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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 TRILL Working Group Donald Eastlake 2 INTERNET-DRAFT Huawei 3 Intended status: Proposed Standard Bob Briscoe 4 Simula Research Lab 5 Expires: September 11, 2017 March 12, 2017 7 TRILL: ECN (Explicit Congestion Notification) Support 8 10 Abstract 12 Explicit congestion notification (ECN) allows a forwarding element to 13 notify downstream devices, including the destination, of the onset of 14 congestion without having to drop packets. This can improve network 15 efficiency through better flow control without packet drops. This 16 document extends ECN to TRILL switches, including integration with IP 17 ECN, and provides for ECN marking in the TRILL Header Extension Flags 18 Word (see RFC 7179). 20 Status of This Memo 22 This Internet-Draft is submitted to IETF in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Distribution of this document is unlimited. Comments should be sent 26 to the TRILL working group mailing list . 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF), its areas, and its working groups. Note that 30 other groups may also distribute working documents as Internet- 31 Drafts. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 The list of current Internet-Drafts can be accessed at 39 http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft 40 Shadow Directories can be accessed at 41 http://www.ietf.org/shadow.html. 43 Table of Contents 45 1. Introduction............................................3 46 1.1 Conventions used in this document......................4 48 2. The ECN Specific Extended Header Flags..................6 50 3. ECN Support.............................................7 51 3.1 Ingress ECN Support....................................7 52 3.2 Transit ECN Support....................................7 53 3.3 Egress ECN Support.....................................8 55 4. TRILL Support for ECN Variants.........................10 56 4.1 Pre-Congestion Notification (PCN).....................10 57 4.2 Low Latency, Low Loss, Scalable Throughput (L4S)......11 59 5. IANA Considerations....................................12 60 6. Security Considerations................................13 61 7. Acknowledgements.......................................13 63 Normative References......................................14 64 Informative References....................................14 66 Appendix A. TRILL Transit RBridge Behavior to Support L4S.16 68 Authors' Addresses........................................18 70 1. Introduction 72 Explicit congestion notification (ECN [RFC3168]) allows a forwarding 73 element, such as a router, to notify downstream devices, including 74 the destination, of the onset of congestion without having to drop 75 packets. This can improve network efficiency through better flow 76 control without packet drops. The forwarding element can explicitly 77 mark a proportion of packets in an ECN field instead of dropping the 78 packet. For example, a two-bit field is available for ECN marking in 79 IP headers. 81 ............................. 82 . . 83 +---------+ . 84 +------+ | Ingress | . 85 |Source| +->| RBridge | . +----------+ 86 +---+--+ | | RB1 | . |Forwarding| 87 | | +------+--+ +----------+ . | Element | 88 v | . | | Transit | . | Y | 89 +-------+--+ . +---->| RBridges | . +--------+-+ 90 |Forwarding| . | RBn | . ^ | 91 | Element | . +-------+--+ +---------+ | v 92 | X | . | | Egress | | +-----------+ 93 +----------+ . +---->| RBridge +-+ |Destination| 94 . | RB9 | +-----------+ 95 . TRILL +---------+ 96 . campus . 97 ............................. 99 Figure 1. Example Path Forwarding Nodes 101 In [RFC3168] it was recognized that tunnels and lower layer protocols 102 would need to support ECN, and ECN markings would need to be 103 propagated, as headers were encapsulated and decapsulated. 