Transferring file immediately through proxy server

Question

I'd like to set-up following configuration:

S - HTTP File Server <-> P - Proxy Server <-> C - HTTP Client

Now, I'm downloading a file from the file server through the proxy server. I'm wondering if proxy will wait to receive the whole file from the file server before it send it to the client or will immediately transfer packages without waiting the whole file?

I'm not asking about progressive download or streaming, nor specific proxy or file server.

I was looking for the answer but most of the explanations don't go to details. Sorry if there was a question like this before.

Answer 1

Probably depends on the proxy. Squid immediately transfer.