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Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Outdated reference: A later version (-28) exists of draft-ietf-tcpm-accurate-ecn-06 -- Obsolete informational reference (is this intentional?): RFC 8312 (Obsoleted by RFC 9438) Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group N. Khademi 3 Internet-Draft M. Welzl 4 Intended status: Experimental University of Oslo 5 Expires: September 21, 2018 G. Armitage 6 Swinburne University of Technology 7 G. Fairhurst 8 University of Aberdeen 9 March 20, 2018 11 TCP Alternative Backoff with ECN (ABE) 12 draft-ietf-tcpm-alternativebackoff-ecn-07 14 Abstract 16 Active Queue Management (AQM) mechanisms allow for burst tolerance 17 while enforcing short queues to minimise the time that packets spend 18 enqueued at a bottleneck. This can cause noticeable performance 19 degradation for TCP connections traversing such a bottleneck, 20 especially if there are only a few flows or their bandwidth-delay- 21 product is large. An Explicit Congestion Notification (ECN) signal 22 indicates that an AQM mechanism is used at the bottleneck, and 23 therefore the bottleneck network queue is likely to be short. This 24 document therefore proposes an update to RFC3168, which changes the 25 TCP sender-side ECN reaction in congestion avoidance to reduce the 26 Congestion Window (cwnd) by a smaller amount than the congestion 27 control algorithm's reaction to inferred packet loss. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at https://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on September 21, 2018. 46 Copyright Notice 48 Copyright (c) 2018 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (https://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 64 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 3. Specification . . . . . . . . . . . . . . . . . . . . . . . . 3 66 4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 4 67 4.1. Why Use ECN to Vary the Degree of Backoff? . . . . . . . 4 68 4.2. Focus on ECN as Defined in RFC3168 . . . . . . . . . . . 5 69 4.3. Choice of ABE Multiplier . . . . . . . . . . . . . . . . 5 70 5. ABE Deployment Requirements . . . . . . . . . . . . . . . . . 7 71 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 72 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 73 8. Implementation Status . . . . . . . . . . . . . . . . . . . . 8 74 9. Security Considerations . . . . . . . . . . . . . . . . . . . 9 75 10. Revision Information . . . . . . . . . . . . . . . . . . . . 9 76 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 77 11.1. Normative References . . . . . . . . . . . . . . . . . . 10 78 11.2. Informative References . . . . . . . . . . . . . . . . . 11 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 81 1. Introduction 83 Explicit Congestion Notification (ECN) [RFC3168] makes it possible 84 for an Active Queue Management (AQM) mechanism to signal the presence 85 of incipient congestion without incurring packet loss. This lets the 86 network deliver some packets to an application that would have been 87 dropped if the application or transport did not support ECN. This 88 packet loss reduction is the most obvious benefit of ECN, but it is 89 often relatively modest. Other benefits of deploying ECN have been 90 documented in RFC8087 [RFC8087]. 92 The rules for ECN were originally written to be very conservative, 93 and required the congestion control algorithms of ECN-Capable 94 transport protocols to treat ECN congestion signals exactly the same 95 as they would treat an inferred packet loss [RFC3168]. 97 Research has demonstrated the benefits of reducing network delays 98 that are caused by interaction of loss-based TCP congestion control 99 and excessive buffering [BUFFERBLOAT]. This has led to the creation 100 of new AQM mechanisms like PIE [RFC8033] and CoDel 101 [CODEL2012][RFC8289], which prevent bloated queues that are common 102 with unmanaged and excessively large buffers deployed across the 103 Internet [BUFFERBLOAT]. 105 The AQM mechanisms mentioned above aim to keep a sustained queue 106 short while tolerating transient (short-term) packet bursts. 