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That's great! Regarding retries, this can be reduced to almost zero even when you're at capacity if you get the concurrency/rate "just right", but it's tough. :) You should be able to eliminate timeouts entirely by reducing the load just a little bit -- timeouts suggest you're seeing quite a lot more retries than I'd expect, because it means the same flow had to have multiple retransmits. It's tough to eliminate retries entirely when you're near capacity limits (on any type of device), but it's definitely possible to minimize the impact. In a world with fast retransmits, TCP timestamps, and SACK, losing a random packet here and there doesn't have a practical impact on users/servers, and it's to be expected when you're up against the device capacity.

 

 

Some ideas to help dial it in:

 

1) Reduce the simuser constraint by increments that are a multiple of the number of physical ports (i.e. 12)

 

2) Change the congestion control algorithm on your TCP profile to "highspeed"

 

3) Disable rfc1323 on the TCP profile.

 

4) Reduce the send/recv buffer sizes on BIG-IP (or Ixia) in 8KB increments.

 

... this sort of tuning can take a while, but if you really want to get perfect results at the edge of capacity, it's what you need to do. :)

 

 

Good luck!

 

 

Mike Lowell