by December 2, 2003 0 comments

The size of an organization determines its network design. So, the network design for a small office with 50 users will be different from that of an organization with 200 users. And, a design for a large enterprise setup will be entirely different from the above two. Here, we’ll consider the first two setups of 50 and 200 users. And since the topic of network design is very vast, we’ll focus on the key points. 

Network design depends not only on the size but also on the nature of your business. For instance, for a financial firm of about 50 seats a 10 Mbps shared network would be good enough. But if the same sized organization were into 3D graphics, then a 10/100 Mbps switched network would be more suitable. However, a shared/ switched mix network would be the right option if the organization runs more than some basic office applications, but are less throughput intensive than 3D graphics. In case of the financial firm example, if its size were 200 users, then a 10 Mbps switched connectivity on each desktop and 100 Mbps for the backbone connectivity would be required. 

The objective is to have a network that can handle all traffic from your current applications and be scalable too. For instance, it shouldn’t come down to a crawl the moment you add say a new DTP application on it. 

The other important element of any network is the documentation, and no network is complete without it. A good and updated document helps you track your network assets and keep them in order.

Wired or Wireless
Next step is to choose between wired and wireless connectivity. In case of wired, a proper structured cabling setup is recommended instead of just hooking up your computers to a bunch of network cables through a hub or switch which become very messy to handle. 

The current and future growth of the network should be kept in mind while doing structured cabling as it is a long-term investment. Also, the type of cable that you choose makes a difference. In most cases it is between various categories of unshielded twisted pair cable. The common options are Cat 5 and enhanced Cat 5 and now Cat 6. These differ in terms of the maximum throughput they support and are priced accordingly. The key point to remember here is that throughputs vary for different portions of the network. So, you will need to choose the right cable for each. The network backbone, for instance, carries more data than a network segment. Throughput is also affected by the cable length and the number of 90 degree bends the cables go through while being laid out.

A wireless network, on the other hand, is suitable for a rented place, or a place where it’s extremely difficult to layout the cabling, or an office where most of the users are mobile (that is,
have laptops). It can also be used to extend your network, or to provide instant connectivity to temporary staff. 

Choosing the right hardware
Networking hardware includes things such as hubs, switches, routers, firewalls, servers, and of course desktops. We’ll not get into which server or desktop to choose here as it’s being covered separately in this story. Here what’s important to understand is that the server should be capable of handling higher throughputs than the clients. So if your clients are on 10 Mbps, then the server should be on 100 Mbps. 

The question now is whether to use a hub or switch, or a combination of both. A hub basically provides shared bandwidth to all nodes that connect to it. That means, if you have a 24-port, 100 Mbps hub, then this 100 Mbps bandwidth is shared by the 24 nodes that connect to it. Hence the term shared network. 

A switch on the other hand provides dedicated point-to-point bandwidth to each node. So on a 10 Mbps switch, if a node on port 1 wants to communicate with a node on port 2, it will get the entire 10 Mbps bandwidth. Hence the name switched network. A hybrid network could have a single
switch with hubs connected on different ports. 

Since switch prices have come down over the past few years it’s a better option than a hub. Today, switches are available with 10/100 and 1 Gbps throughput capabilities. A 200-node network for instance, could go for a Gigabit Ethernet switch for the backbone, which directly connects to all the servers, while the remaining nodes connect through 10/100 Mbps switches.

n Define your business

This would determine the applications you need, which in turn decides the maximum throughput required 
n Wired or Wireless

Go for structured cabling for wired, with choice of cable determining the throughputs you can get. Wireless is good for temporary setups, or where its difficult to lay cables, or if there are many mobile users
n Choose the hardware.
Choose between a hub and a switch for shared/switched connectivity; Router plus firewall for Internet access. Servers should have higher network bandwidth available than clients
n Essential services. 
Basic file and print, data backup, DHCP and name resolution, SMTP and local mail routing, proxy, anti-virus, anti-spam, Internet and network monitoring

Or if your bandwidth requirements aren’t so high, then you can opt for 100 Mbps connectivity for the servers, and 10 Mbps for the nodes. 

Based on the above explanation you can now decide whether to use a hub or switch. Another popular concept in switches these days is port trunking, wherein you can combine the bandwidth of multiple ports of a single switch. 

A router is basically used to interconnect two completely different networks. In a small to medium sized organization, it’s usually placed between the internal network and the Internet connection. 

So, if you have a DSL line coming in for Internet connectivity, then it would terminate into a DSL router placed on your premises. The other end of this router would be connected to your organization’s internal network. 

It’s also recommended that you put a firewall between this router and your remaining network to prevent anybody from the Internet from entering your network. 

Essential network services
While every organization would define the services it wants to run on its network, there are a few mandatory ones for every network. These include basic file and print, data backup, DHCP and name resolution, SMTP and local mail routing, proxy, anti-virus, anti-spam and of course Internet connectivity. 

Plus, every network today, should build in network monitoring capabilities. Most of these are software services, but would require one or more hardware servers to run them.

Anil Chopra

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