draft-ietf-rmcat-coupled-cc-08.txt   draft-ietf-rmcat-coupled-cc-09.txt 
RTP Media Congestion Avoidance Techniques (rmcat) S. Islam RTP Media Congestion Avoidance Techniques (rmcat) S. Islam
Internet-Draft M. Welzl Internet-Draft M. Welzl
Intended status: Experimental S. Gjessing Intended status: Experimental S. Gjessing
Expires: July 14, 2019 University of Oslo Expires: February 23, 2020 University of Oslo
January 10, 2019 August 22, 2019
Coupled congestion control for RTP media Coupled congestion control for RTP media
draft-ietf-rmcat-coupled-cc-08 draft-ietf-rmcat-coupled-cc-09
Abstract Abstract
When multiple congestion controlled Real-time Transport Protocol When multiple congestion controlled Real-time Transport Protocol
(RTP) sessions traverse the same network bottleneck, combining their (RTP) sessions traverse the same network bottleneck, combining their
controls can improve the total on-the-wire behavior in terms of controls can improve the total on-the-wire behavior in terms of
delay, loss and fairness. This document describes such a method for delay, loss and fairness. This document describes such a method for
flows that have the same sender, in a way that is as flexible and flows that have the same sender, in a way that is as flexible and
simple as possible while minimizing the amount of changes needed to simple as possible while minimizing the amount of changes needed to
existing RTP applications. It specifies how to apply the method for existing RTP applications. It specifies how to apply the method for
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This Internet-Draft will expire on July 14, 2019. This Internet-Draft will expire on February 23, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Architectural overview . . . . . . . . . . . . . . . . . . . 5 4. Architectural overview . . . . . . . . . . . . . . . . . . . 5
5. Roles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Roles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. SBD . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. SBD . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.2. FSE . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.2. FSE . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.3. Flows . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.3. Flows . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.3.1. Example algorithm 1 - Active FSE . . . . . . . . . . 9 5.3.1. Example algorithm 1 - Active FSE . . . . . . . . . . 9
5.3.2. Example algorithm 2 - Conservative Active FSE . . . . 11 5.3.2. Example algorithm 2 - Conservative Active FSE . . . . 10
6. Application . . . . . . . . . . . . . . . . . . . . . . . . . 11 6. Application . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1. NADA . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6.1. NADA . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.2. General recommendations . . . . . . . . . . . . . . . . . 12 6.2. General recommendations . . . . . . . . . . . . . . . . . 11
7. Expected feedback from experiments . . . . . . . . . . . . . 12 7. Expected feedback from experiments . . . . . . . . . . . . . 12
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10. Security Considerations . . . . . . . . . . . . . . . . . . . 13 10. Security Considerations . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
11.1. Normative References . . . . . . . . . . . . . . . . . . 14 11.1. Normative References . . . . . . . . . . . . . . . . . . 13
11.2. Informative References . . . . . . . . . . . . . . . . . 14 11.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Application to GCC . . . . . . . . . . . . . . . . . 16 Appendix A. Application to GCC . . . . . . . . . . . . . . . . . 16
Appendix B. Scheduling . . . . . . . . . . . . . . . . . . . . . 16 Appendix B. Scheduling . . . . . . . . . . . . . . . . . . . . . 16
Appendix C. Example algorithm - Passive FSE . . . . . . . . . . 16 Appendix C. Example algorithm - Passive FSE . . . . . . . . . . 16
C.1. Example operation (passive) . . . . . . . . . . . . . . . 19 C.1. Example operation (passive) . . . . . . . . . . . . . . . 19
Appendix D. Change log . . . . . . . . . . . . . . . . . . . . . 23 Appendix D. Change log . . . . . . . . . . . . . . . . . . . . . 23
D.1. draft-welzl-rmcat-coupled-cc . . . . . . . . . . . . . . 23 D.1. draft-welzl-rmcat-coupled-cc . . . . . . . . . . . . . . 23
D.1.1. Changes from -00 to -01 . . . . . . . . . . . . . . . 23 D.1.1. Changes from -00 to -01 . . . . . . . . . . . . . . . 23
D.1.2. Changes from -01 to -02 . . . . . . . . . . . . . . . 23 D.1.2. Changes from -01 to -02 . . . . . . . . . . . . . . . 23
D.1.3. Changes from -02 to -03 . . . . . . . . . . . . . . . 23 D.1.3. Changes from -02 to -03 . . . . . . . . . . . . . . . 23
D.1.4. Changes from -03 to -04 . . . . . . . . . . . . . . . 24 D.1.4. Changes from -03 to -04 . . . . . . . . . . . . . . . 24
