ICMP is an auxiliary protocol, which provides routing, diagnostic and error functionality for IP. It is described in [INTERNET:8]. A router MUST support ICMP.
ICMP messages are grouped in two classes that are discussed in the following sections:
ICMP error messages:
Destination Unreachable Section 126.96.36.199 Redirect Section 188.8.131.52 Source Quench Section 184.108.40.206 Time Exceeded Section 220.127.116.11 Parameter Problem Section 18.104.22.168 ICMP query messages: Echo Section 22.214.171.124 Information Section 126.96.36.199 Timestamp Section 188.8.131.52 Address Mask Section 184.108.40.206 Router Discovery Section 220.127.116.11General ICMP requirements and discussion are in the next section.