draft-ietf-tsvwg-l4s-arch-20.original   draft-ietf-tsvwg-l4s-arch-21v2.txt 
Transport Area Working Group B. Briscoe, Ed. Transport Area Working Group B. Briscoe, Ed.
Internet-Draft Independent Internet-Draft Independent
Intended status: Informational K. De Schepper Intended status: Informational K. De Schepper
Expires: 2 March 2023 Nokia Bell Labs Expires: April 10, 2023 Nokia Bell Labs
M. Bagnulo Braun M. Bagnulo Braun
Universidad Carlos III de Madrid Universidad Carlos III de Madrid
G. White G. White
CableLabs CableLabs
29 August 2022 October 7, 2022
Low Latency, Low Loss, Scalable Throughput (L4S) Internet Service: Low Latency, Low Loss, Scalable Throughput (L4S) Internet Service:
Architecture Architecture
draft-ietf-tsvwg-l4s-arch-20 draft-ietf-tsvwg-l4s-arch-21
Abstract Abstract
This document describes the L4S architecture, which enables Internet This document describes the L4S architecture, which enables Internet
applications to achieve Low queuing Latency, Low Loss, and Scalable applications to achieve Low queuing Latency, Low Loss, and Scalable
throughput (L4S). L4S is based on the insight that the root cause of throughput (L4S). L4S is based on the insight that the root cause of
queuing delay is in the capacity-seeking congestion controllers of queuing delay is in the capacity-seeking congestion controllers of
senders, not in the queue itself. With the L4S architecture all senders, not in the queue itself. With the L4S architecture all
Internet applications could (but do not have to) transition away from Internet applications could (but do not have to) transition away from
congestion control algorithms that cause substantial queuing delay, congestion control algorithms that cause substantial queuing delay,
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This Internet-Draft will expire on 2 March 2023. This Internet-Draft will expire on April 10, 2023.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Document Roadmap . . . . . . . . . . . . . . . . . . . . 5 1.1. Document Roadmap . . . . . . . . . . . . . . . . . . . . 5
2. L4S Architecture Overview . . . . . . . . . . . . . . . . . . 5 2. L4S Architecture Overview . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. L4S Architecture Components . . . . . . . . . . . . . . . . . 9 4. L4S Architecture Components . . . . . . . . . . . . . . . . . 9
4.1. Protocol Mechanisms . . . . . . . . . . . . . . . . . . . 9 4.1. Protocol Mechanisms . . . . . . . . . . . . . . . . . . . 9
4.2. Network Components . . . . . . . . . . . . . . . . . . . 10 4.2. Network Components . . . . . . . . . . . . . . . . . . . 10
4.3. Host Mechanisms . . . . . . . . . . . . . . . . . . . . . 13 4.3. Host Mechanisms . . . . . . . . . . . . . . . . . . . . . 13
5. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1. Why These Primary Components? . . . . . . . . . . . . . . 15 5.1. Why These Primary Components? . . . . . . . . . . . . . . 14
5.2. What L4S adds to Existing Approaches . . . . . . . . . . 18 5.2. What L4S adds to Existing Approaches . . . . . . . . . . 17
6. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 21 6. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 21
6.1. Applications . . . . . . . . . . . . . . . . . . . . . . 21 6.1. Applications . . . . . . . . . . . . . . . . . . . . . . 21
6.2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . 22 6.2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . 22
6.3. Applicability with Specific Link Technologies . . . . . . 24 6.3. Applicability with Specific Link Technologies . . . . . . 23
6.4. Deployment Considerations . . . . . . . . . . . . . . . . 25 6.4. Deployment Considerations . . . . . . . . . . . . . . . . 24
6.4.1. Deployment Topology . . . . . . . . . . . . . . . . . 25 6.4.1. Deployment Topology . . . . . . . . . . . . . . . . . 25
6.4.2. Deployment Sequences . . . . . . . . . . . . . . . . 26 6.4.2. Deployment Sequences . . . . . . . . . . . . . . . . 26
6.4.3. L4S Flow but Non-ECN Bottleneck . . . . . . . . . . . 29 6.4.3. L4S Flow but Non-ECN Bottleneck . . . . . . . . . . . 29
6.4.4. L4S Flow but Classic ECN Bottleneck . . . . . . . . . 30 6.4.4. L4S Flow but Classic ECN Bottleneck . . . . . . . . . 30
6.4.5. L4S AQM Deployment within Tunnels . . . . . . . . . . 30 6.4.5. L4S AQM Deployment within Tunnels . . . . . . . . . . 30
7. IANA Considerations (to be removed by RFC Editor) . . . . . . 30 7. IANA Considerations (to be removed by RFC Editor) . . . . . . 30
8. Security Considerations . . . . . . . . . . . . . . . . . . . 31 8. Security Considerations . . . . . . . . . . . . . . . . . . . 30
8.1. Traffic Rate (Non-)Policing . . . . . . . . . . . . . . . 31 8.1. Traffic Rate (Non-)Policing . . . . . . . . . . . . . . . 30
8.1.1. (Non-)Policing Rate per Flow . . . . . . . . . . . . 31 8.1.1. (Non-)Policing Rate per Flow . . . . . . . . . . . . 30
8.1.2. (Non-)Policing L4S Service Rate . . . . . . . . . . . 31 8.1.2. (Non-)Policing L4S Service Rate . . . . . . . . . . . 31
8.2. 'Latency Friendliness' . . . . . . . . . . . . . . . . . 32 8.2. 'Latency Friendliness' . . . . . . . . . . . . . . . . . 32
8.3. Interaction between Rate Policing and L4S . . . . . . . . 34 8.3. Interaction between Rate Policing and L4S . . . . . . . . 34
8.4. ECN Integrity . . . . . . . . . . . . . . . . . . . . . . 35 8.4. ECN Integrity . . . . . . . . . . . . . . . . . . . . . . 35
8.5. Privacy Considerations . . . . . . . . . . . . . . . . . 35 8.5. Privacy Considerations . . . . . . . . . . . . . . . . . 35
9. Informative References . . . . . . . . . . . . . . . . . . . 36 9. Informative References . . . . . . . . . . . . . . . . . . . 35
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 45 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 44
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 45 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 45
1. Introduction 1. Introduction
At any one time, it is increasingly common for all of the traffic in At any one time, it is increasingly common for all of the traffic in
a bottleneck link (e.g. a household's Internet access) to come from a bottleneck link (e.g. a household's Internet access) to come from
applications that prefer low delay: interactive Web, Web services, applications that prefer low delay: interactive Web, Web services,
voice, conversational video, interactive video, interactive remote voice, conversational video, interactive video, interactive remote
presence, instant messaging, online gaming, remote desktop, cloud- presence, instant messaging, online gaming, remote desktop, cloud-
based applications and video-assisted remote control of machinery and based applications and video-assisted remote control of machinery and
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Active Queue Management (AQM) is part of the solution to queuing Active Queue Management (AQM) is part of the solution to queuing
under load. AQM improves performance for all traffic, but there is a under load. AQM improves performance for all traffic, but there is a
limit to how much queuing delay can be reduced by solely changing the limit to how much queuing delay can be reduced by solely changing the
network; without addressing the root of the problem. network; without addressing the root of the problem.
The root of the problem is the presence of standard congestion The root of the problem is the presence of standard congestion
control (Reno [RFC5681]) or compatible variants control (Reno [RFC5681]) or compatible variants
(e.g. CUBIC [RFC8312]) that are used in TCP and in other transports (e.g. CUBIC [RFC8312]) that are used in TCP and in other transports
such as QUIC [RFC9000]. We shall use the term 'Classic' for these such as QUIC [RFC9000]. We shall use the term 'Classic' for these
Reno-friendly congestion controls. Classic congestion controls Reno-friendly congestion controls. Classic congestion controls
induce relatively large saw-tooth-shaped excursions up the queue and induce relatively large saw-tooth-shaped excursions of queue
down again, which have been growing as flow rate scales [RFC3649]. occupancy. So if a network operator naively attempts to reduce
So if a network operator naively attempts to reduce queuing delay by queuing delay by configuring an AQM to operate at a shallower queue,
configuring an AQM to operate at a shallower queue, a Classic a Classic congestion control will significantly underutilize the link
congestion control will significantly underutilize the link at the at the bottom of every saw-tooth. These sawteeth have also been
bottom of every saw-tooth. growing in duration as flow rate scales [RFC3649].
It has been demonstrated that if the sending host replaces a Classic It has been demonstrated that if the sending host replaces a Classic
congestion control with a 'Scalable' alternative, when a suitable AQM congestion control with a 'Scalable' alternative, when a suitable AQM
is deployed in the network the performance under load of all the is deployed in the network the performance under load of all the
above interactive applications can be significantly improved. For above interactive applications can be significantly improved. For
instance, queuing delay under heavy load with the example DCTCP/DualQ instance, queuing delay under heavy load with the example DCTCP/DualQ
solution cited below on a DSL or Ethernet link is roughly 1 to 2 solution cited below on a DSL or Ethernet link is roughly 1 to 2
milliseconds at the 99th percentile without losing link utilization milliseconds at the 99th percentile without losing link utilization
[DualPI2Linux], [DCttH19] (for other link types, see Section 6.3). [L4Seval22], [DualPI2Linux] (for other link types, see Section 6.3).
