O2 GPRS Compression

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peter.tobin@gmail.com - 29 Apr 2006 18:54 GMT

Hi, I am using O2 GPRS via a data cable or Bluetooth to connect my
laptop to the Internet while I have been travelling. There is
obviously something going on as the pictures on many of the websites
appear blurry and the download speeds I get are over 200kbps via
bandwidthplace.com. I can view the non-blurry images but I have to put
my mouse on the image and press alt and R or something similar.

Could someone tell me what is going on here? Do O2 have some automatic
server side compression running or something like that? If so, I
assume something like Onspeed would be a waste of time.

Thanks in advance.

Pete

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Jon - 29 Apr 2006 22:32 GMT

peter.tobin@gmail.com declared for all the world to hear...

> Hi, I am using O2 GPRS via a data cable or Bluetooth to connect my
> laptop to the Internet while I have been travelling. There is
[quoted text clipped - 6 lines]
> server side compression running or something like that? If so, I
> assume something like Onspeed would be a waste of time.

You are correct in all of your assumptions. Jpeg compression is common
with mobile networks data offerings, Orange and Vodafone do it for sure.

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Regards
Jon

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Taylor - 30 Apr 2006 00:27 GMT

> peter.tobin@gmail.com declared for all the world to hear...
>> Hi, I am using O2 GPRS via a data cable or Bluetooth to connect my
[quoted text clipped - 10 lines]
> You are correct in all of your assumptions. Jpeg compression is common
> with mobile networks data offerings, Orange and Vodafone do it for sure.

I've personally had mixed experiences with o2 GPRS; one APN didn't compress
anything, the other did. To be honest with teh amoutn of pointless graphics
on (non-compliant!) websites these days I think it's a good thing.

Another wee point, your phone may have an option for 'enable GPRS
compression', which will not affect pictures, but can reduce your bandwidth
usage; and I found that to be the case when I enabled it. Also enable IP
header compression, but the effects of that may be minor, depending on your
usage.

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Peter - 30 Apr 2006 10:53 GMT

>Hi, I am using O2 GPRS via a data cable or Bluetooth to connect my
>laptop to the Internet while I have been travelling. There is
[quoted text clipped - 6 lines]
>server side compression running or something like that? If so, I
>assume something like Onspeed would be a waste of time.

Have a look at

http://www.peter2000.co.uk/gprs/gprs.html

It applies to Vodafone but I think most of the GPRS networks implement
some sort of image compression on their www gateways.

As I explain in that link, you can circumvent it by using a 3rd party
data compression service (Onspeed in my case) which, as a result of
doing compression, hides the content from the GPRS provider's www
gateway so the NP is unable to do any compression.

IMHO everybody on GPRS should be using Onspeed (or similar) as the
cost savings are likely to far outweigh the cost of Onspeed, and you
get the added benefit of having decent control on how much image
quality you are willing to chuck away, versus the compression level.

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Soruk - 30 Apr 2006 11:27 GMT

>IMHO everybody on GPRS should be using Onspeed (or similar) as the
>cost savings are likely to far outweigh the cost of Onspeed, and you
>get the added benefit of having decent control on how much image
>quality you are willing to chuck away, versus the compression level.

Most of my net use is outside of a browser (email, remote logins), so for
that SSH tunnelling with maximum compression is a big win for me. Though,
tunnelling WWW with graphics would also cause the graphics recompression
to be missed, so wouldn't be such a good idea.

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Peter - 30 Apr 2006 11:39 GMT

>Most of my net use is outside of a browser (email, remote logins), so for
>that SSH tunnelling with maximum compression is a big win for me. Though,
>tunnelling WWW with graphics would also cause the graphics recompression
>to be missed, so wouldn't be such a good idea.

True; however to run SSH (or any other sort of VPN) youneed a gateway
to connect to. Presumably you are connecting to a server at your place
of work or at home.

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peter.tobin@gmail.com - 30 Apr 2006 12:33 GMT

Thanks for the input guys. Looks like Onspeed or something similar may
be worth looking at especially as I use GPRS for VPN access as well
rather than just WWW. I don't pay per MB for my GPRS as I have a
corporate bundle deal, from an end user perspective does the
performance improvement over Onspeed outweigh the bursty nature of the
transmission? I have been trying the Google Web Accelerator on my home
broadband connection and I find that quite annoying at times and have
switched it off.

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peter.tobin@gmail.com - 30 Apr 2006 12:50 GMT

Sorry it's a Sunday morning. It obviously won't speed up VPN traffic
as it can't see it!

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Peter - 30 Apr 2006 14:12 GMT

>from an end user perspective does the
>performance improvement over Onspeed outweigh the bursty nature of the
>transmission?

Definitely, IME. But it depends on the data. I download aviation
weather charts, so an extra minute and then suddenly getting the whole
page pop up doesn't matter.

As for stuff which bored businessmen might be doing in their hotel
rooms on GPRS (why else would one want a 1GB monthly allowance? :) )
probably not :)

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