This chapter demonstrates about the HTTP2 Header Compression which provides the information about the requests and responses and following are the concepts covered in this chapter.

• About Header Compression

In Header Compression Each and every HTTP transfer carries a set of headers which defines transferred resources and its properties. In HTTP/1.x meta data which always sent in plain text and which adds 500 to 800 bytes of overhead per each transfer and which also add some kilobytes if HTTP cookies are more used for which user need to see Measuring and Controlling Protocol Overhead In order to reduce the over head and improve performance HTTP/2 compresses request and response header metadata using HPACK compression format which have some techniques as shown below.

• Which allows transmitted header fields which encoded via static Huffman code and which reduce its transfer size.
• Which requires update and maintain the both fields like indexed fields and already seen fields.

In Header Compression Huffman coding allows individual values compressed when the values transferred and indexed list of previously transferred values  which allows to encode the duplicate values which is shown in below image. HTTP/2 compression is not like request/response compression instead of that which is technique of not sending the same header again . HPACK compression consist dynamic and static tables in which static table provides common HTTP header fields and the dynamic table initially empty and which are used updated based on exchanged values with in the particular connection. 

• HTTP transfers 500-800 bytes of overhead per each transfer.
• HTTP/2 compress request and response by using HPACK.
• HPACK consist of dynamic and static tables.