Ping

From Wikipedia, the free encyclopedia ping ping ICMP packet Bit 0 - 7 IP Header (160 bits OR 20 Bytes) Version/IHL Identification Time To Live(TTL) Source IP address Destination IP address ICMP Payload (64+ bits OR 8+ Bytes) Type of message Quench Data (optional) 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 measures the round-trip time[1] and records any packet loss, and prints when finished a statistical summary of the echo response packets received, the minimum, mean, max and in some versions the standard deviation of the round trip time. The word ping is also frequently used as a verb or noun, where it is usually incorrectly used to refer to the round-trip time, or measuring the round-trip time. The tool is used in a type of simple denialof-service attack, known as a ping flood, in which the attacker overwhelms the victim with ICMP echo request packets. 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). [1][2] 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 RFC 1122 prescribes that any host must accept an echo-request and issue an echo-reply in return, this is supposedly a security risk. Thus, hosts that no longer follow this standard are frequent on the public Internet. Code Checksum Protocol Bit 8 - 15 Type of service Bit 16 - 23 Length flags and offset Checksum Bit 24 - 31 History A server denying a ping request because of the request’s size. ICMP packet Generic composition of an ICMP packet[3] • Header (in blue): 1 From Wikipedia, the free encyclopedia • Protocol set to 1 and Type of Service set to 0. • Payload (in red): • Type of ICMP message (8 bits) • Code (8 bits) • Checksum (16 bits), calculated with the ICMP part of the packet (the header is not used) • The ICMP ’Quench’ (32 bits) field, which in this case (ICMP echo request and replies), will be composed of identifier (16 bits) and sequence number (16 bits). • Data load for the different kind of answers (Can be an arbitrary length, left to implementation detail. However must be less than the maximum MTU of the network). ping While a ping session is running, under some Linux systems, you can get the overall status of the session without quitting by sending the Ctrl+\ key combination. This will give you a summary similar to the following. 6/6 packets, 0% loss, min/avg/ewma/max = 15.30 Sample with Windows The following is a sample output of pinging en.wikipedia.org under Windows (Windows 7 used in the following example) from within the Command Prompt: Sample pinging Sample with Linux The following is a sample output of pinging en.wikipedia.org under Linux with the iputils version of ping: Pinging rr.pmtpa.wikimedia.org [208.80.152.2] Reply from 208.80.152.2: bytes=32 time=80ms TT Reply from 208.80.152.2: bytes=32 time=81ms TT Reply from 208.80.152.2: bytes=32 time=84ms TT Reply from 208.80.152.2: bytes=32 time=84ms TT Ping statistics for 208.80.152.2: Packets: Sent = 4, Received = 4, Lost = 0 ( Approximate round trip times in milli-seconds: Minimum = 80ms, Maximum = 84ms, Average = 8 Windows appears not to inform the user about duplicated return packets. admin@localhost# ping en.wikipedia.org While a ping session is running you can PING rr.pmtpa.wikimedia.org (66.230.200.100) 56(84) bytes of the session without get the overall status of data. 64 bytes from rr.pmtpa.wikimedia.org (66.230.200.100): icmp_seq=1 ttl=52 time=87.7 ms quitting by sending the Ctrl+Break key 64 bytes from rr.pmtpa.wikimedia.org (66.230.200.100): icmp_seq=2 ttl=52 time=95.6 ms combination. 64 bytes from rr.pmtpa.wikimedia.org (66.230.200.100): icmp_seq=3 ttl=52 time=85.4 ms 64 bytes from rr.pmtpa.wikimedia.org (66.230.200.100):Mac OS X ttl=52 time=95.8 ms Sample with icmp_seq=4 64 bytes from rr.pmtpa.wikimedia.org (66.230.200.100): icmp_seq=5 ttl=52 time=87.0 ms The following is a sample output of pinging 64 bytes from rr.pmtpa.wikimedia.org (66.230.200.100): icmp_seq=6 ttl=52 time=97.6 ms en.wikipedia.org under Mac OS X Leopard using the Terminal: --- rr.pmtpa.wikimedia.org ping statistics --10 packets transmitted, 10 received, 0% packet loss, time 8998ms Macintosh:~ user$ ping -c 10 en.wikipedia.org rtt min/avg/max/mdev = 78.162/89.213/97.695/6.836 ms PING rr.knams.wikimedia.org (91.198.174.2): 56 64 bytes from 91.198.174.2: icmp_seq=0 ttl=53 This output shows that en.wikipedia.org is 64 bytes from 91.198.174.2: icmp_seq=1 ttl=53 a DNS CNAME record for rr.pmtpa.wiki64 bytes from 91.198.174.2: icmp_seq=2 ttl=53 media.org which then resolves to 64 bytes from 91.198.174.2: icmp_seq=3 ttl=53 66.230.200.100. 