A front end developer should understand that a TCP request (i.e what an HTTP request is) consists of a handshake which means to receive a file from a server, it takes roughly 5/6 calls to and from the server. So if your UI consists of 1000 100b files, that's 6000 calls. So you would probably be better concatenating them to a single 10Kb file.

But then you need to understand the differences between HTTP 1.1 and 2.0 and how it handles multiple requests from the same page. 1.1, you would probably be better off with a single concatenated file, 2.0, perhaps several. And then what about compression? Any good UI developer should be considering compression of that file, cache control, etc.

I see too many front end developers shy away from this stuff and create bloated monstrosities. They feel it's someone else's job... but if not the UI developer, then who??

I guess my point was more that even just if you understand HTTP then you'll get all those insights already. A bit pedantic I suppose.

This stuff does get pretty complicated. Mainly because the tech is evolving fast (browsers do a lot of tricks now). Even in HTTP 1.1, there are times where multiple files might be more interesting due to how large files are handled

But can you really understand HTTP without understanding TCP?

I prefer to work with a frontend engineer that knows a little bit about packet loss, routing, load balancing, white/black listing, retransmission, packet fragmentation, latency, mobile connections, socket limits, common error messages on network diagnostics, etc... that with an engineer that just knows "the page is slow".

Well, indeed, the higher level protocols, like HTTP, DNS, etc, are more useful on a daily basis.