced in the sub-TLV affects any 200 of the LSPs for which it is ingress. If there are, then: 202 B) Determine whether those LSPs still meet end-to-end performance 203 objectives. If not, then: 205 C) The node could then conceivably move affected traffic to a pre- 206 established protection LSP or establish a new LSP and place the 207 traffic in it. 209 If link performance then improves beyond a configurable minimum value 210 (reuse threshold), that sub-TLV can be re-advertised with the 211 Anomalous bit cleared. In this case, a receiving node can 212 conceivably do whatever re-optimization (or failback) it wishes to do 213 (including nothing). 215 Note that when a sub-TLV does not include the A bit, that sub-TLV 216 cannot be used for failover purposes. The A bit was intentionally 217 omitted from some sub-TLVs to help mitigate oscillations. See 218 Section 5 for more information. 220 Consistent with existing IS-IS TE specifications [RFC5305], the 221 bandwidth advertisements defined in this draft MUST be encoded as 222 IEEE floating point values. The delay and delay variation 223 advertisements defined in this draft MUST be encoded as integer 224 values. Delay values MUST be quantified in units of microseconds, 225 packet loss MUST be quantified as a percentage of packets sent, and 226 bandwidth MUST be sent as bytes per second. All values (except 227 residual bandwidth) MUST be calculated as rolling averages where the 228 averaging period MUST be a configurable period of time. See 229 Section 5 for more information. 231 3. Interface and Neighbor Addresses 233 The use of TE Metric Extensions SubTLVs is not confined to the TE 234 context. In other words, IS-IS TE Metric Extensions SubTLVs defined 235 in this document can also be used for computing paths in the absence 236 of a TE subsystem. 238 However, as for the TE case, Interface Address and Neighbor Address 239 SubTLVs (IPv4 or IPv6) MUST be present. The encoding is defined in 240 [RFC5305] for IPv4 and in [RFC6119] for IPv6. 242 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: 250 0 1 2 3 251 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 1 252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 | Type | Length | 254 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 255 |A| RESERVED | Delay | 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 where: 260 Figure 1 262 Type: TBA 264 Length: 4 266 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 267 when the measured value of this parameter exceeds its configured 268 maximum threshold. The A bit is cleared when the measured value 269 falls below its configured reuse threshold. If the A-bit is clear, 270 the sub-TLV represents steady state link performance. 272 RESERVED. This field is reserved for future use. It MUST be set to 273 0 when sent and MUST be ignored when received. 275 Delay. This 24-bit field carries the average link delay over a 276 configurable interval in micro-seconds, encoded as an integer value. 277 When set to the maximum value 16,777,215 (16.777215 sec), then the 278 delay is at least that value and may be larger. If there is no value 279 to send (unmeasured and not statically specified), then the sub-TLV 280 should not be sent or be withdrawn. 282 4.2. Min/Max Unidirectional Link Delay Sub-TLV 284 This sub-TLV advertises the minimum and maximum delay values between 285 two directly connected IS-IS neighbors. The delay advertised by this 286 sub-TLV MUST be the delay from the local neighbor to the remote one 287 (i.e. the forward path latency). The format of this sub-TLV is shown 288 in the following diagram: 290 0 1 2 3 291 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 1 292 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 293 | Type | Length | 294 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 295 |A| RESERVED | Low Delay | 296 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 297 | RESERVED | High Delay | 298 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 300 where: 302 Figure 2 304 Type: TBA 306 Length: 8 308 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 309 when the measured value of this parameter exceeds its configured 310 maximum threshold. The A bit is cleared when the measured value 311 falls below its configured reuse threshold. If the A-bit is clear, 312 the sub-TLV represents steady state link performance. 314 RESERVED. This field is reserved for future use. It MUST be set to 315 0 when sent and MUST be ignored when received. 