This compares with 5-20 ms on _average_ with a Classic congestion This compares with 5-20 ms on _average_ with a Classic congestion
control and current state-of-the-art AQMs such as FQ-CoDel [RFC8290], control and current state-of-the-art AQMs such as FQ-CoDel [RFC8290],
PIE [RFC8033] or DOCSIS PIE [RFC8034] and about 20-30 ms at the 99th PIE [RFC8033] or DOCSIS PIE [RFC8034] and about 20-30 ms at the 99th
percentile [DualPI2Linux]. percentile [DualPI2Linux].
L4S is designed for incremental deployment. It is possible to deploy L4S is designed for incremental deployment. It is possible to deploy
the L4S service at a bottleneck link alongside the existing best the L4S service at a bottleneck link alongside the existing best
efforts service [DualPI2Linux] so that unmodified applications can efforts service [DualPI2Linux] so that unmodified applications can
start using it as soon as the sender's stack is updated. Access start using it as soon as the sender's stack is updated. Access
networks are typically designed with one link as the bottleneck for networks are typically designed with one link as the bottleneck for
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protocol is defined separately [I-D.ietf-tsvwg-ecn-l4s-id] as an protocol is defined separately [I-D.ietf-tsvwg-ecn-l4s-id] as an
experimental change to Explicit Congestion Notification (ECN). This experimental change to Explicit Congestion Notification (ECN). This
document describes and justifies the component parts and how they document describes and justifies the component parts and how they
interact to provide the scalable, low latency, low loss Internet interact to provide the scalable, low latency, low loss Internet
service. It also details the approach to incremental deployment, as service. It also details the approach to incremental deployment, as
briefly summarized above. briefly summarized above.
1.1. Document Roadmap 1.1. Document Roadmap
This document describes the L4S architecture in three passes. First This document describes the L4S architecture in three passes. First
this brief overview gives the very high level idea and states the the brief overview in Section 2 gives the very high level idea and
main components with minimal rationale. This is only intended to states the main components with minimal rationale. This is only
give some context for the terminology definitions that follow in intended to give some context for the terminology definitions that
Section 3, and to explain the structure of the rest of the document. follow in Section 3, and to explain the structure of the rest of the
Then Section 4 goes into more detail on each component with some document. Then Section 4 goes into more detail on each component
rationale, but still mostly stating what the architecture is, rather with some rationale, but still mostly stating what the architecture
than why. Finally, Section 5 justifies why each element of the is, rather than why. Finally, Section 5 justifies why each element
solution was chosen (Section 5.1) and why these choices were of the solution was chosen (Section 5.1) and why these choices were
different from other solutions (Section 5.2). different from other solutions (Section 5.2).
Having described the architecture, Section 6 clarifies its Having described the architecture, Section 6 clarifies its
applicability; that is, the applications and use-cases that motivated applicability; that is, the applications and use-cases that motivated
the design, the challenges applying the architecture to various link the design, the challenges applying the architecture to various link
technologies, and various incremental deployment models: including technologies, and various incremental deployment models: including
the two main deployment topologies, different sequences for the two main deployment topologies, different sequences for
incremental deployment and various interactions with pre-existing incremental deployment and various interactions with pre-existing
approaches. The document ends with the usual tailpieces, including approaches. The document ends with the usual tailpieces, including
extensive discussion of traffic policing and other security extensive discussion of traffic policing and other security
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mandated for L4S AQMs. Appendices of mandated for L4S AQMs. Appendices of
[I-D.ietf-tsvwg-aqm-dualq-coupled] give non-normative examples [I-D.ietf-tsvwg-aqm-dualq-coupled] give non-normative examples
that have been implemented and evaluated, and give recommended that have been implemented and evaluated, and give recommended
default parameter settings. It is expected that L4S experiments default parameter settings. It is expected that L4S experiments
will improve knowledge of parameter settings and whether the set will improve knowledge of parameter settings and whether the set
of marking algorithms needs to be limited. of marking algorithms needs to be limited.
3) Protocol: A sending host needs to distinguish L4S and Classic 3) Protocol: A sending host needs to distinguish L4S and Classic
packets with an identifier so that the network can classify them packets with an identifier so that the network can classify them
into their separate treatments. The L4S identifier into their separate treatments. The L4S identifier
spec. [I-D.ietf-tsvwg-ecn-l4s-id] concludes that all alternatives spec [I-D.ietf-tsvwg-ecn-l4s-id] concludes that all alternatives
involve compromises, but the ECT(1) and CE codepoints of the ECN involve compromises, but the ECT(1) and CE codepoints of the ECN
field represent a workable solution. As already explained, the field represent a workable solution. As already explained, the
network also uses ECN to immediately signal the very start of network also uses ECN to immediately signal the very start of
queue growth to the transport. queue growth to the transport.
3. Terminology 3. Terminology
[Note to the RFC Editor (to be removed before publication as an RFC): [Note to the RFC Editor (to be removed before publication as an RFC):
The following definitions are copied from the L4S ECN The following definitions are copied from the L4S ECN
spec [I-D.ietf-tsvwg-ecn-l4s-id] for the reader's convenience. spec [I-D.ietf-tsvwg-ecn-l4s-id] for the reader's convenience.
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co-exist with standard Reno [RFC5681] without causing co-exist with standard Reno [RFC5681] without causing
significantly negative impact on its flow rate [RFC5033]. The significantly negative impact on its flow rate [RFC5033]. The
scaling problem with Classic congestion control is explained, with scaling problem with Classic congestion control is explained, with
examples, in Section 5.1 and in [RFC3649]. examples, in Section 5.1 and in [RFC3649].
Scalable Congestion Control: A congestion control where the average Scalable Congestion Control: A congestion control where the average
time from one congestion signal to the next (the recovery time) time from one congestion signal to the next (the recovery time)
remains invariant as the flow rate scales, all other factors being remains invariant as the flow rate scales, all other factors being
equal. For instance, DCTCP averages 2 congestion signals per equal. For instance, DCTCP averages 2 congestion signals per
round-trip whatever the flow rate, as do other recently developed round-trip whatever the flow rate, as do other recently developed
scalable congestion controls, e.g. Relentless TCP [Mathis09], TCP scalable congestion controls, e.g. Relentless
Prague [I-D.briscoe-iccrg-prague-congestion-control], TCP [I-D.mathis-iccrg-relentless-tcp], TCP Prague
[PragueLinux], BBRv2 [BBRv2], [I-D.briscoe-iccrg-prague-congestion-control], [PragueLinux],
[I-D.cardwell-iccrg-bbr-congestion-control] and the L4S variant of BBRv2 [BBRv2], [I-D.cardwell-iccrg-bbr-congestion-control] and the
SCReAM for real-time media [SCReAM], [RFC8298]). See Section 4.3 L4S variant of SCReAM for real-time media [SCReAM], [RFC8298]).
of [I-D.ietf-tsvwg-ecn-l4s-id] for more explanation. See Section 4.3 of [I-D.ietf-tsvwg-ecn-l4s-id] for more
explanation.
Classic service: The Classic service is intended for all the Classic service: The Classic service is intended for all the
congestion control behaviours that co-exist with Reno [RFC5681] congestion control behaviours that co-exist with Reno [RFC5681]
(e.g. Reno itself, Cubic [RFC8312], (e.g. Reno itself, Cubic [RFC8312],
Compound [I-D.sridharan-tcpm-ctcp], TFRC [RFC5348]). The term Compound [I-D.sridharan-tcpm-ctcp], TFRC [RFC5348]). The term
'Classic queue' means a queue providing the Classic service. 'Classic queue' means a queue providing the Classic service.
Low-Latency, Low-Loss Scalable throughput (L4S) service: The 'L4S' Low-Latency, Low-Loss Scalable throughput (L4S) service: The 'L4S'
service is intended for traffic from scalable congestion control service is intended for traffic from scalable congestion control
algorithms, such as the Prague congestion algorithms, such as the Prague congestion
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'flow'. For example: an L4S packet means a packet with an L4S 'flow'. For example: an L4S packet means a packet with an L4S
identifier sent from an L4S congestion control. identifier sent from an L4S congestion control.
Both Classic and L4S services can cope with a proportion of Both Classic and L4S services can cope with a proportion of
unresponsive or less-responsive traffic as well, but in the L4S unresponsive or less-responsive traffic as well, but in the L4S
case its rate has to be smooth enough or low enough to not build a case its rate has to be smooth enough or low enough to not build a
queue (e.g. DNS, VoIP, game sync datagrams, etc.). queue (e.g. DNS, VoIP, game sync datagrams, etc.).
Reno-friendly: The subset of Classic traffic that is friendly to the Reno-friendly: The subset of Classic traffic that is friendly to the
standard Reno congestion control defined for TCP in [RFC5681]. standard Reno congestion control defined for TCP in [RFC5681].
The TFRC spec. [RFC5348] indirectly implies that 'friendly' is The TFRC spec [RFC5348] indirectly implies that 'friendly' is
defined as "generally within a factor of two of the sending rate defined as "generally within a factor of two of the sending rate
of a TCP flow under the same conditions". Reno-friendly is used of a TCP flow under the same conditions". Reno-friendly is used
here in place of 'TCP-friendly', given the latter has become here in place of 'TCP-friendly', given the latter has become
imprecise, because the TCP protocol is now used with so many imprecise, because the TCP protocol is now used with so many
different congestion control behaviours, and Reno is used in non- different congestion control behaviours, and Reno is used in non-
TCP transports such as QUIC [RFC9000]. TCP transports such as QUIC [RFC9000].
