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The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Internet Layer (OSI Network Layer) Protocols            9  Internet Control Message Protocol (ICMP/ICMPv4 and ICMPv6)                 9  ICMP Message Types and Formats                      9  ICMP Version 4 (ICMPv4) Error Message Types and Formats

ICMPv4 Source Quench Messages 1 2 3 ICMPv4 Redirect Messages

ICMPv4 Time Exceeded Message Format

Table 91 and Figure 142 show the specific format for ICMPv4 Time Exceeded messages.

Table 91: ICMPv4 Time Exceeded Message Format

Field Name	Size (bytes)	Description
Type	1	Type: Identifies the ICMP message type; for Time Exceeded messages this is set to 11.
Code	1	Code: Identifies the “subtype” of error being communicated. A value of 0 indicates expiration of the IP Time To Live field; a value of 1 indicates that the fragment reassembly time has been exceeded.
Checksum	2	Checksum: 16-bit checksum field for the ICMP header, as described in the topic on the ICMP common message format.
Unused	4	Unused: 4 bytes that are left blank and not used.
Original Datagram Portion	Variable	Original Datagram Portion: The full IP header and the first 8 bytes of the payload of the datagram that was dropped due to expiration of the TTL field or reassembly timer.

ICMPv4 Source Quench Messages 1 2 3 ICMPv4 Redirect Messages

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