317 Low Delay. This 24-bit field carries minimum measured link delay 318 value (in microseconds) over a configurable interval, encoded as an 319 integer value. 321 High Delay. This 24-bit field carries the maximum measured link 322 delay value (in microseconds) over a configurable interval, encoded 323 as an integer value. 325 Implementations MAY also permit the configuration of a static (non 326 dynamic) offset value (in microseconds) to be added to the measured 327 delay value, to facilitate the communication of operator specific 328 delay constraints. 330 It is possible for the high delay and low delay to be the same value. 332 When the delay value (Low or High) is set to maximum value 16,777,215 333 (16.777215 sec), then the delay is at least that value and may be 334 larger. 336 4.3. Unidirectional Delay Variation Sub-TLV 338 This sub-TLV advertises the average link delay variation between two 339 directly connected IS-IS neighbors. The delay variation advertised 340 by this sub-TLV MUST be the delay from the local neighbor to the 341 remote one (i.e. the forward path latency). The format of this sub- 342 TLV is shown in the following diagram: 343 0 1 2 3 344 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 1 345 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 346 | Type | Length | 347 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 348 |A| RESERVED | Delay Variation | 349 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 351 where: 353 Figure 3 355 Type: TBA. 357 Lenght: 4. 359 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 360 when the measured value of this parameter exceeds its configured 361 maximum threshold. The A bit is cleared when the measured value 362 falls below its configured reuse threshold. If the A-bit is clear, 363 the sub-TLV represents steady state link performance. 365 RESERVED. This field is reserved for future use. It MUST be set to 366 0 when sent and MUST be ignored when received. 368 Delay Variation. This 24-bit field carries the average link delay 369 variation over a configurable interval in micro-seconds, encoded as 370 an integer value. When set to 0, it has not been measured. When set 371 to the maximum value 16,777,215 (16.777215 sec), then the delay is at 372 least that value and may be larger. 374 4.4. Unidirectional Link Loss Sub-TLV 376 This sub-TLV advertises the loss (as a packet percentage) between two 377 directly connected IS-IS neighbors. The link loss advertised by this 378 sub-TLV MUST be the packet loss from the local neighbor to the remote 379 one (i.e. the forward path loss). The format of this sub-TLV is 380 shown in the following diagram: 382 0 1 2 3 383 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 1 384 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 385 | Type | Length | 386 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 387 |A| RESERVED | Link Loss | 388 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 390 This sub-TLV has a type of TBD3. 391 The length is 4. 393 where: 395 Type: TBA. 397 Length: 4. 399 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 400 when the measured value of this parameter exceeds its configured 401 maximum threshold. The A bit is cleared when the measured value 402 falls below its configured reuse threshold. If the A-bit is clear, 403 the sub-TLV represents steady state link performance. 405 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 406 when the measured value of this parameter exceeds its configured 407 maximum threshold. The A bit is cleared when the measured value 408 falls below its configured reuse threshold. If the A-bit is clear, 409 the sub-TLV represents steady state link performance. 411 RESERVED. This field is reserved for future use. It MUST be set to 412 0 when sent and MUST be ignored when received. 414 Link Loss. This 24-bit field carries link packet loss as a 415 percentage of the total traffic sent over a configurable interval. 416 The basic unit is 0.000003%, where (2^24 - 2) is 50.331642%. This 417 value is the highest packet loss percentage that can be expressed 418 (the assumption being that precision is more important on high speed 419 links than the ability to advertise loss rates greater than this, and 420 that high speed links with over 50% loss are unusable). Therefore, 421 measured values that are larger than the field maximum SHOULD be 422 encoded as the maximum value. When set to a value of all 1s (2^24 - 423 1), the link packet loss has not been measured. 