Classic ECN: The original Explicit Congestion Notification (ECN) Classic ECN: The original Explicit Congestion Notification (ECN)
protocol [RFC3168], which requires ECN signals to be treated as protocol [RFC3168], which requires ECN signals to be treated as
equivalent to drops, both when generated in the network and when equivalent to drops, both when generated in the network and when
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Experienced. A packet marked with the CE codepoint is termed Experienced. A packet marked with the CE codepoint is termed
'ECN-marked' or sometimes just 'marked' where the context makes 'ECN-marked' or sometimes just 'marked' where the context makes
ECN obvious. ECN obvious.
Site: A home, mobile device, small enterprise or campus, where the Site: A home, mobile device, small enterprise or campus, where the
network bottleneck is typically the access link to the site. Not network bottleneck is typically the access link to the site. Not
all network arrangements fit this model but it is a useful, widely all network arrangements fit this model but it is a useful, widely
applicable generalization. applicable generalization.
Traffic policing: Limiting traffic by dropping packets or shifting Traffic policing: Limiting traffic by dropping packets or shifting
them to lower service class (as opposed to introducing delay, them to a lower service class (as opposed to introducing delay,
which is termed traffic shaping). Policing can involve limiting which is termed traffic shaping). Policing can involve limiting
average rate and/or burst size. Policing focused on limiting average rate and/or burst size. Policing focused on limiting
queuing but not average flow rate is termed congestion policing, queuing but not average flow rate is termed congestion policing,
latency policing, burst policing or queue protection in this latency policing, burst policing or queue protection in this
document. Otherwise, the term rate policing is used. document. Otherwise, the term rate policing is used.
4. L4S Architecture Components 4. L4S Architecture Components
The L4S architecture is composed of the elements in the following The L4S architecture is composed of the elements in the following
three subsections. three subsections.
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an ECN signal to be treated as equivalent to drop, both when it an ECN signal to be treated as equivalent to drop, both when it
is generated in the network and when it is responded to by hosts. is generated in the network and when it is responded to by hosts.
L4S needs networks and hosts to support a more fine-grained L4S needs networks and hosts to support a more fine-grained
meaning for each ECN signal that is less severe than a drop, so meaning for each ECN signal that is less severe than a drop, so
that the L4S signals: that the L4S signals:
* can be much more frequent; * can be much more frequent;
* can be signalled immediately, without the significant delay * can be signalled immediately, without the significant delay
required to smooth out fluctuations in the queue. required to smooth out fluctuations in the queue.
To enable L4S, the standards track Classic ECN spec. [RFC3168] To enable L4S, the standards track Classic ECN spec [RFC3168] has
has had to be updated to allow L4S packets to depart from the had to be updated to allow L4S packets to depart from the
'equivalent to drop' constraint. [RFC8311] is a standards track 'equivalent to drop' constraint. [RFC8311] is a standards track
update to relax specific requirements in RFC 3168 (and certain update to relax specific requirements in RFC 3168 (and certain
other standards track RFCs), which clears the way for the other standards track RFCs), which clears the way for the
experimental changes proposed for L4S. Also, the ECT(1) experimental changes proposed for L4S. Also, the ECT(1)
codepoint was previously assigned as the experimental ECN codepoint was previously assigned as the experimental ECN
nonce [RFC3540], which RFC 8311 recategorizes as historic to make nonce [RFC3540], which RFC 8311 recategorizes as historic to make
the codepoint available again. the codepoint available again.
b. [I-D.ietf-tsvwg-ecn-l4s-id] specifies that ECT(1) is used as the b. [I-D.ietf-tsvwg-ecn-l4s-id] specifies that ECT(1) is used as the
identifier to classify L4S packets into a separate treatment from identifier to classify L4S packets into a separate treatment from
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possible [I-D.ietf-tsvwg-aqm-dualq-coupled] without specifying possible [I-D.ietf-tsvwg-aqm-dualq-coupled] without specifying
the particular AQMs to use in the two queues so that designers the particular AQMs to use in the two queues so that designers
are free to implement diverse ideas. Informational appendices in are free to implement diverse ideas. Informational appendices in
that draft give pseudocode examples of two different specific AQM that draft give pseudocode examples of two different specific AQM
approaches: one called DualPI2 (pronounced Dual PI approaches: one called DualPI2 (pronounced Dual PI
Squared) [DualPI2Linux] that uses the PI2 variant of PIE, and a Squared) [DualPI2Linux] that uses the PI2 variant of PIE, and a
zero-config variant of RED called Curvy RED. A DualQ Coupled AQM zero-config variant of RED called Curvy RED. A DualQ Coupled AQM
based on PIE has also been specified and implemented for Low based on PIE has also been specified and implemented for Low
Latency DOCSIS [DOCSIS3.1]. Latency DOCSIS [DOCSIS3.1].
(3) (2) (3) (2)
.-------^------..------------^------------------. .-------^------..------------^------------------.
,-(1)-----. _____ ,-(1)-----. _____
; ________ : L4S -------. | | ; ________ : L4S -------. | |
:|Scalable| : _\ ||__\_|mark | :|Scalable| : _\ ||__\_|mark |
:| sender | : __________ / / || / |_____|\ _________ :| sender | : __________ / / || / |_____|\ _________
:|________|\; | |/ -------' ^ \1|condit'nl| :|________|\; | |/ -------' ^ \1|condit'nl|
`---------'\_| IP-ECN | Coupling : \|priority |_\ `---------'\_| IP-ECN | Coupling : \|priority |_\
________ / |Classifier| : /|scheduler| / ________ / |Classifier| : /|scheduler| /
|Classic |/ |__________|\ -------. __:__ / |_________| |Classic |/ |__________|\ -------. __:__ / |_________|
| sender | \_\ || | ||__\_|mark/|/ | sender | \_\ || | ||__\_|mark/|/
|________| / || | || / |drop | |________| / || | || / |drop |
Classic -------' |_____| Classic -------' |_____|
Figure 1: Components of an L4S DualQ Coupled AQM Solution: 1) Figure 1: Components of an L4S DualQ Coupled AQM Solution: 1)
Scalable Sending Host; 2) Isolation in separate network Scalable Sending Host; 2) Isolation in separate network queues; and
queues; and 3) Packet Identification Protocol 3) Packet Identification Protocol
b. Per-Flow Queues and AQMs: A scheduler with per-flow queues such b. Per-Flow Queues and AQMs: A scheduler with per-flow queues such
as FQ-CoDel or FQ-PIE can be used for L4S. For instance within as FQ-CoDel or FQ-PIE can be used for L4S. For instance within
each queue of an FQ-CoDel system, as well as a CoDel AQM, there each queue of an FQ-CoDel system, as well as a CoDel AQM, there
is typically also the option of ECN marking at an immediate is typically also the option of ECN marking at an immediate
(unsmoothed) shallow threshold to support use in data centres (unsmoothed) shallow threshold to support use in data centres
(see Sec.5.2.7 of the FQ-CoDel spec [RFC8290]). In Linux, this (see Sec.5.2.7 of the FQ-CoDel spec [RFC8290]). In Linux, this
has been modified so that the shallow threshold can be solely has been modified so that the shallow threshold can be solely
applied to ECT(1) packets [FQ_CoDel_Thresh]. Then, if there is a applied to ECT(1) packets [FQ_CoDel_Thresh]. Then, if there is a
flow of non-ECN or ECT(0) packets in the per-flow-queue, the flow of non-ECN or ECT(0) packets in the per-flow-queue, the
skipping to change at page 19, line 42 skipping to change at page 19, line 27
AQMs like FQ-CoDel would still not be able to support applications AQMs like FQ-CoDel would still not be able to support applications
that need both very low delay and high bandwidth, e.g. video-based that need both very low delay and high bandwidth, e.g. video-based
control of remote procedures, or interactive cloud-based video control of remote procedures, or interactive cloud-based video
(see Note 1 below). (see Note 1 below).
Although per-flow techniques are not incompatible with L4S, it is Although per-flow techniques are not incompatible with L4S, it is
important to have the DualQ alternative. This is because handling important to have the DualQ alternative. This is because handling
end-to-end (layer 4) flows in the network (layer 3 or 2) precludes end-to-end (layer 4) flows in the network (layer 3 or 2) precludes
some important end-to-end functions. For instance: some important end-to-end functions. For instance:
a. Per-flow forms of L4S like FQ-CoDel are incompatible with full A. Per-flow forms of L4S like FQ-CoDel are incompatible with full
end-to-end encryption of transport layer identifiers for end-to-end encryption of transport layer identifiers for
privacy and confidentiality (e.g. IPSec or encrypted VPN privacy and confidentiality (e.g. IPSec or encrypted VPN
tunnels, as opposed to DTLS over UDP), because they require tunnels, as opposed to DTLS over UDP), because they require
packet inspection to access the end-to-end transport flow packet inspection to access the end-to-end transport flow
identifiers. identifiers.
In contrast, the DualQ form of L4S requires no deeper In contrast, the DualQ form of L4S requires no deeper
inspection than the IP layer. So, as long as operators take inspection than the IP layer. So, as long as operators take
the DualQ approach, their users can have both very low queuing the DualQ approach, their users can have both very low queuing
delay and full end-to-end encryption [RFC8404]. delay and full end-to-end encryption [RFC8404].
b. With per-flow forms of L4S, the network takes over control of B. With per-flow forms of L4S, the network takes over control of
the relative rates of each application flow. Some see it as the relative rates of each application flow. Some see it as
an advantage that the network will prevent some flows running an advantage that the network will prevent some flows running
faster than others. Others consider it an inherent part of faster than others. Others consider it an inherent part of
the Internet's appeal that applications can control their rate the Internet's appeal that applications can control their rate
while taking account of the needs of others via congestion while taking account of the needs of others via congestion
signals. They maintain that this has allowed applications signals. They maintain that this has allowed applications
with interesting rate behaviours to evolve, for instance, with interesting rate behaviours to evolve, for instance,
variable bit-rate video that varies around an equal share variable bit-rate video that varies around an equal share
rather than being forced to remain equal at every instant, or rather than being forced to remain equal at every instant, or
e2e scavenger behaviours [RFC6817] that use less than an equal e2e scavenger behaviours [RFC6817] that use less than an equal
share of capacity [LEDBAT_AQM]. share of capacity [LEDBAT_AQM].
