“Ping” (short for Packet Internet Groper) is without doubt one of the tools of network administration best known. Yet this is one of the most simple since it allows, through the sending packets to verify if a remote machine responds and, by extension, it is accessible via the network.
The ping tool allows to diagnose network connectivity with a command like:
ping name.of.machine
name.of.machine represents the IP address of the machine or its name. It is usually best at first to test with the IP address of the machine.
Operation table
Ping uses the ICMP protocol , to diagnose the transmission conditions. He thus uses two types of protocol messages (out of 18 proposed by ICMP):
Type 0 is an “echo request”, issued by the source machine;
The type 8 corresponding to an “echo reply”, issued;
At regular intervals (default every second), the source machine (the one on which the ping command is executed) sends a command “echo requests’ to the target machine. Upon receipt of the package “echo reply”, the source machine displays a line containing a certain amount of information. In case of non receipt of the response, a line that says “timeout” error.
Result of ping
Depending on the operating system, display the output of a ping may be slightly different.
The result of such a command under GNU / Linux:
ping www.mynetworkdictionary.com
ping www.mynetworkdictionary.com (163.5.255.85): 56 data bytes
64 bytes from 163.5.255.85: icmp_seq = 0 ttl = 56 time = 7.7 ms
64 bytes from 163.5.255.85: icmp_seq = 1 ttl = 56 time = 6.0 ms
64 bytes from 163.5.255.85: icmp_seq = 2 ttl = 56 time = 5.5 ms
64 bytes from 163.5.255.85: icmp_seq = 3 ttl = 56 time = 6.0 ms
64 bytes from 163.5.255.85: icmp_seq = 4 ttl = 56 time = 5.3 ms
64 bytes from 163.5.255.85: icmp_seq = 5 ttl = 56 time = 5.6 ms
64 bytes from 163.5.255.85: icmp_seq = 6 ttl = 56 time = 7.0 ms
64 bytes from 163.5.255.85: icmp_seq = 7 ttl = 56 time = 6.0 ms
--- Ping statistics --- www.mynetworkdictionary.com
Transmitted packets 8, 8 packets received, 0% packet loss
round-trip min / avg / max = 5.3/6.1/7.7 ms
The result of such a command as a Windows system:
ping www.mynetworkdictionary.com
Pinging www.mynetworkdictionary.com [205.234.219.179] with 32 bytes of data:
Response 205.234.219.179: bytes = 32 time = 34 ms = 54 TTL
Response 205.234.219.179: bytes = 32 time = 37 ms TTL = 54
Response 205.234.219.179: bytes = 32 time = 32ms TTL = 54
Response 205.234.219.179: bytes = 32 time = 33 ms TTL = 54
Ping statistics for 205.234.219.179:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip in milliseconds:
Minimum = 32ms, Maximum = 37ms, Average = 34ms
The output of the ping command allows to know:
- The IP address matches the name of the remote machine;
- The ICMP sequence number;
- The lifetime of a packet (TTL Time To Live). The field of life (TTL) indicates the number of routers traversed by the packet in the exchange between the two machines. Each IP packet has a TTL field set to a relatively high value. Each time a router, the field is decremented. If it happens that the field reaches zero, the router will perform the packet in a loop and destroy it.
- The round trip delay time (round-trip delay) corresponding to the duration in milliseconds for a round trip between the source and the target machine. A package should normally have a propagation delay less than 200 ms.
- The number of lost packets.