following problems:

      1. Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
         this was incorrectly placing a requirement on the behavior of
         an implementation of a future version of HTTP/1.x

      2. Made it clear that user-agents should retry requests, not
         "clients" in general.

      3. Converted requirements for clients to ignore unexpected 100
         (Continue) responses, and for proxies to forward 100 responses,
         into a general requirement for 1xx responses.

      4. Modified some TCP-specific language, to make it clearer that
         non-TCP transports are possible for HTTP.

      5. Require that the origin server MUST NOT wait for the request
         body before it sends a required 100 (Continue) response.

      6. Allow, rather than require, a server to omit 100 (Continue) if
         it has already seen some of the request body.

      7. Allow servers to defend against denial-of-service attacks and
         broken clients.

   This change adds the Expect header and 417 status code. The message
   transmission requirements fixes are in sections 8.2, 10.4.18,
   8.1.2.2, 13.11, and 14.20.

   Proxies should be able to add Content-Length when appropriate.
   (Section 13.5.2)

   Clean up confusion between 403 and 404 responses. (Section 10.4.4,
   10.4.5, and 10.4.11)

   Warnings could be cached incorrectly, or not updated appropriately.
   (Section 13.1.2, 13.2.4, 13.5.2, 13.5.3, 14.9.3, and 14.46) Warning
   also needed to be a general header, as PUT or other methods may have
   need for it in requests.




 
RFC 2616                        HTTP/1.1                       June 1999


   Transfer-coding had significant problems, particularly with
   interactions with chunked encoding. The solution is that transfer-
   codings become as full fledged as content-codings. This involves
   adding an IANA registry for transfer-codings (separate from content
   codings), a new header field (TE) and enabling trailer headers in the
   future. Transfer encoding is a major performance benefit, so it was
   worth fixing [39]. TE also solves another, obscure, downward
   interoperability problem that could have occurred due to interactions
   between authentication trailers, chunked encoding and HTTP/1.0
   clients.(Section 3.6, 3.6.1, and 14.39)

   The PATCH, LINK, UNLINK methods were defined but not commonly
   implemented in previous versions of this specification. See RFC 2068
   [33].

   The Alternates, Content-Version, Derived-From, Link, URI, Public and
   Content-Base header fields were defined in previous versions of this
   specification, but not commonly implemented. See RFC 2068 [33].

20 Index

   Please see the PostScript version of this RFC for the INDEX.