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Name: Michael
Status: Student
Age: 20s
Location: N/A
Country: N/A
Date: Around 1999


Question:
Data communications:

have you heard of the ICMP ping command?,can you tell me what it is about and what does it do?.Thanks



Replies:
This is a great question, first off I will give some explanation on the protocols used here.

ICMP is the Internet Control Message Protocol, (ICMP) this is a reporting protocol used to provide feedback on specific conditions. ICMP messages are only sent by a router or a destination node in response to a Packet Internet Gopher (PING) request. PING is used to check the state of a remote machine via the TCP/IP protocol. For example, you would ping a specific computer over the internet or intranet and the computer would send back a ICMP response, these responses are usually 32bits and are usually sent in sets of 4.

If there is a problem and the computer or router cannot functioning properly, it will send back a response giving it's current state. If the router/computer is not up or function properly the ICMP response would send back a "No Response" or "Request Timed Out" statement to the users letting them know that the router/computer is not responding. If the router/computer is up and well, it will send back a response sating the time it takes for the PING to complete a round trip from the sender to the host and back to the sender.

This is a nice protocol if used properly. Denial of Service attacks have been in the news lately, when CNN, Yahoo, and others were crippled by hackers, they used a fancy version of PING. Denial of service attacks are brought on by large amounts of PING request and ICMP responses. If one or many, flooded a given computer/router at one time with PING requests, this would take up bandwidth and CPU utilization in response to all the PING's it was receiving. For every PING, it sends a ICMP response, if you send 1 million PING's that computer would have to process 1 million ICMP responses, thus bringing that computer/router to it's knees. I hope this helps

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Joe Noga MCSE, N+
Windows NT/2000 Server Specialist
Arthur Andersen


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