What is the difference between a virtual circuit and a logic channel

A virtual circuit is a virtual connection between DTE-DET and exists between end-to-end; A logical channel is an allocable resource on a DTE-DCE interface or trunk that exists between points and nodes. There can be multiple logical channels on a line, and the logical channel number of each line is assigned independently, and a virtual circuit is composed of multiple logical channels, and the logical channel number (LCN) of the same virtual circuit on different lines may be different.

In addition, the logic channel has always existed, it is divided into two states: occupied and idle, and the virtual circuit (excluding the permanent virtual circuit) is established with the start of communication and cleared with the end of communication.

The main differences between virtual circuits and logic channels are:

1) The virtual circuit is a virtual connection established between the master and the called DTE; The logical channel is assigned on the interface between the DTE and the switch or on the trunk in the network, and represents a numbering resource of the channel. A virtual circuit is composed of multiple logical channels linked, and the allocation of logical channel numbers for each line is carried out independently.

2) A virtual circuit has call setup, data transmission, and call release processes. Permanent virtual circuits can be established by the network at the time of appointment and can also be cleared by appointment; Whereas, the logical channel is an objective existence, which has a difference between occupied and idle, but it will not disappear.

A virtual circuit is one of the two modes of transmission in packet switching. In communications and networking, virtual circuits are connection-oriented communication services provided by packet-switched communications. After a logical connection or virtual circuit is established between two nodes or application processes, each packet can be sent sequentially between the two nodes, and the order in which the receiver receives the packets must be the same as the order in which the sender sends them, so the receiver is not responsible for reordering the packets after collecting them.

The virtual circuit protocol hides the process of splitting data into segments, packets, or frames from higher-level protocols.

First, the meaning is different:

Physical channels generally refer to channels that rely on physical media to transmit information, such as: ** line, optical fiber, coaxial, microwave, etc.

A logical channel generally refers to an artificially defined information transmission channel. There are a lot of them, mostly some encoding or dividing into different time slots to transmit different information.

Second, the role is different:

The logical channel MAC layer provides data transmission services on the logical channel, and the logical channel type set is defined for the different types of data transmission services provided by the MAC layer.

Logical channels can generally be divided into two categories: control channels and service channels.

The control channel is used to transmit control plane information, while the service channel is used to transmit user plane information.

Third, the composition is different:

A logical channel defines the type of information that is transmitted, either in separate chunks or in interspersed data streams with a defined starting bit, which includes data for all users.

The physical channel is to determine the carrier frequency, scrambling code, spread spectrum code, start and end time of the transmission channel data stream belonging to different users and different functions according to the corresponding rules, and finally modulate it into an analog radio frequency signal and transmit it; Data streams on different physical channels belong to different users or functions.

In the protocol of the air interface, the physical, transmission, and logical channels are defined.

1. The logical channel describes the type of information, that is, it defines what information is transmitted.

2. The transmission channel describes the way information is transmitted, that is, it defines how the information is transmitted.

3. The physical channel is used by the physical layer for the transmission of specific signals.