Physical Design and Logical Design

Logical and Physical Network Design

Network design is a detailed, labor-intensive activity. During the design process, all key aspects of the network are examined in terms of how they meet current needs and how they must be adapted or enlarged as network usage grows. This includes the hardware which constitutes the physical network, the software used to give that network its structure and organization, and the firmware which gives the network interface controllers and hubs their functionality. The goal is to design a network that is cost-effective, easy to manage, and has the flexibility to adapt as the company's business and technical requirements grow and change. The logical design represents how the network operates. The physical design represents the actual locations of networking equipment, servers, and clients.

Connecting computers together to create a network greatly increases the communication capabilities and can even save a company substantial amounts of time and money. A well thought out network design from a small home network to a large corporate intranet can be a deciding factor in the success of a network. Two important steps in the designing of a successful network are the logical designing phase and physical designing phase. The difference between the two and the importance of each are explained in the following pages.

A logical network design refers to the logical addressing used to describe the network or the networks it connects to. A logical network design displays the IP Addresses linked with each component of the network. Typically, a logical network is a straightforward Class C network such as 192.168.0.0 with the default subnet mask of 255.255.255.0.; this allots up to 254 hosts to be connected directly to it without requiring router. Additionally, some consider it to be a good practice to leave the first 10 or 20 IP Addresses for critical network devices/hosts, such as gateways, routers, switches, servers and printers. Overall, the physical design deals with everything defined in the logical design; these designs are considered to be integral parts to effectively and efficiently designing a network. (Walters 2000)

There are several important facts that one should acquire in order to develop a logical design, such as who are the clients; what are their needs; what services will be provided; what protocol will be used; can they tolerate downtime; is there a need for an Internet connection specifically for internal network’s users, or will only outside vendors access to the network? If designing a logical network one should take into consideration the future growth and expansion; some recommend that designers allot for an additional 50-60% growth of its current size; otherwise one