107 However, currently used loss-based congestion control mechanisms 108 cannot always utilise a bottleneck link well where there are short 109 queues. For example, a TCP sender must be able to store at least an 110 end-to-end bandwidth-delay product (BDP) worth of data at the 111 bottleneck buffer if it is to maintain full path utilisation in the 112 face of loss-induced reduction of cwnd [RFC5681], which effectively 113 doubles the amount of data that can be in flight, the maximum round- 114 trip time (RTT) experience, and the path's effective RTT using the 115 network path. 117 Modern AQM mechanisms can use ECN to signal the early signs of 118 impending queue buildup long before a tail-drop queue would be forced 119 to resort to dropping packets. It is therefore appropriate for the 120 transport protocol congestion control algorithm to have a more 121 measured response when an early-warning signal of congestion is 122 received in the form of an ECN CE-marked packet. Recognizing these 123 changes in modern AQM practices, more recent rules have relaxed the 124 strict requirement that ECN signals be treated identically to 125 inferred packet loss [RFC8311]. Following these newer, more flexible 126 rules, this document defines a new sender-side-only congestion 127 control response, called "ABE" (Alternative Backoff with ECN). ABE 128 improves TCP's average throughput when routers use AQM controlled 129 buffers that allow for short queues only. 131 2. Definitions 133 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 134 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 135 document are to be interpreted as described in RFC 2119 [RFC2119]. 137 3. Specification 139 This specification updates the congestion control algorithm of an 140 ECN-Capable TCP transport protocol by changing the TCP sender 141 response to feedback from the TCP receiver that indicates reception 142 of a CE-marked packet, i.e., receipt of a packet with the ECN-Echo 143 flag (defined in [RFC3168]) set. 145 It updates the following text in section 6.1.2 of the ECN 146 specification [RFC3168] : 148 The indication of congestion should be treated just as a 149 congestion loss in non-ECN-Capable TCP. That is, the TCP source 150 halves the congestion window "cwnd" and reduces the slow start 151 threshold "ssthresh". 153 Replacing this with: 155 Receipt of a packet with the ECN-Echo flag SHOULD trigger the TCP 156 source to set the slow start threshold (ssthresh) to 0.8 times the 157 FlightSize, with a lower bound of 2 * SMSS applied to the result. 158 As in [RFC5681], the TCP sender also reduces the cwnd value to no 159 more than the new ssthresh value. RFC 3168 section 6.1.2 provides 160 guidance on setting a cwnd less than 2 * SMSS. 162 4. Discussion 164 Much of the technical background to ABE can be found in a research 165 paper [ABE2017]. This paper used a mix of experiments, theory and 166 simulations with NewReno [RFC5681] and CUBIC [RFC8312] to evaluate 167 the technique. The technique was shown to present "...significant 168 performance gains in lightly-multiplexed [few concurrent flows] 169 scenarios, without losing the delay-reduction benefits of deploying 170 CoDel or PIE". The performance improvement is achieved when reacting 171 to ECN-Echo in congestion avoidance (when ssthresh > cwnd) by 172 multiplying cwnd and ssthresh with a value in the range [0.7,0.85]. 173 Applying ABE when cwnd <= ssthresh is not currently recommended, but 174 may benefit from additional attention, experimentation and 175 specification. 177 4.1. Why Use ECN to Vary the Degree of Backoff? 