Subject: Advanced Network Technologies

Topic: Network Design

Difficulty: High

SWITCH:

The Switch is the star of the network, it is the most active device, in charge of making sure that frames go where they need to go. These frames are units of data at Layer 2 (the Data-Link layer), of the 7 layers OSI reference model, and this is why switches are refer to as “Layer 2 devices”. A frame comes into one of the ports, and the switch “switches” the frame out of another port that points to the frame’s final destination. This is possible because switches actively learn MAC addresses (a MAC address is the physical address of a device) and they keep a table, called the “MAC Table”, with entries matching MAC – to – port, so switches know off of which port, devices are reachable.Switches communicate at Full-Duplex. This means that each one of its ports is able to send and receive data at the same time and this is because in Full-Duplex communication, two wires (inside the network cable) are used, one for transmitting and the other for receiving. This communication type makes it impossible for Collision to occur.

ROUTER:

Just like switches are used to connect devices, Routers are used to connect networks. Routers process packets, which are units of data at Layer 3, the Network layer, this is why Routers are refer to as “Layer 3 devices”. A Router receives a packet and examines the destination IP address information to determine what network the packet needs to reach, and then sends the packet out of the corresponding interface.

BRIDGE:

The Bridge, like a Switch, works at layer 2, the Data-Link layer. Bridges are even rarer than Hubs, almost obsolete we could say, but they were very popular during the early years due to the necessity to interconnect mixed network types such as Ethernet and Token-Ring and also, as networks started getting larger, it became necessary to break up Collision domains. A Collision happens when more than one device transmits data at the same time, and this can significantly slow a large network down. This is why Collision becomes an issue on large networks, the more devices trying to communicate, the greater the chances of Collisions.