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

Cameron Byrne cb.list6 at gmail.com
Tue Jun 28 15:35:16 CDT 2011


On Tue, Jun 28, 2011 at 1:24 PM, PC <paul4004 at gmail.com> wrote:
> 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).
>

AFAIK, Verizon and all the other 4 largest mobile networks in the USA
have transparent TCP proxies in place.

My point was that if end-hosts had Hybla or something similar, these
proxies can be removed providing a better end-to-end solution.

Cameron

> 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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>> >
>>
>
>




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