The Illustrated Network- P62:In this chapter, you will learn about the protocol stack used on the global public Internet and how these protocols have been evolving in today’s world. We’ll review some key basic defi nitions and see the network used to illustrate all of the examples in this book, as well as the packet content, the role that hosts and routers play on the network, and how graphic user and command line interfaces (GUI and CLI, respectively) both are used to interact with devices. | CHAPTER 22 Hypertext Transfer Protocol 579 Table HTTP Response Headers and Their Uses Header Use Accept-Ranges Tells client if server accepts partial content requests using Range request header. Typical values are in bytes or none for no support. Age Tells the client the approximate age of the resource. ETag Gives the entity tag for the entity in the response. Location Gives client a new URL to use instead of one requested. Proxy-Authenticate Tells client how the proxy requires authentication both method and parameters needed. Retry-After Tells client to try the request again later seconds or by date time. Server Server version of User-Agent request header used for server details. Vary Used by caching devices to make decisions. WWW-Authenticate Tells client how the Web site requires authentication both method and parameters needed. Table HTTP Entity Headers and Their Uses Header Use Allow Lists methods that apply to this resource. Content-Encoding Describes optional encoding method usually the compression algorithm used so that the client can decompress the entity. Content-Language Specifies the human language used by the entity. It is optional and can specify multiple languages. Content-Length Size of the entity in bytes octets . Not used in chunked transfers. Content-Location Resource location as URL. Optional but used if entity is in multiple places. Content-MD5 Used for message integrity checking with Message Digest 5. Content-Range Used for entities that are part of the complete resource. Content-Type Similar to MIME type and subtype but not exactly the same. Expires Data and time after which entity is considered stale. Last-Modified Date and time server believes entity last changed. Entity Headers Finally entity headers describe the resource carried in the body of the HTTP message. They usually appear in responses but can appear in PUT and POST requests. Many of the entity headers have the same names as the MIME types they are based on but with .
