Adopting A Business-Oriented Approach To Bandwidth Management - Technology Information

Computer Technology Review, March, 2000 by Peter Cruz

As the corporate network has evolved from a simple information transport mechanism into a formidable business tool, it is rapidly becoming viewed as a critical utility. IT executives must transform their organizations into utility providers, for they are now expected to deliver the same dependable level of service the electric and gas utilities provide. For user services to achieve such reliability, the IT manager must make sure sufficient bandwidth will always be available.

The first challenge lies in understanding all of the factors that contribute to a user's perception of the service levels they are receiving. With the exponential growth of content-rich applications and Internet computing demands, users often perceive that there is insufficient bandwidth available to completely satisfy the needs of the business. Users measure bandwidth in terms of the response times they experience. While related, however, response times are not an accurate measurement of bandwidth and capacity. Many networks where users experience slow response times actually have more than enough total bandwidth; the bottleneck may well be caused by another component such as a server, an application, storage device or the user's own PC.

The first stage of bandwidth management, then, is to accurately measure the service levels being provided--from the users' standpoint. The enterprise network management system is effective in collecting performance data for any given device, but in order to make any informed decision regarding the adequacy of the service levels delivered, this raw data must be rolled up and interpreted in terms of business metrics as experienced by each user. While calculating service levels manually is very time-consuming, there is a new generation of software tools now available to help the IT executive assess and track actual service levels according to meaningful business metrics--and to identify whether bottlenecks are equipment, application, or bandwidth-related.

How Much Bandwidth Is Enough?

The goal of managing network capacity is to have the right amount of bandwidth in the right place at the right time for the right set of users and applications. Network components have two common characteristics: a finite transmission capacity and a measurable utilization or load. Bandwidth management requires that the load/capacity relationship of key facilities be understood, in order to ensure bandwidth sufficient to keep a business or a service functioning properly and profitably. Each environment is different. To ensure enough bandwidth, bottlenecks must be identified and dealt with on a case-by-case basis, based on business priorities. In each organization, the service levels for application performance will vary based on the delivery priority of particular information applications--and this delivery priority must meet the objectives of the business model.

Managing Bandwidth

Six steps should be taken to measure and plan bandwidth capacity (Fig 1).

* Identify current bottlenecks

* Provide increased capacity to meet current demands

* Project the historical demand levels into the future requirement

* Put plans in place to supplement current capacity before future bottlenecks occur

* Eliminate or downsize any costly, underutilized facilities to reduce waste

* Balance demand across time in order to more efficiently use available capacity

Obtaining the information necessary for performing these steps successfully can be a challenge. Here are some of the problems and common mistakes, as well as the new approaches available to address bandwidth management issues.

Traditional bandwidth management tools are not designed for continuous capacity assurance, nor are they integrated into the overall management infrastructure. They are typically stand-alone point products that collect raw statistical information. Raw data, in and of itself, is not useful for business analysis. For example, a graph that displays InOctet and OutOctet values over time doesn't really tell you whether there is adequate bandwidth to meet the needs of the business. Simply having that information does not illustrate how well the route, from which the data was collected, is functioning in terms of its primary purpose--enabling information flow throughout the enterprise. What's needed are appropriate business metrics for really understanding capacity issues.

Bi-Directional Data Links And Circuits

A data link provides a connection between two or more computers. A circuit is a virtualized data link. It is important to note that most communication systems are highly layered and what appears to be a link to one person may be considered a circuit by another. From a capacity planning point of view, all such connections are considered links.

A link contains one or two facilities. A half-duplex or shared link like Ethernet has a single capacity, or bandwidth, that is shared among all attached devices and is treated as a single facility. A full-duplex link, on the other hand, contains two independent facilities, each of which has its own capacity and load. Capacity planning must be performed or a facility basis; in no case should the capacities or loads be aggregated among the link's facilities. It is entirely possible for one facility of a link to be saturated while the other is underutilized. Aggregating the two would produce a facility with a mid-level load that does not correspond to anything in the real world and could obscure potential problems or bottlenecks.