We have clients uploading documents (usually PDFs under 3MB in size) up to a web interface (using http only) on an internal web server. They clients are using the latest version of AnyConnect for windows and connecting to an ASA5510 running the latest 8.3 firmware. They are connecting from their home network over a cable or DSL connection.
I disabled Threat detection and can't see anything being blocked by the firewall. Everything else that our user are doing seems to be working flawlessly.
I ran a packet capture with wireshark and noticed a lot of packet loss. I have attached a screen shot.
Any advice would be greatly appreciated.
I would suggest that you reduce the MSS size configured on the ASA to 1300 as follows:
sysopt connection tcpmss 1300
Reconnect uploading the documents via SSL VPN after the changes above.
Hope that helps.
Is it possible that there is another network issue causing this?
Check the duplex/speed settings from edge to webserver, check for interface errors on ports, etc. Duplicate ACKs are caused by lost packets, out-of-order packets, etc.