[142515] in North American Network Operators' Group
RE: [pfSense Support] Strange TCP connection behavior 2.0 RC2 (+3)
daemon@ATHENA.MIT.EDU (Leigh Porter)
Wed Jun 29 10:45:21 2011
From: Leigh Porter <leigh.porter@ukbroadband.com>
To: Cameron Byrne <cb.list6@gmail.com>, Mikael Abrahamsson <swmike@swm.pp.se>
Date: Wed, 29 Jun 2011 14:45:12 +0000
In-Reply-To: <BANLkTi=YCgTvVZ3KWX6dtPJRu7obTeOujw@mail.gmail.com>
Cc: NANOG list <nanog@nanog.org>,
"williamejsalt@googlemail.com" <williamejsalt@googlemail.com>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
> >
> >
> > Well, then you run into the nice problem of the RNCs only having 400
> kilobytes of buffers per session and will drop packets if they receive
> more
> packets than that, or sometimes even just because they receive a burst
> of a
> few tens of packets at GigE linerate (because the customer with large
> TCP
> window size is talking to a GigE connected server).
> >
> > The recommended "solution" from the vendor was to tune the client to
> a
> smaller TCP window size so that their RNC wouldn't get such a large
> burst.
> >
> > *sigh*
> >
>=20
> Sounds like a vendor specific issue :(
>=20
> Good tcp vs default tcp will not close the window tight due to some
> ephemeral loss or delay. The penalties are generally too strong in tcp
> for
> the issues of delay and loss in 3g ... this is one of the main selling
> points for tcp proxies .... but better done with modern tcp on the
> clients
> instead of a middle box
Indeed it does sound like a vendor issue. The network I was running did ju=
st fine with the FastSoft proxy boxes. In fact, they were so effective tha=
t we almost doubled our TCP throughput overnight! We did not quite get a c=
hance to explore the interaction between the TCP proxies and the algorithm=
s that supposedly fixed TCP in the vendors GGSN (TCP window size fiddling)=
and the interaction of the new TCP protocol with the 3G base station sche=
duler, but the results kind of spoke for themselves really.
Similarly we have had good results with WiMAX networks.
--
Leigh Porter
UK Broadband
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