Understanding the ICMP - Destination Unreachable Message

ICMP Destination Unreachable analysis. This article will analyse all six ICMP destination unreachable messages and explain when each of these messages are used.

http://www.firewall.cx/networking-topics/protocols/icmp-protocol/153-icmp-destination-unreachable.html

ICMP - Echo / Echo Reply (Ping) Message

This article deals with the analysis of the ICMP Echo & Echo Reply (Ping). We examine the ICMP header and fields to show the contents of a ICMP echo/reply (ping/ping-reply) packet to help understand how the message is formatted and used. Pinging bytes, TTL and response time is also analysed.

http://www.firewall.cx/networking-topics/protocols/icmp-protocol/152-icmp-echo-ping.html

Introduction To The ICMP Protocol

This article explains why the ICMP protocol was created and how it is used to troubleshoot networks. Learn which OSI Level ICMP operates and its characteristics.

http://www.firewall.cx/networking-topics/protocols/icmp-protocol/151-icmp-introduction.html