Chapter 9 - Internet control message protocol. Upon completion you will be able to: Be familiar with the ICMP message format, know the types of error reporting messages, know the types of query messages, be able to calculate the ICMP checksum, know how to use the ping and traceroute commands, understand the modules and interactions of an ICMP package. | Chapter 9 Upon completion you will be able to: Internet Control Message Protocol Be familiar with the ICMP message format Know the types of error reporting messages Know the types of query messages Be able to calculate the ICMP checksum Know how to use the ping and traceroute commands Understand the modules and interactions of an ICMP package Objectives TCP/IP Protocol Suite Figure Position of ICMP in the network layer TCP/IP Protocol Suite Figure ICMP encapsulation TCP/IP Protocol Suite TYPES OF MESSAGES ICMP messages are divided into error-reporting messages and query messages. The error-reporting messages report problems that a router or a host (destination) may encounter. The query messages get specific information from a router or another host. TCP/IP Protocol Suite Figure ICMP messages TCP/IP Protocol Suite Table ICMP messages TCP/IP Protocol Suite MESSAGE FORMAT An ICMP message has an 8-byte header and a variable-size data . | Chapter 9 Upon completion you will be able to: Internet Control Message Protocol Be familiar with the ICMP message format Know the types of error reporting messages Know the types of query messages Be able to calculate the ICMP checksum Know how to use the ping and traceroute commands Understand the modules and interactions of an ICMP package Objectives TCP/IP Protocol Suite Figure Position of ICMP in the network layer TCP/IP Protocol Suite Figure ICMP encapsulation TCP/IP Protocol Suite TYPES OF MESSAGES ICMP messages are divided into error-reporting messages and query messages. The error-reporting messages report problems that a router or a host (destination) may encounter. The query messages get specific information from a router or another host. TCP/IP Protocol Suite Figure ICMP messages TCP/IP Protocol Suite Table ICMP messages TCP/IP Protocol Suite MESSAGE FORMAT An ICMP message has an 8-byte header and a variable-size data section. Although the general format of the header is different for each message type, the first 4 bytes are common to all. TCP/IP Protocol Suite Figure General format of ICMP messages TCP/IP Protocol Suite ERROR REPORTING IP, as an unreliable protocol, is not concerned with error checking and error control. ICMP was designed, in part, to compensate for this shortcoming. ICMP does not correct errors, it simply reports them. The topics discussed in this section include: Destination Unreachable Source Quench Time Exceeded Parameter Problem Redirection TCP/IP Protocol Suite ICMP always reports error messages to the original source. Note: TCP/IP Protocol Suite Figure Error-reporting messages TCP/IP Protocol Suite The following are important points about ICMP error messages: ❏ No ICMP error message will be generated in response to a datagram carrying an ICMP error message. ❏ No ICMP error message will be generated for a fragmented datagram that is not the first
