Standalone-vs-Integrated CSU/DSU's

Customers have the choice of purchasing cards for their routers that either require an external CSU/DSU (such as the Cisco WIC-1T card) or have their own internal, integrated CSU/DSU (such as the Cisco WIC-1DSU-T1-V2).

Although more costly, the benefits of running standalone DSU/CSUs usually outweigh the advantages of integrating them into routers.  In most cases the integrated cards work fine though, and they are now chosen more frequently by customers.

Many standalone DSU/CSUs, such as ADTRAN's TSU 100e, TSU 120e and TSU 600e, are outfitted with integrated access capabilities. Such features enable users to consolidate data and voice traffic on a single dedicated, channelized link, then split off voice and direct it to the PSTN. This precludes sites from having to purchase separate access links for different types of traffic. A standalone DSU/CSUs provides a clear demarcation point between the carrier’s network and the customer premise equipment. This demarcation point allows technicians to easily troubleshoot problems associated with the circuit. Integrated solutions do not define a clear boundary between the LAN and the WAN. In addition, ADTRAN’s DSU/CSU provides easy access to diagnostic and testing functions through the front panel, via terminal emulation, SNMP or even telnet access over a TCP/IP network.

The standalone DSU/CSU provides several benefits in resource protection and dial backup. The decision to deploy a standalone DSU/CSU certainly avoids the single point of failure issue where one component affects the functions of the entire device. A standalone DSU/CSU, such as the TSU LT, can also serve as a fuse to absorb power surges or lightning strikes, protecting the expensive CPE equipment. In addition, a TSU ESP or TSU Multiplexer can be configured to backup data across the PSTN. In the case of a Frame Relay circuit, a NxIQ module may be added to provide the functionality of dialing around a frame cloud. Frame Relay statistics are also available from the NxIQ module to monitor your service level agreements.