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[tcpm] ACK aggregation and congestion window growth

Ingemar Johansson S <ingemar.s.johansson@ericsson.com> Fri, 26 April 2019 13:46 UTC

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From: Ingemar Johansson S <ingemar.s.johansson@ericsson.com>
To: "tcpm@ietf.org" <tcpm@ietf.org>
CC: Ingemar Johansson S <ingemar.s.johansson@ericsson.com>
Thread-Topic: ACK aggregation and congestion window growth
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Date: Fri, 26 Apr 2019 13:46:37 +0000
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Subject: [tcpm] ACK aggregation and congestion window growth
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Hi

 

I am experimenting with a simple test setup with 2 Ubuntu 18.04 PCs (Cubic
CC). 

Between these two I have a simple setup that aggregates ACKs so that they
are forwarded to the server only every 10ms. The min RTT is 18ms. 

The problem I see is that even though I should reach 1Gbps throughput, I
only get around 200Mbps. 

I would believe that the congestion window should eventually increase enough
to handle the burstiness given by the ACK aggregation but it seems like this
is not the case. 

Is there a limitation in the Linux stack that prevents congestion window
growth when ACKs arrive in bursts like this ? 

 

/Ingemar

==================================

Ingemar Johansson  M.Sc. 

Master Researcher

 

Ericsson Research

Network Protocols & E2E Performance

Labratoriegränd 11

971 28, Luleå, Sweden

Phone +46-1071 43042

SMS/MMS +46-73 078 3289

ingemar.s.johansson@ericsson.com

www.ericsson.com

 

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