End-to-end and Hop-by-hop Headers-----from HTTP1.1

13.5.1 End-to-end and Hop-by-hop Headers

For the purpose of defining the behavior of caches and non-caching proxies, we divide HTTP headers into two

categories:

· End-to-end headers, which are transmitted to the ultimate recipient of a request or response. End-to-end

headers in responses MUST be stored as part of a cache entry and MUST be transmitted in any response

formed from a cache entry.

· Hop-by-hop headers, which are meaningful only for a single transport-level connection, and are not stored

by caches or forwarded by proxies.

The following HTTP/1.1 headers are hop-by-hop headers:

· Connection

· Keep-Alive

· Proxy-Authenticate

· Proxy-Authorization

· TE

· Trailers

· Transfer-Encoding

· Upgrade

All other headers defined by HTTP/1.1 are end-to-end headers.

Other hop-by-hop headers MUST be listed in a Connection header, (section 14.10) to be introduced into

HTTP/1.1 (or later).