CSU / DSU - an essential component of a WAN

For example, if we open an e-commerce website and do business from home, then the amount of data that needs to be received and processed from Webserver is relatively large (and will continue to grow in the future). The solution is to hire a leased line T1 or a fractional T1 line (with the speed of T1) to telco or a gateway of the provider. Internet service provider, then we will need a CSU / DSU department and the provider also needs another CSU / DSU from their side.

One reason for having to switch signals is the signals in the LAN. Restrictions on transmission distance, due to its encryption and signaling mechanisms, must use WAN transmission techniques, this technique uses use other types of signals, encryption and transmission mechanisms, as well as frame data in a different way so that data can be transmitted further and take advantage of telco's telecommunications network platform.Therefore, it is necessary to have a switch from LAN signal to WAN, this is the mission of CSU / DSU.CSU / DSU must be placed at both ends of the WAN connection, both on the client side and the provider side.

The Channel Service Unit (CSU) is a signal transmitter and receiver on WAN links, it also provides a mechanism to prevent interference (or interference) from both ends of the device.CSU is also responsible for loopback signal feedback testing from telco.

Data Service Unit (DSU) is capable of managing the control and transmission of incoming and outgoing signals between the RS232C, RS-449, or V.xx signal frame standards of LAN with data frame. Data is built according to the time-division multiplexed (TDM) mechanism of T1 DSx lines (DS0, DS1, etc.).DSU monitors and manages errors due to time asynchronous and performs signal reproduction.The DSU provides the same interface as the modem between the computer (acting as DTE) with the CSU device.      

CSU / DSUs can be deployed on discrete products or integrated in a T1-WAN card.A CSU / DSU Data Terminal Equipment interface is usually compatible with V.xx and RS-232C standards or similar interfaces.The main and integrated manufacturers of CSU / DSU products on the market today are Adtran, Cisco, and Memotec.

Although becoming an integral part of today's telecom networks, few know that CSU was born at AT&T as an interface to its non-switching digital data systems.The DSU then serves as the interface to the DTE device using the standard interface (EIA / CCITT).The DSU also provided some simple testing mechanisms.