179 AQM mechanisms such as CoDel [RFC8289] and PIE [RFC8033] set a delay 180 target in routers and use congestion notifications to constrain the 181 queuing delays experienced by packets, rather than in response to 182 impending or actual bottleneck buffer exhaustion. With current 183 default delay targets, CoDel and PIE both effectively emulate a 184 bottleneck with a short queue (section II, [ABE2017]) while also 185 allowing short traffic bursts into the queue. This provides 186 acceptable performance for TCP connections over a path with a low 187 BDP, or in highly multiplexed scenarios (many concurrent transport 188 flows). However, in a lightly-multiplexed case over a path with a 189 large BDP, conventional TCP backoff leads to gaps in packet 190 transmission and under-utilisation of the path. 192 Instead of discarding packets, an AQM mechanism is allowed to mark 193 ECN-Capable packets with an ECN CE-mark. The reception of a CE-mark 194 feedback not only indicates congestion on the network path, it also 195 indicates that an AQM mechanism exists at the bottleneck along the 196 path, and hence the CE-mark likely came from a bottleneck with a 197 controlled short queue. Reacting differently to an ECN-signalled 198 congestion than to an inferred packet loss can then yield the benefit 199 of a reduced back-off when queues are short. Using ECN can also be 200 advantageous for several other reasons [RFC8087]. 202 The idea of reacting differently to inferred packet loss and 203 detection of an ECN-signalled congestion pre-dates this document. 204 For example, previous research proposed using ECN CE-marked feedback 205 to modify TCP congestion control behaviour via a larger 206 multiplicative decrease factor in conjunction with a smaller additive 207 increase factor [ICC2002]. The goal of this former work was to 208 operate across AQM bottlenecks using Random Early Detection (RED) 209 that were not necessarily configured to emulate a short queue (The 210 current usage of RED as an Internet AQM method is limited [RFC7567]). 212 4.2. Focus on ECN as Defined in RFC3168 214 Some transport protocol mechanisms rely on ECN semantics that differ 215 from the original ECN definition [RFC3168]. For instance, Accurate 216 ECN [I-D.ietf-tcpm-accurate-ecn] permits more frequent and detailed 217 feedback. Use of such mechanisms (including Accurate ECN, Datacenter 218 TCP (DCTCP) [RFC8257], or Congestion Exposure (ConEx) [RFC7713]) is 219 out of scope for this document. This specification focuses on ECN as 220 defined in [RFC3168]. 222 4.3. Choice of ABE Multiplier 224 ABE decouples the reaction of a TCP sender to inferred packet loss 225 and ECN-signalled congestion in the congestion avoidance phase. To 226 achieve this, ABE uses a different scaling factor in Equation 4 in 227 Section 3.1 of [RFC5681]. The description respectively uses 228 beta_{loss} and beta_{ecn} to refer to the multiplicative decrease 229 factors applied in response to inferred packet loss, and in response 230 to a receiver indicating ECN-signalled congestion. For non-ECN- 231 enabled TCP connections, only beta_{loss} applies. 233 In other words, in response to inferred packet loss: 235 ssthresh = max (FlightSize * beta_{loss}, 2 * SMSS) 237 and in response to an indication of an ECN-signalled congestion: 239 ssthresh = max (FlightSize * beta_{ecn}, 2 * SMSS) 241 and 243 cwnd = ssthresh 245 (If ssthresh == 2 * SMSS, RFC 3168 section 6.1.2 provides guidance 246 on setting a cwnd lower than 2 * SMSS.) 248 where FlightSize is the amount of outstanding data in the network, 249 upper-bounded by the smaller of the sender's cwnd and the receiver's 250 advertised window (rwnd) [RFC5681]. The higher the values of 251 beta_{loss} and beta_{ecn}, the less aggressive the response of any 252 individual backoff event. 254 The appropriate choice for beta_{loss} and beta_{ecn} values is a 255 balancing act between path utilisation and draining the bottleneck 256 queue. More aggressive backoff (smaller beta_*) risks underutilising 257 the path, while less aggressive backoff (larger beta_*) can result in 258 slower draining of the bottleneck queue. 260 The Internet has already been running with at least two different 261 beta_{loss} values for several years: the standard value is 0.5 262 [RFC5681], and the Linux implementation of CUBIC [RFC8312] has used a 263 multiplier of 0.7 since kernel version 2.6.25 released in 2008. ABE 264 proposes no change to beta_{loss} used by current TCP 265 implementations. 