Troubleshooting slow / intermittent internet access on a network (LAN)

Dear xperts

What is the best way to troubleshoot / diagnose slow / intermittent internet access from a desktop machine on a business LAN.  I know this is a very open question but I do have some details to help:

1) I believe we are using a local proxy server
2) our DNS is handled by a dedicated "infoblox" box
3) we have a 30mbps pipe to the internet (but all sites access this from across the uk)

The internet is so slow at times it's unusable.  I work in the IT department and I've never know anything like this before.  What are the best methods that I can use to diagnose this issue from my workstation ?  Are there any good tools out there that could help me to identify the source of the problem i.e. the bottleneck?

Thanks xperts - I need your best advice because I've logged the call with our helpdesk but to be honest with you I don't think they are interested in fixing the issue and keep fobbing me off with basic tests like they ping my workstation and then the router and say that everything is fine - I mean what the f**k !?
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you could try the following -
Open the Configuration Panel, Network connections. Select the network connection that's giving you troubles. Right click on it, select properties. Remove QOS service, if it's there.

3) we have a 30mbps pipe to the internet (but all sites access this from across the uk)

I take it you're using a switch and not a router? If it is a switch let me know the model, there should be netdiag software for it.

As ALL sites from across the UK are using your single 30mbps line, it's quite possible that the intense traffic requests are coming from another site. Who knows one of the people there could be streaming video all day long.

As much as I hate to say is but ISA server is at least good at this, you can specify exactly how much bandwidth each site can use as well as on a user by user basis.

My suspicions are there's one 'git' somewhere on your network abusing bandwidth. You first need to locate which site this is coming from and then track down which user.

All the best
Sci-Fi Si

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richardstuartpowellAuthor Commented:
Thanks guys - much appreciated !

I will try to find the git concerned !

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