Date: Fri, 13 Nov 2009 11:16:56 +0100 From: Gary Jennejohn <gary.jennejohn@freenet.de> To: Sean Hamilton <sh@bel.bc.ca> Cc: freebsd-hackers@freebsd.org Subject: Re: NUMA support; tweaking TCP for GPRS Message-ID: <20091113111656.5dd3beaa@ernst.jennejohn.org> In-Reply-To: <20091113020835.GE12442@visor.slugabed.org> References: <20091113020835.GE12442@visor.slugabed.org>
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On Thu, 12 Nov 2009 18:08:35 -0800 Sean Hamilton <sh@bel.bc.ca> wrote: > Second, I am using a FreeBSD server to talk to equipment > which has a GPRS internet connection. This is fairly high > latency (approximately one second RTT) and is prone to > bursts of packet loss, or bursts of extremely high latency > -- perhaps up to a minute. These intervals cause many > retransmissions, which I presume is a good strategy over the > internet, but not so good for GPRS. > > For my application, latency is mostly irrelevant. However, > data over GPRS is very expensive, so I would like to reduce > as much as possible the number of TCP retransmissions made > on the FreeBSD side, possibly at the expense of latency. > > So, I am looking for suggestions on how to achieve this, via > sysctl, setsockopt, etc. There seems to be a lot of > literature regarding TCP tuning, but usually the focus is on > improving performance, not reducing network traffic. The > "rexmit_min" and "rexmit_sop" sysctls mentioned in tcp(4) > seem interesting, but it's not clear to me exactly how they > might be adjusted for this purpose. > > Thanks in advance, > Highjacking this thread. This won't help you, but it would be interesting to have the new Delay Tolerant Networking protocol developed by Vint Cerf for NASA in FreeBSD. Supposedly it's already in Android. --- Gary Jennejohn
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