Hypertext caching protocol
Encyclopedia
Hypertext Caching Protocol (abbreviated to HTCP) is used for discovering HTTP caches and cached data, managing sets of HTTP caches and monitoring cache activity. It permits full request and response headers to be used in cache management and expands the domain of cache management to include monitoring a remote cache's additions and deletions, requesting immediate deletions and sending hints about web objects such as the third party locations of cacheable objects or unavailability of web objects.
HTCP protocol elements are transmitted in network byte order. All reserved fields should be set to binary zero by senders and left unexamined by receivers. Headers must be presented with the CRLF line termination, as in HTTP.
Any hostname
s specified should be compatible between sender and receiver, such that if a private naming scheme (such as HOSTS.TXT or NIS) is in use, names depending on such schemes will only be sent to HTCP neighbors who are known to participate in said schemes. Raw addresses (dotted quad IPv4
, or colon-format IPv6
) are universal, as are public DNS
names. Use of private names or addresses will require special operational care.
UDP
must be supported. HTCP agents must not be isolated from network failures and delays. An HTCP agent should be prepared to act in useful ways when no response is forthcoming, or when responses are delayed or reordered or damaged. TCP
is optional and is expected to be used only for protocol debugging. The IANA
has assigned port 4827 as the standard TCP
and UDP
port number for HTCP.
An HTCP Message has the following general format:
+---------------------+
| HEADER | tells message length and protocol versions
+---------------------+
| DATA | HTCP message (varies per major ver. number)
+---------------------+
| AUTH | optional authentication for transaction
+---------------------+
Features
All multi-octetOctet (computing)
An octet is a unit of digital information in computing and telecommunications that consists of eight bits. The term is often used when the term byte might be ambiguous, as there is no standard for the size of the byte.-Overview:...
HTCP protocol elements are transmitted in network byte order. All reserved fields should be set to binary zero by senders and left unexamined by receivers. Headers must be presented with the CRLF line termination, as in HTTP.
Any hostname
Hostname
A hostname is a label that is assigned to a device connected to a computer network and that is used to identify the device in various forms of electronic communication such as the World Wide Web, e-mail or Usenet...
s specified should be compatible between sender and receiver, such that if a private naming scheme (such as HOSTS.TXT or NIS) is in use, names depending on such schemes will only be sent to HTCP neighbors who are known to participate in said schemes. Raw addresses (dotted quad IPv4
IPv4
Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...
, or colon-format IPv6
IPv6
Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...
) are universal, as are public DNS
Domain name system
The Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities...
names. Use of private names or addresses will require special operational care.
UDP
User Datagram Protocol
The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...
must be supported. HTCP agents must not be isolated from network failures and delays. An HTCP agent should be prepared to act in useful ways when no response is forthcoming, or when responses are delayed or reordered or damaged. TCP
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
is optional and is expected to be used only for protocol debugging. The IANA
Internet Assigned Numbers Authority
The Internet Assigned Numbers Authority is the entity that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System , media types, and other Internet Protocol-related symbols and numbers...
has assigned port 4827 as the standard TCP
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
and UDP
Domain name system
The Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities...
port number for HTCP.
An HTCP Message has the following general format:
+---------------------+
| HEADER | tells message length and protocol versions
+---------------------+
| DATA | HTCP message (varies per major ver. number)
+---------------------+
| AUTH | optional authentication for transaction
+---------------------+