| 8.1 |  | Overview of TCP/IP Error Message |
| 8.1.1 |  | Internet Control Message Protocol (ICMP) |

| IP is an unreliable method for delivery of network data. It is known as a best effort delivery mechanism. It has no built-in processes to ensure that data is delivered in the event that problems exist with network communication. If an intermediary device such as a router fails, or if a destination device is disconnected from the network, data cannot be delivered. Additionally, nothing in its basic design allows IP to notify the sender that a data transmission has failed. Internet Control Message Protocol (ICMP) is the component of the TCP/IP protocol stack that addresses this basic limitation of IP. ICMP does not overcome the unreliability issues in IP. Reliability must be provided by upper layer protocols if it is needed.
| Web Links Introduction to ICMP http://www.cisco.com/en/US/tech/tk826/ tk364/tk344/tech_ protocol_home.html