Competitive Mode Enhancement for Delay-Based Congestion Control Algorithms
draft-zhao-iccrg-competitive-mode-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Author | Guangyu Zhao | ||
| Last updated | 2025-07-01 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
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draft-zhao-iccrg-competitive-mode-00
iccrg G. Zhao
Internet-Draft China Mobile
Intended status: Informational 1 July 2025
Expires: 2 January 2026
Competitive Mode Enhancement for Delay-Based Congestion Control
Algorithms
draft-zhao-iccrg-competitive-mode-00
Abstract
This document proposes introducing a "Competitive Mode" into delay-
based congestion control algorithms to improve their competitiveness
and fairness during coexistence scenarios.
Status of This Memo
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This Internet-Draft will expire on 2 January 2026.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introducing Competitive Mode into Delay-Based Congestion
Control Algorithms . . . . . . . . . . . . . . . . . . . 2
2.1. Method for Determining Competitive Mode . . . . . . . . . 2
2.2. Congestion Window Compensation in Competition Mode . . . 3
3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Copa with Competitive Mode . . . . . . . . . . . . . . . 3
3.2. Vegas with Competitive Mode . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . 3
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . 4
8.2. Informative References . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
Congestion control algorithms can be categorized into loss-based and
delay-based algorithms based on their congestion detection
mechanisms. Loss-based congestion control algorithms typically fill
the link buffer until packet loss occurs, then reduce the sending
rate. In contrast, delay-based congestion control algorithms
proactively reduce the sending rate when queuing delay increases.
Representative delay-based congestion control algorithms (e.g.,
Vegas[Vegas], FAST[FAST], Copa[Copa]) measure RTT or queuing delay,
calculate the expected throughput based on delay variations,
determine congestion, and adjust the congestion window size.
While delay-based algorithms generally exhibit lower packet loss
rates and smaller queuing delays than loss-based algorithms, they
fail to fairly share link bandwidth with loss-based algorithms (e.g.,
Cubic) when both types of traffic coexist.
2. Introducing Competitive Mode into Delay-Based Congestion Control
Algorithms
2.1. Method for Determining Competitive Mode
Determine whether the current flow is in a coexistence/competition
phase with Cubic traffic based on the magnitude of queuing delay
variation. The COPA provides a method to determine whether it is in
competitive mode.
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Specifically, upon receiving an ACK, the algorithm calculates the RTT
for each flow and maintains a historical minimum RTT value(min_rtt).
Based on RTT samples, it records the maximum(max_delay) and
minimum(min_delay) RTT values over a 4-RTT window. Competitive Mode
is triggered based on the following inequality.
min_delay < min_rtt + 0.1(max_delay - min_rtt) Formula 1
Here, max_delay and min_delay represent the maximum and minimum RTT
values within the last 4 RTT intervals, and min_rtt is the historical
minimum RTT. The difference between min_delay and min_rtt represents
the minimum queuing delay at the bottleneck link during this period,
while the difference between max_delay and min_rtt represents the
maximum queuing delay. If the inequality is not satisfied, it
indicates that the bottleneck link's queue has not emptied during
this period, suggesting likely competition from Cubic-like flows.
Consequently, the algorithm enters Competitive Mode. If the
inequality holds, the algorithm operates in Default Mode.
2.2. Congestion Window Compensation in Competition Mode
When the algorithm determines it is in Competition Mode, it
introduces an additional congestion window gain factor to moderately
increase the congestion window size.
TBD.
3. Examples
3.1. Copa with Competitive Mode
TBD.
3.2. Vegas with Competitive Mode
TBD.
4. IANA Considerations
TBD.
5. Security Considerations
TBD.
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6. Contributors
The following people have substantially contributed to this document:
Zhiqiang Li
lizhiqiangyjy@chinamobile.com
Hongwei Yang
yanghongwei@chinamoblie.com
7. Acknowledgements
TBD.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References
[Vegas] Brakmo, L., O'Malley, S., and L. Peterson, "TCP Vegas: New
Techniques for Congestion Detection and Avoidance", ACM
SIGCOMM Computer Communication Review 24.4(1994) , August
1994.
[FAST] Wei, D., Jin, C., and S. Low, "FAST TCP : motivation,
architecture, algorithms, performance", IEEE/ACM
Transactions on Networking 14(2006) , December 2006.
[Copa] Arun, V. and H. Hari, "Practical delay-based congestion
control for the internet", the Applied Networking Research
Workshop 2018. , April 2018.
[I-D.ietf-ccwg-bbr]
Cardwell, N., Swett, I., and J. Beshay, "BBR Congestion
Control", Work in Progress, Internet-Draft, draft-ietf-
ccwg-bbr-02, 28 February 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-ccwg-
bbr-02>.
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Author's Address
Guangyu Zhao
China Mobile
No.32 XuanWuMen West Street
Beijing
100053
China
Email: zhaoguangyu@chinamobile.com
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