104 [ECNencapGuide] gives guidelines on the addition of ECN to protocols 105 like TRILL that often encapsulate IP packets, including propagation 106 of ECN from and to IP. 108 In the figure above, assuming IP traffic, RB1 is an encapsulator and 109 RB9 a decapsulator. Traffic from Source to RB1 might or might not get 110 marked as having experienced congestion in forwarding elements, such 111 as X, before being encapsulated at ingress RB1. Any such ECN marking 112 is encapsulated with a TRILL Header [RFC6325]. 114 This specification provides for any ECN marking in the traffic at the 115 ingress to be copied into the TRILL Extension Header Flags Word. It 116 also enables congestion marking by a congested RBridge such as RBn or 117 RB1 above in the TRILL Header Extension Flags Word [RFC7179]. 119 At RB9, the TRILL egress, it specifies how any ECN markings in the 120 TRILL Header Flags Word and in the encapsulated traffic are combined 121 so that subsequent forwarding elements, such as Y and the 122 Destination, can see if congestion was experienced at any previous 123 point in the path from Source. 125 A large part of the guidelines for adding ECN to lower layer 126 protocols [ECNencapGuide] concerns safe propagation of congestion 127 notifications in scenarios where some of the nodes do not support or 128 understand ECN. Such ECN ignorance is not a major problem with 129 RBridges using this specification because the method specified 130 assures that, if an egress RBridge is ECN ignorant (so it cannot 131 further propagate ECN) and congestion has been encountered, the 132 egress RBridge will at least drop the packet and this drop will 133 itself indicate congestion to end stations. 135 1.1 Conventions used in this document 137 The terminology and acronyms defined in [RFC6325] are used herein 138 with the same meaning. 140 In this documents, "IP" refers to both IPv4 and IPv6. 142 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 143 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 144 document are to be interpreted as described in [RFC2119]. 146 Acronyms: 148 AQM - Active Queue Management 150 CCE - Critical Congestion Experienced 152 CE - Congestion Experienced 154 CItE - Critical Ingress-to-Egress 156 ECN - Explicit Congestion Notification 158 ECT - ECN Capable Transport 160 L4S - Low Latency, Low Loss, Scalable throughput 162 NCHbH - Non-Critical Hop-by-Hop 164 NCCE - Non-Critical Congestion Experienced 166 Not-ECT - Not ECN-Capable Transport 167 PCN - Pre-Congestion Notification 169 2. The ECN Specific Extended Header Flags 171 The extension header fields for explicit congestion notification 172 (ECN) in TRILL are defined as a two-bit TRILL-ECN field and a one-bit 173 Critical Congestion Experienced (CCE) field in the 32-bit TRILL 174 Header Extension Flags Word [RFC7780]. 176 These fields are show in Figure 2 as "ECN" and "CCE". The TRILL-ECN 177 field consists of bits 12 and 13, which are in the range reserved for 178 non-critical hop-by-hop (NCHbH) bits. The CCE field consists of bit 179 26, which is in the range reserved for Critical Ingress-to-Egress 180 (CItE) bits. The CRItE bit is the critical Ingress-to-Egress summary 181 bit and will be one if and only if any of the bits in the CItE range 182 (21-26) is one or there is a critical feature invoked in some further 183 extension of the TRILL Header after the Extesnion Flags Word. The 184 other bits and fields shown in Figure 2 are not relevant to ECN. See 185 [RFC7780], [RFC7179], and [IANAthFlags] for the meaning of these 186 other bits and fields. 188 0 1 2 3 189 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 1 190 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 191 |Crit.| CHbH | NCHbH |CRSV | NCRSV | CItE | NCItE | 192 |.....|.........|...........|.....|.......|...........|.........| 193 |C|C|C| |C|N| | | | | | | | | 194 |R|R|R| |R|C| |ECN| Ext | | |C|Ext| | 195 |H|I|R| |C|C| | | Hop | | |C|Clr| | 196 |b|t|s| |A|A| | | Cnt | | |E| | | 197 |H|E|v| |F|F| | | | | | | | | 198 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 200 Figure 2 The ECN and CCE TRILL Header Extension Flags Word Fields 202 Table 1 shows the meaning of the codepoints in the TRILL-ECN field. 