Unicast,Multicast,Broadcast

Unicast:Unicast traffic is traffic addressed to a single device on the network.Unicast packets are sent from host to host. The communication is from a single host to another single host. There is one device transmitting a message destined for one reciever.Unicast uses IP delivery methods such as Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), which are session-based protocols. When a Windows Media Player client connects using unicast to a Windows Media server, that client has a direct relationship to the server.

Multicast:Multicast is a special protocol for use with IP. Multicast enables a single device to communicate with a specific set of hosts, not defined by any standard IP address and mask combination. This allows for communication that resembles a conference call.Multicast is a true broadcast. The multicast source relies on multicast-enabled routers to forward the packets to all client subnets that have clients listening. There is no direct relationship between the clients and Windows Media server. The Windows Media server generates an .nsc (NetShow channel) file when the multicast station is first created. Typically, the .nsc file is delivered to the client from a Web server.

Broadcast:Broadcast is when a single device is transmitting a message to all other devices in a given address range. This broadcast could reach all hosts on the subnet, all subnets, or all hosts on all subnets. Broadcast packets have the host (and/or subnet) portion of the address set to all ones. By design, most modern routers will block IP broadcast traffic and restrict it to the local subnet.

Ethernet

The ethernet is a system for connecting computers within a building using hardware running from machine to machine. It differs from the Internet, which connects remotely located computers by telephone line, software protocol and some hardware. Ethernet uses some software (borrowed from Internet Protocol), but the connecting hardware was the basis of the patent (#4,063,220) involving newly designed chips and wiring. The patent* describes ethernet as a "multipoint data communication system with collision detection".

In simple terms ethernet is the most common LAN (Local Area Network) technology in use today.Ethernet was developed by Xerox in the 1970s, and became popular after Digital Equipment Corporation and Intel joined Xerox in developing the Ethernet standard in 1980.Ethernet was officially accepted as IEEE standard 802.3 in 1985.
The original Xerox Ethernet operated at 3Mbps. Ethernet networks up to 10Gbps now exist.

Ethernet uses CSMA/CD when transmitting packets. The Carrier Sense Multiple Access with Collision Detection (CSMA/CD) is an algorithm, for transmitting and receiving packets over a common network hardware medium, by aiding in avoiding transmission collisions. The network is checked for other transmissions; when the way is clear, the computer transmissions can begin. If a collision is detected the packet is retransmitted later.

Thin Ethernet Wiring

A second generation of Ethernet wiring uses a thinner,more flexible cable than the original thick wiring.Formally named as a 10 Base2 and informally named as thin wire Ethernet or Thinnet.This wiring scheme differs from Thicknet wiring scheme in three important ways.First,Thinnet generally costs less to install and operate than Thicknet.Second,because the hardware that performs the transceiver function is built into the NIC,no external transceivers are needed.Third,Thinnet does not use an AUI cable to attach the NIC to a communication medium.Instead,Thinnet attachs directly to the back of each computer using BNC connector.In a Thinnet installation,a coaxial cable stretches between each pair of machines.The cable doesn't need to follow a straight line-it may lie loosely on the tabletop between computers,run under floor,or run in a conduit.Although,wiring for a thin Ethernet appears to be completely different than the wiring for a thick Ethernet,the two schemes share several important properties.Both thick and thin cables are coaxial,meaning that they shield signals from outer interference.Both thick and thin cables requires termination,and both use the bus topology.Most important,because two wiring systems have similar electrical characteristics,that means signals propagate along the cable is in the same way.

Concept of ISDN

Integrated Services Digital Network(ISDN) is launched by telephone companies and used to provide large scale digital services to subscribers.ISDN provides digitized voice and data to subscribers over conventional local wiring.ISDN uses the same type of twisted pair copper wiring as the analog telephone system.If we discuss from the subscribers point of view then ISDN offers three separate digital channels designated B,B and D(usually written 2B+D).The two B channels operates at a speed of 64 Kbps,are intended to carry digitized voice and data or compresses videos, on the other hand the D channel which operates at 16 Kbps,is intended as a control channel.In general,a subscriber uses the D channel to request services which are then supplied over the B channels.The subscriber can also use the D channel to manage a session that is in progress or to terminate a session.Finally,both the B channels can be combined or bonded together to produce a single channel with effective data rate at 128 Kbps.The 2B+D channels are known as ISDN Basic Rate Interface(BRI).Infact,ISDN uses a form of time division multiplexing to provide the illusion of multiple channels of data to travel over a single pair of wires.