The Internet Control Message Protocol (ICMP)

JMU

The Internet Control Message Protocol (ICMP)
An Introduction

Prof. David Bernstein
James Madison University

Computer Science Department

bernstdh@jmu.edu

Overview

Purpose:
- Used to communicate IP status and error messages
Specifications:
- RFC 792
Note:
- ICMP describes the format of the payload of "special" IP frames

Frame Format

Header
- Type (8 bits)
- Code (8 bits)
- Checksum (16 bits)
Body
- Varies by type

Message Types

Echo (a.k.a., ping) Reply
Destination Unreachable
Source Quench
Redirect
Echo (a.k.a., ping)
Time Exceeded
Parameter Problem
Timestamp
Timestamp Reply
Information Request
Information Reply
Address Mask Request
Address Mask Reply