Internet Control Message Protocol

1. ICMP
INTERNET CONTROL MESSAGE PROTOCOL
By
Naveed Ahmed Channa

2. ICMP:
 The Internet Control Message Protocol (ICMP) is an integral part
of the TCP/IP protocol suite.
 Unlike error messages, control messages are not the results of
lost packets o
r error conditions which occur during packet transmission.
 Like all ICMP messages, ICMP control messages are
encapsulated within an IP datagram.
 Multiple types of control messages are used by ICMP

3. ICMP

4. TERMS
Destination Unreachable
Echo Reply
Echo Request
Packet Too Big
Parameter Problem
Path MTU Discovery (PMTUD)
Redirect Message
Source Quench
Time Exceeded

5. ICMP Example
Serial connectivity of on NAC-R2 is down.
NAC-PC1 is trying to communicate with NAC-PC2 what we get…?
NAC-R2 will use ICMP to inform NAC-PC1 that NAC-PC2 cant be reached
NAC-R2 will send an ICMP destination unreachable message.

6. ICMP runs on top of IP
In parallel to TCP and UDP
Though still viewed as an integral part of IP
Diagnostics
Triggered when an IP packet encounters a problem E.g.,
time exceeded or destination unreachable
ICMP packet sent back to the source IP address
Includes the error information (e.g., type and code)
and an excerpt of the original data packet for
identification
 Source host receives the ICMP packet
 Inspects the except of the packet (e.g., protocol and
ports)
 To identify which socket should receive the error