Packet Analysis (Score 1)

as far as open source is concerned, where you are managing multiple segments and to identify bottleneck and throughput, you should look into www.ntop.org. we use this in two of our data center off of our MDF. although we can't do straight packet analysis, but at least we could analyze the header information and others to isolate problems. ntop could also be used to identify security problems, related to p2p type also. check it out!