Hey all !

This is my first Tutorial ... well..actually my second attempt to write one .The first one didn't

turn out to be a tutorial and i had to move it to the General Discussions Forum .I

guess it will help newbies to get a basic understanding of the various networking devices...




[glowpurple]NETWORKING DEVICES[/glowpurple]




[gloworange]Network Interface Card [/gloworange]


This is a device with many names like LAN adapter,Network Interface Unit,Network Card.It is

commonly referred to as NIC. An NIC helps a computer to communicate with the Network with

the help of drivers and the computer's OS. So if u want to create a network of pcs, you

should purchase NICs for every pc connected .They usually fit into the expansion slots.

Sometimes they come Onboard with the motherboard.It is also important to note that NICs

differ with the network architecture they support.




[gloworange]Repeater[/gloworange]

When the physical distance of a network topology has to be increased, a device called

repeater operating at the physical layer is used.A repeater takes the input signal and

regenerates it by amplifying it.In thisway it overcomes the distance limitation.When a signal is

regenerated,there is also a possibility of "noise" being regenerated.It also increases the

latency thereby increasing the chances for timeouts.





[gloworange]Hubs[/gloworange]


Hubs are multiport repeaters operating at the physical layer.It amplifies the input signal and

sends it to all the nodes connected to the hub without looking at the data.It has therfore only

a single collision domain.Hubs create a physical star network where the hub is the device is

central device.But unlike a star network the hub does not forward data only to the destination

node but sends it to all the nodes.





[gloworange]Bridges[/gloworange]


Bridges are used to breakup collision domains,combine two different networks or to

regenerate the input signal(like a repeater).They operate at the Data Link Layer of the OSI

layer.They can also be used to filter out specific types os traffic like ARP,SAP etc.Bridges are

software based and therefore increase the latency to a great extend( i guess about 30%).

Therefore there is a good chance for TIMEOUTS.So its better to use combinations of hubs and

switches to break up collision domains.





[gloworange]Routers[/gloworange]


They devices operate at the Network layer of the OSI model.They are used to breakup

broadcast domains,control multicast traffic,connect between different topologies.Their

decisions are based on logical addressing rather then physical.





[gloworange]Switches[/gloworange]


Similar to bridges they break up collision domains.Because of the fact that the decisions are

hardware based they reduce the latency.They are in effect like multiport bridges.The

forwarding decisions are based on the physical address.By using ASICS (Application specified

integrated circuits) higher speeds can be achieved.




[gloworange]Firewall[/gloworange]

Firewalls are software based,hardware based or a combination of both .A hardware firewall

is made up of a router or access servers.There are several types of firewall techniques:

Packet filter->It checks every packet that comes in.

Application gateway-> application specific security mechanisms

Proxy server->This hides the true network address.All the transmitted data is intercepted


[glowpurple]Layers[/glowpurple]

Throughout this tutorial i have talked about different devices operating at certain layers.

Networking is very complex and inorder to make it simpler, each networking operation

is divided into different layers.The ISO OSI has divided these tasks into seven layers.


Application Layer : Interface between user and the network eg.Browser,Ftp client


Presentation Layer : Presents data and does operations like encryption

Session Layer : Keeps different applications data separate

Transport Layer: Error correction as well as reliable or unreliable delivery

Network Layer: Routing and logical addressing

Data Layer: Converts packets to bits and bits to frames,error detection(no correction)

Physical Layer: Moves bits over the transmission medium,specifies voltage etc.


Each device operating at a specified layer performs its own specified tasks


[pong]Happy Networking ![/pong]