D.1.5. Changes from -04 to -05 . . . . . . . . . . . . . . . 24 D.1.5. Changes from -04 to -05 . . . . . . . . . . . . . . . 24
D.2. draft-ietf-rmcat-coupled-cc . . . . . . . . . . . . . . . 24 D.2. draft-ietf-rmcat-coupled-cc . . . . . . . . . . . . . . . 24
D.2.1. Changes from draft-welzl-rmcat-coupled-cc-05 . . . . 24 D.2.1. Changes from draft-welzl-rmcat-coupled-cc-05 . . . . 24
D.2.2. Changes from -00 to -01 . . . . . . . . . . . . . . . 24 D.2.2. Changes from -00 to -01 . . . . . . . . . . . . . . . 24
D.2.3. Changes from -01 to -02 . . . . . . . . . . . . . . . 24 D.2.3. Changes from -01 to -02 . . . . . . . . . . . . . . . 24
D.2.4. Changes from -02 to -03 . . . . . . . . . . . . . . . 24 D.2.4. Changes from -02 to -03 . . . . . . . . . . . . . . . 24
D.2.5. Changes from -03 to -04 . . . . . . . . . . . . . . . 25 D.2.5. Changes from -03 to -04 . . . . . . . . . . . . . . . 24
D.2.6. Changes from -04 to -05 . . . . . . . . . . . . . . . 25 D.2.6. Changes from -04 to -05 . . . . . . . . . . . . . . . 25
D.2.7. Changes from -05 to -06 . . . . . . . . . . . . . . . 25 D.2.7. Changes from -05 to -06 . . . . . . . . . . . . . . . 25
D.2.8. Changes from -06 to -07 . . . . . . . . . . . . . . . 25 D.2.8. Changes from -06 to -07 . . . . . . . . . . . . . . . 25
D.2.9. Changes from -07 to -08 . . . . . . . . . . . . . . . 25 D.2.9. Changes from -07 to -08 . . . . . . . . . . . . . . . 25
D.2.10. Changes from -08 to -09 . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25
1. Introduction 1. Introduction
When there is enough data to send, a congestion controller attempts When there is enough data to send, a congestion controller attempts
to increase its sending rate until the path's capacity has been to increase its sending rate until the path's capacity has been
reached. Some controllers detect path capacity by increasing the reached. Some controllers detect path capacity by increasing the
sending rate further, until packets are ECN-marked [RFC8087] or sending rate further, until packets are ECN-marked [RFC8087] or
dropped, and then decreasing the sending rate until that stops dropped, and then decreasing the sending rate until that stops
happening. This process inevitably creates undesirable queuing delay happening. This process inevitably creates undesirable queuing delay
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o P(f) - The priority of flow f which is received from the flow's o P(f) - The priority of flow f which is received from the flow's
congestion controller; the FSE uses this variable for calculating congestion controller; the FSE uses this variable for calculating
FSE_R(f). FSE_R(f).
o S_P - The sum of all the priorities. o S_P - The sum of all the priorities.
o TLO - The total leftover rate: the sum of rates that could not be o TLO - The total leftover rate: the sum of rates that could not be
assigned to flows that were limited by their desired rate. assigned to flows that were limited by their desired rate.
o S_P2 - The sum of all the priorities of flows to which a share of o AR - The aggregate rate that is assigned to flows that are not
the TLO can be assigned. limited by their desired rate.
5.3.1. Example algorithm 1 - Active FSE 5.3.1. Example algorithm 1 - Active FSE
This algorithm was designed to be the simplest possible method to This algorithm was designed to be the simplest possible method to
assign rates according to the priorities of flows. Simulations assign rates according to the priorities of flows. Simulations
results in [fse] indicate that it does however not significantly results in [fse] indicate that it does however not significantly
reduce queuing delay and packet loss. reduce queuing delay and packet loss.
(1) When a flow f starts, it registers itself with SBD and the FSE. (1) When a flow f starts, it registers itself with SBD and the FSE.
FSE_R(f) is initialized with the congestion controller's initial FSE_R(f) is initialized with the congestion controller's initial
rate. SBD will assign the correct FGI. When a flow is assigned rate. SBD will assign the correct FGI. When a flow is assigned
an FGI, it adds its FSE_R(f) to S_CR. an FGI, it adds its FSE_R(f) to S_CR.
(2) When a flow f stops or pauses, its entry is removed from the (2) When a flow f stops or pauses, its entry is removed from the
list. list.
(3) Every time the congestion controller of the flow f determines a (3) Every time the congestion controller of the flow f determines a
new sending rate CC_R(f), the flow calls UPDATE, which carries new sending rate CC_R(f), the flow calls UPDATE, which carries
out the tasks listed below to derive the new sending rates for out the tasks listed below to derive the new sending rates for
all the flows in the FG. A flow's UPDATE function uses three all the flows in the FG. A flow's UPDATE function uses three
local (i.e. per-flow) temporary variables: S_P, TLO and S_P2. local (i.e. per-flow) temporary variables: S_P, TLO and AR.
