How do I enable the TCP Window Scaling option?
I've been doing some performance tests uploading and download large files over SSL with an F5 LTM in the middle. The virtual server setup is standard, using the default tcp profile.
In most performance tests going via the LTM compared to straight to the server gives about the same result, but as the latency increases, speed doing via the LTM starts to fall below going straight to the server thru the firewall.
One key difference that's shown up in packet captures - in the initial SYN+ACK the server sends back to the client, it shows the server supports TCP Window Scaling option, or WSOPT as it's abbreviated in Wireshark. I've been trying to figure out how to support this option on the F5, can't make it happen. TCP Window Scaling is part of RFC 1323 so it should be included in the default tcp profile, but I don't see it in the capture.
Is anyone out there familiar with this option, and knowledgeable of the trick to making it work?
what version are you running? have you tried to increase send/receive buffer e.g. 65536 bytes?
Note: Beginning in 11.4.0, the window scale functionality is built into the TCP profile and cannot be manually disabled or enabled; it will be negotiated if the send or receive buffer is larger than 65535 bytes.
sol7559: Overview of the TCP profile
https://support.f5.com/kb/en-us/solutions/public/7000/500/sol7559.html