Network delay is an important design and performance characteristic of a computer network

Computer network

A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....

 or telecommunications network

Telecommunications network

A telecommunications network is a collection of terminals, links and nodes which connect together to enable telecommunication between users of the terminals. Networks may use circuit switching or message switching. Each terminal in the network must have a unique address so messages or connections...

. The delay of a network specifies how long it takes for a bit of data to travel across the network from one node or endpoint to another. It is typically measured in multiples or fractions of seconds. Delay may differ slightly, depending on the location of the specific pair of communicating nodes. Although users only care about the total delay of a network, engineers need to perform precise measurements. Thus, engineers usually report both the maximum and average delay, and they divide the delay into several parts:

• Processing delay
  Processing delay
  In a network based on packet switching, processing delay is the time it takes routers to process the packet header. Processing delay is a key component in network delay....
  
   - time routers take to process the packet header
• Queuing delay
  Queuing delay
  In telecommunication and computer engineering, the queuing delay is the time a job waits in a queue until it can be executed. It is a key component of network delay....
  
   - time the packet spends in routing queues
• Transmission delay
  Transmission delay
  In a network based on packet switching, transmission delay is the amount of time required to push all of the packet's bits into the wire. In other words, this is the delay caused by the data-rate of the link....
  
   - time it takes to push the packet's bits onto the link
• Propagation delay
  Propagation delay
  Propagation delay is a technical term that can have a different meaning depending on the context. It can relate to networking, electronics or physics...
  
   - time for a signal to reach its destination

There is a certain minimum level of delay that will be experienced due to the time it takes to transmit

Data transmission

Data transmission, digital transmission, or digital communications is the physical transfer of data over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optical fibres, wireless communication channels, and storage media...

 a packet serially through a link

Data link

In telecommunication a data link is the means of connecting one location to another for the purpose of transmitting and receiving information. It can also refer to a set of electronics assemblies, consisting of a transmitter and a receiver and the interconnecting data telecommunication circuit...

. Onto this is added a more variable level of delay due to network congestion

Network congestion

In data networking and queueing theory, network congestion occurs when a link or node is carrying so much data that its quality of service deteriorates. Typical effects include queueing delay, packet loss or the blocking of new connections...

. IP network delays can range from just a few milliseconds to several hundred milliseconds.