(a) It updates S_CR. (a) It updates S_CR.
S_CR = S_CR + CC_R(f) - FSE_R(f) S_CR = S_CR + CC_R(f) - FSE_R(f)
(b) It calculates the sum of all the priorities, S_P. (b) It calculates the sum of all the priorities, S_P, and
initializes FSE_R.
S_P = 0 S_P = 0
for all flows i in FG do for all flows i in FG do
S_P = S_P + P(i) S_P = S_P + P(i)
FSE_R(i) = 0
end for end for
(c) It calculates the sending rates for all the flows in an FG, (c) It distributes S_CR among all flows, ensuring that each
the total leftover rate (TLO) from flows that are limited flow's desired rate is not exceeded.
by their desired rate, and the sum of the priorities of all
other flows, S_P2.
TLO = 0
S_P2 = 0
for all flows i in FG do
FSE_R(i) = P(i) * S_CR /S_P
if FSE_R(i) >= DR(i) then
TLO = TLO + FSE_R(i) - DR(i)
FSE_R(i) = DR(i)
else
S_P2 = S_P2 + P(i)
end if
end for
(d) It checks if there are flows that are limited by their DR
and cannot accept their share of the TLO, and updates TLO
and S_P2 accordingly.
for all flows i in FG do TLO = S_CR
if FSE_R(i) < DR(i) then while(TLO-AR>0 and S_P>0)
if FSE_R(i) + TLO * P(i) / S_P2 > DR(i) then AR = 0
TLO = TLO - ( DR(i) - FSE_R(i) ) for all flows i in FG do
FSE_R(i) = DR(i) if FSE_R[i] < DR[i] then
S_P2 = S_P2 - P(i) if TLO * P[i] / S_P >= DR[i] then
TLO = TLO - DR[i]
FSE_R[i] = DR[i]
S_P = S_P - P[i]
else
FSE_R[i] = TLO * P[i] / S_P
AR = AR + TLO * P[i] / S_P
end if
end if end if
end if end for
end for end while
(e) It assigns the non-limited flow their share of the total (d) It distributes FSE_R to all the flows.
leftover rate and sends all the rates to all the flows.
for all flows i in FG do for all flows i in FG do
if FSE_R(i) < DR(i) then
FSE_R(i) = FSE_R(i) + P(i) * TLO / S_P2
end if
send FSE_R(i) to the flow i send FSE_R(i) to the flow i
end for end for
5.3.2. Example algorithm 2 - Conservative Active FSE 5.3.2. Example algorithm 2 - Conservative Active FSE
This algorithm changes algorithm 1 to conservatively emulate the This algorithm changes algorithm 1 to conservatively emulate the
behavior of a single flow by proportionally reducing the aggregate behavior of a single flow by proportionally reducing the aggregate
rate on congestion. Simulations results in [fse] indicate that it rate on congestion. Simulations results in [fse] indicate that it
can significantly reduce queuing delay and packet loss. can significantly reduce queuing delay and packet loss.
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testers are invited to document their findings in an Internet draft. testers are invited to document their findings in an Internet draft.
8. Acknowledgements 8. Acknowledgements
This document has benefitted from discussions with and feedback from This document has benefitted from discussions with and feedback from
Andreas Petlund, Anna Brunstrom, Colin Perkins, David Hayes, David Andreas Petlund, Anna Brunstrom, Colin Perkins, David Hayes, David
Ros (who also gave the FSE its name), Ingemar Johansson, Karen Ros (who also gave the FSE its name), Ingemar Johansson, Karen
Nielsen, Kristian Hiorth, Mirja Kuehlewind, Martin Stiemerling, Nielsen, Kristian Hiorth, Mirja Kuehlewind, Martin Stiemerling,
Spencer Dawkins, Varun Singh, Xiaoqing Zhu, and Zaheduzzaman Sarker. Spencer Dawkins, Varun Singh, Xiaoqing Zhu, and Zaheduzzaman Sarker.
The authors would like to especially thank Xiaoqing Zhu and Stefan The authors would like to especially thank Xiaoqing Zhu and Stefan
Holmer for helping with NADA and GCC, and Julius Flohr for helping us Holmer for helping with NADA and GCC, and Anna Brunstrom as well as
correct the active algorithm for the case of application-limited Julius Flohr for helping us correct the active algorithm for the case
flows. of application-limited flows.
