Where have all the CSU/DSUs gone?

Communications News, Feb, 1998 by Jesse Price

According to Dataquest of Santa Clara, Calif., there was a 10% decline in stand-alone DSU shipments over over the past two years, with an estimated 10% to 15% additional decline into the year 2000 -- yet end users are purchasing T1 circuits at an increasing rate.

So where are all the CSU/DSUs going? They are being integrated into other devices, especially routers.

Combining CSU/DSU functionality into routers, digital cross-connect systems, and even ATM switches has created a new opportunity for vendors such as Cisco, Motorola, Eastern Research, and Ascend Communications.

Network managers are quickly realizing that integrated CSU/DSUS represent cost and space savings. End users get the same functionality without having to pay for an external chassis and power supply.

Internet Service Providers (ISPs) view integrated CSU/DSUs in terms of revenue generated in relation to the number of ports utilized. These devices eliminate the need for additional hardware inventory, spare parts, and management. Integrated router vendors are seen to provide higher-density solutions, with greater value and revenue-generating opportunities for ISPs.

Some integrated units on the market today save end users about 25% in cost of ownership, according to the Gartner Group's Jay Pultz. "When considering the total cost of choosing a router, with or without an integrated CSU/DSU, it is important to evaluate capital costs, maintenance time, and density," he says.

Using integrated CSU/DSUs allows for more growth since an extra router, channel bank, etc, can be installed later. There is more free space on a communications room rack when the functionality of a CSU/DSU is integrated into a single router unit.

And the set-up time is greatly reduced. A customer can configure the CSU/DSU and router at the same time, while dealing with only one vendor.

Small businesses and enterprises with many remote locations are finding it increasingly difficult to maintain, configure, and manage network equipment. Integrated functionality offers the advantages of combined diagnostics under a single platform and the elimination of cabling problems.

Integrating any type of transmission device -- whether it is a CSU/DSU, ISDN BRI, or modem -- into a single chassis simplifies remote management, enhances reliability, and eliminates problems between different types of signaling implementations.

In some applications, the customer may want to combine various types of traffic onto a single access line. Multiport CSU/DSUs have been designed for applications allowing data, video, and voice to be integrated and transported through public networks without the use of a multiplexer.

Some earlier integrated CSU/DSU router products lacked diagnostic control and were unable to isolate problems -- there weren't enough built-in diagnostics, such as loopbacks and test pattern generators. In the last 12 months, however, improvements have been made in CSU/DSU/routers so that most customer needs are satisfied.

CSU/DSUs have also been integrated into other products. Motorola has incorporated CSU/DSU technology into its Vanguard FRAD (frame relay access device) product line. Eastern Research offers integrated CSU/DSUs in its digital cross-connect system, the DNX-digital Network Exchange.

Ascend Communications' MAX remote access concentrator and its new ATM switch also have integrated CSUs. According to Ascend Communications, all of its products that support a dedicated link will eventually have an integrated CSU/DSU.

In the future, stand-alone devices will continue to be enhanced with user interfaces and management features. Integration will continue to take place in all segments of the market, but the future may also see digital subscriber line (DSL) technology as an alternative to traditional CSU/DSUs as the service becomes a reality.