中文版也是有的，也曾下载看过，不过翻译质量实在不敢恭维。
还是和英文书一样，看原版吧。

非常有论文风格的一个标准。
一开始先是下定义，不过有几个定义我反复看了几次，还是不清楚具体的区别。

proxy
An intermediary program which acts as both a server and a client for the purpose of making requests on behalf
of other clients. Requests are serviced internally or by passing them on, with possible translation, to other
servers. A proxy MUST implement both the client and server requirements of this specification. A “transparent proxy” is a proxy that does not modify the request or response beyond what is required for proxy authentication and identification. A “non-transparent proxy” is a proxy that modifies the request or response in order to provide some added service to the user agent, such as group annotation services, media type transformation, protocolreduction, or anonymity filtering. Except where either transparent or non-transparent behavior is explicitly stated, the HTTP proxy requirements apply to both types of proxies.
gateway
A server which acts as an intermediary for some other server. Unlike a proxy, a gateway receives requests as if it were the origin server for the requested resource; the requesting client may not be aware that it is
communicating with a gateway.
tunnel
An intermediary program which is acting as a blind relay between two connections. Once active, a tunnel is not considered a party to the HTTP communication, though the tunnel may have been initiated by an HTTP request. The tunnel ceases to exist when both ends of the relayed connections are closed.

有些实际例子就好了。