Slow Internet Speed since upgrading to 16.05.0

Question

Hi, since upgrading to XG 16.05.0 our internet speed has dropped from 13Mb/s to 300kb/s without any policy change apart from subscribing to the Sandstorm trial (but not activating it). I tried disabling all firewall rules apart from web access and removed all web filtering without success. I also started having email delivery failure errors with a Sophos firewall message of "Internal Server Error") in the email delivery notification failure message. I eventually decided to revert back to 16.01.2 and the issue resolved immediately with speeds back to 13Mb/s. Any idea of what the issue may be? The logs don't appear to help.

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rfcat_vk · Answer

Try resetting your IPS DOS values. There are a number of threads on reducing a value from 80 to 8. 
 I removed my DOS settings some time ago and I am slowly putting them back in place after upgrading to 16.5 GA and reducing the IPS value in console. 
 I can't remember which command to use. 
 
 Update. I turned the TCP flood on both source and destination and lost about 0.5mb/s download. Turned off destination TCP flood, not much affect, turned off tcp flood source and immediately back to nearly 5mb/s download speed from speedof.me

sachingurung · Answer

Hi Tony, 
 As suggested by our mentors, do the following: 
 1. Define a measured value in the Anti-DoS settings for TCP/UDP flooding. 
 2. Set the IPS maxpkts to 8. To do that, take SSH to XG and go to option 4. Device Console. Execute, set ips maxpkts 8 
 3. I haven't come across configuring the TSO off on an interface over this issue but, I please provide us with the feedback. 
 Finally, check #4 in my guide here to make sure other configurations are up to the mark. 
 Hope that helps