HTTP communication issue throught VPN-SSL

Hi Community,

 

Having trouble with VPN-SSL access on APM, and not able to find the root-cause. Need your help to find it or the way to do debugging. Here the issue:

 

I try to mount a VPN-SSL from IE 11 to access a centos server over HTTP and SSH ports. I am working on version v11.5.4 HF3 of bigip appliance.

 

No issue with SSH, it's working perfectly. But for HTTP access (to an apache2 server) i'm facing a communication issue. IE or Firefox can't download completly big files ( > 3ko about) like images. For a CSS file, a 4.8ko data file, download block every time at 89% for example.

 

The issue is not visible when i connect the computer directly on LAN. And it's not reproducible for a similar HTTP site hosted on windows IIS server, but reproducible for another web site hosted on a CentOs Apache2 server.

 

Searching for issue of TCP segmentation or MTU size limit, but regarding the tcdump trace taking from F5 all seems ok. Data are received by the client, a 200 OK HTTP response is acknokedge at the end for the CSS file for example. Nevertheless the file can't be fully downloaded.

 

To finish, i just found a solution that working perfeclty: Activate the optimization functionnality for my centos host server on Network Access ressource.

 

An idea of the issue i am facing? And why the optimization functionnality resolv it?

 

Thanks in advance for your help.