The L4S architecture does not require the IETF to commit to The L4S architecture does not require the IETF to commit to
one approach over the other, because it supports both, so that one approach over the other, because it supports both, so that
the 'market' can decide. Nonetheless, in the spirit of 'Do the 'market' can decide. Nonetheless, in the spirit of 'Do
one thing and do it well' [McIlroy78], the DualQ option one thing and do it well' [McIlroy78], the DualQ option
provides low delay without prejudging the issue of flow-rate provides low delay without prejudging the issue of flow-rate
control. Then, flow rate policing can be added separately if control. Then, flow rate policing can be added separately if
desired. This allows application control up to a point, but desired. A policer would allow application control up to a
the network can still choose to set the point at which it point, but the network would still be able choose to set the
intervenes to prevent one flow completely starving another. point at which it intervened to prevent one flow completely
starving another.
Note: Note:
1. It might seem that self-inflicted queuing delay within a per- 1. It might seem that self-inflicted queuing delay within a per-
flow queue should not be counted, because if the delay wasn't flow queue should not be counted, because if the delay wasn't
in the network it would just shift to the sender. However, in the network it would just shift to the sender. However,
modern adaptive applications, e.g. HTTP/2 [RFC9113] or some modern adaptive applications, e.g. HTTP/2 [RFC9113] or some
interactive media applications (see Section 6.1), can keep low interactive media applications (see Section 6.1), can keep low
latency objects at the front of their local send queue by latency objects at the front of their local send queue by
shuffling priorities of other objects dependent on the shuffling priorities of other objects dependent on the
skipping to change at page 21, line 32 skipping to change at page 21, line 19
6. Applicability 6. Applicability
6.1. Applications 6.1. Applications
A transport layer that solves the current latency issues will provide A transport layer that solves the current latency issues will provide
new service, product and application opportunities. new service, product and application opportunities.
With the L4S approach, the following existing applications also With the L4S approach, the following existing applications also
experience significantly better quality of experience under load: experience significantly better quality of experience under load:
* Gaming, including cloud based gaming; o Gaming, including cloud based gaming;
* VoIP; o VoIP;
* Video conferencing; o Video conferencing;
* Web browsing; o Web browsing;
* (Adaptive) video streaming; o (Adaptive) video streaming;
* Instant messaging. o Instant messaging.
The significantly lower queuing latency also enables some interactive The significantly lower queuing latency also enables some interactive
application functions to be offloaded to the cloud that would hardly application functions to be offloaded to the cloud that would hardly
even be usable today: even be usable today:
* Cloud based interactive video; o Cloud based interactive video;
* Cloud based virtual and augmented reality. o Cloud based virtual and augmented reality.
The above two applications have been successfully demonstrated with The above two applications have been successfully demonstrated with
L4S, both running together over a 40 Mb/s broadband access link L4S, both running together over a 40 Mb/s broadband access link
loaded up with the numerous other latency sensitive applications in loaded up with the numerous other latency sensitive applications in
the previous list as well as numerous downloads - all sharing the the previous list as well as numerous downloads - all sharing the
same bottleneck queue simultaneously [L4Sdemo16]. For the former, a same bottleneck queue simultaneously [L4Sdemo16]. For the former, a
panoramic video of a football stadium could be swiped and pinched so panoramic video of a football stadium could be swiped and pinched so
that, on the fly, a proxy in the cloud could generate a sub-window of that, on the fly, a proxy in the cloud could generate a sub-window of
the match video under the finger-gesture control of each user. For the match video under the finger-gesture control of each user. For
the latter, a virtual reality headset displayed a viewport taken from the latter, a virtual reality headset displayed a viewport taken from
skipping to change at page 22, line 39 skipping to change at page 22, line 26
Without the low queuing delay of L4S, cloud-based applications like Without the low queuing delay of L4S, cloud-based applications like
these would not be credible without significantly more access these would not be credible without significantly more access
bandwidth (to deliver all possible video that might be viewed) and bandwidth (to deliver all possible video that might be viewed) and
more local processing, which would increase the weight and power more local processing, which would increase the weight and power
consumption of head-mounted displays. When all interactive consumption of head-mounted displays. When all interactive
processing can be done in the cloud, only the data to be rendered for processing can be done in the cloud, only the data to be rendered for
the end user needs to be sent. the end user needs to be sent.
Other low latency high bandwidth applications such as: Other low latency high bandwidth applications such as:
* Interactive remote presence; o Interactive remote presence;
* Video-assisted remote control of machinery or industrial o Video-assisted remote control of machinery or industrial
processes. processes.
are not credible at all without very low queuing delay. No amount of are not credible at all without very low queuing delay. No amount of
extra access bandwidth or local processing can make up for lost time. extra access bandwidth or local processing can make up for lost time.
6.2. Use Cases 6.2. Use Cases
The following use-cases for L4S are being considered by various The following use-cases for L4S are being considered by various
interested parties: interested parties:
* Where the bottleneck is one of various types of access network: o Where the bottleneck is one of various types of access network:
e.g. DSL, Passive Optical Networks (PON), DOCSIS cable, mobile, e.g. DSL, Passive Optical Networks (PON), DOCSIS cable, mobile,
satellite (see Section 6.3 for some technology-specific details) satellite (see Section 6.3 for some technology-specific details)
* Private networks of heterogeneous data centres, where there is no o Private networks of heterogeneous data centres, where there is no
single administrator that can arrange for all the simultaneous single administrator that can arrange for all the simultaneous
changes to senders, receivers and network needed to deploy DCTCP: changes to senders, receivers and network needed to deploy DCTCP:
- a set of private data centres interconnected over a wide area * a set of private data centres interconnected over a wide area
with separate administrations, but within the same company with separate administrations, but within the same company
- a set of data centres operated by separate companies * a set of data centres operated by separate companies
interconnected by a community of interest network (e.g. for the interconnected by a community of interest network (e.g. for the
finance sector) finance sector)
- multi-tenant (cloud) data centres where tenants choose their * multi-tenant (cloud) data centres where tenants choose their
operating system stack (Infrastructure as a Service - IaaS) operating system stack (Infrastructure as a Service - IaaS)
* Different types of transport (or application) congestion control: o Different types of transport (or application) congestion control:
- elastic (TCP/SCTP); * elastic (TCP/SCTP);
- real-time (RTP, RMCAT); * real-time (RTP, RMCAT);
- query (DNS/LDAP). * query-response (DNS/LDAP).
* Where low delay quality of service is required, but without o Where low delay quality of service is required, but without
inspecting or intervening above the IP layer [RFC8404]: inspecting or intervening above the IP layer [RFC8404]:
- mobile and other networks have tended to inspect higher layers * mobile and other networks have tended to inspect higher layers
in order to guess application QoS requirements. However, with in order to guess application QoS requirements. However, with
growing demand for support of privacy and encryption, L4S growing demand for support of privacy and encryption, L4S
offers an alternative. There is no need to select which offers an alternative. There is no need to select which
traffic to favour for queuing, when L4S can give favourable traffic to favour for queuing, when L4S can give favourable
queuing to all traffic. queuing to all traffic.
* If queuing delay is minimized, applications with a fixed delay o If queuing delay is minimized, applications with a fixed delay
budget can communicate over longer distances, or via a longer budget can communicate over longer distances, or via a longer
chain of service functions [RFC7665] or onion routers. chain of service functions [RFC7665] or onion routers.
* If delay jitter is minimized, it is possible to reduce the o If delay jitter is minimized, it is possible to reduce the
dejitter buffers on the receive end of video streaming, which dejitter buffers on the receive end of video streaming, which
should improve the interactive experience should improve the interactive experience
6.3. Applicability with Specific Link Technologies 6.3. Applicability with Specific Link Technologies
Certain link technologies aggregate data from multiple packets into Certain link technologies aggregate data from multiple packets into
bursts, and buffer incoming packets while building each burst. Wi- bursts, and buffer incoming packets while building each burst. Wi-
Fi, PON and cable all involve such packet aggregation, whereas fixed Fi, PON and cable all involve such packet aggregation, whereas fixed
Ethernet and DSL do not. No sender, whether L4S or not, can do Ethernet and DSL do not. No sender, whether L4S or not, can do
anything to reduce the buffering needed for packet aggregation. So anything to reduce the buffering needed for packet aggregation. So
an AQM should not count this buffering as part of the queue that it an AQM should not count this buffering as part of the queue that it
controls, given no amount of congestion signals will reduce it. controls, given no amount of congestion signals will reduce it.
