Is the following an appropriate question to ask here? if not, where should it go?

At my place of work there have been consistent though sporadic network issues for a long time, a couple of years, though in the last 6 months the troubles are increasing, sometimes to the point where my home 16mbps-down/768kbit-up cable connection is outperforming our work 100mbps connection.

I administer a handful of Win2003 servers but my network admin activities are limited to routing cables in the wiring room to free ports. I've brought the issue up with the next level of IT support, who commiserate but tell me there's nothing they can do because the switches are under control of central IT, and their pleas to have central IT look into things have fallen on deaf ears, or at least unresponsive ones.

We have access to all of the physical infrastructure in our building, so I could, for example, put in a passive something or other in-line for monitoring or benchmarking (provided there's a non-interference guarantee).

We're pretty much a 100% Microsoft shop, with authentication etc. handled by Active Directory, though there are a scattering of linux servers and VMs here and there doing odd jobs.

What can I do from the bottom of the chain to prove or disprove there really is a problem? and assuming there is one, localise it? (on 2nd floor, between machine X and external uplink, etc.)

What do you, as a top of the chain network administrator, need to hear to convince you there is something to investigate?