TCP/IP Guide

HTTP Data Length Issues, Chunked Transfers, and Message Trailers

As you've learned, two different levels of encodings are used in HTTP: content encodings, which are applied to HTTP entities, and transfer encodings, which are used over entire HTTP messages. Content encodings are used for convenience to package entities for transmission. Transfer encodings are hop-specific, and they are intended for use in situations where data needs to be made safe for transfer.

However, we've already seen that HTTP can transport arbitrary binary data, so unlike the situation where MIME needed to make binary data safe (as defined in RFC 822), this is not an issue with HTTP. Therefore, why are transport encodings needed at all? In theory, they are not, and HTTP/1.0 ...