Certain link technologies also add buffering for other reasons, Certain link technologies also add buffering for other reasons,
specifically: specifically:
* Radio links (cellular, Wi-Fi, satellite) that are distant from the o Radio links (cellular, Wi-Fi, satellite) that are distant from the
source are particularly challenging. The radio link capacity can source are particularly challenging. The radio link capacity can
vary rapidly by orders of magnitude, so it is considered desirable vary rapidly by orders of magnitude, so it is considered desirable
to hold a standing queue that can utilize sudden increases of to hold a standing queue that can utilize sudden increases of
capacity; capacity;
* Cellular networks are further complicated by a perceived need to o Cellular networks are further complicated by a perceived need to
buffer in order to make hand-overs imperceptible; buffer in order to make hand-overs imperceptible;
L4S cannot remove the need for all these different forms of L4S cannot remove the need for all these different forms of
buffering. However, by removing 'the longest pole in the tent' buffering. However, by removing 'the longest pole in the tent'
(buffering for the large sawteeth of Classic congestion controls), (buffering for the large sawteeth of Classic congestion controls),
L4S exposes all these 'shorter poles' to greater scrutiny. L4S exposes all these 'shorter poles' to greater scrutiny.
Until now, the buffering needed for these additional reasons tended Until now, the buffering needed for these additional reasons tended
to be over-specified - with the excuse that none were 'the longest to be over-specified - with the excuse that none were 'the longest
pole in the tent'. But having removed the 'longest pole', it becomes pole in the tent'. But having removed the 'longest pole', it becomes
skipping to change at page 26, line 4 skipping to change at page 25, line 28
known-bottleneck case tends to be applicable whatever the access link known-bottleneck case tends to be applicable whatever the access link
technology; whether xDSL, cable, PON, cellular, line of sight technology; whether xDSL, cable, PON, cellular, line of sight
wireless or satellite. wireless or satellite.
Therefore, the full benefit of the L4S service should be available in Therefore, the full benefit of the L4S service should be available in
the downstream direction when an L4S AQM is deployed at the ingress the downstream direction when an L4S AQM is deployed at the ingress
to this bottleneck link. And similarly, the full upstream service to this bottleneck link. And similarly, the full upstream service
will be available once an L4S AQM is deployed at the ingress into the will be available once an L4S AQM is deployed at the ingress into the
upstream link. (Of course, multi-homed sites would only see the full upstream link. (Of course, multi-homed sites would only see the full
benefit once all their access links were covered.) benefit once all their access links were covered.)
______ ______
( ) ( )
__ __ ( ) __ __ ( )
|DQ\________/DQ|( enterprise ) |DQ\________/DQ|( enterprise )
___ |__/ \__| ( /campus ) ___ |__/ \__| ( /campus )
( ) (______) ( ) (______)
( ) ___||_ ( ) ___||_
+----+ ( ) __ __ / \ +----+ ( ) __ __ / \
| DC |-----( Core )|DQ\_______________/DQ|| home | | DC |-----( Core )|DQ\_______________/DQ|| home |
+----+ ( ) |__/ \__||______| +----+ ( ) |__/ \__||______|
(_____) __ (_____) __
|DQ\__/\ __ ,===. |DQ\__/\ __ ,===.
|__/ \ ____/DQ||| ||mobile |__/ \ ____/DQ||| ||mobile
\/ \__|||_||device \/ \__|||_||device
| o | | o |
`---' `---'
Figure 2: Likely location of DualQ (DQ) Deployments in common Figure 2: Likely location of DualQ (DQ) Deployments in common access
access topologies topologies
Deployment in mesh topologies depends on how overbooked the core is. Deployment in mesh topologies depends on how overbooked the core is.
If the core is non-blocking, or at least generously provisioned so If the core is non-blocking, or at least generously provisioned so
that the edges are nearly always the bottlenecks, it would only be that the edges are nearly always the bottlenecks, it would only be
necessary to deploy an L4S AQM at the edge bottlenecks. For example, necessary to deploy an L4S AQM at the edge bottlenecks. For example,
some data-centre networks are designed with the bottleneck in the some data-centre networks are designed with the bottleneck in the
hypervisor or host NICs, while others bottleneck at the top-of-rack hypervisor or host NICs, while others bottleneck at the top-of-rack
switch (both the output ports facing hosts and those facing the switch (both the output ports facing hosts and those facing the
core). core).
skipping to change at page 29, line 49 skipping to change at page 29, line 27
6.4.3. L4S Flow but Non-ECN Bottleneck 6.4.3. L4S Flow but Non-ECN Bottleneck
If L4S is enabled between two hosts, the L4S sender is required to If L4S is enabled between two hosts, the L4S sender is required to
coexist safely with Reno in response to any drop (see Section 4.3 of coexist safely with Reno in response to any drop (see Section 4.3 of
the L4S ECN spec [I-D.ietf-tsvwg-ecn-l4s-id]). the L4S ECN spec [I-D.ietf-tsvwg-ecn-l4s-id]).
Unfortunately, as well as protecting Classic traffic, this rule Unfortunately, as well as protecting Classic traffic, this rule
degrades the L4S service whenever there is any loss, even if the degrades the L4S service whenever there is any loss, even if the
cause is not persistent congestion at a bottleneck, e.g.: cause is not persistent congestion at a bottleneck, e.g.:
* congestion loss at other transient bottlenecks, e.g. due to bursts o congestion loss at other transient bottlenecks, e.g. due to bursts
in shallower queues; in shallower queues;
* transmission errors, e.g. due to electrical interference; o transmission errors, e.g. due to electrical interference;
* rate policing.
o rate policing.
Three complementary approaches are in progress to address this issue, Three complementary approaches are in progress to address this issue,
but they are all currently research: but they are all currently research:
* In Prague congestion control, ignore certain losses deemed o In Prague congestion control, ignore certain losses deemed
unlikely to be due to congestion (using some ideas from unlikely to be due to congestion (using some ideas from
BBR [I-D.cardwell-iccrg-bbr-congestion-control] regarding isolated BBR [I-D.cardwell-iccrg-bbr-congestion-control] regarding isolated
losses). This could mask any of the above types of loss while losses). This could mask any of the above types of loss while
still coexisting with drop-based congestion controls. still coexisting with drop-based congestion controls.
* A combination of RACK, L4S and link retransmission without o A combination of RACK, L4S and link retransmission without
resequencing could repair transmission errors without the head of resequencing could repair transmission errors without the head of
line blocking delay usually associated with link-layer line blocking delay usually associated with link-layer
retransmission [UnorderedLTE], [I-D.ietf-tsvwg-ecn-l4s-id]; retransmission [UnorderedLTE], [I-D.ietf-tsvwg-ecn-l4s-id];
* Hybrid ECN/drop rate policers (see Section 8.3). o Hybrid ECN/drop rate policers (see Section 8.3).
L4S deployment scenarios that minimize these issues (e.g. over L4S deployment scenarios that minimize these issues (e.g. over
wireline networks) can proceed in parallel to this research, in the wireline networks) can proceed in parallel to this research, in the
expectation that research success could continually widen L4S expectation that research success could continually widen L4S
applicability. applicability.
6.4.4. L4S Flow but Classic ECN Bottleneck 6.4.4. L4S Flow but Classic ECN Bottleneck
Classic ECN support is starting to materialize on the Internet as an Classic ECN support is starting to materialize on the Internet as an
increased level of CE marking. It is hard to detect whether this is increased level of CE marking. It is hard to detect whether this is
skipping to change at page 36, line 14 skipping to change at page 35, line 45
identifying features [RFC6973]. There may be some types of traffic identifying features [RFC6973]. There may be some types of traffic
that prefer not to use L4S, but the coarse binary categorization of that prefer not to use L4S, but the coarse binary categorization of
traffic reveals very little that could be exploited to compromise traffic reveals very little that could be exploited to compromise
privacy. privacy.
9. Informative References 9. Informative References
[AFCD] Xue, L., Kumar, S., Cui, C., Kondikoppa, P., Chiu, C-H., [AFCD] Xue, L., Kumar, S., Cui, C., Kondikoppa, P., Chiu, C-H.,
and S-J. Park, "Towards fair and low latency next and S-J. Park, "Towards fair and low latency next
generation high speed networks: AFCD queuing", Journal of generation high speed networks: AFCD queuing", Journal of
Network and Computer Applications 70:183--193, July 2016, Network and Computer Applications 70:183--193, July 2016.
<https://doi.org/10.1016/j.jnca.2016.03.021>.
[BBRv2] Cardwell, N., "TCP BBR v2 Alpha/Preview Release", GitHub [BBRv2] Cardwell, N., "TCP BBR v2 Alpha/Preview Release", GitHub
repository; Linux congestion control module, repository; Linux congestion control module,
<https://github.com/google/bbr/blob/v2alpha/README.md>. <https://github.com/google/bbr/blob/v2alpha/README.md>.
[BDPdata] Briscoe, B., "PI2 Parameters", Technical Report TR-BB- [BDPdata] Briscoe, B., "PI2 Parameters", Technical Report TR-BB-
2021-001 arXiv:2107.01003 [cs.NI], July 2021, 2021-001 arXiv:2107.01003 [cs.NI], July 2021,
<https://arxiv.org/abs/2107.01003>. <https://arxiv.org/abs/2107.01003>.
[BufferSize] [BufferSize]
Appenzeller, G., Keslassy, I., and N. McKeown, "Sizing Appenzeller, G., Keslassy, I., and N. McKeown, "Sizing
Router Buffers", In Proc. SIGCOMM'04 34(4):281--292, Router Buffers", In Proc. SIGCOMM'04 34(4):281--292,
September 2004, <https://doi.org/10.1145/1015467.1015499>. September 2004, <https://doi.org/10.1145/1015467.1015499>.
