8.1 Overview of TCP/IP Error Message  
  8.1.3 ICMP message delivery  
ICMP messages are encapsulated into datagrams in the same way any other data is delivered using IP. Figure displays the encapsulation of ICMP data within an IP datagram.

Since ICMP messages are transmitted in the same way as any other data, they are subject to the same delivery failures. This creates a scenario where error reports could generate more error reports, causing increased congestion on an already ailing network. For this reason, errors created by ICMP messages do not generate their own ICMP messages. It is thus possible to have a datagram delivery error that is never reported back to the sender of the data.

 

Web Links

Best Effort Delivery

http://oucsace.cs.ohiou.edu/~osterman/ class/cs444.archive/ notes/icmp.pdf