267 The recommendation in Section 3 in this document corresponds to a 268 value of beta_{ecn}=0.8. This recommended beta_{ecn} value is only 269 applicable for the standard TCP congestion control [RFC5681]. The 270 selection of beta_{ecn} enables tuning the response of a TCP 271 connection to shallow AQM marking thresholds. beta_{loss} 272 characterizes the response of a congestion control algorithm to 273 packet loss, i.e., exhaustion of buffers (of unknown depth). 274 Different values for beta_{loss} have been suggested for TCP 275 congestion control algorithms. Consequently, beta_{ecn} is likely to 276 be an algorithm-specific parameter rather than a constant multiple of 277 the algorithm's existing beta_{loss}. 279 A range of tests (section IV, [ABE2017]) with NewReno and CUBIC over 280 CoDel and PIE in lightly-multiplexed scenarios have explored this 281 choice of parameter. The results of these tests indicate that CUBIC 282 connections benefit from beta_{ecn} of 0.85 (cf. beta_{loss} = 0.7), 283 and NewReno connections see improvements with beta_{ecn} in the range 284 0.7 to 0.85 (cf. beta_{loss} = 0.5). 286 5. ABE Deployment Requirements 288 This update is a sender-side only change. Like other changes to 289 congestion control algorithms, it does not require any change to the 290 TCP receiver or to network devices. It does not require any ABE- 291 specific changes in routers or the use of Accurate ECN feedback 292 [I-D.ietf-tcpm-accurate-ecn] by a receiver. 294 RFC3168 states that the congestion control response to an ECN- 295 signalled congestion is the same as the response to a dropped packet 296 [RFC3168]. [RFC8311] updates this specification to allow systems to 297 provide a different behaviour when they experience ECN-signalled 298 congestion rather than packet loss. The present specification 299 defines such an experiment and has thus been assigned an Experimental 300 status before being proposed as a Standards-Track update. 302 The purpose of the Internet experiment is to collect experience with 303 deployment of ABE, and confirm the safety in deployed networks using 304 this update to TCP congestion control. 306 When used with bottlenecks that do not support ECN-marking the 307 specification does not modify the transport protocol. 309 To evaluate the benefit, this experiment therefore requires support 310 in AQM routers for ECN-marking of packets carrying the ECN-Capable 311 Transport, ECT(0), codepoint [RFC3168]. 313 If the method is only deployed by some senders, and not by others, 314 the senders that use this method can gain some advantage, possibly at 315 the expense of other flows that do not use this updated method. 316 Because this advantage applies only to ECN-marked packets and not to 317 packet loss indications, an ECN-Capable bottleneck will still fall 318 back to dropping packets if an TCP sender using ABE is too 319 aggressive, and the result is no different than if the TCP sender was 320 using traditional loss-based congestion control. 322 A TCP sender reacts to loss or ECN marks only once per round-trip 323 time. Hence, if a sender would first be notified of an ECN mark and 324 then learn about loss in the same round-trip, it would only react to 325 the first notification (ECN) but not to the second (loss). RFC3168 326 specified a reaction to ECN that was equal to the reaction to loss 327 [RFC3168]. 329 ABE also responds to congestion once per RTT, and therefore it does 330 not respond to further loss within the same RTT, since ABE has 331 already reduced the congestion window. If congestion persists after 332 such reduction, ABE continues to reduce the congestion window in each 333 consecutive RTT. This consecutive reduction can protect the network 334 against long-standing unfairness in the case of AQM algorithms that 335 do not keep a small average queue length. 337 The result of this Internet experiment ought to include an 338 investigation of the implications of experiencing an ECN-CE mark 339 followed by loss within the same RTT. At the end of the experiment, 340 this will be reported to the TCPM WG (or IESG). 342 6. Acknowledgements 344 Authors N. Khademi, M. Welzl and G. Fairhurst were part-funded by 345 the European Community under its Seventh Framework Programme through 346 the Reducing Internet Transport Latency (RITE) project (ICT-317700). 