Argh, I just realized that some of my email is bogus. I was thinking that
the MSS was much larger than what you using (or even your 64K trick), not simply
roughly 10x. At that point it becomes more an issue of using a larger but still
reasonable granularity chunk. It would still scare people running it
onto a hybrid network such as the greater Internet or even busy LAN
(which has a surprisingly terrible effect on your sat bandwidth from my
experience) on one end for classical reasons as already mentioned. But
for a private network satellite hookup, it's more viable as a tuning
option given the bandwidth you're playing with. Interesting...
Charlie
Charlie Younghusband wrote:
It does not surprise me that you received performance gains. Looking
at
the simple single connection over an uncongested direct satellite link
as
part of another project I worked on, we did a simple mathematical
formula
where we asked how low does the BER have to go before the largest (RFC
compliant) TCP MSS size available was no longer optimal, and factoring
in
header overhead the answer was ridiculously low (like 10e-3). By
extension, it was clear that a larger MSS was much more efficient on the
higher bandwidth links seen today. I'm not sure where you got the 16208
MSS
size, but I suspect that it is link bandwidth specific and if for some
reason your bandwidth was seriously suddenly reduced (such as a
competing
data stream) you'd suddenly have virtually no bandwidth available to
either
data stream as neither would complete a TCP segment very often. Still,
it
is an interesting tuning idea for a single TCP connection over a
satellite
link with no other competition when the bandwidth is known and
fixed. Other
than that case, things fall apart quickly as there is poor scaling and
little adaption. As Gorry Fairhurst pointed out, run it with anything
else
and then see. There are other better options. (I'll also point out that
you're still only at best about 73% link efficiency with your
modifications,
so even if this specific case always applies to your usage, wasting over
2Mbps of satellite bandwidth probably won't please whoever pays for it
:))
Cheers,
Charlie
---
Charlie Younghusband
Network Software Engineering
Xiphos Technologies http://www.xiphos.ca/
514-848-9640
This archive was generated by hypermail 2b29 : Tue Aug 28 2001 - 03:27:25 EDT