425 4.5. Unidirectional Residual Bandwidth Sub-TLV 427 This TLV advertises the residual bandwidth between two directly 428 connected IS-IS neighbors. The residual bandwidth advertised by this 429 sub-TLV MUST be the residual bandwidth from the system originating 430 the LSA to its neighbor. 431 0 1 2 3 432 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 1 433 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 434 | Type | Length |A| RESERVED | 435 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 436 | Residual Bandwidth | 437 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 439 where: 441 Type: TBA. 443 Length: 4. 445 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 446 when the measured value of this parameter exceeds its configured 447 maximum threshold. The A bit is cleared when the measured value 448 falls below its configured reuse threshold. If the A-bit is clear, 449 the sub-TLV represents steady state link performance. 451 RESERVED. This field is reserved for future use. It MUST be set to 452 0 when sent and MUST be ignored when received. 454 Residual Bandwidth. This field carries the residual bandwidth on a 455 link, forwarding adjacency [RFC4206], or bundled link in IEEE 456 floating point format with units of bytes per second. For a link or 457 forwarding adjacency, residual bandwidth is defined to be Maximum 458 Bandwidth [RFC3630] minus the bandwidth currently allocated to 459 RSVP-TE LSPs. For a bundled link, residual bandwidth is defined to 460 be the sum of the component link residual bandwidths. 462 The calculation of Residual Bandwidth is different than that of 463 Unreserved Bandwidth [RFC3630]. Residual Bandwidth subtracts tunnel 464 reservations from Maximum Bandwidth (i.e. the link capacity) 465 [RFC3630] and provides an aggregated remainder across QoS classes. 466 Unreserved Bandwidth [RFC3630], on the other hand, is subtracted from 467 the Maximum Reservable Bandwidth (the bandwidth that can 468 theoretically be reserved) [RFC3630] and provides per-QoS-class 469 remainders. Residual Bandwidth and Unreserved Bandwidth [RFC3630] 470 can be used concurrently, and each has a separate use case (e.g. the 471 former can be used for applications like Weighted ECMP while the 472 latter can be used for call admission control). 474 4.6. Unidirectional Available Bandwidth Sub-TLV 476 This Sub-TLV advertises the available bandwidth between two directly 477 connected IS-IS neighbors. The available bandwidth advertised by 478 this sub-TLV MUST be the available bandwidth from the system 479 originating this Sub-TLV. The format of this Sub-TLV is shown in the 480 following diagram: 481 0 1 2 3 482 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 1 483 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 484 | Type | Length |A| RESERVED | 485 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 486 | Available Bandwidth | 487 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 489 where: 491 Figure 4 493 Type: TBA. 495 Length: 4. 497 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 498 when the measured value of this parameter exceeds its configured 499 maximum threshold. The A bit is cleared when the measured value 500 falls below its configured reuse threshold. If the A-bit is clear, 501 the sub-TLV represents steady state link performance. 503 RESERVED. This field is reserved for future use. It MUST be set to 504 0 when sent and MUST be ignored when received. 506 Available Bandwidth. This field carries the available bandwidth on a 507 link, forwarding adjacency, or bundled link in IEEE floating point 508 format with units of bytes per second. For a link or forwarding 509 adjacency, available bandwidth is defined to be residual bandwidth 510 minus the measured bandwidth used for the actual forwarding of non- 511 RSVP-TE LSP packets. For a bundled link, available bandwidth is 512 defined to be the sum of the component link available bandwidths 513 minus the measured bandwidth used for the actual forwarding of non- 514 RSVP-TE Label Switched Paths packets. For a bundled link, available 515 bandwidth is defined to be the sum of the component link available 516 bandwidths. 518 4.7. Unidirectional Utilized Bandwidth Sub-TLV 520 This Sub-TLV advertises the bandwidth utilization between two 521 directly connected IS-IS neighbors. The bandwidth utilization 522 advertised by this sub-TLV MUST be the bandwidth from the system 523 originating this Sub-TLV. The format of this Sub-TLV is shown in the 524 following diagram: 526 0 1 2 3 527 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 1 528 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 529 | Type | Length |A| RESERVED | 530 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 531 | Bandwidth Utilization | 532 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 534 where: 536 Figure 5 538 Type: TBA. 540 Length: 4. 