Lots of duplicate ACKs and TCP re-transmissions

Hello –

Can anyone give me some advice on what to look at when I’m seeing tons of TCP retransmissions and duplicate ACKs in my analyzer traces? We are an almost 100% Cisco environment using primarily Dell servers. It seems that I see these TCP retransmissions on traffic that goes to port 80 or 443, but also on FTP traffic. We have a Cisco ASA as our f/w and the local university is our ISP. I do NOT see these results at our remote locations where our ISP is Comcast and our firewalls are SonicWall boxes.

Any thoughts on what to look at?

Thanks.