Difference Between Logical Design and Physical Design

Difference between Logical Design and Physical Design

NTC 410

August 8, 2006

Understanding network topology can tell one a great deal about installing or expanding a network. At its basic level, the topology of a network refers to the way in which all its pieces have been connected. That is, it refers to the layout of the computers, printers, and other equipment hooked to the network (TechTarget 2006). Because cables connect computing resources together for a network, network's topology is also a function of the way in which the cabling is organized, whether it is arrayed in three basic physical topologies available to LAN designers:

* Bus- In the bus topology, all workstations on the network are attached to a single cable i.e. Ethernet, and AppleTalk, are more well know examples of bus-based networks. This sharing of the transmission media or cable has several important consequences. Mainly, it means that the transmission media or cable can carry only one message at a time. Each workstation on the network must have the capability of knowing when it can and cannot access the network using this shared medium (TechTarget 2006).

* Ring- Like the bus, a Token Ring network uses a single cable. Unlike the bus, the cable's ends are looped to form a complete logical circle or ring. Unlike the bus, when a workstation needs to transmit data over the network, it must wait until the token is passed to it by its neighboring station. It takes control of the station and then places a data packet on the network. Only after the data packet has made a full circuit of the ring, returning to its originator, does the station release the token for the next workstation. Token Ring can also be expanded by linking multiple rings together, just like Ethernet (TechTarget 2006).

* Star- The star topology typically consist of a system of terminals or PCs, each wired to a central processor. The principle advantage of the star topology is that it allows centralizing key networking resources i.e. concentrators or line conditioning equipment and also gives the network administrator a central point for network management. If a fault is located the network, the system administrator can troubleshoot from one location like a wiring closet, or possibly from a remote management console (TechTarget 2006).

Recent technical advances have distorted the distinction between physical and logical arrangements; the topology you select or are forced to select may also dictate the media-access control method like Ethernet or Token Ring, under which the network will operate (TechTarget 2006).

Physical topology is the actual physical way the computers are set up and connected to make a network. Physical design refers to the actual layout of the physical part of the network. This includes the cables, switches, workstations etc (Webopedia. 2006). A physical layout or map typically involves a diagram of the actual floor plan with the view from the ceiling, looking down onto the floor. Standard layout of most networks include a central rack located in a computer room or restricted access areas where all network wiring are connected to the back of a patch panel (Webopedia. 2006). From the front side of the patch panel, UTP cables run directly to a switch, interconnecting all network devices. Because the function and performance of an internetworking device depends on its relationship to other devices, inventories should include logical network maps that illustrate the location of each device in relation to end stations, servers, and wide area connections (Webopedia. 2006). See example Figure 1 below .

Figure 1 Example of Physical Design (Concept Draw 2006)

A network's logical layout may differ from its physical layout. The logical topology defines the electrical path; the physical path defines how the cables, concentrators, and nodes are arranged. A "logical" network consists of the logical addressing used to describe the network itself or the network it connects (Webopedia. 2006). One of the most important steps when designing a logical network is future development and improvement. The "Logical Design" is the IP structure of your network. To develop