hypertext caching protocol (HTCP)
The HypertextCaching Protocol (HTCP) is an Internet Engineering Task Force( IETF) standardized protocol( RFC 2756) for discovering and managing HTTP caches and stored data, and for monitoring cache activity.
The first data field of the HTCP header is the 4- byte (32 bits) Message Length data field. This data field specifies the length of the entire header, including the data bytes. This data field can take padding into account and then corresponds to the size of the payload when the UDP protocol is used. The two following data fields are each 1 byte long and contain the version information. These version fields are followed by the 2-byte Data Length data field, which contains the number of bytes reserved for the message, including the data length field. The number may include the padding.
The Opcode data field contains 4 bits to indicate the mode of operation of the HTCP transaction. Such an HTCP transaction may consist of several HTCP messages. For example, a request sent by the initiator or a response from the called party. The following data field is also 4 bits long and contains the code for the transaction. This is followed by a Reserved data field with a length of 6 bits, which is followed by two 1-bit data fields: Response Desired/Message Overall( RD/ MO, or F1) and Request/Response( RR).
The following data field Trans- ID comprises 4 bytes and is used in combination with the network address for the identification of this HTCP transaction. Another 2 byte data field is the Auth Length. It is the first data field in the Auth Section and contains the number of bytes that comprise the Auth Section and Auth Length fields combined. It is followed by the 4 byte signature fields the Sig-Time and the Sig-Expire. These data fields store the date and time when the signatug was generated or expires.
The HTCP protocol is transmitted with the UDP protocol, optionally also with the TCP protocol. HTCP is intended to replace the other cache protocols such as the Internet Cache Protocol( ICP), the Web Cache Control Protocol( WCCP) and the Cache ArrayRouting Protocol( CARP).