[COBALT] Palmei, J., Gupta, S., Imputato, P., Morton, J., [COBALT] Palmei, J., Gupta, S., Imputato, P., Morton, J.,
Tahiliani, M. P., Avallone, S., and D. Täht, "Design and Tahiliani, M., Avallone, S., and D. Taeht, "Design and
Evaluation of COBALT Queue Discipline", In Proc. IEEE Evaluation of COBALT Queue Discipline", In Proc. IEEE
Int'l Symp. Local and Metropolitan Area Networks Int'l Symp. Local and Metropolitan Area Networks
(LANMAN'19) 2019:1-6, July 2019, (LANMAN'19) 2019:1-6, July 2019,
<https://ieeexplore.ieee.org/abstract/document/8847054>. <https://ieeexplore.ieee.org/abstract/document/8847054>.
[DCttH19] De Schepper, K., Bondarenko, O., Tilmans, O., and B.
Briscoe, "`Data Centre to the Home': Ultra-Low Latency for
All", Updated RITE project Technical Report , July 2019,
<https://bobbriscoe.net/pubs.html#DCttH_TR>.
[DOCSIS3.1] [DOCSIS3.1]
CableLabs, "MAC and Upper Layer Protocols Interface CableLabs, "MAC and Upper Layer Protocols Interface
(MULPI) Specification, CM-SP-MULPIv3.1", Data-Over-Cable (MULPI) Specification, CM-SP-MULPIv3.1", Data-Over-Cable
Service Interface Specifications DOCSIS® 3.1 Version i17 Service Interface Specifications DOCSIS(R) 3.1 Version i17
or later, 21 January 2019, <https://specification- or later, January 2019, <https://specification-
search.cablelabs.com/CM-SP-MULPIv3.1>. search.cablelabs.com/CM-SP-MULPIv3.1>.
[DOCSIS3AQM] [DOCSIS3AQM]
White, G., "Active Queue Management Algorithms for DOCSIS White, G., "Active Queue Management Algorithms for DOCSIS
3.0; A Simulation Study of CoDel, SFQ-CoDel and PIE in 3.0; A Simulation Study of CoDel, SFQ-CoDel and PIE in
DOCSIS 3.0 Networks", CableLabs Technical Report , April DOCSIS 3.0 Networks", CableLabs Technical Report , April
2013, <{https://www.cablelabs.com/wp- 2013, <{https://www.cablelabs.com/wp-
content/uploads/2013/11/ content/uploads/2013/11/
Active_Queue_Management_Algorithms_DOCSIS_3_0.pdf>. Active_Queue_Management_Algorithms_DOCSIS_3_0.pdf>.
skipping to change at page 37, line 23 skipping to change at page 37, line 6
<https://www.netdevconf.org/0x13/session.html?talk- <https://www.netdevconf.org/0x13/session.html?talk-
DUALPI2-AQM>. DUALPI2-AQM>.
[Dukkipati06] [Dukkipati06]
Dukkipati, N. and N. McKeown, "Why Flow-Completion Time is Dukkipati, N. and N. McKeown, "Why Flow-Completion Time is
the Right Metric for Congestion Control", ACM CCR the Right Metric for Congestion Control", ACM CCR
36(1):59--62, January 2006, 36(1):59--62, January 2006,
<https://dl.acm.org/doi/10.1145/1111322.1111336>. <https://dl.acm.org/doi/10.1145/1111322.1111336>.
[FQ_CoDel_Thresh] [FQ_CoDel_Thresh]
Høiland-Jørgensen, T., "fq_codel: generalise ce_threshold Hoeiland-Joergensen, T., "fq_codel: generalise
marking for subset of traffic", Linux Patch Commit ID: ce_threshold marking for subset of traffic", Linux
dfcb63ce1de6b10b, 20 October 2021, Patch Commit ID: dfcb63ce1de6b10b, October 2021,
<https://git.kernel.org/pub/scm/linux/kernel/git/netdev/ <https://git.kernel.org/pub/scm/linux/kernel/git/netdev/
net-next.git/commit/?id=dfcb63ce1de6b10b>. net-next.git/commit/?id=dfcb63ce1de6b10b>.
[Hohlfeld14] [Hohlfeld14]
Hohlfeld, O., Pujol, E., Ciucu, F., Feldmann, A., and P. Hohlfeld , O., Pujol, E., Ciucu, F., Feldmann, A., and P.
Barford, "A QoE Perspective on Sizing Network Buffers", Barford, "A QoE Perspective on Sizing Network Buffers",
Proc. ACM Internet Measurement Conf (IMC'14) hmm, November Proc. ACM Internet Measurement Conf (IMC'14) pp333--346,
2014, <https://doi.acm.org/10.1145/2663716.2663730>. November 2014.
[I-D.briscoe-conex-policing] [I-D.briscoe-conex-policing]
Briscoe, B., "Network Performance Isolation using Briscoe, B., "Network Performance Isolation using
Congestion Policing", Work in Progress, Internet-Draft, Congestion Policing", draft-briscoe-conex-policing-01
draft-briscoe-conex-policing-01, 14 February 2014, (work in progress), February 2014.
<https://www.ietf.org/archive/id/draft-briscoe-conex-
policing-01.txt>.
[I-D.briscoe-docsis-q-protection] [I-D.briscoe-docsis-q-protection]
Briscoe, B. and G. White, "The DOCSIS(r) Queue Protection Briscoe, B. and G. White, "Queue Protection to Preserve
Algorithm to Preserve Low Latency", Work in Progress, Low Latency", draft-briscoe-docsis-q-protection-00 (work
Internet-Draft, draft-briscoe-docsis-q-protection-06, 13 in progress), July 2019.
May 2022,
<https://datatracker.ietf.org/api/v1/doc/document/draft-
briscoe-docsis-q-protection/>.
[I-D.briscoe-iccrg-prague-congestion-control] [I-D.briscoe-iccrg-prague-congestion-control]
Schepper, K. D., Tilmans, O., and B. Briscoe, "Prague Schepper, K. D., Tilmans, O., and B. Briscoe, "Prague
Congestion Control", Work in Progress, Internet-Draft, Congestion Control", draft-briscoe-iccrg-prague-
draft-briscoe-iccrg-prague-congestion-control-01, 11 July congestion-control-01 (work in progress), July 2022,
2022, <https://datatracker.ietf.org/api/v1/doc/document/ <https://www.ietf.org/archive/id/draft-briscoe-iccrg-
draft-briscoe-iccrg-prague-congestion-control/>. prague-congestion-control-01.txt>.
[I-D.briscoe-tsvwg-l4s-diffserv] [I-D.briscoe-tsvwg-l4s-diffserv]
Briscoe, B., "Interactions between Low Latency, Low Loss, Briscoe, B., "Interactions between Low Latency, Low Loss,
Scalable Throughput (L4S) and Differentiated Services", Scalable Throughput (L4S) and Differentiated Services",
Work in Progress, Internet-Draft, draft-briscoe-tsvwg-l4s- draft-briscoe-tsvwg-l4s-diffserv-02 (work in progress),
diffserv-02, 2 July 2018, November 2018.
<https://datatracker.ietf.org/api/v1/doc/document/draft-
briscoe-tsvwg-l4s-diffserv/>.
[I-D.cardwell-iccrg-bbr-congestion-control] [I-D.cardwell-iccrg-bbr-congestion-control]
Cardwell, N., Cheng, Y., Yeganeh, S. H., Swett, I., and V. Cardwell, N., Cheng, Y., Yeganeh, S., and V. Jacobson,
Jacobson, "BBR Congestion Control", Work in Progress, "BBR Congestion Control", draft-cardwell-iccrg-bbr-
Internet-Draft, draft-cardwell-iccrg-bbr-congestion- congestion-control-00 (work in progress), July 2017.
control-02, 7 March 2022,
<https://datatracker.ietf.org/api/v1/doc/document/draft-
cardwell-iccrg-bbr-congestion-control/>.
[I-D.ietf-tcpm-accurate-ecn] [I-D.ietf-tcpm-accurate-ecn]
Briscoe, B., Kühlewind, M., and R. Scheffenegger, "More Briscoe, B., Kuehlewind, M., and R. Scheffenegger, "More
Accurate ECN Feedback in TCP", Work in Progress, Internet- Accurate ECN Feedback in TCP", draft-ietf-tcpm-accurate-
Draft, draft-ietf-tcpm-accurate-ecn-20, 25 July 2022, ecn-14 (work in progress), February 2021.
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ietf-tcpm-accurate-ecn/>.
[I-D.ietf-tsvwg-aqm-dualq-coupled] [I-D.ietf-tsvwg-aqm-dualq-coupled]
Schepper, K. D., Briscoe, B., and G. White, "DualQ Coupled Schepper, K., Briscoe, B., and G. White, "DualQ Coupled
AQMs for Low Latency, Low Loss and Scalable Throughput AQMs for Low Latency, Low Loss and Scalable Throughput
(L4S)", Work in Progress, Internet-Draft, draft-ietf- (L4S)", draft-ietf-tsvwg-aqm-dualq-coupled-14 (work in
tsvwg-aqm-dualq-coupled-24, 7 July 2022, progress), March 2021.
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ietf-tsvwg-aqm-dualq-coupled/>.
[I-D.ietf-tsvwg-ecn-encap-guidelines] [I-D.ietf-tsvwg-ecn-encap-guidelines]
Briscoe, B. and J. Kaippallimalil, "Guidelines for Adding Briscoe, B. and J. Kaippallimalil, "Guidelines for Adding
Congestion Notification to Protocols that Encapsulate IP", Congestion Notification to Protocols that Encapsulate IP",
Work in Progress, Internet-Draft, draft-ietf-tsvwg-ecn- draft-ietf-tsvwg-ecn-encap-guidelines-15 (work in
encap-guidelines-17, 11 July 2022, progress), March 2021.
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ietf-tsvwg-ecn-encap-guidelines/>.
