On Tue, Jun 28, 2011 at 1:24 PM, PC <paul4004@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@gmail.com> wrote:
On Tue, Jun 28, 2011 at 9:11 AM, Leigh Porter <leigh.porter@ukbroadband.com> wrote:
-----Original Message----- From: Cameron Byrne [mailto:cb.list6@gmail.com] Sent: 28 June 2011 16:53 To: Leigh Porter Cc: Andreas Ott; Eugen Leitl; williamejsalt@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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