Questions to ask to determine WAN bandwidth requirements

existing network topology issues will affect your decisions. Should you look at your bandwidth requirements in terms of the whole network or parts of it? Perhaps you can segment and subdivide your network so that issues in any one part won't limit your ability to address unique requirements of other parts.

In order to develop a network that fulfills your requirements today and can accommodate future demands, it makes sense to develop a migration path on a network-by-network basis, then revisit and reassess each element in that path over time. With market, business, and technology dynamics changing quickly, you must keep a watchful eye on your network so that it can dynamically support opportunities as they occur.

Gathering business information
When addressing bandwidth management, business issues cannot be overlooked. This means that as a network manager you must identify several key factors:

1. Current and potential users of network resources
2. Primary activities, such as email, file transfers and the applications to support them
3. Types of devices to be used, such as PCs, laptops and printers
4. Expectations for network performance
5. Other applications currently being used, such as voice, and video
6. Applications planned for future use
7. Amount and frequency of data users plan to download or upload
8. Security issues like data encryption.

Unlike servers and routers, which can be configured and reconfigured at any time, bandwidth as a network design element should be done correctly (e.g., optimized) the first time, when the network is first launched. After that, regular reviews of network performance are necessary to ensure that sufficient bandwidth is available.

Questions to identify bandwidth requirements
We can convert the above criteria into specific interview questions to ask when identifying bandwidth requirements. Schedule appointments with your key technical users, such as applications programming, database management, information security and data center, and key business departments such as human resources, legal, and administration.

For each current and potential department using network resources, ask:

How many users do you currently have in this department?

How many of them require network connections?

How many additions/deletions to staff are you anticipating in the next three to six months?

Where are your staff members located (time zones)?

How many will require remote access?

For primary activities and the applications to support them, ask:

What are their primary functions?

Best practices for WAN design and capacity planning WAN design: What to consider WAN capacity planning: Building a methodology Determining WAN bandwidth requirements

What applications (financial, email) do they currently use?

How frequently do they use these applications?

For types of devices to be used, ask:

What devices do your employees currently use on their desktops?

How many have attached printers?

What other devices are used?

What devices will be used for remote access?

How many will be remotely accessing the network?

For expectations for network performance, ask:

What is your current assessment of response time (excellent, fair, poor)?

What level of response time would you like to see in the office?

What level of response time would you like to see for remote access?

For other applications currently being used, ask:

How much does your department depend on voice communications?

How many calls does your department generate in a typical day?

Aside from applications such as Microsoft Office and email, what other applications are being used (such as video conferencing)?

For applications planned for future use, ask:

What new applications are planned for your department?

How many people will be using them?

When are you planning to implement them?

For amount of data users plan to download or upload, ask:

Typically what kinds of files are being uploaded or downloaded?

How often does your staff download or upload data, e.g., files, Internet?

For security issues, ask:

How much of the information you utilize requires encryption?

What additional requirements for data security do you have, such as passwords?

Once you have gathered subjective information about your user community, next begin gathering empirical network performance data. This information can be obtained using network analyzers. Continue with network design and configuration tools, test the network configuration, compare the carrier service offerings, and soon you'll have an efficient and cost-effective WAN.

So, how much bandwidth is enough for your organization? Think of the answer in terms of "as much as you can deliver." And before you roll out any complex network analyzers, simulation software or other tools, be sure you understand the current and long-term requirements of your customers. With all the options available today, you can build the WAN you and your organization need.

About the author: Paul F. Kirvan, FBCI, CBCP, CISSP, has more than 35 years experience in telecommunications and information technology as a practitioner, consultant, author and educator. He also specializes in business continuity and disaster recovery.