Network design for the overworked administrator
System administrators have a full plate. Maintenance, monitoring, and management of their organization’s IT infrastructure keep them busy, leaving few opportunities to complete a thorough network design. A poorly designed or unorganized network, however, often requires more attention, and can be costlier down the road, making it worth the time investment up front.
If you have an opportunity to address the key requirements of your network infrastructure and organization as a whole, administration becomes easier in the long run. Here are three major steps for approaching network design to put you on the right path.
Gather initial network requirements
- Know your network. How many users connect to your network — 100 or 10,000? Do you have enough bandwidth to support those users? What kind of traffic profile are you looking at? Understanding the traffic on your network will help you make decisions down the road in terms of capacity and what protocols need to be addressed.
- Understand your organization’s expectations. What are the requirements for overall uptime for the network? Does your organization need three nines? Five nines? It doesn’t have to be exact, but you want to have an idea of what your business expects so you can design a network to support that. If your organization doesn’t require anything beyond two nines, putting in secondary power supplies would be foolish. At the same time, if your organization requires five nines, then not having the second power supply is just as foolish.
- Determine the budget available and how that fits your requirements. The right products for your network depend heavily on budget. The perfect network switch might be too expensive for some organizations, but they still need to choose the right switch family or product line. The switch might need to support certain features, like dual power supplies and layer 3 or light layer 3 protocols. It might need to do some kind of inter-VLAN routing, and should provide a command-line and web-based interface. If these requirements are missed initially, it’s almost impossible to get them later on after the purchase.
Know your requirements and the best equipment you can get for the budget you have.
Follow key principles of network design
- Eliminate all single points of failure. This includes any links between switches. There should be redundancies built into the system, including power supplies and links, to keep the network running even when components fail.
- Address potential bottlenecks. Ensure there’s enough bandwidth to go around for all users and systems. The traffic on your system should run smoothly, and addressing any bottlenecks will allow your users to work without sacrificing speed or experiencing any other issues.
- Find a product line and stick with it. Avoid mixing switches from different vendors, if possible. It’s much easier to manage a switch environment if you manage them the same way. You don’t want to learn a new interface or work differently with another set of switches within your network unless absolutely necessary. Supporting one product and one vendor is not only easier, it can also lead to better pricing.
- Separate the core from distribution. All network design starts with some sort of core, and where the services are located — the virtual servers, virtual hosts, even some physical hosts — should be connected to a pair of redundant switches. That is, every server should have one connection to one switch, and one connection to the other switch. That’s just a basic network requirement. The core switch obviously needs to have more bandwidth and more horsepower than distribution because it handles most of the traffic between virtual machines or physical hosts on the local network.
Document, document, document
- Create a visual understanding of the network and protocols. Regardless of your skill level, create some type of documentation to describe the requirements of the network, its design, and how the design meets those requirements. Create diagrams that depict what the network will look like when you’re done. This is critical because it’s almost impossible to explain what a network topology looks like. Ensure the requirements of the network are written down and relevant stakeholders see, understand, and agree with them.
- Review your network’s design. Networks tend to grow organically, without regard to their original design. There should be an ongoing process of reviewing the design of the network and looking for ways to improve it or modify it so that it continues to meet the needs of your organization. Consider growth and scalability. The network will grow and change over time, and some effort should be made to understand its current state and record it. If you’re changing or adding to the network often, it might be worth reviewing its design every quarter. If the design is fairly static, review it once a year.
By collecting user and organizational requirements for the network, following some basic principles, and documenting the network’s design, overworked admins can make their lives a little simpler and avoid some of the maintenance and problems that crop up with poor network design.