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World Community Grid Forums
Category: Retired Forums
Forum: Member-to-Member Support [Read Only]
Thread: Accessing grid server via GPRS |
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Thread Status: Active Total posts in this thread: 8
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davidhobbs
Senior Cruncher England Joined: Dec 30, 2004 Post Count: 151 Status: Offline Project Badges: 
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One of my devices is a laptop running XP-Pro, and it is normally connected to the internet by a wireless network connection to my ADSL router/firewall. When I'm away from home I use a Vodafone GPRS card to access the internet. I find the grid agent will happily send results to the grid server over GPRS but does not successfully receive a new work unit.
Normally the agent will report, for example, "receiving 1020 bytes of 345000 bytes; 2345 bytes of 345000; 4651 of 345000" and so on. However, when connected over GPRS the two figures are always the same, and increasing. So it looks something like "receiving 1020 bytes of 1020 bytes; 2345 of 2345; 4651 of 4651" and so on. Eventually, (typically at 1MB or so) the agent will report "Unable to process data - backing off". Is there an expert out there who can explain why this is so? Everything else seems to work fine over my GPRS link, if a little slowly. Thanks, David. |
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David Autumns
Ace Cruncher UK Joined: Nov 16, 2004 Post Count: 11062 Status: Offline Project Badges: 
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Hi David,
----------------------------------------There is a timeout on the download and I'm not sure that the 19.2K or thereabouts of a GPRS connection will be able to download sufficient data in time to beat the timeout. The timeout is there so that the client deliberately goes into back off mode (retrying after another timeout has expired) for the few occasions when the WCG is down or unreachable across the net. The second possibility is that you have something Like McAffee security suite on your laptop. I had a problem with McAffee parental controls with similar symptoms. Hope this helps. Could you let us know if we're on the right track. Regards Dave  |
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Viktors
Former World Community Grid Tech Joined: Sep 20, 2004 Post Count: 653 Status: Offline Project Badges: 
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One of the agent requirements to qualify for new work is to have at least a 28kbps Internet link. I bet your GPRS phone link might be apparently slower than that.
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davidhobbs
Senior Cruncher England Joined: Dec 30, 2004 Post Count: 151 Status: Offline Project Badges:
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Hmm,
It doesn't look like a timeout though, it seems to be more like indegestion! I'm not running McAffee but I do have Trend internet security running, although this has never caused me any issues before. Thanks, David. |
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davidhobbs
Senior Cruncher England Joined: Dec 30, 2004 Post Count: 151 Status: Offline Project Badges:
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Thanks,
I hadn't noticed the minimum speed requirement on the connection. My GPRS card always shows it has connected at 42Kbps, but I suspect being a packet system it does go much slower than this for much of the time. Perhaps you've identified the problem. Funny it always sends the results successfully though. No crunching when away from home then... David. |
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davidhobbs
Senior Cruncher England Joined: Dec 30, 2004 Post Count: 151 Status: Offline Project Badges:
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PROBLEM SOLVED!
You started me thinking about what else was running, and then I remembered the Macara client. This is a Vodafone-supplied optimisation tool that works by compressing data at the transmitting end and de-compressing at the receiving end. I disabled this and voila! So now I CAN go crunching away from home. Many thanks, David. |
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David Autumns
Ace Cruncher UK Joined: Nov 16, 2004 Post Count: 11062 Status: Offline Project Badges:
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Good news
----------------------------------------One for the note book for the future I think Thanks for the feedback Regards Dave |
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Viktors
Former World Community Grid Tech Joined: Sep 20, 2004 Post Count: 653 Status: Offline Project Badges:
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The data the agent sends is already compressed. So, your compression activity would potentially slow down the communication and not achieve any further coimpression for all the effort. This might explain it.
The server only checks the minimum connection bandwidth requirement when sending new work to the agent, not when it is returning work. This explains why you were always able to return work over your GPRS configuration. |
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