[I-D.ietf-tsvwg-ecn-l4s-id] [I-D.ietf-tsvwg-ecn-l4s-id]
Schepper, K. D. and B. Briscoe, "Explicit Congestion Schepper, K. and B. Briscoe, "Explicit Congestion
Notification (ECN) Protocol for Very Low Queuing Delay Notification (ECN) Protocol for Ultra-Low Queuing Delay
(L4S)", Work in Progress, Internet-Draft, draft-ietf- (L4S)", draft-ietf-tsvwg-ecn-l4s-id-14 (work in progress),
tsvwg-ecn-l4s-id-28, 8 August 2022, March 2021.
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ietf-tsvwg-ecn-l4s-id/>.
[I-D.ietf-tsvwg-l4sops] [I-D.ietf-tsvwg-l4sops]
White, G., "Operational Guidance for Deployment of L4S in White, G., "Operational Guidance for Deployment of L4S in
the Internet", Work in Progress, Internet-Draft, draft- the Internet", draft-ietf-tsvwg-l4sops-03 (work in
ietf-tsvwg-l4sops-03, 28 April 2022, progress), April 2022, <https://www.ietf.org/archive/id/
<https://datatracker.ietf.org/api/v1/doc/document/draft- draft-ietf-tsvwg-l4sops-03.txt>.
ietf-tsvwg-l4sops/>.
[I-D.ietf-tsvwg-nqb] [I-D.ietf-tsvwg-nqb]
White, G. and T. Fossati, "A Non-Queue-Building Per-Hop White, G. and T. Fossati, "A Non-Queue-Building Per-Hop
Behavior (NQB PHB) for Differentiated Services", Work in Behavior (NQB PHB) for Differentiated Services", draft-
Progress, Internet-Draft, draft-ietf-tsvwg-nqb-10, 4 March ietf-tsvwg-nqb-05 (work in progress), March 2021.
2022, <https://datatracker.ietf.org/api/v1/doc/document/
draft-ietf-tsvwg-nqb/>.
[I-D.ietf-tsvwg-rfc6040update-shim] [I-D.ietf-tsvwg-rfc6040update-shim]
Briscoe, B., "Propagating Explicit Congestion Notification Briscoe, B., "Propagating Explicit Congestion Notification
Across IP Tunnel Headers Separated by a Shim", Work in Across IP Tunnel Headers Separated by a Shim", draft-ietf-
Progress, Internet-Draft, draft-ietf-tsvwg-rfc6040update- tsvwg-rfc6040update-shim-13 (work in progress), March
shim-15, 11 July 2022, 2021.
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ietf-tsvwg-rfc6040update-shim/>. [I-D.mathis-iccrg-relentless-tcp]
Mathis, M., "Relentless Congestion Control", draft-mathis-
iccrg-relentless-tcp-00 (work in progress), March 2009.
[I-D.morton-tsvwg-codel-approx-fair] [I-D.morton-tsvwg-codel-approx-fair]
Morton, J. and P. G. Heist, "Controlled Delay Approximate Morton, J. and P. Heist, "Controlled Delay Approximate
Fairness AQM", Work in Progress, Internet-Draft, draft- Fairness AQM", draft-morton-tsvwg-codel-approx-fair-01
morton-tsvwg-codel-approx-fair-01, 9 March 2020, (work in progress), March 2020.
<https://www.ietf.org/archive/id/draft-morton-tsvwg-codel-
approx-fair-01.txt>.
[I-D.sridharan-tcpm-ctcp] [I-D.sridharan-tcpm-ctcp]
Sridharan, M., Tan, K., Bansal, D., and D. Thaler, Sridharan, M., Tan, K., Bansal, D., and D. Thaler,
"Compound TCP: A New TCP Congestion Control for High-Speed "Compound TCP: A New TCP Congestion Control for High-Speed
and Long Distance Networks", Work in Progress, Internet- and Long Distance Networks", draft-sridharan-tcpm-ctcp-02
Draft, draft-sridharan-tcpm-ctcp-02, 29 October 2007, (work in progress), November 2008.
<https://datatracker.ietf.org/api/v1/doc/document/draft-
sridharan-tcpm-ctcp/>.
[I-D.stewart-tsvwg-sctpecn] [I-D.stewart-tsvwg-sctpecn]
Stewart, R. R., Tuexen, M., and X. Dong, "ECN for Stream Stewart, R., Tuexen, M., and X. Dong, "ECN for Stream
Control Transmission Protocol (SCTP)", Work in Progress, Control Transmission Protocol (SCTP)", draft-stewart-
Internet-Draft, draft-stewart-tsvwg-sctpecn-05, 15 January tsvwg-sctpecn-05 (work in progress), January 2014.
2014, <https://www.ietf.org/archive/id/draft-stewart-
tsvwg-sctpecn-05.txt>.
[L4Sdemo16] [L4Sdemo16]
Bondarenko, O., De Schepper, K., Tsang, I., and B. Bondarenko, O., De Schepper, K., Tsang, I., and B.
Briscoe, "Ultra-Low Delay for All: Live Experience, Live Briscoe, "Ultra-Low Delay for All: Live Experience, Live
Analysis", Proc. MMSYS'16 pp33:1--33:4, May 2016, Analysis", Proc. MMSYS'16 pp33:1--33:4, May 2016,
<https://dl.acm.org/citation.cfm?doid=2910017.2910633 <https://dl.acm.org/citation.cfm?doid=2910017.2910633
(videos of demos: (videos of demos:
https://riteproject.eu/dctth/#1511dispatchwg )>. https://riteproject.eu/dctth/#1511dispatchwg )>.
[L4Seval22]
De Schepper, K., Albisser, O., Tilmans, O., and B.
Briscoe, "Dual Queue Coupled AQM: Deployable Very Low
Queuing Delay for All", Preprint submitted to IEEE/ACM
Transactions on Networking arXiv:2209.01078 [cs.NI],
September 2022, <https://arxiv.org/abs/2209.01078>.
[LEDBAT_AQM] [LEDBAT_AQM]
Al-Saadi, R., Armitage, G., and J. But, "Characterising Al-Saadi, R., Armitage, G., and J. But, "Characterising
LEDBAT Performance Through Bottlenecks Using PIE, FQ-CoDel LEDBAT Performance Through Bottlenecks Using PIE, FQ-CoDel
and FQ-PIE Active Queue Management", Proc. IEEE 42nd and FQ-PIE Active Queue Management", Proc. IEEE 42nd
Conference on Local Computer Networks (LCN) 278--285, Conference on Local Computer Networks (LCN) 278--285,
2017, <https://ieeexplore.ieee.org/document/8109367>. 2017, <https://ieeexplore.ieee.org/document/8109367>.
[lowat] Meenan, P., "Optimizing HTTP/2 prioritization with BBR and [lowat] Meenan, P., "Optimizing HTTP/2 prioritization with BBR and
tcp_notsent_lowat", Cloudflare Blog , 12 October 2018, tcp_notsent_lowat", Cloudflare Blog , October 2018,
<https://blog.cloudflare.com/http-2-prioritization-with- <https://blog.cloudflare.com/http-2-prioritization-with-
nginx/>. nginx/>.
[Mathis09] Mathis, M., "Relentless Congestion Control", PFLDNeT'09 ,
May 2009, <https://www.gdt.id.au/~gdt/
presentations/2010-07-06-questnet-tcp/reference-
materials/papers/mathis-relentless-congestion-
control.pdf>.
[McIlroy78] [McIlroy78]
McIlroy, M.D., Pinson, E. N., and B. A. Tague, "UNIX Time- McIlroy, M., Pinson, E., and B. Tague, "UNIX Time-Sharing
Sharing System: Foreword", The Bell System Technical System: Foreword", The Bell System Technical Journal
Journal 57:6(1902--1903), July 1978, 57:6(1902--1903), July 1978,
<https://archive.org/details/bstj57-6-1899>. <https://archive.org/details/bstj57-6-1899>.
[Nadas20] Nádas, S., Gombos, G., Fejes, F., and S. Laki, "A [Nadas20] Nadas, S., Gombos, G., Fejes, F., and S. Laki, "A
Congestion Control Independent L4S Scheduler", Proc. Congestion Control Independent L4S Scheduler", Proc.
Applied Networking Research Workshop (ANRW '20) 45--51, Applied Networking Research Workshop (ANRW '20) 45--51,
July 2020, <https://doi.org/10.1145/3404868.3406669>. July 2020.
[NASA04] Bailey, R.R., Trey Arthur III, J.J., and S.P. Williams, [NASA04] Bailey, R., Trey Arthur III, J., and S. Williams, "Latency
"Latency Requirements for Head-Worn Display S/EVS Requirements for Head-Worn Display S/EVS Applications",
Applications", SPIE Defense and Security SPIE Defense and Security Symposium LF99-1955, April 2004,
Symposium LF99-1955, April 2004,
<https://ntrs.nasa.gov/api/citations/20120009198/ <https://ntrs.nasa.gov/api/citations/20120009198/
downloads/20120009198.pdf?attachment=true>. downloads/20120009198.pdf?attachment=true>.
[PragueLinux] [PragueLinux]
Briscoe, B., De Schepper, K., Albisser, O., Misund, J., Briscoe, B., De Schepper, K., Albisser, O., Misund, J.,
Tilmans, O., Kühlewind, M., and A.S. Ahmed, "Implementing Tilmans, O., Kuehlewind, M., and A. Ahmed, "Implementing
the `TCP Prague' Requirements for Low Latency Low Loss the `TCP Prague' Requirements for Low Latency Low Loss
Scalable Throughput (L4S)", Proc. Linux Netdev 0x13 , Scalable Throughput (L4S)", Proc. Linux Netdev 0x13 ,
March 2019, <https://www.netdevconf.org/0x13/ March 2019, <https://www.netdevconf.org/0x13/
session.html?talk-tcp-prague-l4s>. session.html?talk-tcp-prague-l4s>.
