Latency: what is it?

Have you ever been faced with a connection Internet slowly while your children are playing or watching netflix in the other room? The amount of data that can be passed through the stream is limited. The more congested your data stream, the more lag you will experience while browsing the internet. This is called latency.

What is latency?

Latency is the time it takes for a packet of data to get from point A to point B. Together, bandwidth and latency define the speed and the capacity of a network. Latency is usually expressed in milliseconds and can be measured using a ping command from your computer.

When you ping, a small packet of data (usually 32 bytes) is sent to another machine, with the round trip time measured in milliseconds. The ping command measures the time it takes for the data packet to leave the source computer, travel to the destination computer, and return to the source computer.

The bandwidth is expressed in bits per second. It refers to the amount of data that can be transferred in one second. Obviously, the wider the band, the more bits can be transferred per second. And if your bandwidth is congested, your latency (delay) is increased. Think of it like a crowded freeway. The more vehicles on the highway, the more congested the traffic. Therefore, everyone is forced to drive slower.

What causes latency?

One of the main causes of network latency is distance, specifically the distance between the client devices making requests and the servers who respond to it. If a website is hosted in a data center in Paris, it will receive requests from users in Amiens (about 130 km away) fairly quickly, probably within 5 to 10 milliseconds. On the other hand, requests from users of Los Angeles (about 9,000 km) will take longer to arrive. Data traversing the Internet typically has to traverse not one, but multiple networks.

More the number of networks than the answer HTTP has to cross, the more possibilities there are for delay. For example, when data packets traverse networks, they pass through exchange points. The routers must process and route data packets, and sometimes routers must break them into smaller packets, which adds a few milliseconds to the round trip time.