Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Theory = is WAAS to fast for PC loaded down with Antivirus and personal FW

I know this question may sounds dumb. Lets say you have a PC that uses Antivirus along with personal FW. Many other applications running in background etc. I recently ran a tethereal capture on the WAAS and reviewed it to troubleshoot an application performance problem with Lotus-notes server slowness. The capture showed that the Lotus-notes server was sending way more data than what is currently capable on the WAN circuit, it was even evident while looking at the router statistics at the same time, show int, sho ip cache flow. I didnt get the DRE/TFO statistics but the capture revealed well over 1000Kb per sec and the router was not even exceeding 200Kb with a 768Kb frame cir. These are really good numbers.

Question, Is the WAAS using sliding windows on the client side to dynamically adjust speed for largly cached objects. The capture showed that the tcp window size from the client was 65535, really rare in my opinion for windows OS or any application. the Server-side tcp window was 5635. It looked like the PC was biting off more than it could chew or the WAAS was manipulating the window size for the client-side to be the max. Either way Im going to tune the pc and disable antivirus and all programs and retest. I wanted to throw this out there as a theory for now regarding system performance in relation with WAAS over-performance. im reletivly new to the WAAS app and im working an account where they have a huge worldwide deployment of WAAS and everytime I see this problem it has to do with a Antivirus running realtime and Personal FW etc.


Re: Theory = is WAAS to fast for PC loaded down with Antivirus a

First, it sounds like the server is running low on resources. It is not uncommon for clients to advertise a max window (65535). The server's window of 5635 indicates a lack of receive buffers preventing window from increasing.

In terms of WAAS - WAAS utilizes TFO (TCP Flow Optimization) to compensate for poor performing WANs. During periods of WAN congestion WAAS TFO will improve TCP slow start by dropping cwind by 1/8 as opposed to 1/2 and and provide 3 x MTU for ramp up as opposed to 1 MTU during normal TCP slow start.

Combined with SACK, LZ and DRE clients can achieve upwrads to 410M perceived throughput