Computer Network (sec 02)

Network Topology

Computer networks, whether LANs, MANs, or WANs, are constructed based on a topology. There are several topologies including the following popular ones.

Mesh Topology

A mesh topology allows multiple access links between network elements, unlike other types of topologies.

Tree Topology

A more common type of network topology is the tree topology. In the tree topology, network elements are put in a hierarchical structure in which the most predominant element is called the root of the tree, and all other elements in the network share a child–parent relationship.

Bus Topology

A more popular topology, especially for LANs, is the bus topology. Elements in a network using a bus topology always share a bus and, therefore, have equal access to all LAN resources.

Star Topology

Another very popular topology, especially in LAN network technologies, is a star topology. A star topology is characterized by a central prominent node that connects to every other element in the network. So all the elements in the network are connected to a central element.

Ring Topology

Finally, another popular network topology is the ring topology. In this topology, each computing element in a network using a ring topology is directly connected to the transmitting medium via a unidirectional connection so that information put on the transmission medium can reach all computing elements in the network through a mechanism of taking turns in sending information around the ring.

Network Connectivity and Protocols

Open System Interconnection (OSI) Protocol Suite

The development of the OSI model was based on the secure premise that a communication task over a network can be broken into seven layers, where each layer represents a different portion of the task. Different layers of the protocol provide different services and ensure that each layer can communicate only with its own neighboring layers.

Transport Control Protocol/Internet Protocol ( TCP/IP) Model

Among the OSI rivals was the TCP/IP, which was far less complex and more historically established by the time the OSI came on the market. The TCP/IP model does not exactly match the OSI model.

Network Connecting Devices

LAN Connecting Devices

• A Hub – This is the simplest in the family of network connecting devices since it connects the LAN components with identical protocols.
• A Repeater – A network repeater is a low-level local communication device at the physical layer of the network that receives network signals, amplifies them to restore them to full strength, and then retransmits them to another node in the network.
• A Bridge – A bridge is like a repeater but differs in that a repeater amplifies electrical signals because it is deployed at the physical layer; a bridge is deployed at the data link and therefore amplifies digital signals.
• A Switch – A switch is a network device that connects segments of a network or two small networks such as Ethernet or token ring LANs.

Internetworking Devices

• Routers – Routers are general-purpose devices that interconnect two or more heterogeneous networks represented by IP subnets or unnumbered point-to-point lines.
• Gateways – Gateways are more versatile devices than routers. They perform protocol conversion between different types of networks, architectures, or applications and serve as translators and interpreters for network computers that communicate in different protocols and operate in dissimilar networks.

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