203 The first three have the same meaning as the corresponding ECN field 204 codepoints in the IPv4 or IPv6 header as defined in [RFC3168]. 205 However codepoint 0b11 is called Non-Critical Congestion Experienced 206 (NCCE) to distinguish it from Congestion Experienced in IP. 208 Binary Name Meaning 209 ------ ------- ----------------------------------- 210 00 Not-ECT Not ECN-Capable Transport 211 01 ECT(1) ECN-Capable Transport (1) 212 10 ECT(0) ECN-Capable Transport (0) 213 11 NCCE Non-Critical Congestion Experienced 215 Table 1. TRILL-ECN Field Codepoints 217 3. ECN Support 219 The subsections below describe the required behavior to support ECN 220 at TRILL ingress, transit, and egress. The ingress behavior occurs as 221 a native frame is encapsulated with a TRILL Header to produce a TRILL 222 Data packet. The transit behavior occurs in all RBridges where TRILL 223 Data packets are queued, usually at the output port. The egress 224 behavior occurs where a TRILL Data packet is decapsulated and output 225 as a native frame through an RBridge port. 227 An RBridge that supports ECN MUST behave as described in the relevant 228 subsections below, which correspond to the recommended provisions of 229 [ECNencapGuide]. Nonetheless, the scheme is designed to safely 230 propagate some form of congestion notification even if some RBridges 231 in the path followed by a TRILL Data packet support ECN and others do 232 not. 234 3.1 Ingress ECN Support 236 The behavior at an ingress RBridge is as follows: 238 o When encapsulating an IP frame, the ingress RBridge MUST: 240 + set the F flag in the main TRILL header [RFC7780]; 241 + create a Flags Word as part of the TRILL Header; 242 + copy the two ECN bits from the IP header into the TRILL-ECN 243 field (Flags Word bits 12 and 13) 244 + ensure the CCE flag is set to zero (Flags Word bit 26). 246 o When encapsulating a frame for a non-IP protocol, where that 247 protocol has a means of indicating ECN that is understood by the 248 ingress RBridge, it MUST follow the guidelines in [ECNencapGuide] 249 to add a Flags Word to the TRILL Header. For a non-IP protocol 250 with a similar ECN field to IP, this would be achieved by copying 251 into the TRILL-ECN field from the encapsulated native frame. 253 3.2 Transit ECN Support 255 The transit behavior, shown below, is required at all RBridges where 256 TRILL Data packets are queued, usually at the output port. 258 o An RBridge that supports ECN MUST implement some form of active 259 queue management (AQM) according to the guidelines of [RFC7567]. 260 The RBridge detects congestion either by monitoring its own queue 261 depth or by participating in a link-specific protocol. 263 o If the TRILL Header Flags Word is present, whenever the AQM 264 algorithm decides to indicate congestion on a TRILL Data packet it 265 MUST set the CCE flag (Flags Word bit 26). 267 o If the TRILL header Flags Word is not present, to indicate 268 congestion the RBridge will either drop the packet or it MAY do 269 all of the following instead: 271 + set the F flag in the main TRILL header; 272 + add a Flags Word to the TRILL Header; 273 + set the TRILL-ECN field to Not-ECT (00); 274 + and set the CCE flag and the Ingress-to-Egress critical summary 275 bit (CRIbE). 277 Note that a transit RBridge that supports ECN does not refer to the 278 TRILL-ECN field before signalling CCE in a packet. It signals CCE 279 irrespective of whether the packet indicates that the transport is 280 ECN-capable. The egress/decapsulation behavior (described next) 281 ensures that a CCE indication is converted to a drop if the transport 282 is not ECN-capable. 284 3.3 Egress ECN Support 286 If the egress RBridge does not support ECN, that RBridge will ignore 287 bits 12 and 13 of any Flags Word that is present, because it does not 288 contain any special ECN logic. Nonetheless, if a transit RBridge has 289 set the CCE flag, the egress will drop the packet. This is because 290 drop is the default behavior for an RBridge decapsulating a Critical 291 Ingress-to-Egress flag when it has no specific logic to understand 292 it. Drop is the intended behavior for such a packet, as required by 293 [ECNencapGuide]. 