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TCP/IP Illustrated, Volume 1: The Protocols by W. Richard Stevens

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Chapter 7. Ping Program

Introduction

The name "ping" is taken from the sonar operation to locate objects. The Ping program was written by Mike Muuss and it tests whether another host is reachable. The program sends an ICMP echo request message to a host, expecting an ICMP echo reply to be returned. (Figure 6.3 lists all the ICMP message types.)

Normally if you can't Ping a host, you won't be able to Telnet or FTP to that host. Conversely, if you can't Telnet to a host, Ping is often the starting point to determine what the problem is. Ping also measures the round-trip time to the host, giving us some indication of how "far away" that host is.

In this chapter we'll use Ping as a diagnostic tool and to further explore ICMP. Ping also gives us an opportunity ...

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