Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide

NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

Searchable, convenient, complete TCP/IP information.
The TCP/IP Guide

Custom Search

Table Of Contents  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

Previous Topic/Section
HTTP Response Headers
Previous Page
Pages in Current Topic/Section
Next Page
HTTP Entities, Transfers, Coding Methods and Content Management
Next Topic/Section

HTTP Entity Headers
(Page 2 of 3)


Describes any optional method that may have been used to encode the entity. This header is most often used when transferring entities that have been compressed; it tells the recipient what algorithm has been used so the entity can be uncompressed. Note that this header only describes transformations performed on the entity in a message; the Transfer-Encoding header describes encodings done on the message as a whole. See the topic on content codings and transfer codings for more details.


Specifies the natural (human) language intended for using the entity. This is an optional header, and may not be appropriate for all resource types. Multiple languages may be specified, if needed.

This header is intended to provide guidance so the entity can be presented to the correct audience; thus, the language should be selected based on who would best use the material, which may not necessarily include all of the languages used in the entity. For example, a German analysis of Italian operas would probably best tagged only with the language “de”. (They do have German analyses of Italian operas, don’t they? J)


Indicates the size of the entity in octets. This header is important, as it is used by the recipient to determine the end of a message. However, it may only be included in cases where the length of a message can be fully determined prior to transmitting the entity. This is not always possible in the case of dynamically-generated content, which complicates message length calculation; the discussion of data length and the “chunked” transfer encoding contains a full exploration of this issue.


Specifies the resource location of the entity, in the form of an absolute or relative uniform resource locator (URL). This is an optional header, and is normally included only in cases where the entity has been supplied from a location different from the one specified in the request. This may occur if a particular resource is stored in multiple places.


Contains an MD5 digest for the entity, used for message integrity checking.


Sent when a message contains an entity that is only part of a complete resource; for example, a fragment of a file sent in response to an HTTP GET request containing the Range header. The Content-Range header Indicates what portion of the overall file this message contains, as well as the total size of the resource. This information is given as a byte range, with the first byte numbered 0; for example, if the entity contains the first 1,200 bytes of a 2,000-byte file, this header would have a value of “0-1199/2000”.

Previous Topic/Section
HTTP Response Headers
Previous Page
Pages in Current Topic/Section
Next Page
HTTP Entities, Transfers, Coding Methods and Content Management
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $

Home - Table Of Contents - Contact Us

The TCP/IP Guide (
Version 3.0 - Version Date: September 20, 2005

Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.