[svlug] Reprise: Adjusting retransmission parameters

[Eric Nickell]

Jeffrey Siegal wrote:
> 
> There is really no way to get "good" performance from TCP with packet
> loss rates of 50%.  If you can maintain connectivity at all, you are
> doing well.  If your packet loss rate is really that bad, you will need
> to get Sprint to fix it, or just suffer.

I agree with you.  I don't expect to get anything done when the packet
losses are that high.  However, I'm currently stymied even when the
losses are 1-3% as my X window will stop responding to mouse click for
15 seconds or a minute.  It is this latter that I'd like to fix.

> Once you can reduce packet loss to a reasonable level, you'll probably
> get better performance over a high bandwidth, high latency connection
> when talking to systems that support the LFN extensions from RFC 1072.
> Linux does, but other systems don't.

I don't have control over the system that I'm connecting to.  That's why
I was trying to learn about things that I can change inside my Linux box
to improve the situation.

> My guess is that Sprint's connection is asymmetric.

I would agree.  Mostly, I'm guessing there are packet collisions on the
uplink, and none on the downlink.

> The performance you
> can get out of an asymmetric connection is limited by fundamental design
> weaknesses in TCP in dealing with such connections.  There have been
> some improvements proposed, but not widely implemented.  For more info
> on this, see
> http://www.ietf.org/internet-drafts/draft-ietf-pilc-asym-02.txt

In the meantime, is there no short-term relief?

Eric