How to assess and plan for physical infrastructure

The physical network infrastructure of your LAN is made up of cabling, switches, routers, wireless access points, NICs and other network devices. Saving money in the short run can cost more later if you find yourself needing to "rip and replace" in order to meet your users' bandwidth needs.

When you move your business into new offices, you may be faced with the task of running Ethernet cabling for your computer systems. Of course, in many cases the building is pre-wired—but that doesn't necessarily mean there are outlets in all the locations where you want to put computers, nor does it mean the cabling that's there now will be sufficient for your needs as your company grows.

Now maybe you figure that if the business grows that much, you'll be moving to a different building anyway, but many companies find that growth doesn't just involve the number of employees you have. Network bandwidth usage and needs can outgrow your infrastructure before you outgrow your offices in other ways, and replacing the cabling infrastructure later can be costly and disruptive.

Planning for a scalable physical infrastructure from the beginning can save dollars and distress in the future.

How to assess physical infrastructure needs

The first step in planning your physical infrastructure is to assess your needs, and then compare it to what you've got. In many cases, a network cabling infrastructure "just grows that way." New cables may have been run at different times, as additional computers were added. The decision on where to place the server room or closet is an important one, too. The easy option is to duplicate the network layout of the company that previously occupied the space, but this may not be the best choice for your company's needs.

Some questions to ask in the planning process include:

  • How many servers do you have now and where will they be placed within the building?
  • How many servers do you realistically anticipate adding over the course of the next several years?
  • How many workstations do you need and where will they be located?
  • Where do you anticipate needing to add workstations over the next several years?
  • What are your current LAN bandwidth requirements, based on the amount of internal traffic you have and the applications you use?
  • How much do you expect LAN bandwidth requirements to increase over the next several years?

Planning ahead

Ideally, the server room should be centrally located to minimize the lengths of cable required to reach all workstations. It should be large enough to comfortably accommodate the servers, routers, switches, firewalls and other network devices you have now or plan to deploy in the future. Take into consideration that the number of physical server machines may actually decrease in the future, if you plan to use virtualization technology to consolidate multiple server operating systems on one machine. On the other hand, you may be adding other equipment to the network, such as Voice over IP (VoIP) equipment.

If workstations need to be added in locations that haven't been cabled (more than one fast-growing company has ended up creating offices in rooms that were once used as large closets), you may find it more cost effective to use wireless networking to connect those computers to the LAN—but keep in mind that deploying a wireless network raises security concerns you'll need to address. A good practice is to set up your wireless access points on a completely separate network and have wireless users VPN into the Ethernet LAN.

The need for speed

Almost a decade ago, when my husband and I first installed cabling for our small business, we were still operating at 10Mbps on the LAN, and that seemed fast enough. The cat5 cable we used was rated to support 100Mbps, so we figured we had plenty of room to grow. Within a few years, though, we found ourselves needing to transfer larger and larger files over the LAN. It was a relatively easy thing to upgrade our computers' NICs and our switches to 100Mbps.

The next step, though, wasn't as simple. The volume of traffic on the LAN grew heavier, and video applications and huge files that needed to be backed up over the network every night made 100Mbps seem a lot more limited than it used to. The logical solution was to upgrade again, to gigabit Ethernet.

You may have read that you can run at 1000Mbps (1Gbps) over Cat5 cable, and that statement is true—as far as it goes. The problem is that not all Cat5 cable is created equal. If your Cat5 has 8 wires (4 pair), it may support gigabit speeds. If you opted to save money in the short term by using less expensive Cat5 cabling that only has 4 wires, you'll need to rewire (Cat5e supports 1000Mbps).

Luckily, before we had to make that decision, we ended up moving to a new physical location. The first thing we did was have Cat6 cable installed. That will support our 1000Mbps network for a while. Faster speeds generally rely on fiber optic cabling, although the IEEE has proposed a 10GBaseT standard for running at 10Gbps over Cat6 or Cat7 Ethernet copper cables.

The point is that LAN speeds that seem more than adequate today may not measure up a few years down the road. In planning your physical cabling infrastructure, always plan for more bandwidth than you think you'll really need.

The same goes for your wireless infrastructure. Many companies that installed 802.11b wireless equipment have had to replace them with faster 802.11g to maintain sufficient performance as data transfer volume has increased. You may find that spending a little more money in the first place saves money in the long run. On the other hand, the cost of new technology comes down fast, so it usually doesn't pay (budget-wise) to be on the "cutting edge" and deploy the new, faster equipment as soon as it's available. A few years ago, an 8 port 1000Mbps switch was priced at several hundred dollars. Today you can find low-end gigabit switches for $50.

Remember, though, that the physical infrastructure of the network includes more than just the cables or wireless access point. Switches/hubs and network interface cards on all the servers and workstations must also support the higher transfer speeds.


Debra Littlejohn Shinder, MCSE, MVP is a technology consultant, trainer, and writer who has authored a number of books on computer operating systems, networking, and security. Deb is a tech editor, developmental editor, and contributor to over 20 add...

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