295 If an RBridge supports ECN, the egress behavior is as follows: 297 o When decapsulating an inner IP packet, the RBridge sets the ECN 298 field of the outgoing native IP packet using Table 2. It MUST set 299 the ECN field of the outgoing IP packet to the codepoint at the 300 intersection of the row for the arriving encapsulated IP packet 301 and the column for 3-bit ECN codepoint in the arriving outer TRILL 302 Data packet TRILL Header. If no TRILL Header Extension Flags Word 303 is present, the 3-bit ECN codepoint is assumed to be all zero 304 bits. 305 The name of the TRILL 3-bit ECN codepoint is defined using the 306 combination of the TRILL-ECN and CCE fields in Table 3. 307 Specifically, the TRILL 3-bit ECN codepoint is called CE if either 308 NCCE or CCE is set in the TRILL Header Extension Flags Word. 309 Otherwise it has the same name as the 2-bit TRILL-ECN codepoint. 310 In the case where the TRILL 3-bit ECN codepoint indicates 312 congestion experienced (CE) but the encapsulated native IP frame 313 indicates a not ECN-capable transport (Not-ECT), the RBridge MUST 314 drop the packet. Such packet dropping is necessary because a 315 transport above the IP layer that is not ECN-capable will have no 316 ECN logic, so it will only understand dropped packets as an 317 indication of congestion. 319 o When decapsulating a non-IP protocol frame with a means of 320 indicating ECN that is understood by the RBridge, it MUST follow 321 the guideines in [ECNencapGuide] when setting the ECN information 322 in the decapsulated native frame. For a non-IP protocol with a 323 similar ECN field to IP, this would be achieved by combining the 324 information in the TRILL Header Flags Word with the encapsulated 325 non-IP native frame, as specified in Table 2. 327 +---------+----------------------------------------------+ 328 | Inner | Arriving TRILL 3-bit ECN Codepoint Name | 329 | Native +---------+------------+------------+----------+ 330 | Header | Not-ECT | ECT(0) | ECT(1) | CE | 331 +---------+---------+------------+------------+----------+ 332 | Not-ECT | Not-ECT | Not-ECT(*) | Not-ECT(*) | | 333 | ECT(0) | ECT(0) | ECT(0) | ECT(1) | CE | 334 | ECT(1) | ECT(1) | ECT(1)(*) | ECT(1) | CE | 335 | CE | CE | CE | CE(*) | CE | 336 +---------+---------+------------+------------+----------+ 338 Table 2: Egress ECN Behavior 340 An asterisk in the above table indicates a currently unused 341 combination that SHOULD be logged. In contrast to [RFC6040], in TRILL 342 the drop condition is the result of a valid combination of events and 343 need not be logged. 345 +------------+-----+---------------------+ 346 | TRILL-ECN | CCE | Arriving TRILL 3-bit| 347 | | | ECN codepoint name | 348 +------------+-----+---------------------+ 349 | Not-ECT 00 | 0 | Not-ECT | 350 | ECT(1) 01 | 0 | ECT(1) | 351 | ECT(0) 10 | 0 | ECT(0) | 352 | NCCE 11 | 0 | CE | 353 | Not-ECT 00 | 1 | CE | 354 | ECT(1) 01 | 1 | CE | 355 | ECT(0) 10 | 1 | CE | 356 | NCCE 11 | 1 | CE | 357 +------------+-----+---------------------+ 359 Table 3: Mapping of TRILL-ECN and CCE Fields to TRILL 3-bit ECN 360 Codepoint Name 362 4. TRILL Support for ECN Variants 364 This section is informative, not normative. 366 Section 3 specifies interworking between TRILL and the original 367 standardized form of ECN in IP [RFC3168]. 369 The ECN wire protocol for TRILL (Section 2) has been designed to 370 support the other known variants of ECN, as detailed below. New 371 variants of ECN will have to comply with the guidelines for defining 372 alternative ECN semantics [RFC4774]. It is expected that the TRILL 373 ECN wire protocol is generic enough to support such potential future 374 variants. 376 4.1 Pre-Congestion Notification (PCN) 378 The PCN wire protocol [RFC6660] is recognised by the use of a PCN- 379 compatible Diffserv codepoint in the IP header and a non-zero IP-ECN 380 field. For TRILL or any lower layer protocol, equivalent traffic 381 classification codepoints would have to be defined, but that is 382 outside the scope of the current document. 