What is packet loss?

Packet loss describes a type of network issue where devices do not receive all data sent to them via network protocols.

A packet in networking is data, or a formatted unit of data sent across a network. Packets carry data sent between network devices. When a device on a network is sending and receiving data via the Internet, it is sending and receiving packets. If you’re loading a web page on your phone, your phone is communicating with the web server, and the web server is returning packets to your phone to populate the page in your browser.

Packet loss is measured when a portion of what is being sent to a specific network device isn’t being received. A common tool to measure possible packet loss is the ping command (more about the ping command here).

Above is an example of an error message generated by using ping. A network device sent a ping but the ping response wasn't received. As a result, the request timed out, and this packet is considered lost. 

Above are total results of a ping command with no packet loss. Packet loss is typically measured in percentage form.

What causes packet loss?  There are several possible packet loss causes: 

• Network congestion: If a server or device is overwhelmed by requests, this may result in packet loss. Your packet travels through routers, servers and computers, and if those devices are overwhelmed your packet may get lost in transit.
• Packet discarding: Some routers or devices will discard ICMP or ping packets due to high volume, rate limiting or network rule settings.
• Routing issue: If you’re communicating with a device via the Internet, your packets are being routed to their destination. If the routing employed is incorrect, your packet may not reach its destination. This can be tested by using traceroute (see more on traceroute command here).
• Bandwidth: If a device on your network is utilizing the entirety of your bandwidth, this could result in packet loss on your network.
• Wiring fault/network hardware: Failing network hardware could result in packet loss. A bad wire termination or aging cable could be at fault.
• Wireless interference: Wireless devices that experience packet loss may be a result of wireless interference (see more on wireless issues here). Disruption in wireless signal can lead to lost packets.
• Software/driver issues: Outdated network drivers may cause packet loss. A bug in network device operating systems may impact network performance in the way of packet loss.