How does a cascading http proxy server works?

Question

Software like CCProxy in windows allows you to setup a cascading proxy. In squid we can do the same by mentioning a cache_peer directive?

How does this work at application and TCP/IP layer ? Does it form a socket connection to the upstream proxy server ? Any details or RFCs in relation to this?

PS - I want to implement it in Python for some testing purposes.

Answer 1

Cascading proxy is just the proxy connecting to an upstream proxy. It speaks the same HTTP proxy requests to the upstream proxy as a browser does, e.g. using full urls (method://host[:port]/path..) in the requests instead of just /path and using CONNECT for https tunneling instead of directly connecting with SSL.