I've got a LAN with somewhere between 20-30 systems connected which has recently started running incredibly slowly. By slowly I mean network traffic, especially related to Internet services. I have run virus scans and they have come back clean.
I want to find some tools / software which I can install on a system within the LAN to try and establish what's causing the slowdown. I know about Wireshark, although I'm a relative novice. I know how to inspect the I/O graphs which will be a good starting place.
What I would really like is a piece of software which I can run, and it builds up a graphical representation of network traffic, with source & destination IPs and ports etc. I expect this exists, but I must be Googling the wrong terminology as I can't find what I want. I have a fairly limited budget for this, so enterprise $$ software is out of the question.
If anyone can point me in the right direction would be very grateful.