ICMP protocol and analysis of packet capture
The Internet Message Control Protocol (ICMP) specifies a variety of message types, the purpose of which is to manage the network.
ICMP messages are divided into error messages, request messages and response messages.
General ICMP packet format
ICMP packet type field and code field
Wirehark packet capture analysis
Data link layer
Network layer
1. Response request
ping command: response request (Type = 8) and response request (Type = 0)
2. Time stamp:
time stamp request message (Type = 13) time stamp response message (Type = 14) for testing The transmission time of a data packet back and forth between two hosts.
3 important types:
Route advertisement (router advertisement) and route selection (router selection): Type 9 and Type 10 respectively, they are used in ICMP Route Discovery Protocol (IRDP). IRDP protocol is used in some operating systems to discover local routers
Redirection: ICMP type 5 is used by routers to notify the host to go to the gateway of the specified target, which is another router on the data link.