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The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  TCP/IP Key Applications and Application Protocols            9  TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)                 9  TCP/IP World Wide Web (WWW, "The Web") and the Hypertext Transfer Protocol (HTTP)                      9  TCP/IP Hypertext Transfer Protocol (HTTP)                           9  HTTP Message Headers

HTTP Request Headers 1 2 HTTP Entity Headers

The counterpart to request headers, response headers appear only in HTTP responses sent by servers or intermediaries. They provide additional data that expands upon the summary information that is present in the status line at the beginning of each server reply. Many of the response headers are sent only in response to the receipt of specific types of requests, or even particular headers within certain requests.

There are nine response headers defined for HTTP/1.1.

Tells the client whether or not the server accepts partial content requests using the Range request header, and if so, what type. Typical examples include “Accept-Range: bytes” if the server accepts byte ranges, or “Accept-Range: none” if range requests are not supported.

Note that this is header is different from the other “Accept-” headers, which are used in HTTP requests to perform content negotiation.

Tells the client the approximate age of the resource, as calculated by the device sending the response.

Specifies the entity tag for the entity included in the response. This value can be used by the client in future requests to uniquely identify an entity, using the If-Match request header or similar.

Indicates a new URL that the server is instructing the client to use in place of the one the client initially requested. This header is normally used when the server redirects a client request to a new location, using a 301, 302 or 307 reply. It is also used to indicate the location of a created resource in a 201 (“Created”) response to a PUT request.

Note that this is not the same as the Content-Location entity header, which is used to indicate the location of the originally-requested resource.

HTTP Request Headers 1 2 HTTP Entity Headers