Sizing Remote Access: A Straight Shot In The Dark

By Mike Fratto  Al you really need to know about sizing remote access is 8:1. With eight users for every one port (ISDN or modem), you should have adequate service with minimal complaints. At least that's what the industry says is the magic ratio for average remote-access solutions. Many VARs and system integrators use 8:1, or 10:1, as a starting point for sizing remote access. How well that ratio holds up over time depends largely on a number of factors that, individually, are seemingly tangential, yet when taken together have a profound impact on the actual user-to-port ratio necessary to roll out and manage a successful remote-access solution. Along with determining user needs, in terms of applications that will be used, user priorities and access method (ISDN or modem), policy issues, including usage restrictions such as those regarding maximum connect time, time of day, number of connections and network access, are implemented at the system level. Unlike the methods used for sizing voice networks, which have been developed over the past 90 years or so, sizing remote access is far less formal and difficult to do with any real precision (see "Sizing With Erlang-B" on page 144). But as more companies implement and monitor remote access, the body of data collected should provide fodder for traffic analysis and development of more precise metrics. Initially, you can estimate the average amount of data that will be transferred during a typical session and the time to complete common tasks and derive estimates for sizing. Note, however, that time online will increase as applications and data needs grow. For sizing remote access, you must combine both your policy concerns and your data bandwidth needs into an overall picture of your expected user population. Only when you have considered all the issues can you make an intelligent decision about the number of ports required. Sizing is an ongoing process. Plan on revisiting it often and examining usage logs and statistics for forecasting future needs. It's Not All Bits and Bytes Policies shape the levels of access, time restrictions, network access and any other issues that affect remote-access usage. Policies not only state what can be done and when, but also indicate your strategy and the focus of the remote-access solution. Additionally, policies lay out acceptable levels of service expected from a remote-access solution. In remote access, service levels typically define the availability of ports and what can be accomplished with the system. A large research hospital in the Midwest is testing and rolling out a remote-access solution for its user base and wrestling with these very issues. Driving the remote-access i nitiative is the need to provide enhanced services to users from home and access to key network and administrative managers. The initial user base is approximately 200 users, which is expected to grow to more than 2,500 in the next two years. This hospital is rolling out its remote access in stages--first to a small group of administrators and researchers, then to the population at large. It expects users will be accessing e-mail, transferring data within Novell GroupWise and using the Web for research. Other applications will follow. Connections will be made with modems at first, though ISDN is a strong possibility for the future. One of the first issues to settle, and possibly one of the most explosive, is whether remote users will have access to the Internet or will be granted access only to specific Internet sites. Some estimates put remote-access costs upwards of $100 per user annually. For even a small population of 200 users, that's $20,000. It's easy to see how illegitimate uses of this connecti vity can cost a bundle.

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