384 The PCN wire protocol is similar to ECN, except it indicates 385 congestion with two levels of severity. It uses: 387 o 11 (CE) as the most severe, termed the Excess-traffic-marked (ETM) 388 codepoint 390 o 01 ECT(1) as a lesser severity level, termed the Threshold-Marked 391 (ThM) codepoint. (This difference between ECT(1) and ECT(0) only 392 applies to PCN, not to the classic ECN support specified for TRILL 393 in this document before Section 4.) 395 To implement PCN on a transit RBridge would require a detailed 396 specification. But in brief: 398 o the TRILL Critical Congestion Experienced (CCE) flag would be used 399 for the Excess-Traffic-Marked (ETM) codepoint; 401 o ECT(1) in the TRILL-ECN field would be used for the Threshold- 402 Marked codepoint. 404 Then the ingress and egress behaviors defined in Section 3 would not 405 need to be altered to ensure support for PCN as well as ECN. 407 4.2 Low Latency, Low Loss, Scalable Throughput (L4S) 409 L4S is currently only a proposal being considered for adoption onto 410 the IETF's experimental track. An outline of how a transit TRILL 411 RBridge would support L4S [ECNL4S] is given in Appendix A. 413 5. IANA Considerations 415 IANA is requested to update the TRILL Extended Header Flags registry 416 by replacing the lines for bits 9-13 and for bits 21-26 with the 417 following: 419 Bits Purpose Reference 420 ----- ------- --------- 421 9-11 available non-critical hop-by-hop flags 422 12-13 TRILL-ECN (Explicit Congestion Notification) [this doc] 424 21-25 available critical ingress-to-egress flags 425 26 Critical Congestion Experienced (CCE) [this doc] 427 6. Security Considerations 429 TRILL support of ECN is a straight forward combination of previously 430 specified ECN and TRILL with no significnat new security 431 considerations. 433 For ECN tunneling security considerations, see [RFC6040]. 435 For general TRILL protocol security considerations, see [RFC6325]. 437 7. Acknowledgements 439 This document was prepared with basic NROFF. All macros used were 440 defined in the source file. 442 Normative References 444 [RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate 445 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, 446 March 1997, . 448 [RFC3168] - Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 449 of Explicit Congestion Notification (ECN) to IP", RFC 3168, DOI 450 10.17487/RFC3168, September 2001, . 453 [RFC4774] - Floyd, S., "Specifying Alternate Semantics for the 454 Explicit Congestion Notification (ECN) Field", BCP 124, RFC 455 4774, DOI 10.17487/RFC4774, November 2006, . 458 [RFC6325] - Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A. 459 Ghanwani, "Routing Bridges (RBridges): Base Protocol 460 Specification", RFC 6325, DOI 10.17487/RFC6325, July 2011, 461 . 463 [RFC7179] - Eastlake 3rd, D., Ghanwani, A., Manral, V., Li, Y., and 464 C. Bestler, "Transparent Interconnection of Lots of Links 465 (TRILL): Header Extension", RFC 7179, DOI 10.17487/RFC7179, May 466 2014, . 468 [RFC7567] - Baker, F., Ed., and G. Fairhurst, Ed., "IETF 469 Recommendations Regarding Active Queue Management", BCP 197, 470 RFC 7567, DOI 10.17487/RFC7567, July 2015, . 473 [RFC7780] - Eastlake 3rd, D., Zhang, M., Perlman, R., Banerjee, A., 474 Ghanwani, A., and S. Gupta, "Transparent Interconnection of 475 Lots of Links (TRILL): Clarifications, Corrections, and 476 Updates", RFC 7780, DOI 10.17487/RFC7780, February 2016, 477 . 479 [ECNencapGuide] - B. Briscoe, J. Kaippallimalil, P. Thaler, 480 "Guidelines for Adding Congestion Notification to Protocols 481 that Encapsulate IP", draft-ietf-tsvwg-ecn-encap-guidelines, 482 work in progress. 484 Informative References 486 [ECNL4S] - K. De Schepper, B. Briscoe, I. Tsang, "Identifying 487 Modified Explicit Congestion Notification (ECN) Semantics for 488 Ultra-Low Queueing Delay", draft-briscoe-tsvwg-ecn-l4s-id, work 489 in progress. 