Bug or Problem in VS TCP behavior ?

I'm looking at performance's problem that we had since some days on 8800 and 8900 in version 10.2.1 and 10.2.0 (with an HotFix) on some standard VS

Standard HTTP VS seems to slow down TCP connection at client side (HTTP requester/client) from times to times, and so webpage objects like images are taking 5s to load ...

If I do a tcpdump on interface 0.0 on F5 and on the client, I see :

• no TCP problems between HTTP VS and the server (to and from our own caching solution or simply an Apache / IIS customer's server)
• TCP desynchronisation and so lot of retransmission between the HTTP VS and the client / requester, and with long null activity times (between 1,2s and more than 2s without any trafic or ACK / Retransmit on client or on F5 HTTP VS) for some TCP stream (majority of them are ok and fast even with TCP desync and retransmit).

The result is a complete webpage with 30 to 50 objects (jpeg, js, and other static objects) is sometimes loaded in more than 10/15 sec in our LAN and in our country providers, and problem seems to be amplified in foreign countries, due to transit, but without enormous loading times (more than 60sec in some tries ...). Problem is always due to few objects loaded (1 or 2 images or JS of less than 20KB loaded through LAN in more than 4/5 sec which is the time of page full loading approximatively).

I was thinking first it can be due to our providers or our LAN, but with FastL4, I didn't see any signs of the previous mentionned problem.

So I started playing with TCP profile (http profile is wan optimize with compression) to try to find some improvements. Disabling Nagle's, Bandwidth delays, Slow Start (etc, etc) as suggested in some of this forum's posts, I see some improvements but random problem of some object loading time and null activity times in TCP transmit are always here and appears totally randomly (in our two F5 8800 / 8900 hardwares which are in 2 different datacenters with different telco providers and different VS).

Before opening a case to F5 support, I would know if I can try other options or configurations ? Is v10.2.0/1 well known to have TCP bugs like this inactivity times through HTTP VS trafic ? I will try to reproduce on 6400 we have in spare tomorrow @work, and upgrade to v11 to see if it's a v10.x problem, but any advises are welcome !!!

Thanks in advance for your advises and help !