[QDyn] Briscoe, B., "Rapid Signalling of Queue Dynamics", [QDyn] Briscoe, B., "Rapid Signalling of Queue Dynamics",
bobbriscoe.net Technical Report TR-BB-2017-001; bobbriscoe.net Technical Report TR-BB-2017-001;
arXiv:1904.07044 [cs.NI], September 2017, arXiv:1904.07044 [cs.NI], April 2019,
<https://arxiv.org/abs/1904.07044>. <https://arxiv.org/abs/1904.07044>.
[Raaen14] Raaen, K. and T-M. Grønli, "Latency thresholds for [Raaen14] Raaen, K. and T-M. Groenli, "Latency thresholds for
usability in games: A survey", Norsk IKT-konferanse for usability in games: A survey", Norsk IKT-konferanse for
forskning og utdanning , 2014, forskning og utdanning , 2014,
<http://ojs.bibsys.no/index.php/NIK/article/view/9/6>. <http://ojs.bibsys.no/index.php/NIK/article/view/9/6>.
[Rajiullah15] [Rajiullah15]
Rajiullah, M., "Towards a Low Latency Internet: Rajiullah, M., "Towards a Low Latency Internet:
Understanding and Solutions", Master's Thesis; Karlstad Understanding and Solutions", Master's Thesis; Karlstad
Uni, Dept of Maths & CS 2015:41, 2015, <https://www.diva- Uni, Dept of Maths & CS 2015:41, 2015, <https://www.diva-
portal.org/smash/get/diva2:846109/FULLTEXT01.pdf>. portal.org/smash/get/diva2:846109/FULLTEXT01.pdf>.
[RFC0970] Nagle, J., "On Packet Switches With Infinite Storage", [RFC0970] Nagle, J., "On Packet Switches With Infinite Storage",
RFC 970, DOI 10.17487/RFC0970, December 1985, RFC 970, DOI 10.17487/RFC0970, December 1985,
<https://www.rfc-editor.org/info/rfc970>. <https://www.rfc-editor.org/info/rfc970>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998, Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<https://www.rfc-editor.org/info/rfc2475>. <https://www.rfc-editor.org/info/rfc2475>.
skipping to change at page 42, line 5 skipping to change at page 41, line 10
[RFC2884] Hadi Salim, J. and U. Ahmed, "Performance Evaluation of [RFC2884] Hadi Salim, J. and U. Ahmed, "Performance Evaluation of
Explicit Congestion Notification (ECN) in IP Networks", Explicit Congestion Notification (ECN) in IP Networks",
RFC 2884, DOI 10.17487/RFC2884, July 2000, RFC 2884, DOI 10.17487/RFC2884, July 2000,
<https://www.rfc-editor.org/info/rfc2884>. <https://www.rfc-editor.org/info/rfc2884>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP", of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001, RFC 3168, DOI 10.17487/RFC3168, September 2001,
<https://www.rfc-editor.org/info/rfc3168>. <https://www.rfc-editor.org/info/rfc3168>.
[RFC3246] Davie, B., Charny, A., Bennet, J.C.R., Benson, K., Le [RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec,
Boudec, J.Y., Courtney, W., Davari, S., Firoiu, V., and D. J., Courtney, W., Davari, S., Firoiu, V., and D.
Stiliadis, "An Expedited Forwarding PHB (Per-Hop Stiliadis, "An Expedited Forwarding PHB (Per-Hop
Behavior)", RFC 3246, DOI 10.17487/RFC3246, March 2002, Behavior)", RFC 3246, DOI 10.17487/RFC3246, March 2002,
<https://www.rfc-editor.org/info/rfc3246>. <https://www.rfc-editor.org/info/rfc3246>.
[RFC3540] Spring, N., Wetherall, D., and D. Ely, "Robust Explicit [RFC3540] Spring, N., Wetherall, D., and D. Ely, "Robust Explicit
Congestion Notification (ECN) Signaling with Nonces", Congestion Notification (ECN) Signaling with Nonces",
RFC 3540, DOI 10.17487/RFC3540, June 2003, RFC 3540, DOI 10.17487/RFC3540, June 2003,
<https://www.rfc-editor.org/info/rfc3540>. <https://www.rfc-editor.org/info/rfc3540>.
[RFC3649] Floyd, S., "HighSpeed TCP for Large Congestion Windows", [RFC3649] Floyd, S., "HighSpeed TCP for Large Congestion Windows",
skipping to change at page 45, line 23 skipping to change at page 44, line 28
<https://www.rfc-editor.org/info/rfc9000>. <https://www.rfc-editor.org/info/rfc9000>.
[RFC9113] Thomson, M., Ed. and C. Benfield, Ed., "HTTP/2", RFC 9113, [RFC9113] Thomson, M., Ed. and C. Benfield, Ed., "HTTP/2", RFC 9113,
DOI 10.17487/RFC9113, June 2022, DOI 10.17487/RFC9113, June 2022,
<https://www.rfc-editor.org/info/rfc9113>. <https://www.rfc-editor.org/info/rfc9113>.
[SCReAM] Johansson, I., "SCReAM", GitHub repository; , [SCReAM] Johansson, I., "SCReAM", GitHub repository; ,
<https://github.com/EricssonResearch/scream/blob/master/ <https://github.com/EricssonResearch/scream/blob/master/
README.md>. README.md>.
[TCP-CA] Jacobson, V. and M.J. Karels, "Congestion Avoidance and [TCP-CA] Jacobson, V. and M. Karels, "Congestion Avoidance and
Control", Laurence Berkeley Labs Technical Report , Control", Laurence Berkeley Labs Technical Report ,
November 1988, <https://ee.lbl.gov/papers/congavoid.pdf>. November 1988, <https://ee.lbl.gov/papers/congavoid.pdf>.
[UnorderedLTE] [UnorderedLTE]
Austrheim, M.V., "Implementing immediate forwarding for 4G Austrheim, M., "Implementing immediate forwarding for 4G
in a network simulator", Master's Thesis, Uni Oslo , June in a network simulator", Master's Thesis, Uni Oslo , June
2019. 2019.
Acknowledgements Acknowledgements
Thanks to Richard Scheffenegger, Wes Eddy, Karen Nielsen, David Thanks to Richard Scheffenegger, Wes Eddy, Karen Nielsen, David
Black, Jake Holland, Vidhi Goel, Ermin Sakic, Praveen Black, Jake Holland, Vidhi Goel, Ermin Sakic, Praveen
Balasubramanian, Gorry Fairhurst, Mirja Kuehlewind, Philip Eardley, Balasubramanian, Gorry Fairhurst, Mirja Kuehlewind, Philip Eardley,
Neal Cardwell, Pete Heist and Martin Duke for their useful review Neal Cardwell, Pete Heist and Martin Duke for their useful review
comments. Thanks also to the area reviewers: Marco Tiloca, Lars comments. Thanks also to the area reviewers: Marco Tiloca, Lars
skipping to change at page 46, line 4 skipping to change at page 45, line 8
Bob Briscoe and Koen De Schepper were part-funded by the European Bob Briscoe and Koen De Schepper were part-funded by the European
Community under its Seventh Framework Programme through the Reducing Community under its Seventh Framework Programme through the Reducing
Internet Transport Latency (RITE) project (ICT-317700). The Internet Transport Latency (RITE) project (ICT-317700). The
contribution of Koen De Schepper was also part-funded by the 5Growth contribution of Koen De Schepper was also part-funded by the 5Growth
and DAEMON EU H2020 projects. Bob Briscoe was also part-funded by and DAEMON EU H2020 projects. Bob Briscoe was also part-funded by
the Research Council of Norway through the TimeIn project, partly by the Research Council of Norway through the TimeIn project, partly by
CableLabs and partly by the Comcast Innovation Fund. The views CableLabs and partly by the Comcast Innovation Fund. The views
expressed here are solely those of the authors. expressed here are solely those of the authors.
Authors' Addresses Authors' Addresses
Bob Briscoe (editor) Bob Briscoe (editor)
Independent Independent
United Kingdom UK
Email: ietf@bobbriscoe.net Email: ietf@bobbriscoe.net
URI: https://bobbriscoe.net/ URI: https://bobbriscoe.net/
Koen De Schepper Koen De Schepper
Nokia Bell Labs Nokia Bell Labs
Antwerp Antwerp
Belgium Belgium
Email: koen.de_schepper@nokia.com
URI: https://www.bell-labs.com/about/researcher-profiles/ Email: koen.de_schepper@nokia.com
koende_schepper/ URI: https://www.bell-labs.com/about/researcher-profiles/koende_schepper/
Marcelo Bagnulo Marcelo Bagnulo
Universidad Carlos III de Madrid Universidad Carlos III de Madrid
Av. Universidad 30 Av. Universidad 30
Leganes, Madrid 28911 Leganes, Madrid 28911
Spain Spain
Phone: 34 91 6249500 Phone: 34 91 6249500
Email: marcelo@it.uc3m.es Email: marcelo@it.uc3m.es
URI: https://www.it.uc3m.es URI: https://www.it.uc3m.es
Greg White Greg White
CableLabs CableLabs
United States of America US
Email: G.White@CableLabs.com Email: G.White@CableLabs.com
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