Transmission

Simplex
 In a simplex transmission, data is sent or transmitted in one direction. Examples are keyboards or television connections

Half Duplex
In a half duplex transmission, data can be sent in both directions ,but at different times. Examples of this would be a hard disk of a computer, CD/DVD storage

A network transfer files or data at a certain speed, depending on the file size and method of transmission. The speed at which data is sent across networks is measured using different rates.

        Rate                                       Measurement
Bits Per Second              Number of bits of data that are transmitted or received in one second.
Baud Rate                      Number of times per second the medium sends in discrete signals.

Data Transmission types

There are two ways to send or transmit data along a communication line/link from one device to another. Parallel or serial transfer.

Parallel transfer transmits each bit in a byte along individual channels so that multiple bits are sent at the same time. A minimum of 8 channels are required.Used in shorter distances

Serial transmission transmits all bits one after another.Bits will be leave the sender first and arrives at the receiver first and so on. Two wires are needed for a serial link . Used in longer distances.

Bandwidth- what is it?
 Bandwidth is simply the capacity of the transmission medium to handle a specific amount of data in a given time. So higher bandwidth > more data transmitted.
Baseband and Broadband are examples of a bandwidth.

Wired Media.
  They are transmission medium that contain a wire for the transmission of data. They include twisted pair cable , coaxial cable and fibre optics.

Twisted pair cable=pairs of copper wires twisted in a rope fashion to reduce interference

Coaxial cable = thick core of copper wire surrounded by insulating material. The copper wire is surrounded by a plastic layer for protection for the prevention of interference.

Fibre Optic Cable=a grou of hair-thin glass fibres that permit electrical signals to be transmitted as light pulses.The light that carries the data is transited by laser pulses.

Packet Switching

    A method of breaking down a message into packets. It is used to provide a more efficient way to transfer data across a network.Each packet can be sent by a different route to its destination and then reassembled into the original message. A packet is a group of binary digits containing data and control characters that form part of a complete digital message.The control characters are used to check and correctly reassemble the message.

  A data packet is composed of the data , a header and a tail. The header will have information about the source,intended destination,number of packets sent , packet identifier and information about the data while the tail is an error checking code which enables the receiver to confirm that there are no errors in the data from transmission.

   A computer uses a PAD, packet assembly or disassembly facility to convert the transmitted data into specifically sized packets at the transmission end and to reassemble the packets at the receiving end into the correct form for transmission to the receiving computer.

Networks 

LAN - Local Area Network.

A communication network for connecting computers within a small area. A LAN have 3 configurations : bus , star and a ring.

A bus is a main channel to which nodes or secondary channels are connecting in a branching structure 

A ring is a main channel in which each computer is connecting to two neighbouring computers to form a closed circuit.
A star is a main channel in which each computer is linked directly to a central computer and only indirectly to one another.

Wide Area Network

A computer network that spans a larger geographical area. Usually occurs when one LAN is connected to another LAN. The internet for example. is a WAN.

Client Server Network

Client servers are made up of clients and servers. Each machine on the network is the either two.

  Servers provide services such as file transfer and web services. Clients request those services.

A client server network the network operating system is installed  and run on a computer called the network server and a service will be provided by a server and accessed by clients.The server will continuously monitor the incoming service requests.

Peer to Peer Network

 A type of network in which a group of computers communicate directly with each other. Resources on one computer are accessible directly from another computer. In P2P networks,each workstation has similar capabilities and responsibilities.

Torrent 

a torrent file is a computer file that contains metadata about files and folders be distributed and usually also a list of the network locations of trackers,computers that help participants in the system find each other and form efficient distribution groups called swarms.A torrent file contains only information about those files such as names,sizes ,folder structure and has values. It uses P2P network for sharing content.An example of a torrent program would be uTorrent and Bittorrent.