347 The views expressed are solely those of the authors. 349 The authors would like to thank Stuart Cheshire for many suggestions 350 when revising the draft, and the following people for their 351 contributions to [ABE2017]: Chamil Kulatunga, David Ros, Stein 352 Gjessing, Sebastian Zander. Thanks also to (in alphabetical order) 353 Roland Bless, Bob Briscoe, David Black, Markku Kojo, John Leslie, 354 Lawrence Stewart, Dave Taht and the TCPM working group for providing 355 valuable feedback on this document. 357 The authors would finally like to thank everyone who provided 358 feedback on the congestion control behaviour specified in this update 359 received from the IRTF Internet Congestion Control Research Group 360 (ICCRG). 362 7. IANA Considerations 364 XX RFC ED - PLEASE REMOVE THIS SECTION XXX 366 This document includes no request to IANA. 368 8. Implementation Status 370 ABE is implemented as a patch for Linux and FreeBSD. It is meant for 371 research and available for download from 372 http://heim.ifi.uio.no/naeemk/research/ABE/. This code was used to 373 produce the test results that are reported in [ABE2017]. The FreeBSD 374 code has been committed to the mainline kernel on March 19, 2018 375 [ABE-FreeBSD]. 377 9. Security Considerations 379 The described method is a sender-side only transport change, and does 380 not change the protocol messages exchanged. The security 381 considerations for ECN [RFC3168] therefore still apply. 383 This is a change to TCP congestion control with ECN that will 384 typically lead to a change in the capacity achieved when flows share 385 a network bottleneck. This could result in some flows receiving more 386 than their fair share of capacity. Similar unfairness in the way 387 that capacity is shared is also exhibited by other congestion control 388 mechanisms that have been in use in the Internet for many years 389 (e.g., CUBIC [RFC8312]). Unfairness may also be a result of other 390 factors, including the round trip time experienced by a flow. ABE 391 applies only when ECN-marked packets are received, not when packets 392 are lost, hence use of ABE cannot lead to congestion collapse. 394 10. Revision Information 396 XX RFC ED - PLEASE REMOVE THIS SECTION XXX 398 -07. Addressed comments following WGLC. 400 o Updated Reference citations 402 o Removed paragraph containing a wrong statement related to timeout 403 in section 4.1. 405 o Discuss what happens when cwnd <= ssthresh 407 o Added text on Concern about lower bound of 2*SMSS 409 -06. Addressed Michael Scharf's comments. 411 -05. Refined the description of the experiment based on feedback at 412 IETF-100. Incorporated comments from David Black. 414 -04. Incorporates review comments from Lawrence Stewart and the 415 remaining comments from Roland Bless. References are updated. 417 -03. Several review comments from Roland Bless are addressed. 418 Consistent terminology and equations. Clarification on the scope of 419 recommended beta_{ecn} value. 421 -02. Corrected the equations in Section 4.3. Updated the 422 affiliations. Lower bound for cwnd is defined. A recommendation for 423 window-based transport protocols is changed to cover all transport 424 protocols that implement a congestion control reduction to an ECN 425 congestion signal. Added text about ABE's FreeBSD mainline kernel 426 status including a reference to the FreeBSD code review page. 427 References are updated. 429 -01. Text improved, mainly incorporating comments from Stuart 430 Cheshire. The reference to a technical report has been updated to a 431 published version of the tests [ABE2017]. Used "AQM Mechanism" 432 throughout in place of other alternatives, and more consistent use of 433 technical language and clarification on the intended purpose of the 434 experiments required by EXP status. There was no change to the 435 technical content. 437 -00. draft-ietf-tcpm-alternativebackoff-ecn-00 replaces draft- 438 khademi-tcpm-alternativebackoff-ecn-01. Text describing the nature 439 of the experiment was added. 