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ICMP is part of the Internet protocol suite as defined in RFC 792. ICMP messages are typically used for diagnostic or control purposes or generated in response to errors in IP operations (as specified in RFC 1122). ICMP errors are directed to the source IP address of the originating packet. [3]
ICMPv6 provides a minimal level of message integrity verification by the inclusion of a 16-bit checksum in its header. The checksum is calculated starting with a pseudo-header of IPv6 header fields according to the IPv6 standard, [6] which consists of the source and destination addresses, the packet length and the next header field, the latter of which is set to the value 58.
The Internet checksum is used to detect errors in ICMP packets (including data payload). Computation. The checksum calculation is defined as follows: [5]
For ICMP flows, the Source Port is zero, and the Destination Port number field codes ICMP message Type and Code (port = ICMP-Type * 256 + ICMP-Code) [citation needed]. The source and destination Autonomous System (AS) number fields can report the destination AS (last AS of AS-Path) or the immediate neighbor AS (first AS of AS-Path) depending on ...
ICMP The ICMP performance object consists of counters that measure the rates at which messages are sent and received by using ICMP protocols. It also includes counters that monitor ICMP protocol errors. IPsec Connections IPsec Connections is the set of Internet Protocol security (IPsec) counters that apply to IPsec encapsulated connections ...
Many network security devices block all ICMP messages for perceived security benefits, including the errors that are necessary for the proper operation of PMTUD. This can result in connections that complete the TCP three-way handshake correctly but then hang when attempting to transfer data. This state is referred to as a black hole connection. [7]
Proceeding in this way, traceroute uses the returned ICMP Time Exceeded messages to build a list of routers that packets traverse, until the destination is reached and returns an ICMP Destination Unreachable message if UDP packets are being used or an ICMP Echo Reply message if ICMP Echo messages are being used. [10]
A checksum of a message is a modular arithmetic sum of message code words of a fixed word length (e.g., byte values). The sum may be negated by means of a ones'-complement operation prior to transmission to detect unintentional all-zero messages. Checksum schemes include parity bits, check digits, and longitudinal redundancy checks.