491 [IANAthFlags] - IANA TRILL Extended Header word flags: 492 http://www.iana.org/assignments/trill-parameters/trill- 493 parameters.xhtml#extended-header-flags 495 [RFC6040] - Briscoe, B., "Tunnelling of Explicit Congestion 496 Notification", RFC 6040, DOI 10.17487/RFC6040, November 2010, 497 . 499 [RFC6660] - Briscoe, B., Moncaster, T., and M. Menth, "Encoding Three 500 Pre-Congestion Notification (PCN) States in the IP Header Using 501 a Single Diffserv Codepoint (DSCP)", RFC 6660, DOI 502 10.17487/RFC6660, July 2012, . 505 Appendix A. TRILL Transit RBridge Behavior to Support L4S 507 An initial specification of the Low Latency, Low Loss, Scalable 508 throughput (L4S) wire protocol for IP is given in [ECNL4S]. It is 509 similar to the original ECN wire protoocl for IP [RFC3168], except: 511 o An AQM that supports L4S classifies packets with ECT(1) or CE in 512 the IP header into an L4S queue and a "Classic" queue otherwise. 514 o the meaning of CE markings applied by an L4S queue is not the same 515 as the meaning of a drop by a "Classic" queue (contrary to the 516 original requirement for ECN [RFC3168]). Instead the likelihood 517 that the Classic queue drops packets is defined as the square of 518 the likelihood that the L4S queue marks packets (e.g. when there 519 is a drop probability of 0.0009 (0.09%) the L4S marking 520 probability will be 0.03 (3%)). 522 This seems to present a problem for the way that a transit TRILL 523 RBridge defers the choice between marking and dropping to the egress. 524 Nonetheless, the following pseudocode outlines how a transit TRILL 525 RBridge can implement L4S marking in such a way that the egress 526 behavior already described in Section 3.3 for Classic ECN [RFC3168] 527 will produce the desired outcome. 529 /* p is an internal variable calculated by any L4S AQM 530 * dependent on the delay being experienced in the Classic queue. 531 * bit13 is the least significant bit of the TRILL-ECN field 532 */ 534 % On TRILL transit 535 if (bit13 == 0 ) { 536 % Classic Queue 537 if (p > max(random(), random()) ) 538 mark(CCE) % likelihood: p^2 540 } else { 541 % L4S Queue 542 if (p > max(random()) ) { 543 if (p > max(random()) ) 544 mark(CCE) % likelihood: p^2 545 else 546 mark(NCCE) % likelihood: p - p^2 547 } 548 } 550 With the above transit behavior, an egress that supports ECN (Section 551 3.3) will drop packets or propagate their ECN markings depending on 552 whether the arriving inner header is from a non-ECN-capable or ECN- 553 capable transport. 555 Even if an egress has no L4S-specific logic of its own, it will drop 556 packets with the square of the probability that an egress would if it 557 did support ECN, for the following reasons: 559 o Egress with ECN support: 561 + L4S: propagates both the Critical and Non-Critical CE marks 562 (CCE & NCCE) as a CE mark. 564 Likelihood: p^2 + p - p^2 = p 566 + Classic: Propagates CCE marks as CE or drop, depending on 567 inner. 569 Likelihood: p^2 571 o Egress without ECN support: 573 + L4S: does not propagate NCCE as a CE mark, but drops CCE marks. 575 Likelihood: p^2 577 + Classic: drops CCE marks. 579 Likelihood: p^2 581 Authors' Addresses 583 Donald E. Eastlake, 3rd 584 Huawei Technologies 585 155 Beaver Street 586 Milford, MA 01757 USA 588 Tel: +1-508-333-2270 589 Email: d3e3e3@gmail.com 591 Bob Briscoe (editor) 592 Simula Research Lab 594 Email: ietf@bobbriscoe.net 595 URI: http://bobbriscoe.net/ 597 Copyright and IPR Provisions 599 Copyright (c) 2017 IETF Trust and the persons identified as the 600 document authors. All rights reserved. 602 This document is subject to BCP 78 and the IETF Trust's Legal 603 Provisions Relating to IETF Documents 604 (http://trustee.ietf.org/license-info) in effect on the date of 605 publication of this document. Please review these documents 606 carefully, as they describe your rights and restrictions with respect 607 to this document. Code Components extracted from this document must 608 include Simplified BSD License text as described in Section 4.e of 609 the Trust Legal Provisions and are provided without warranty as 610 described in the Simplified BSD License. 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