Ping_Zen and the Art of the Internet

The ping command allows the user to check if another system is

currently "up" and running. The general form of the command

is ping system. {The usage will, again, vary.}

For example,

ping cs.widener.edu

will tell you if the main machine in Widener University's Computer

Science lab is currently online (we certainly hope so!).

Many implementations of ping also include an option to let you

see how fast a link is running (to give you some idea of the load on

the network). For example:

% ping -s cs.swarthmore.edu

PING cs.swarthmore.edu: 56 data bytes

64 bytes from 130.58.68.1: icmp_seq=0 ttl=251 time=66 ms

64 bytes from 130.58.68.1: icmp_seq=1 ttl=251 time=45 ms

64 bytes from 130.58.68.1: icmp_seq=2 ttl=251 time=46 ms

--- cs.swarthmore.edu ping statistics ---

3 packets transmitted, 3 packets received, 0% packet loss

round-trip min/avg/max = 45/52/66 ms

This case tells us that for cs.swarthmore.edu it takes about 46

milliseconds for a packet to go from Widener to Swarthmore College and

back again. It also gives the average and worst-case speeds, and any

packet loss that may have occurred (e.g. because of network

congestion).

While ping generally doesn't hurt network performance, you

shouldn't use it too often---usually once or twice will leave

you relatively sure of the other system's state.