The Difference Between Logical and Physical Design of a Network

Abstract

This paper will explain several differences between a logical network design and the physical design of a network. Most people tend to think of it as the logical meaning the functional part and the physical as the seeing it part. With saying that one must understand that there is more to the logical and physical design of a network than just the functional and seeing parts. In order for one to understand the differences of how the two operate and work from one to the other, one would need more information than just the functionality and seeing parts. In the following paragraphs of this paper, by trying to outline what makes up the differences between logical and physical design of a network one should then understand his/her purpose.

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.

When speaking of the network design world, one must understand the importance of what the logical network design is and how it works; in addition, one must know and understand what the physical network design is. These two common design types are different in several ways but first let's understand what they are. When looking at a logical network design, it easier to describe it as how the network will be structured, basically it focuses on all the logical aspects of the network. According to Webopedia, "the logical topology is the way that the signals act on the network media, or the way the data passes through the network from one device to the next without regard to the physical interconnection of the devices." http://www.bibiesse.org/digitctionary/logical_topology.shtml

In a logical network layout, IP addresses are shown to be associated with each part of the network. "In most cases, the logical network is in a Class C network such as 192.168.0.0 with the default subnet mask of 255.255.255.0. Therefore, this type of network allows up to 254 hosts to be connected directly to it without the need of any routing." http://www.firewall.cx/cabling_utp.php To add on this information, there are elements of a logical network which includes IP addresses that are assigned to devices such as routers, switches, servers, workstations and other devices used on a network. In addition, a logical design in most cases will not usually show the actual interfaces and physical cables in their diagrams which are shown in Diagram 1.

There are important steps to remember when designing a logical network that would be beneficial in the near future growth and expansion for a company. For instance, some people tend to overlook problems that they must face when running out of available IP Addresses. As such, if one designs a network, he or she would probably consider leaving room for an addition 50-60% growth of its current size. Therefore, this would mean that if asked to design a network with 60 workstations, one should be able to design it with at least 100 workstations, giving and additional 40 IP Addresses. Of course, this would only refer to one or two networks at the most, and even then it can easily be assigned which is known as one full Class C network. One must also keep in mind to leave atlas the first 10 or 20 IP Addresses available because of the importance with the network have critical devices/hosts. For instance, there are such as gateways, there are routers or even switches, servers and printers, which leads to handing out the remainder IP Addresses to users.

Now it is time to speak on the physical design network which is referred to as the actual layout of the physical part of a network. The physical part of a network consists of switches, workstations, the cables, and more that are associated with the physical aspect of the network. A physical layout which is also called a map would normally involve a diagram of the actual floor itself. This is where one could visually see a diagram as if he or she was looking from a ceiling down towards to the floor. "In addition, the classical physical design of most networks involves a central rack located in a computer room or a restricted access room which is show in Diagram 2. This is where all wiring from the wall terminates and connects 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." http://www.firewall.cx/cabling_utp.php

Example of Logical Network Design - Diagram 1

Logical Topology

"Also called signal topology. Every LAN has a topology, or the way that the devices on a network are arranged and how they communicate with each other. The way that the workstations are connected to the network through the actual cables that transmit data -- the physical structure of the network -- is called the physical topology. The logical topology, in contrast, is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices.

Logical topologies are bound to the network protocols that direct how the data moves across a network. The Ethernet protocol is a common logical bus topology protocol. Local Talk is a common logical bus or star topology protocol. IBM's Token Ring is a common logical ring topology protocol.

A network's logical topology is