Forum Discussion
santosh_81454
Nimbostratus
NimbostratusCalculate latency caused by F5 boxes..?
Hi,
I would like to know if there is any command or method to calculate the latency caused by the F5 boxes.
The scenario is: A website is being hosted and load balanced by the F5, say http://www.abc.com and is run on the pool members 10.0.0.1 :100, 10.0.0.1 :101, 10.0.0.1 :102
(I need to calculate the latency caused by the F5 as in our environment when we are trying http://www.abc.com the page take almost 40 sec, but when tried http://10.0.0.1 :100 it takes only 20 sec.)
Wanted to know if the F5 is causing the delay or is it the network delay.
- Chris_Miller
Altostratus
This link might be a good read for you:
http://devcentral.f5.com/Forums/tabid/1082223/asg/52/showtab/groupforums/aff/31/aft/31604/afv/topic/Default.aspx
Are your clients on a WAN or LAN? It's probably worth using a tcp-optimized profile to see if that improves your results. 
santosh_81454Hi Chris,
Thanks for your reply. Our clients are in LAN and we are running the test sites.
I checked the link and it was mostly into comparison between using Fastl4 and tcp optimized profile.
I would like to know if there is any method to calculate the time delay caused by the F5 box to process the packet and send it to the next network device.?- Chris_MillerSantosh...the reason that I used that link was that it discusses how some of the F5's default settings can introduce latency. By using a tcp-lan-optimized client profile, you disable certain settings that might introduce latency.
While I'm not sure of how you can measure the latency of the F5 (from the F5 anyways), I'd change your tcp client profile from what I assume to be tcp, to tcp-lan-optimized and see if you still have the issues. - santosh_81454Hi Chris,
Yes, you are correct. Previously the settings on the F5 VS was tcp and now I have changed it to tcp-lan-optimized.
After changing the profile, the links reponse time was better. Thank you for your help.
I will check with F5 support if they could help in finding the latency caused by F5. - santosh_81454The reply I received from F5 support was to perform a packet capture on both client side and server side VLAN at the same time and analyze the time delay using tools like Wireshark.
To perform TCP dump the link provided was:
https://support.f5.com/kb/en-us/solutions/public/0000/400/sol411.html