441 Individual draft -01. This I-D now refers to draft-black-tsvwg-ecn- 442 experimentation-02, which replaces draft-khademi-tsvwg-ecn- 443 response-00 to make a broader update to RFC3168 for the sake of 444 allowing experiments. As a result, some of the motivating and 445 discussing text that was moved from draft-khademi-alternativebackoff- 446 ecn-03 to draft-khademi-tsvwg-ecn-response-00 has now been re- 447 inserted here. 449 Individual draft -00. draft-khademi-tsvwg-ecn-response-00 and draft- 450 khademi-tcpm-alternativebackoff-ecn-00 replace draft-khademi- 451 alternativebackoff-ecn-03, following discussion in the TSVWG and TCPM 452 working groups. 454 11. References 456 11.1. Normative References 458 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 459 Requirement Levels", BCP 14, RFC 2119, 460 DOI 10.17487/RFC2119, March 1997, 461 . 463 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 464 of Explicit Congestion Notification (ECN) to IP", 465 RFC 3168, DOI 10.17487/RFC3168, September 2001, 466 . 468 [RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion 469 Control", RFC 5681, DOI 10.17487/RFC5681, September 2009, 470 . 472 [RFC7567] Baker, F., Ed. and G. Fairhurst, Ed., "IETF 473 Recommendations Regarding Active Queue Management", 474 BCP 197, RFC 7567, DOI 10.17487/RFC7567, July 2015, 475 . 477 [RFC8257] Bensley, S., Thaler, D., Balasubramanian, P., Eggert, L., 478 and G. Judd, "Data Center TCP (DCTCP): TCP Congestion 479 Control for Data Centers", RFC 8257, DOI 10.17487/RFC8257, 480 October 2017, . 482 [RFC8311] Black, D., "Relaxing Restrictions on Explicit Congestion 483 Notification (ECN) Experimentation", RFC 8311, 484 DOI 10.17487/RFC8311, January 2018, 485 . 487 11.2. Informative References 489 [ABE-FreeBSD] 490 "ABE patch review in FreeBSD", 491 . 494 [ABE2017] Khademi, N., Armitage, G., Welzl, M., Fairhurst, G., 495 Zander, S., and D. Ros, "Alternative Backoff: Achieving 496 Low Latency and High Throughput with ECN and AQM", IFIP 497 NETWORKING 2017, Stockholm, Sweden, June 2017. 499 [BUFFERBLOAT] 500 Gettys, J. and K. Nichols, "Bufferbloat: Dark Buffers in 501 the Internet", November 2011. 503 [CODEL2012] 504 Nichols, K. and V. Jacobson, "Controlling Queue Delay", 505 July 2012, . 507 [I-D.ietf-tcpm-accurate-ecn] 508 Briscoe, B., Kuehlewind, M., and R. Scheffenegger, "More 509 Accurate ECN Feedback in TCP", draft-ietf-tcpm-accurate- 510 ecn-06 (work in progress), March 2018. 512 [ICC2002] Kwon, M. and S. Fahmy, "TCP Increase/Decrease Behavior 513 with Explicit Congestion Notification (ECN)", IEEE 514 ICC 2002, New York, New York, USA, May 2002, 515 . 517 [RFC7713] Mathis, M. and B. Briscoe, "Congestion Exposure (ConEx) 518 Concepts, Abstract Mechanism, and Requirements", RFC 7713, 519 DOI 10.17487/RFC7713, December 2015, 520 . 522 [RFC8033] Pan, R., Natarajan, P., Baker, F., and G. White, 523 "Proportional Integral Controller Enhanced (PIE): A 524 Lightweight Control Scheme to Address the Bufferbloat 525 Problem", RFC 8033, DOI 10.17487/RFC8033, February 2017, 526 . 528 [RFC8087] Fairhurst, G. and M. Welzl, "The Benefits of Using 529 Explicit Congestion Notification (ECN)", RFC 8087, 530 DOI 10.17487/RFC8087, March 2017, 531 . 533 [RFC8289] Nichols, K., Jacobson, V., McGregor, A., Ed., and J. 534 Iyengar, Ed., "Controlled Delay Active Queue Management", 535 RFC 8289, DOI 10.17487/RFC8289, January 2018, 536 . 538 [RFC8312] Rhee, I., Xu, L., Ha, S., Zimmermann, A., Eggert, L., and 539 R. Scheffenegger, "CUBIC for Fast Long-Distance Networks", 540 RFC 8312, DOI 10.17487/RFC8312, February 2018, 541 . 543 Authors' Addresses 545 Naeem Khademi 546 University of Oslo 547 PO Box 1080 Blindern 548 Oslo N-0316 549 Norway 551 Email: naeemk@ifi.uio.no 553 Michael Welzl 554 University of Oslo 555 PO Box 1080 Blindern 556 Oslo N-0316 557 Norway 559 Email: michawe@ifi.uio.no 560 Grenville Armitage 561 Internet For Things (I4T) Research Group 562 Swinburne University of Technology 563 PO Box 218 564 John Street, Hawthorn 565 Victoria 3122 566 Australia 568 Email: garmitage@swin.edu.au 570 Godred Fairhurst 571 University of Aberdeen 572 School of Engineering, Fraser Noble Building 573 Aberdeen AB24 3UE 574 UK 576 Email: gorry@erg.abdn.ac.uk