Logical Network Topologies& Network Control Strategies

Logical Topologies& Network Control Strategies

Logical Topology

Logical topologies describe how network messages travel and get delivered across a network. It would be easy to visualize the connections of physical topologies if the nodes simply connected to each other. However, this is not the case in newer LAN arrangements. This is due to the fact that most LAN installations employ connection devices, such as hubs and routers, which alter the appearance of the actual connection scheme.

Therefore, the logical topology will not match the appearance of the physical topology. The particulars of the connection scheme are hidden inside the connecting device. As an illustration, the following figure shows a typical network connection scheme using a router. The physical topology appears as a star. However, the internal wiring of the connecting router provides a logical bus topology.
It is not uncommon for a logical ring or mesh topology to be implemented in a physical star topology.

Logical Network Topology

Network Control Strategies

When you begin to connect computers to other computers and devices over a LAN so that they can share resources and data, the issue of how and who will control the network comes up. In some applications, such as developing a book like this one, it is good for the author, artists, and pagination people to be able to share access to text and graphics files, as well as access to devices such as printers. However, in a business network, companies must have control to provide access to sensitive information and company resources.


Control of a network can be implemented in two ways:

• As a peer-to-peer network where each computer is attached to the network in a ring or bus fashion and is equal to the other units on the network.
  
• As a client/server network where dependent workstations, referred to as clients, operate in conjunction with a dedicated master computer.

The following figure shows a typical peer-to-peer network arrangement. In this arrangement, the users connected to the network can share access to different network resources, such as hard drives and printers. However, the control of the local unit is fairly independent. The nodes in this type of network configuration usually contain local hard drives and printers that the local computer has control of. These resources can be shared at the discretion of the individual user. A common definition of a peer-to-peer network is one in which all nodes can act as both clients and servers of the other nodes under different conditions.

Peer-To-Peer Network

The following figure shows a typical client/server LAN configuration. In this type of LAN, control tends to be very centralized. The server typically holds the programs and data for its client computers. It also provides security and network policy enforcement.

Client-Server Network

In some cases, the client units do not even include a local hard drive or floppy drive unit. The bootup process is performed through onboard BIOS, and no data is stored at the client machine. This type of client is referred to as a diskless workstation.
The major advantages of the client/server networking arrangement include:

• Centralized administration
• Data and resource security

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