Forum Discussion

gersbah's avatar
gersbah
Icon for Cirrostratus rankCirrostratus
Apr 28, 2021

What does "Proxy Options" do in a tcp profile?

I recently had a case where disabling the "Proxy Options" flag in the server side tcp profile solved a massive performance issue (page load times went from 10-20 seconds with this setting to millisec...
application delivery
BIG-IP
LTM
Niels_van_Sluis's avatar
Niels_van_Sluis
Icon for MVP rankMVP
May 04, 2021

About the impact, the site below claims:

 

The timestamps option in TCP enables the endpoints to keep a current measurement of the roundtrip time (RTT) of the network between them. This value helps each TCP stack to set and adjust its retransmission timer. There are other benefits, but RTT measurement is the major one.

 

https://www.networkdatapedia.com/post/2018/10/08/how-tcp-works-the-timestamp-option#:~:text=What%20is%20a%20TCP%20Timestamp,measurement%20is%20the%20major%20one.

  • gersbah's avatar
    gersbah
    Icon for Cirrostratus rankCirrostratus
    May 04, 2021

    Yes, I also have a sneaking suspicion now that the option did not really fix the problem with this particular web server. There's some packet loss on the way back from the web server to the bigip and timestamps allow the server to retransmit those packets more quickly. I'll try to get a capture from the server side to confirm.

     

    What I can already confirm, is that "Proxy Options" indeed only affects timestamps. At least in my case that was the only difference I observed. With "Proxy Options" disabled, timestamps turned on, but other options like MSS or SACK permitted remained the same and I didn't see any other options added.