542 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set 543 when the measured value of this parameter exceeds its configured 544 maximum threshold. The A bit is cleared when the measured value 545 falls below its configured reuse threshold. If the A-bit is clear, 546 the sub-TLV represents steady state link performance. 548 RESERVED. This field is reserved for future use. It MUST be set to 549 0 when sent and MUST be ignored when received. 551 Bandwidth Utilization. This field carries the bandwidth utilization 552 on a link, forwarding adjacency, or bundled link in IEEE floating 553 point format with units of bytes per second. For a link or 554 forwarding adjacency, bandwidth utilization represent the actual 555 utilization of the link (i.e.: as measured in the router). For a 556 bundled link, bandwidth utilization is defined to be the sum of the 557 component link bandwidth utilization. 559 5. Announcement Thresholds and Filters 561 The values advertised in all sub-TLVs (except Low/High delay and 562 residual bandwidth) MUST represent an average over a period or be 563 obtained by a filter that is reasonably representative of an average. 564 For example, a rolling average is one such filter. 566 Low or High delay MAY be the lowest and/or highest measured value 567 over a measurement interval or MAY make use of a filter, or other 568 technique to obtain a reasonable representation of a low and high 569 value representative of the interval with compensation for outliers. 571 The measurement interval, any filter coefficients, and any 572 advertisement intervals MUST be configurable per sub-TLV. 574 In addition to the measurement intervals governing re-advertisement, 575 implementations SHOULD provide per sub-TLV configurable accelerated 576 advertisement thresholds, such that: 577 1. If the measured parameter falls outside a configured upper 578 bound for all but the low delay metric (or lower bound for 579 low-delay metric only) and the advertised sub-TLV is not 580 already outside that bound or, 582 2. If the difference between the last advertised value and 583 current measured value exceed a configured threshold then, 585 3. The advertisement is made immediately. 587 4. For sub-TLVs which include an A-bit (except low/high 588 delay), an additional threshold SHOULD be included 589 corresponding to the threshold for which the performance 590 is considered anomalous (and sub-TLVs with the A-bit are 591 sent). The A-bit is cleared when the sub-TLV's performance 592 has been below (or re-crosses) this threshold for an 593 advertisement interval(s) to permit fail back. 595 To prevent oscillations, only the high threshold or the low threshold 596 (but not both) may be used to trigger any given sub-TLV that supports 597 both. 599 Additionally, once outside of the bounds of the threshold, any 600 readvertisement of a measurement within the bounds would remain 601 governed solely by the measurement interval for that sub-TLV. 603 6. Announcement Suppression 605 When link performance values change by small amounts that fall under 606 thresholds that would cause the announcement of a sub-TLV, 607 implementations SHOULD suppress sub-TLV readvertisement and/or 608 lengthen the period within which they are refreshed. 610 Only the accelerated advertisement threshold mechanism may shorten 611 the re-advertisement interval. All suppression and re-advertisement 612 interval backoff timer features SHOULD be configurable. 614 7. Network Stability and Announcement Periodicity 616 Section 5 and Section 6 provide configurable mechanisms to bound the 617 number of re-advertisements. Instability might occur in very large 618 networks if measurement intervals are set low enough to overwhelm the 619 processing of flooded information at some of the routers in the 620 topology. Therefore care SHOULD be taken in setting these values. 622 Additionally, the default measurement interval for all sub-TLVs 623 SHOULD be 30 seconds. 625 Announcements MUST also be able to be throttled using configurable 626 inter-update throttle timers. The minimum announcement periodicity 627 is 1 announcement per second. The default value SHOULD be set to 120 628 seconds. 630 Implementations SHOULD NOT permit the inter-update timer to be lower 631 than the measurement interval. 