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When connecting to a customers hosting service via Sql Server Management Studio on an internet connection that also has other activity on it, the Sql Server connection to the hosting service is often dropped.

An obvious work around to this problem is to NOT have additional traffic on the connection but it still begs the question "Why the Sql Server connection is so unstable?".

If there is, for arguments sake, 100kb of bandwidth and a couple of downloads running that are being serviced at 35kB each then there is 30kB bandwidth spare capacity. If a 3rd download is started, that can be serviced at 35kB by the server, it will top out at 30kB and leave zero spare capacity. This is fine and all downloads get along nicely.

However it seems that with Sql Server connections it doesn't matter if there is spare bandwidth. Sql Server regularly times out if there is any additional activity on the connection even if i have 1024kB spare bandwidth capacity. This has been experienced across different customer hosting providers over the years and so the assumption is that it's Sql Server related.

Why does Sql Server (apparently) require exclusive access to the internet connection in order to maintain a connection... even if that connection has plenty of spare capacity over and above any additional activity on the connection?

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2 Answers 2

I believe it sounds like a SQL Server issue indeed, but if you are getting connection timeouts it most likely has nothing to do with bandwidth and everything to do with connection memory on the server. Unless you have your own server, you are at the mercy of other applications hitting that SQL instance. Either someone is holding connections open or the servers buffers are simply overloaded. Query timeouts are obviously a different story. Unless the host has done some tricky scripting, there is a maximum number of connections that can be made at a time.

Alternatively, it is just possible the TCP packets are dropping somewhere along the line of firewalls/etc or just a bad internet connection.

Ruling all local issues out (your internet connection, your connection string, etc) I would try to work with your host to figure this out as it might be in their responsibility to fix.

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Its very specific to when Im downloading. If i stop downloading all the 'issues' go away. I'd like to be able to 'multi task' every now while working with Sql Server. But it's either all or nothing. I have a work around as above i.e. dont download but I just wondered what the underlying reason behind the timeouts is especially given I often have more than enough spare bandwidth. You may have a point about packets being dropped. Maybe the host has a really short time out on the connection...although I still come back to if i have the bandwith wouldn't the packets be getting out 'in time'? –  intermension Jan 6 '10 at 7:22

Are the downloads single TCP connections? If they are torrents then it's no longer a simple matter of 35kb vs 30kb vs 30kb, it's 1 SQL server connection vs 500 others

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Yes. Microsoft etc. If i was pulling down a torrent I could understand it. Thanks –  intermension Jan 6 '10 at 7:24

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