Communication & Computer Network - "Propagation delay" and "Transmission delay"

Propagation delay

The time when data (more specifically, photoelectric signal, because data is hidden in the photoelectric signal during transmission) propagates from one end of the network through the medium to the other end.

Determinant

This mainly depends on the propagation speed of the photoelectric signal in the medium and the length of the direct medium at both ends.

Transmission delay

It may be clearer to change the transmission delay to the transmission delay. Computer Network (the seventh edition, edited by Xie Xiren) is translated as transmission delay, which is easy to be ambiguous for Chinese. The following text also adds a special note to understand it as transmission.

Determinant

Actually, it refers to the time required from the start of data transmission to the completion of data transmission. This actually has a great relationship with the channel transmission rate. Note that there is no ambiguity when it comes to speed, and there is ambiguity when it comes to speed.

An analogy used to easily understand the difference between the two

Transmission delay is also called transmission delay. The example of a bus can be used for analogy. The transmission delay is similar to that before the bus arrives at the platform, the time spent by the passengers waiting for the bus on the platform from the first boarding to the last boarding is the transmission delay; The time taken by the bus to carry passengers from one station to the next is the propagation delay. In the network structure, the process of sending data to the media is the process of passengers boarding; The time taken for data to propagate on the propagation medium in the form of electromagnetic signals or optical signals is the propagation delay.

Other delays

Queuing delay

When a packet is transmitted through a network, it passes through many routers. After entering the router, you should queue in the input queue for processing. After the router determines the forwarding interface, it must queue in the output queue for forwarding

Nodal processing delay

The time generated by the node to store and forward messages (such as parsing messages, looking up routing tables, etc.)