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The ICMP header starts after the IPv4 header and is identified by its protocol number, 1. [6] All ICMP packets have an eight-byte header and variable-sized data section. The first four bytes of the header have fixed format, while the last four bytes depend on the type and code of the ICMP packet.
A functionality which lets a computer A find out whether a computer B is reachable and responding is built into the Internet Control Message Protocol (ICMP). Through an "Echo Request" Computer A asks B to send back an "Echo Reply". [2] These two messages are also sometimes called "ping" and "pong" for historical purposes. [citation needed]
This article lists protocols, categorized by the nearest layer in the Open Systems Interconnection model.This list is not exclusive to only the OSI protocol family.Many of these protocols are originally based on the Internet Protocol Suite (TCP/IP) and other models and they often do not fit neatly into OSI layers.
For IPv4, a network may also be characterized by its subnet mask or netmask, which is the bitmask that, when applied by a bitwise AND operation to any IP address in the network, yields the routing prefix.
Traceroute can help identify incorrect routing table definitions or firewalls that may be blocking ICMP traffic, or high port UDP in Unix ping, to a site. [clarify] A correct traceroute response does not guarantee connectivity for applications as a firewall may permit ICMP packets but not permit packets of other protocols.
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ICMP hole punching is a technique employed in network address translator (NAT) applications for maintaining Internet Control Message Protocol (ICMP) packet streams that traverse the NAT. NAT traversal techniques are typically required for client-to-client networking applications on the Internet involving hosts connected in private networks ...
The ICMP Router Solicitation message is sent from a computer host to any routers on the local area network to request that they advertise their presence on the network. The ICMP Router Advertisement message is sent by a router on the local area network to announce its IP address as available for routing.