1. ICMP: Internet Control Message Protocol
Reading: Section 14.4
Fall 2004
FSU CIS 5930 Internet Protocols

2. Structure of ICMP packet
Version
IHL
TOSt/Codepoint 3 7 15 31
IP packet format
Total length
Identification D F M
Fragment Offset
Time to Live
Protocol
Checksum
Source address
Destination address
Optionens (optional)
padding
type
code
Checksum
ICMP data (variable)
Fall 2004
FSU CIS 5930 Internet Protocols

3. FSU CIS 5930 Internet Protocols
Sending ICMP packets
icmp_send()
Some sanity check
Preparing ICMP packet
Copy some data from the concerned packet
ip_build_xmit()
Fall 2004
FSU CIS 5930 Internet Protocols

4. Handling incoming ICMP packets
icmp_recv()
Some sanity check
icmp_reply()
Replying ICMP request message
icmp_redirect()
Updating routing table when Redirect ICMP recved
icmp_unreach()
Handling: destination unreachable, source quench, and time exceeded
icmp_echo(), icmp_timestamp()
Handling Echo and Timestamp requests
Fall 2004
FSU CIS 5930 Internet Protocols