What are the three communication modes used in WAN?

There are three communication modes in WAN: point-to-point connection, circuit switching and packet switching.

1. Point-to-point connection

Point-to-point (PPP) connection, also known as line lease, is a dedicated communication channel for two user points provided by telecom operators, and it is a permanent dedicated physical channel, such as DDN(Digital).

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2. Circuit switching

Circuit switching is also a wide area network switching method. The network temporarily establishes a dedicated physical circuit for each communication session through the carrier wave on the medium link, and keeps the circuit until the connection is terminated after the communication, such as ISDN and PSTN.

3. Packet switching technology

Packet switching network uses virtual circuit and data message to realize network communication. The so-called virtual circuit mode is to establish several logical virtual circuits on a physical link by using multiplexing technology to realize one-to-many simultaneous communication. The so-called data message service refers to the storage through the packet switch, and then the packets are forwarded according to different paths, so that the bandwidth of the line can be dynamically utilized. For example, Frame Relay, X.25 and ATM are all packet-switched communication modes.