Updated: May 16
Ping is a network diagnostic tool used primarily to test the connectivity between two nodes or devices. To ping a destination node, an Internet Control Message Protocol (ICMP) echo request packet is sent to that node.
If a connection is available, the destination node responds with an echo reply. Ping calculates the round-trip time of the data packet’s route from its source to the destination and back, and determines whether any packets were lost during the trip.
If you’ve been browsing the Web long enough or love playing multiplayer games, you may have come across the term “ping.” You may know already that the lower the ping is, the better your connection is. But what is a “ping” really? What does it mean in the computing world, and why does it have such an odd name?
Using ping to check the status of a server is very handy when trying to solve a network problem. Networks are typically made up of a lot of different servers. If one of them goes down or is acting slow, it can prevent you from connecting to the server you want to access. Even worse, there will be very little feedback on which server, exactly, is the one causing the issues!
By pinging from your computer to the target server, you can see the steps your communication takes as it makes its journey. If the communication “trips up” at a specific part, your computer will let you know that the signal got lost. This means you can diagnose what step of the journey has gone bad and can fix the problem accordingly.
The payload of the echo request packet often consists of American Standard Code for Information Interchange (ASCII) characters with variable adjustable lengths. Round-trip time is calculated by noting the local time of the source node clock when the IP datagram leaves the source node, then subtracting that time from the time at which the echo reply arrives.
Depending on the operating system, ping utility output varies. However, almost all ping outputs display the following:
Destination IP address
ICMP sequence number
Time to live (TTL)
The number of packets lost during transmission
The ping tool displays various error messages if a round trip is not completed successfully. They include the following:
TTL Expired in Transit: Determines the maximum amount of time an IP packet may live over the network before being discarded if it has not reached its destination. To address this error, try to increase TTL value by using the ping -i switch.
Destination Host Unreachable: Indicates that the destination node is down or is not operating on the network. It may even occur due to the non-existence of a local or remote route for the destination host. To address this error, modify the local route table or switch the node on.
Request Timed Out: Indicates that the ping command timed out because there was no reply from the host. It indicates that no echo reply messages were received due to network traffic, failure of Address Resolution Protocol (ARP) request packet filtering or a router error. Increasing the wait time using the ping –w switch may address this problem.
Unknown Host: Indicates that the IP address or the host name does not exist in the network or that the destination host name cannot be resolved. To address this issue, verify the name and availability of the domain name system (DNS) servers.