Ch3 - Communication Systems Flashcards
What are the 5 components of a communication system?
- Data source
- Transmitter
- Transmission medium
- Receiver
- Destination
What is a protocol?
A set of rules that govern the transfer of data between computers.
What is handshaking?
A discussion between two computers prior to communication to establish the protocol and settings to use for the communication.
What are the two methods of handshaking?
- Hardware flow control
2. Software flow control
What are the three levels of the Communication System Framework
- Application
- Communication Control and Addressing
- Transmission
What are the 5 layers of the TCP model?
- Application
- Transport
- Internet
- Data link
- Physical
What are the 7 layers of the OSI model?
- Application
- Presentation
- Session
- Transport
- Network
- Data link
7, Physical
What is bandwidth?
The capacity of a channel or transmission medium.
What is the difference between Bits per second and Baud rate?
Bits per second is how many bits are transferred in a second whilst baud is how many symbols that can be transmitted in one second.
What are the three types of error checking studied?
- Parity
- Checksum
- Cyclic Redundancy Check ( CRC )
What are the two types of Parity checking?
Even and Odd
How does parity checking work?
A bit is added to the end of the message to make the total number of ‘1’s either even or odd in number.
What does EFTPOS stand for?
Electronic Funds Transfer at Point of Sale
What is Parallel transmission?
When data is transferred over multiple lines on the transmission medium simultaneously.
What is Serial transmission?
When data is transferred over a single line with all the bits transferred one after the other.
What is Asynchronous transmission?
Timing is not involved and start and stop bits are used to indicate when messages are being sent.
What is Synchronous transmission?
The sending of data is timed and synchronised to a clock. Start and stop bits are not required.
What is simplex?
When data may only be transferred in one direction over the medium.
What is half-duplex?
When data may be transferred in both directions over the medium but only in one direction at a time.
What is full-duplex?
When data may be transferred in both directions over the medium at the same time.
List some common Applcation level protocols
- HTTP
- SMTP
- SSL
List some common Communication control and Addressing level protocols
- TCP
- IP
List some common Transmission level protocols
- Ethernet
- Token ring
What are three methods of error detection?
- Parity
- Checksum
- Cyclic Redundancy Check ( CRC )
How does parity work?
Parity is either even or odd and is achieved by adding a final bit to make the number of ‘1’s either even or odd.
What is a LAN?
Local Area Network. A network with computers connected over a small geographic area.
What is a WAN?
Wide Area Network. A network with computers connected over a large geographic area.
What is packet switching?
A technique that divides messages into small data packets such that multiple paths may be used to transfer the data between the source and destination.
What are the three main network topologies?
- Bus
- Ring
- Star
Describe a Bus network topology.
This is where every device connects to a common medium. Everyone shares the common medium to communicating.
Describe a Star network topology.
This is where the devices all connect back to a single point which manages and directs all messages.
Describe a Ring network topology.
All the computers are connected in a ring. Each device has two connections. Messages are passed around the network, one machine to another.
What is a Network Interface Card?
NIC for short, it is the hardware that allows a computer or other device to connect to the transmission medium in order to send and receive messages.
What type of servers exist on a network?
- File server
- Print server
- Mail server
- Web server
What is a Router?
A device that connects two or more networks (that may be of different type. It is able to work out the path from a Sender to a Reciever on networks not directly connected to it to route packets to the intended destination.
What is a Switch?
A device that directs data packets within a LAN. It knows which devices are directly connected to it by MAC address and sometimes by IP address.
What is a Bridge?
A device that is able to connect two networks that are of the same type.
What is a Gateway?
A device which can link two networks of different types.
What is a Repeater?
A device which allows a connected to be extended by amplifying and resending the signal.
What is a hub?
Similar to a switch but is not aware of the devices connected to it and just broadcasts all messages to every connected device. Largely been replaced with Switches.
List the common wired transmission media
- Twisted pair
- Coaxial cable
- Fibre optic cable
Describe twisted pair
Pairs of wires are twisted around each other to shield and protect the signal. This is the most common LAN transmission medium with CAT 5 / 6 cables.
Describe Coaxial cable
A single copper wire surrounded by an insulator, shielding and an outer insulator.
Describe fibre optic cable
A very thin glass (or plastic) fibre is surrounded by cladding and an outer covering. Lasers are used to send light beams along the cable which is then read a the other end. Extremely fast but easily damaged if care is not taken.
