Internet Control Message Protocol
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The Internet Control Message Protocol (ICMP) is mainly responsible for the sending of error messages to indicate issues that occur between networked entities on the internet. ICMP is a special-purpose message mechanism, and is considered a required part of the Internet Protocol (IP) which must be included in every IP implementation. Much like other network traffic, ICMP messages travel across the internet in the data portion of IP datagrams. The Internet Control Message Protocol can only report the error back to the original source of the datagram, it is the source's responsibility then to relate the error to a program or take other action to solve the problem. The major advantage of allowing hosts to use ICMP is that it provides a single mechanism for all control and information messages. Other than ping and traceroute, ICMP is not usually used directly by user applications.[1]
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Specification
ICMP messages are created as a response to errors that may occur in IP datagrams or for routing or diagnostic purposes. The ICMP messages are generated at the IP layer, and is encapsulated and then transmitted much like IP datagrams. ICMP messages are generated in several situations, such as when a datagram cannot reach its destination or if the gateway does not have the buffering capacity to forward a datagram. These control messages are not considered reliable, as there is no guarantee that a datagram will be delivered. If reliability is required then higher level protocols which use IP must implement their own reliability procedures. ICMP messages are never sent in response to errors with ICMP messages themselves, as this could result in an infinite amount of messages. [2]
Format
References
- Douglas E. Comer (2000). "Internetworking with TCP/IP Vol.1: Principles, Protocols, and Architecture". Internet Protocol: Error and Control Messages(ICMP) 129-145, Prentice Hall
- Internet Control Message Protocol - DARPA Internet Program Protocol Specification. Retrieved on April 12th, 2009 from http://tools.ietf.org/html/rfc792
- ICMP Type Numbers. Retrieved on April 12th, 2009 from http://www.iana.org/assignments/icmp-parameters.
See also
External links
Internet Control Message Protocol - DARPA Internet Program Protocol Specification
--Collim 21:26, 4 April 2009 (EDT)
