Fundamentals of communication and networking Flashcards
What is serial transmission?
Serial transmission sends and receives data one bit at at time. Serial connections connect peripherals to computers, and computers together to form networks.
What is parallel transmission?
Parallel transmission sends and receives data simultaneously. The more wires in a “bundle”, the more data can be sent at once. (HDMI has 19 wires, for example).
What is one of the issues with parallel cables?
Parallel cables use more wires and are therefore more expensive to produce. Signals also degrade over longer distances due to interference between wires (crosstalk). Timing the wires’ data so it all arrives at the same time and in sequence is also an issue known as synchronisation.
What is bandwidth?
Bandwidth is the term used to describe the amount of data that can be transmitted along a communication channel. It relates to the range of frequencies that are available on the carrier wave that carries the data. The range in this case is the difference between the upper and lower frequencies. Bandwidth is measured in Hertz (s^-1) and represents the number of cycles per second.
What is bit rate?
Bit rate is the term to describe the speed at which transmission is taking place. Measured in bits per second, it is limited by bandwidth because bandwidth determines the amount of data that can be sent, whereas bit rate determines the speed of transmission.
What is the pipe analogy relating bit rate and bandwidth?
Bandwidth can be imagined to be the diameter of a pipe; the larger the diameter, the more water can be sent through in a given instant. Bit rate is the actual amount of water being sent through. As a result of this, bit rate is directly proportional to bandwidth.
What is baud rate?
Baud rate is another term used to describe the speed at which data can be transmitted, but instead relates to the medium of transmission. Traditionally, one bit is sent per state change, so one baud is one BPS. However, it is possible to send more than one bit per state change by using voltage levels to represent bits. in this scenario, you are instead sending “symbols” which can represent multiple bits. If you have 16 different voltage levels, you could encode 4 bits per state change (2^4=16). If you had 400 bits to send at a rate of 400BPS, it would take one second. However, if you had 4 bits in each symbol, it would take a quarter of the time; the baud rate would be 100 baud.
What is latency?
Latency is the term used to refer to and describe the time delay that occurs between a request for an action and an action happening. This can be seen as the delay between a newscaster in England talking to a reporter in a different country; there is a noticeable pause between the newscaster and the reporter’s response, and this is due to latency. There are three main causes to latency: propagation latency (caused by logic gates), transmission latency (caused by the medium) and processing latency (caused by the processing itself).
What is synchronous transmission?
Synchronous transmission is a method of transmission in which the sender, using the system clock, will time their packets in conjunction with the recipient. If the two devices are not synced, data could be lost during transmission. However, once synced, only data needs to be sent.
What is asynchronous transmission?
Unlike synchronous transmission, which requires a permanent syncing of the sender’s and receiver’s clocks, asynchronous transmission only synchronises for the duration of the transmission by sending additional bits called start and stop bits.
Describe the process of asynchronous transmission.
- The start bit causes the receiver to synchronise its clock to the same rate as the sender. This means that timing of the transmission and receipt are the same on both devices.
- Both devices must have already agreed on how many bits of data will follow, whether a parity bit is being used, the type of parity and the number of stop bits.
- The stop bit(s) indicate that the data has arrived so that the receiver’s processor can handle the data accordingly. The stop bit(s) also signal when the next start bit arrives.
What is the main issue with asynchronous transmission?
Asynchronous transmission ends up using more data than synchronous transmission because of the added necessity for start and stop bits. This ends up reducing the amount of actual data that can be transmitted in a given time frame.
What is a protocol?
A protocol is a set of rules established to ensure that different computers can communicate with each other.
What are the 4 common protocols?
TCP/IP: Two protocols that work in tandem so much they are usually referred to as one. Governs the transmission of data around the Internet, and involves splitting, routing and re-assembling data to and from packets.
HTTP: Governs the exchange of different types of file that make up web pages.
FTP: Governs the transfer of files on the Internet, such as when downloading files or creating and uploading web pages to servers.
What is a Network Interface Card?
In order to connect to a network, a computer must have a network adapter (NIC), which is a printed circuit board contained inside the computer just like the graphics and sound cards. The NIC will be specifically designed to connect (either through cable or wirelessly) to the particular network topology being used. The type of card used also dictates the speed of data transmissions.