633 Furthermore, it is RECOMMENDED that any underlying performance 634 measurement mechanisms not include any significant buffer delay, any 635 significant buffer induced delay variation, or any significant loss 636 due to buffer overflow or due to active queue management. 638 8. Enabling and Disabling Sub-TLVs 640 Implementations MUST make it possible to individually enable or 641 disable each sub-TLV based on configuration. 643 9. Static Metric Override 645 Implementations SHOULD permit the static configuration and/or manual 646 override of dynamic measurements data on a per sub-TLV, per metric 647 basis in order to simplify migrations and to mitigate scenarios where 648 measurements are not possible across an entire network. 650 10. Compatibility 652 As per [RFC5305], unrecognized Sub-TLVs should be silently ignored 654 11. Security Considerations 656 This document does not introduce security issues beyond those 657 discussed in [RFC3630] and [RFC5329]. 659 12. IANA Considerations 661 IANA maintains the registry for the sub-TLVs. IS-IS TE Metric 662 Extensions will require one new type code per sub-TLV defined in this 663 document. 665 13. Acknowledgements 667 The authors would like to recognize Ayman Soliman, Nabil Bitar, David 668 McDysan, Les Ginsberg, Edward Crabbe, Don Fedyk and Hannes Gredler 669 for their contributions. 671 The authors also recognize Curtis Villamizar for significant comments 672 and direct content collaboration. 674 14. References 676 14.1. Normative References 678 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 679 Requirement Levels", BCP 14, RFC 2119, March 1997. 681 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 682 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 683 Tunnels", RFC 3209, December 2001. 685 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 686 (TE) Extensions to OSPF Version 2", RFC 3630, 687 September 2003. 689 [RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support 690 of Generalized Multi-Protocol Label Switching (GMPLS)", 691 RFC 4203, October 2005. 693 [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) 694 Hierarchy with Generalized Multi-Protocol Label Switching 695 (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005. 697 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 698 Topology (MT) Routing in Intermediate System to 699 Intermediate Systems (IS-ISs)", RFC 5120, February 2008. 701 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 702 Engineering", RFC 5305, October 2008. 704 [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in 705 Support of Inter-Autonomous System (AS) MPLS and GMPLS 706 Traffic Engineering", RFC 5316, December 2008. 708 [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, 709 "Traffic Engineering Extensions to OSPF Version 3", 710 RFC 5329, September 2008. 712 [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic 713 Engineering in IS-IS", RFC 6119, February 2011. 715 [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay 716 Measurement for MPLS Networks", RFC 6374, September 2011. 718 14.2. Informative References 720 [I-D.atlas-mpls-te-express-path] 721 Atlas, A., Drake, J., Giacalone, S., Ward, D., Previdi, 722 S., and C. Filsfils, "Performance-based Path Selection for 723 Explicitly Routed LSPs using TE Metric Extensions", 724 draft-atlas-mpls-te-express-path-04 (work in progress), 725 September 2013. 727 [I-D.ietf-alto-protocol] 728 Alimi, R., Penno, R., and Y. Yang, "ALTO Protocol", 729 draft-ietf-alto-protocol-20 (work in progress), 730 October 2013. 732 [RFC6375] Frost, D. and S. Bryant, "A Packet Loss and Delay 733 Measurement Profile for MPLS-Based Transport Networks", 734 RFC 6375, September 2011. 736 Authors' Addresses 738 Stefano Previdi (editor) 739 Cisco Systems, Inc. 740 Via Del Serafico 200 741 Rome 00191 742 IT 744 Email: sprevidi@cisco.com 746 Spencer Giacalone 747 Thomson Reuters 748 195 Broadway 749 New York, NY 10007 750 USA 752 Email: Spencer.giacalone@thomsonreuters.com 753 Dave Ward 754 Cisco Systems, Inc. 755 3700 Cisco Way 756 SAN JOSE, CA 95134 757 US 759 Email: wardd@cisco.com 761 John Drake 762 Juniper Networks 763 1194 N. Mathilda Ave. 764 Sunnyvale, CA 94089 765 USA 767 Email: jdrake@juniper.net 769 Alia Atlas 770 Juniper Networks 771 1194 N. Mathilda Ave. 772 Sunnyvale, CA 94089 773 USA 775 Email: akatlas@juniper.net 777 Clarence Filsfils 778 Cisco Systems, Inc. 779 Brussels 780 Belgium 782 Email: cfilsfil@cisco.com 784 Qin Wu 785 Huawei 786 101 Software Avenue, Yuhua District 787 Nanjing, Jiangsu 210012 788 China 790 Email: sunseawq@huawei.com