PacketThirst
September 12th, 2004, 05:52 AM
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 :D .I
guess it will help newbies to get a basic understanding of the various networking devices...
NETWORKING DEVICES
Network Interface Card
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.
Repeater
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.
Hubs
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.
Bridges
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.
Routers
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.
Switches
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.
Firewall
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
Layers
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
Happy Networking !
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 :D .I
guess it will help newbies to get a basic understanding of the various networking devices...
NETWORKING DEVICES
Network Interface Card
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.
Repeater
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.
Hubs
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.
Bridges
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.
Routers
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.
Switches
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.
Firewall
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
Layers
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
Happy Networking !