64 bytes from 91.198.174.2: icmp_seq=4 ttl=53 The output then shows the results of mak64 bytes from 91.198.174.2: icmp_seq=5 ttl=53 ing 10 pings to 66.230.200.100 with the res64 bytes from 91.198.174.2: icmp_seq=6 ttl=53 ults summarized at the end. (To stop the pro64 bytes from 91.198.174.2: icmp_seq=7 ttl=53 gram in Linux or Windows, press Ctrl+C.) 64 bytes from 91.198.174.2: icmp_seq=8 ttl=53 • shortest round trip time was 78.162 64 bytes from 91.198.174.2: icmp_seq=9 ttl=53 milliseconds • average round trip time was 89.213 --- rr.knams.wikimedia.org ping statistics --milliseconds 10 packets transmitted, 10 packets received, 0 • maximum round trip time was 97.695 round-trip min/avg/max/stddev = 40.019/45.575/ milliseconds • Standard deviation of the round-trip time was 6.836 milliseconds 2 From Wikipedia, the free encyclopedia ping 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Type = 8 Identifier Data ::: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Type = 0 Identifier Data ::: While a ping session is running you can get the overall status of the session without quitting by sending the Ctrl+t key combination. This will give you a summary similar to the following. echo requests are associated with the echo replies. • The data received in the echo request must be entirely included in the echo reply. Code = 0 Header Checksum Sequence Number Code = 0 Header Checksum Sequence Number load: 0.37 cmd: ping 1748 running 0.01u 0.07s 255/255 packets received (100%) 18.827 min / 19.975 avg / 29.200 max 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 Echo request 15103, offset 0, flags [none], proto: ICMP (1), The echo request is an ICMP message whose length: 60) 192.168.146.22 > 192.168.144.5: data is expected to be received back in an ICMP echo request, id 1, seq 38, length 40 echo reply ("ping"). The host must respond to 0x0000: 4500 003c 3aff 0000 8001 all echo requests with an echo reply contain0x0010: c0a8 9005 0800 4d35 0001 ing the exact data received in the request 0x0020: 6566 6768 696a 6b6c 6d6e message. 0x0030: 7576 7761 6263 6465 6667 • Type must be set to 8. • Code must be set to 0. • The Identifier and Sequence Number can be used by the client to match the reply In various network multiplayer games, the with the request that caused the reply. In server notes the time it requires for a game practice, most Linux systems use a unique packet to reach a client and a response to be identifier for every ping process, and received. This round-trip time is usually resequence number is an increasing number ported as the player’s ’ping’. It is used as an within that process. Windows uses a fixed effective measurement of the player’s lag, identifier, which varies between Windows with lower ping times being desirable. Note versions, and a sequence number that is that this style of ping typically does not use only reset at boot time. ICMP packets. • The data received by the Echo Request must be entirely included in the Echo Reply. Payload Message format 5c55 c 0026 6 6f70 7 6869 In gaming In common usage Echo reply The echo reply is an ICMP message generated in response to an echo request, and is mandatory for all hosts and routers. • Type and code must be set to 0. • The identifier and sequence number can be used by the client to determine which The term ’ping’ is commonly used to indicate an effectively contentless message. For instance, a short or empty instant message, email, voice mail or "missed call" notification can be used to indicate availability, or anything else that can be conveyed with a single bit of information at a given time. 3 From Wikipedia, the free encyclopedia Occasionally Packet InterNet Groper is suggested as a retronym or backronym, but the original author of ping says that it is based on the sound of a sonar return.[1]. The term ’ping’ has been generalized to a word used to query if someone is available over Instant Messenger. The term is typically used in this fashion among computer professionals or other people who are familiar with the ping utility and its functionality. • • • • List of Unix utilities Ping of death Ping (video games) traceroute, my traceroute ping References [1] ^ "The Story of the PING Program". http://ftp.arl.mil/~mike/ping.html. Retrieved on 29 December 2008. [2] Salus, Peter (1994). A Quarter Century of UNIX. Addison-Wesley. ISBN 0201547775. [3] RFC 792 See also • bing, ping with added throughput measurements • dping, IBM AIX command included in IBM Cluster Systems Management for sending ICMP packets to multiple hosts in parallel • fping, command for sending ICMP packets to multiple hosts in parallel • List of DOS commands External links • ping(1): send ICMP ECHO_REQUEST to network hosts – Linux man page • Ping Animation • WikiHow: To PING an IP address Retrieved from "http://en.wikipedia.org/wiki/Ping" Categories: Network analyzers, Open source network management software, Network-related software, Unix software, Windows communication and services, Windows administration This page was last modified on 20 May 2009, at 12:08 (UTC). All text is available under the terms of the GNU Free Documentation License. (See Copyrights for details.) Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a U.S. registered 501(c)(3) taxdeductible nonprofit charity. Privacy policy About Wikipedia Disclaimers 4