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1) Parallel and serial: transmission of 1Byte of data, parallel transmission requires 8 lines, each cable transmission 1bit
serial transmission transmits 8 bits in one line in turn
(2) asynchronous and synchronous (I also understand the bad): Anyway, it is asynchronous is 1 start bit, data, answer bits in turn, and then synchronization is 1 times encapsulated into a data frame to transmit;
(3) simplex/half Duplex/full duplex: Half-duplex is 1 way to send the time can not receive, when the receipt of the time can not be sent, and other good understanding.
(4) Time Division/Frequency Division/Wavelength Division Multiplexing: Their role is to realize the sharing of the same link. Time Division Multiplexing (TDM) is represented as the transmission of digital signals to a sub-temporal slice;
Frequency Division Multiplexing (FDM) is realized to share the analog signals of different frequencies, and wavelength division multiplexing (WDM) is mainly for optical networks, with different wavelengths of light carrying different data for transmission;
(5) Circuit/packet/cell Exchange: Circuit switching is similar to the call of the kind of exclusive link exchange; Packet switching is the exchange of packets from the source to the host, and the cell exchange is mainly used for ATM networks, which realizes the exchange of certain packets in the fixed length 53byte format of ATM ;
Common Technologies for WANs:
Wan mainly embodies the user to high-speed link access (access network), high-speed link transmission (transmission network), as well as high-speed link to the low-speed network of the sub-load (core network).
1, Access network: The most familiar should be the telephone network ISDN and ADSL. ISDN is the traditional telephone network, through the dial-up circuit exchange, the network layer adopts PPP protocol, the bandwidth is 144K. ADSL is used in the traditional telephone network in the high-frequency portion, the low-frequency portion is still used to transmit voice data, so it is required in the Bureau and the user side of the equipment to be modified to achieve voice and data separation.
There is the cable approach, using the unused bandwidth of the cable TV network. Because the transmission of TV signal is unidirectional and does not need to upload data, the bidirectional transformation of the network can be used for network data transmission.
now the most commonly used should be the way of optical fiber to the household, that is, Fttx+lan, Fiber plus LAN, the way to achieve high bandwidth transmission.
The
most promising should be the wireless way, because this is the most flexible, and low bandwidth cost and meet the requirements of access.
2, transmission network: I only in the optical network, but also only familiar with the optical network, hehe. Anyway, it is said that the most profitable Huawei Optical network, I did not realize, regret.
3, Core network: E1 (bandwidth 2.048mbit/s, China European Standard)/t1 (Bandwidth 1.544mbit/s, Americas standard); X. Packet switching network, Frame Relay network, based on X. NET, but stripped of its connection-oriented features.
Common WAN Transmission Technology
