Slow SSL VPN Performance 300D

[ITGuy11]

Everything is slow while connected to the SSL VPN. File transfers regardless of their size are slow, browsing directories, accessing applications, iPerf tests are slow... 

Per the 300D datasheet the SSL-VPN Throughput is 350Mbps.  I am getting nowhere near that. I performed a test from my house where my internet speed is 100Mbps down/ 20Mbps up.

The SSL VPN speed results are as follows: 16.1Mbps write, 33.8Mbps read. I then connected to the same Fortigate 300D through a IPSec VPN and got these results: 22.4Mbps write, 90.4Mbps read which basically is the max speed of my home internet connection.  I understand that the SSL VPN will have slightly more overhead but this is absurd.

[Wabo84]

Occasionally, SSL VPN performance can be slower than expected. Since the SSL VPN encapsulates a TCP connection within another TCP connection, this can cause interference between timeouts, and other issues. The following external web site provides more information: http://sites.inka.de/bigred/devel/tcp-tcp.html In FortiOS 5.4, it is possible to use DTLS to address this problem.  DTLS has the same security as SSL, but uses UDP instead of TCP. This can improve performance drastically.

Solution

To enable DTLS on SSL VPN, run the following commands:

config vpn ssl settings     set dtls-tunnel enable/disable end