We all use networks on a daily basis. Although the internet is probably the first network that comes to mind we are also often connected on other networks. Networks without connections to the entire world. We are using local networks at home, networks connecting our companies offices together and even sometimes our city may provide networks for us. In my journey to learn networking I’m going to break down some of these different types of networks. Specifically local area networks, metropolitan area networks, and wide area networks. I will also review some of the topologies that are used to set up these networks. This is a very brief introduction and will leave out some details pertaining to the the exact wiring and focus more on the general concepts.
Local area networks (LANs) as the name suggests refer to a network that covers a small area. Usually with just a handful of computers and/or other devices. You may have a local area network set up at home to help transfer files from your different devices and computers or likewise at work to transfer data or connect to a printer. This is a self contained network in a small area. When talking about LANs you have to consider how data will be sent through the network. Two common approaches to transmitting data on LAN networks is via a token ring based approach or a CSMA/CD approach. Token ring approaches are less common today but still do exist. The way token rings transmit data is by having one workstation at a time transmitting onto the wire. They can only transmit if they have the token. This works like a loop where the token is passed around to each computer to ensure all computers can transmit data and no data collisions will occur. Modern token rings use media access units (MAUs) which is a hub that connects all of the workstations together and maintains the logical ring. The CSMA/CD approach in contrast allows data to be transferred simultaneously by multiple devices on the network. The devices will attempt to listen if there is activity on the line currently and if all is clear it will transmit data. Data collisions may occur but if so the devices will re-transmit at a random interval. The CSMA/CD approach is typically used with bus network topologies. Bus network topologies may just have each workstation connected over a single wire or they can have a tree or star design that make use of hubs for connections.
Metropolitan area networks (MANs) are larger in contrast to a local area network. They have to span a greater geographical span and therefore have different cabling requirements. They may be a network covering a city or the greater metropolitan area of a city. Fiber optics have allowed for the growth of these type of larger spanning networks. Fiber distributed data interface (FDDI) is the term for the backbone of these networks. Fiber optics have several advantages over typical copper wiring. It is lighter, faster and more reliable. In terms of transmitting data these networks works similar to a ring based approach but use a dual ring that can transmit data in the other direction in case of failure moving one way. About every 2 km a FDDI requires a repeater so it is not suitable for larger networks such as WANs which will be discussed next.
Wide area networks (WANs) are larger than both MANs and WANs. They provide a network between two geographically distant networks. There are a few approaches to this. The first is first is plain old telephone service (POTS). The POTS can connect two LAN networks at far distances via dialing/calling which are handled by a modem to automatically call and pick up. Another approach is using an Integrated services digital network (ISDN). It works similar to POTS except it integrates an analog and digital signal transmission. ISDNs are capable of providing faster data rates than typical modem based connections but can only call another ISDN subscriber. A third approach is to use leased lines. Examples of these are paying for T1 or T3 lines that connect directly from point to point. If you have requirements where your data doesn’t need a constant connection you can use a frame relay network that can send data in bursts at a time. A final approach to creating a WAN network is through the internet via a Virtual Private Network (VPN). Performance and security aren’t guaranteed in the same way previous approaches are but advantages include cost and ease of setup. VPNs are not necessarily a replacement for point to point connections but are useful if you need a remote client connecting to a main office. VPNs create a secure tunnel or channel over the internet.
Hopefully by now you have a basic understanding of some different types of networks and different approaches in implementing them. As you can see there are tons of different options. The main thing to consider is what requirements you have as an individual, community or business in order to choose wisely.