[pfSense Support] Strange TCP connection behavior 2.0 RC2 (+3)

PC paul4004 at gmail.com
Tue Jun 28 20:24:59 UTC 2011

I have found most/all modern 3g networks can achieve optimal download speed
within their latency limitations (<200ms domestic end-to-end is normal for
most today) when combined with a modern operating system that does automatic
TCP receive window adjustments based on per-flow characteristics.  I never
had a problem getting ~2 megabit from EVDO-revA, and can get ~20 megabit
without issue from the new Verizon LTE network.  (Windows XP is not modern).

As for VSAT, most every vsat equipment manufacturer has TCP
acceleration/proxy support built into the satellite modem.  They basically
forge acks at the hub site to buffer data from the server, then deliver it
it to the remote end in a continuous flow.  Many also have protocol
optimizations for some of the more "chatty" protocols.  If you use it, your
10 megabit should be achievable for typical HTTP/FTP consumer internet
activities, and it's surprisingly fast.  I've sustained 6 without issue on
VSAT, only limited by bandwidth available, doing a simple SCP file transfer.

Of course, none of this is to the scale of transatlantic gigabit transfers
with a single flow...

On Tue, Jun 28, 2011 at 10:16 AM, Cameron Byrne <cb.list6 at gmail.com> wrote:

> On Tue, Jun 28, 2011 at 9:11 AM, Leigh Porter
> <leigh.porter at ukbroadband.com> wrote:
> >
> >
> >> -----Original Message-----
> >> From: Cameron Byrne [mailto:cb.list6 at gmail.com]
> >> Sent: 28 June 2011 16:53
> >> To: Leigh Porter
> >> Cc: Andreas Ott; Eugen Leitl; williamejsalt at googlemail.com; NANOG list
> >> Subject: Re: [pfSense Support] Strange TCP connection behavior 2.0 RC2
> >> (+3)
> >> In the 3G world, i have had good results overcoming longish RTT by
> >> using the Hybla TCP algorithm  http://hybla.deis.unibo.it/
> >>
> >> I am hoping it gets more default traction, especially in wireless
> >> where the radio link is a pretty big latency source
> >>
> >> Cameron
> >
> > How do you implement this for lots of clients and servers that have out
> of the box implementations? The FastSoft box is a TCP man-in-the-middle box
> that essentially implements the FAST TCP algorithm without either end having
> to worry about it.
> >
> You don't, the full benefits only come with a Linux kernel patch.  The
> good news is that it only has to be implemented on the client end.
> > I have also used home-fudged TCP proxies with some success.
> >
> > Some 3G/wireless/VSAT vendors implement their own TCP modification stacks
> but they usually only fiddle with window sizes and such.
> >
> That's why i said i hope it catches on as default :)  If Android
> implemented Hybla, i think it would be a great improvement for user
> experience.  Nobody likes the middleboxes that proxy TCP.... they cost
> money, don't scale well, and are generally fragile.  Hybla is not a
> solution for the OPs issue, just a solution for high RTT links where
> the client can do Hybla.  It an evolutionary step that i think would
> make a great fit in smartphones like Android.
> Cameron
> > --
> > Leigh
> >
> >
> > ______________________________________________________________________
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