Page 46 - M. Abrahim Thesis

Chapter (2) Network Fundamental and Layered Network Architecture

decisions based on network addresses instead of individual Layer 2 MAC addresses. Routers also
can connect different Layer 2 technologies, such as Ethernet, Token Ring, and Fiber Distributed
Data Interface (FDDI). Routers also commonly connect Asynchronous Transfer Mode (ATM) and
serial connections.
However, because of their capability to route packets based on Layer 3 information,
routers have become the backbone of the Internet and run the IP protocol, as shown in Figure
2-19.

Figure 2-19 shown a Router Device

The purpose of a router is to examine incoming packets (Layer 3 data), choose the best
path for them through the network, and then switch them to the proper outgoing port. Routers
are the most important traffic-regulating devices on large networks. Routers let virtually any
type of computer communicate with any other computer anywhere in the world.

https://www.youtube.com/watch?v=AjOyXHWG_x0

https://www.youtube.com/watch?v=eMamgWllRFY

2.10 Network Topologies

2.10.1 Physical Topology

A network topology defines how computers, printers, network devices, and other
devices are connected. In other words, a network topology describes the layout of the wire and
devices as well as the paths used by data transmissions. The topology greatly influences how the
network works. Networks can have both a physical and a logical topology. Physical topology
refers to the physical layout of the devices and media, as shown in Figure 2-20.
Physical topologies that are commonly used are:

• Bus

• Ring

• Star

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