December 1999

THE SERVER SIDE OF 56K

BY EMRE �NDER

With all the discussion surrounding V.90/56K modem connections, it is easy to forget that there are two sides to every connection. Almost all of the hype has been centered on the client side of the connection. There are, however, important considerations for server connections that need to be addressed. Unfortunately, it has been assumed that the Internet Service Providers (ISPs) and corporate intranet implementers will magically solve these server compatibility issues. Following are some of the issues involved with remote access server implementations of 56K and how corporations might evaluate some of the alternatives.

WHAT IS V.90/56K SUPPORT?
V.90/56K service is a higher speed, analog technology. It is also an asymmetric technology which uses two different speeds — one for sending (33.6Kbps) and one for receiving data (today limited to 53Kbps).

With traditional modems, digital signals in a PC are converted to analog signals and transmitted over the telephone network. Typically, the telephone network converts these analog signals back to digital signals to transmit the data over long distances to the receiving end of the line. In this way, the network maximizes its reliability and efficiency.

At the receiving end, the phone company transforms the digital signal back to analog and delivers it to the receiving modem which converts the data back to digital so the receiving computer can use the data. The data is translated at least four times between analog signals and digital, but because there are analog connections on both ends of the connection, the data rate is limited to 33.6Kbps. This is roughly the theoretical limit to analog transmission over voice-grade telephone lines.

A V.90/56K modem connected to an analog line can receive data at 53Kbps, but can only transmit at 33.6Kbps. Basically, V.90/56Kbps support re-quires that the connection through the telephone network, all the way to the server, be completely digital. It then uses some tricks, based on knowledge of the quality of the telephone network, to deliver data to the remote user at 56Kbps, while maintaining a sending data rate from the user of 33.6Kbps. If users install a 56Kbps modem on their remote computer and connect to a server ISP that supports digital connections from the telephone network, the user will get, under ideal conditions, 53Kbps data flow from the server and 33.6Kbps data flow to the server.

WHAT ABOUT THE SERVER SIDE?
The server side of the connection (typically a corporate server or ISP) requires a different type of connection. The physical connection to the network is not as simple as placing an analog modem on the server. The server now requires a full digital connection to the telephone network to provide remote users with V.90/56K support. Digital connections to the telephone network include three basic types: ISDN Basic Rate, ISDN Primary Rate, and T1/E1 connections.

It is important to realize that for full client-side support of V.90/56K, the servers and ISPs that the clients dial in to must implement the proper infrastructure. Digital infrastructure requires new equipment to establish and interpret the V.90/56Kbps calls. This investment is significant, as it includes not only new hardware and software on the servers, but also different (and typically higher priced) digital service from the telephone service provider.

A side benefit to the implementation of V.90/56K in a corporate environment is that users on the “other” side (LAN side) of the corporate server will generally get better performance as well. These users benefit because they are no longer dialing out using 33.6Kbps analog, but are utilizing the digital connection through the server. Corporate users will now get digital service when they access the Internet or ISPs that support digital connections.

ISSUES FOR SUPPORTING 56K
There are two basic issues for supporting 56Kbps from the server perspective: density and management. Products are emerging which address these issues, but they are generally complex and require a good deal of technical innovation.

The density issue surfaces as a very technically challenging problem. In-coming connections from a variety of different types of clients need to be interpreted and processed in a compact communications interface. Essentially, over a single digital connection, any type of call has the potential of being received into the server. Incoming calls will run the gamut from straight analog, 56K analog, digital Basic Rate, or even a combination. The server not only has to recognize the call type, it also needs the associated digital or analog processing hardware to process the call. In simple terms, the server needs to have all these processing capabilities in a very small space without taxing the CPU’s performance.

The benefit of solving this density issue is that it eliminates the need for multiple physical wires for each connected user and provides a single network connection point to manage. An effectively designed server will save money by reducing the number and types of connections needed, as well as reducing demands on network management time.

Another issue is that of managing a complex mix of both analog and digital connections. Even though there is a single connection into the server (in the ideal environment), the network manager needs to be able to manage at the port or connections level. This includes controlling when ports are used, resetting or dropping ports from a management station, gathering usage statistics, and controlling the bandwidth used by users (as is the case with MultiLink PPP). Without management tools to control these connections, network reliability can suffer and costs can soar.

CORPORATE NETWORKS AND V.90/56K
Much of the publicity surrounding 56K support has centered around ISPs and remote user support for ISPs, a driving factor in deciding to use 56K support. However, corporate networks will also need to consider 56K as the compatibility issues become resolved.

For many of the same reasons that users need 56K to an ISP, they also need this speed when accessing their corporate intranet. Even when using traditionally low speed e-mail applications, users generally are transferring more and more data in their messages. Combine this with the onset of graphics-intensive applications, and the need for outside access to Internet resources through the corporate network and the benefits of 56K becomes clear.

CONCLUSION
The remote user’s need for higher speed network access will drive the use of 56K. Since the remote user doesn’t need special telephone lines, but simply requires a different modem, the change is easy on the client side. However, the server side requires not only new digital modem hardware, but also special digital telco connections and potentially more sophisticated software to manage these connections.

It is important for network managers to consider the following before designing and implementing V.90/56K support for their corporate networks:

• Can the server solution support all users, regardless of client devices? (Speed is another issue. Having consistent, reliable access is more important than having occasional, high speed access in corporate networks.)
• Can the remote access server be managed down to the port level? Can it be managed remotely through the network?
• Can the costs of digital service on the server side be justified? (Remember that it’s not as easy as changing a modem.)
• Can the cost of a proprietary Remote Access Server be justified, or is an incremental approach with an open RAS solution a better way to implement?

Emre �nder is vice president of marketing of Brooktrout Technology. Brooktrout Technology, a Brooktrout Company, provides enabling technologies for customers to deliver voice, fax, and data solutions for the electronic communications market. For more information, please visit their Web site at www.brooktrout.com