Ping

Ping is a computer network tool used to test whether a particular host is reachable across an IP network; it is also used to self test the network interface card of the computer, or as a speed test. It works by sending ICMP “echo request” packets to the target host and listening for ICMP “echo response” replies. Ping estimates the round-trip time, generally in milliseconds, records any packet loss, and prints a statistical summary when finished.

The word "ping" is also frequently used as a verb or noun, where it can refer directly to the round-trip time, the act of running a ping program or measuring the round-trip time.

History

Mike Muuss wrote the program in December, 1983, as a tool to troubleshoot odd behavior on an IP network. He named it after the pulses of sound made by a sonar, since its operation is analogous to active sonar in submarines, in which an operator issues a pulse of energy at the target, which then bounces from the target and is received by the operator. (The pulse of energy in sonar is analogous to a network packet in ping.) Later David L. Mills provided a backronym, "Packet InterNet Groper" (sometimes also defined as "Packet Inter-Network Groper").

The usefulness of "ping" in assisting the "diagnosis" of Internet connectivity issues was impaired from late in 2003, when a number of Internet Service Providers began filtering out ICMP Type 8 (echo request) messages at their network boundaries.

This was partly due to the increasing use of ping for target reconnaissance, for example by Internet worms such as Welchia that flood the Internet with ping requests in order to locate new hosts to infect. Not only did the availability of ping responses leak information to an attacker, it added to the overall load on networks, causing problems for routers across the Internet.

Although [http://rfc.net/rfc1122.html#p42 RFC 1122] prescribes that any host must accept an echo-request and issue an echo-reply in return, one finds that this standard is frequently not followed on the public Internet. Notably, Windows XP SP2 will not respond to an echo request on the public Internet in the default configuration. (See [http://technet.microsoft.com/en-us/library/bb457029.aspx Troubleshooting Windows Firewall in Microsoft Windows XP Service Pack 2]

ICMP packet

*"Type" and "code" must be set to 0.
*The "identifier" and "sequence number" can be used by the client to determine which echo requests are associated with the echo replies.
*The data received in the echo request must be entirely included in the echo reply.

Payload

The payload of the packet is generally filled with letters of the alphabet as this ASCII tcpdump shows

16:24:47.966461 IP (tos 0x0, ttl 128, id 15103, offset 0, flags [none] , proto: ICMP (1), length: 60) 192.168.146.22 > 192.168.144.5: ICMP echo request, id 1, seq 38, length 40

0x0000: 4500 003c 3aff 0000 8001 5c55 c0a8 9216 E..<:.....U.... 0x0010: c0a8 9005 0800 4d35 0001 0026 6162 6364 ......M5...&abcd 0x0020: 6566 6768 696a 6b6c 6d6e 6f70 7172 7374 efghijklmnopqrst 0x0030: 7576 7761 6263 6465 6667 6869 uvwabcdefghi

In gaming

In network multiplayer games like Unreal Tournament, Quake, Battlefield 2142, etc., the server notes the time it requires for a game packet to reach a client and a response to be received. This round-trip time is usually reported as the player's 'ping'. It is used as an effective measurement of the player's lag, with lower ping times being desirable. Note that this style of ping typically does not use ICMP packets.

See also

* Traceroute, mtr (My traceroute)
* fping, command for sending ICMP packets to multiple hosts in parallel
* dping, AIX command included in IBM Cluster Systems Management for sending ICMP packets to multiple hosts in parallel
* List of DOS commands
* Pingotron
* Ping (video games)
* Ping of death
* List of Unix programs

[http://www.osischool.com/tools/ping/Ping-basics/ Ping Animation]

References

* RFC 792

External links

* [http://ftp.arl.mil/~mike/ping.html The Story of the PING Program] by its author, Mike Muuss
*
* [http://ping.dtools.net ping any computer in the world] for testing and education
* [http://www.loriotpro.com/Products/On-line_Documentation_V5/LoriotProDoc_EN/J10-Loriotpro_tools/J10-I9_Ping_EN.htm A graphical ping]
* [http://www.infobyip.com/ping.php Online ping tool]