IP header has flexible size, up to 60 bytes: https://networkengineering.stackexchange.com/questions/6855/...

Sure but on the actual internet how often are IP headers larger than 20 bytes because options are turned on? Not very often. The 20 bytes each for TCP and IPv4 is a pretty good assumption.

From the paper "IP Options are not an option" which is good quick read:

"We have studied the dependability of IP options-enabled network packets in the Internet. We found that overall, approximately half of Internet paths drop packets with options"[1]

[1] https://www2.eecs.berkeley.edu/Pubs/TechRpts/2005/EECS-2005-...

Thanks, that's good to know. I've wondered if these options are used in the past.

>"Out of those another 63 are consumed by the HTTP headers"

I am curious how you ended up at 63 for that, can you elaborate?

Viewed the http headers and counted?

Which you can do with curl, Chrome/Safari/FF dev tools, and lots of other tools besides.

Sure I know how to view them. I guess the commenter meant the HTTP headers for just this site were 63 bytes. I thought they were speaking on average like they were for 40 bytes for TCP/IP headers.