Cellular Technology: Past, Present and Future
...cast domain needs to be broken up, though a WAN connection is not required. An example would be a large LAN inside of a single building. The distribution layer would be created for these layer three switches. This would then be used to link individual LANs, created using hubs or layer two switches at the access layer. Following is how a layer 3 switch is used: www.tele.sunyit.edu Addressing One of the most important steps in designing a logical network is to think about the future growth and expansion, many people tend to overlook this point and when the time comes to expand that network, they have or are running out on IP addresses. So when designing a network it is best to include extra address. In order for a network to scale properly it must use an addressing and naming plan that can be broken up as sites are added. It must also have the capacity to handle the planned number of resources on the network. A good form for naming and addressing will also help in managing and troubleshooting. Addressing, especially IP addresses, should be managed from a plan of the required networks. Naming should be managed centrally to insure consistency. Names should reflect the type of device it is and the device's location Security The security and management should be built in to the network from the beginning to insure integrity from the start. “Security must pay attention to: • Assets to protect • Risks to these assets • A clear and enforceable security policy • User community training Some of the ways that security is implemented through are: • Authentication • Authorization • Auditing • Encryption • Connection Control • Physical Protection (www.tele.sunyit.edu)” Management of the network is another important part of designing. Management requires sensible and correct information about the network’s operations. Things that should be managed include: • Performance • Errors • Configuration Performance needs to be checked for all devices that have management capability. This could include things suck as utilization, delay, downtime, and throughput. Errors need to be discovered before they are noticed by the user community. Error management requires that the management tool read log files and test for responsiveness on the network on a regular and scheduled basis. After the management tool has tested the network, the support staff should then be notified of any errors. Network configuration should not just be done when the network is built. It should be rechecked as the network grows and evolves through small changes and upgrades. The following is an illustration of a logical network design. www.microsoft.com Physical network design The Physical design is the actual layout, or topology, of a network. Every thing is included in this part such as the physical cables, switches, routers, workstations etc. A physical layout usually involves a diagram of the actual floor the way all the hardware, including the cabling, would be laid out. The physical design also defines the type of cable used to connect all devices, e.g. Cat 5, Cat 5e or Cat 6, and the distances the devices will have from the switch. Topologies The traditional physical design of most networks involve a central rack located in a computer room or a restricted access room were all wiring from the walls terminate and connect at the back of a patch panel. From the front side of the patch panel, UTP cables run directly to the switch, interconnecting all network devices. Some of the designs for the networks could include Bus, Stare, Token Ring, Ring, Mesh, and tree. The bus network topology, every workstation is connected to a main cable called the bus. This means that each workstation is directly connected to every other workstation in the network. A star network topology, there is a central computer or server to which all the workstations are directly connected. Every workstation is indirectly connected to every other through the central computer. The ring network topology, the workstations are connected in a closed loop configuration. Adjacent pairs of workstations are directly connected. Other pairs of workstations are indirectly connected, the data passing through one or more intermediate nodes. A variation of the ring is a token ring topology. In this design, the signal travels in only one direction or senses around the ring, carried by a so-called token from node to n...