ICMP (Internet Control Message Protocol) headers typically consist of eight bytes. Within these headers, ICMP includes specific fields such as type, code, checksum, and additional data depending on the type of ICMP message. These headers are crucial for network diagnostics and error reporting.
ICMP headers do not directly contain TCP/IP headers. ICMP operates as a separate protocol within the IP layer, where it uses IP headers for routing. TCP/IP headers are used by TCP (Transmission Control Protocol) and IP (Internet Protocol) to manage data transmission and routing.
The size of an ICMPv4 header can vary depending on the specific type of ICMP message being sent or received. Generally, an ICMPv4 header is 8 bytes long. This includes fields such as type, code, checksum, and additional data specific to the type of ICMP message.
In ICMP, the code field provides additional context or details related to the type of ICMP message being sent. It complements the type field by specifying variations or specifics within a particular type of ICMP message. For example, ICMP messages like “Destination Unreachable” or “Redirect” use the code field to indicate the reason for the message, such as unreachable host or network, or a specific redirect instruction. The code field helps to differentiate and provide more detailed information within the broader categories defined by the type field in ICMP messages.