This work was partially funded by the European Community under its This work was partially funded by the European Community under its
Seventh Framework Programme through the Reducing Internet Transport Seventh Framework Programme through the Reducing Internet Transport
Latency (RITE) project (ICT-317700). Latency (RITE) project (ICT-317700).
9. IANA Considerations 9. IANA Considerations
This memo includes no request to IANA. This memo includes no request to IANA.
10. Security Considerations 10. Security Considerations
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Implementers should also be aware of the Security Considerations Implementers should also be aware of the Security Considerations
sections of [RFC3124], [RFC5348], and [RFC7478]. sections of [RFC3124], [RFC5348], and [RFC7478].
11. References 11. References
11.1. Normative References 11.1. Normative References
[I-D.ietf-rmcat-nada] [I-D.ietf-rmcat-nada]
Zhu, X., *, R., Ramalho, M., Cruz, S., Jones, P., Fu, J., Zhu, X., *, R., Ramalho, M., Cruz, S., Jones, P., Fu, J.,
and S. D'Aronco, "NADA: A Unified Congestion Control and S. D'Aronco, "NADA: A Unified Congestion Control
Scheme for Real-Time Media", draft-ietf-rmcat-nada-09 Scheme for Real-Time Media", draft-ietf-rmcat-nada-11
(work in progress), August 2018. (work in progress), July 2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3124] Balakrishnan, H. and S. Seshan, "The Congestion Manager", [RFC3124] Balakrishnan, H. and S. Seshan, "The Congestion Manager",
RFC 3124, DOI 10.17487/RFC3124, June 2001, RFC 3124, DOI 10.17487/RFC3124, June 2001,
<https://www.rfc-editor.org/info/rfc3124>. <https://www.rfc-editor.org/info/rfc3124>.
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2014. 2014.
[fse-noms] [fse-noms]
Islam, S., Welzl, M., Hayes, D., and S. Gjessing, Islam, S., Welzl, M., Hayes, D., and S. Gjessing,
"Managing Real-Time Media Flows through a Flow State "Managing Real-Time Media Flows through a Flow State
Exchange", IEEE NOMS 2016, Istanbul, Turkey , 2016. Exchange", IEEE NOMS 2016, Istanbul, Turkey , 2016.
[I-D.ietf-rmcat-eval-test] [I-D.ietf-rmcat-eval-test]
Sarker, Z., Singh, V., Zhu, X., and M. Ramalho, "Test Sarker, Z., Singh, V., Zhu, X., and M. Ramalho, "Test
Cases for Evaluating RMCAT Proposals", draft-ietf-rmcat- Cases for Evaluating RMCAT Proposals", draft-ietf-rmcat-
eval-test-08 (work in progress), November 2018. eval-test-10 (work in progress), May 2019.
[I-D.ietf-rmcat-gcc] [I-D.ietf-rmcat-gcc]
Holmer, S., Lundin, H., Carlucci, G., Cicco, L., and S. Holmer, S., Lundin, H., Carlucci, G., Cicco, L., and S.
Mascolo, "A Google Congestion Control Algorithm for Real- Mascolo, "A Google Congestion Control Algorithm for Real-
Time Communication", draft-ietf-rmcat-gcc-02 (work in Time Communication", draft-ietf-rmcat-gcc-02 (work in
progress), July 2016. progress), July 2016.
[I-D.ietf-rtcweb-overview] [I-D.ietf-rtcweb-overview]
Alvestrand, H., "Overview: Real Time Protocols for Alvestrand, H., "Overview: Real Time Protocols for
Browser-based Applications", draft-ietf-rtcweb-overview-19 Browser-based Applications", draft-ietf-rtcweb-overview-19
skipping to change at page 25, line 42 skipping to change at page 25, line 35
D.2.8. Changes from -06 to -07 D.2.8. Changes from -06 to -07
o Addressed OPSDIR, SECDIR, GENART, AD and IESG comments. o Addressed OPSDIR, SECDIR, GENART, AD and IESG comments.
D.2.9. Changes from -07 to -08 D.2.9. Changes from -07 to -08
o Updated the algorithms in section 5 to support application-limited o Updated the algorithms in section 5 to support application-limited
flows. Moved definition of Desired Rate from appendix to section flows. Moved definition of Desired Rate from appendix to section
5. Updated references. 5. Updated references.
D.2.10. Changes from -08 to -09
o Minor improvement of the algorithms in section 5.
Authors' Addresses Authors' Addresses
Safiqul Islam Safiqul Islam
University of Oslo University of Oslo
PO Box 1080 Blindern PO Box 1080 Blindern
Oslo N-0316 Oslo N-0316
Norway Norway
Phone: +47 22 84 08 37 Phone: +47 22 84 08 37
Email: safiquli@ifi.uio.no Email: safiquli@ifi.uio.no
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