223102
| Question | Answer |
| What is a communication system? | A system enabling users to send/receive data to nodes in a network |
| Detail the Communications System Framework | 1. Source 2. Transmitter 3. Switiching & Routing 4. Receiver 5. Destination |
| Function of Source? | To produce the data |
| Function of Transmitter | To encode the data |
| Function of Receiever | Decodes data back to original form |
| Function of Destintion? | Receives the information |
| 3 types of Protocol Levels | 1. Application Level 2. Communication control and Addressing Level 3. Transmission Level |
| Function of Application Level? | Produces the data for transmission & reorganising the data once it has been received by Destination |
| Function of Communication Control and Addressing Level? | To establish and maintain the commnication link. Sends data to transmission |
| Function of Transmission Level? | Defines how, and peforms the actual physical transfer of data along transmission mediums, i.e., a channel |
| Pneumonic for the 8 functions performed between Source - Destination? | MOST - SAES |
| M | Message Creation |
| O | Organisation of data pakcets |
| S | Signal generation by transmitter |
| T | Transmission |
| S | Synchronising the transfer |
| A | Addressing and routing (used in IP) |
| E | Error detection and correction |
| S | Security and Management |
| What is Handshaking? | Agreeing upon a common protocol to utilise during transmission |
| What is FLOW CONTROL? | They are commands that inform the other nodes that the sender & receiver are ready. |
| What is E-mail? | The transfer of ASCII text over the internet. (the email address of the receiver is analysed with a domain name server (DNS) to find the IP address of the destination mail transfer agent) |
| What is VOIP? | Voice-over Internet Protocol! Transfers voice calls over the internet. Mainly using a BROADBAND connection |
| Forms of wired transmission media? | Twister Pair Coaxial Cable Optic Fibres |
| Describe Twister Pair? | Copper wires intertwined, insulated by plastic. Used in LANs, ADSL. 10 - 100MBps |
| Describe Coaxial Cable? | Transmits analgoue broadcast TV from antennas to TV sets. Also, used in Broadband connections. |
| Describe Optic Fibres? | A transparent, flexible fibre made up of extruded glass to transmitt light to the ends of the fiber. |
| Forms of Wireless transmission media? | Microwaves, Satellites, Radio & Infrared |
| Describe Microwaves? | Used by satellites. Ground to ground level, provides large bandwidth of high frequencies. * needs direct line of sight |
| Describe Satellites | Satellites use microwaves to transmit data inbetween stations/other satellites. Transponders receive signals on one frequency, ampify it, then transmit on another frequency. |
| Describe Radio | Used within mobile phones and LANs. Low-speed transfer rates |
| Describe infrared | Used between portable devices for remote controls. |
| 3 characteristics of Speed? | 1. Bits per second (Bps) 2. Baud Rate (# signal events p/s) 3. Bandwidth (wide band of frequencies for transmission) |
| Protocols used at APPLICATION level? | 1. HTTP 2. SMTP 3. SSL |
| HTTP? | Hypertext transfer protocol. The web browser receving web pages from the web server. HTML dictates how it'll be displayed |
| SMTP? | Simple Mail Transfer Protocol Uses SMTP servers to relay the message off unto other STMP servers until the message reaches its final destination. |
| SSL? | Secure Sockets Layer Uses 2 keys to encrypt/decrypt data for transmission over the internet |
| Protocols used at COMMUNICATION CONTROL AND ADDRESSING level? | Transmission Control Protocol (TCP) & Internet Protocol (IP) |
| IP??? | Addresses the message...moves data packets...uses IP address to reroute message to most efficient path. |
| TCP?? | Ensures data is delivered correctly. Performs data error and correction. Requires IP |
| Protocols used at TRANSMISSION level? | Ethernet (built into hardware/NICs) Token ring (a special bit pattern traveling around nodes comprising a LAN topology) |
| Causes of data error | Electric, magnetic, thermal interference |
| What is Parity check? | The last bit in a byte maintains an even or odd count of 1's |
| What is Checksum? | A sum is sent in the last byte in a block of data. Receiver compares sum to the sender's sum |
| What is CRC? | Cylic Redundancy Check. Using calcuations, a number is derived from the data. By recalculation the CRC, errors can be detected and corrected. |
| What is a Network Topology? | A description of the layout of a network, including how the nodes interact with each other. |
| Star topology? | |
| Bus topology? | |
| Ring topology? | |
| What is a HUB? | Amplifies and retransmits data packets to attached nodes. |
| What is a SWITCH? | Determines the MAC address of the sender/receiver and connects them. |
| What is a ROUTER? | Uses IP addresses to send messages |
| What is a MODEM? | Modulates the data to analogue form, then demodulates back to digital form. |
| What is a BRIDGE? | Separates different sections of the network into seperate segments |
| What is a GATEWAY? | Connects seperate segments together that use different protocols |
| What are NICs? | Network Interface Cards Connect data between computer into a form suitable for transmission across the network |
| What are WAPs? | Wireless-access points Central nodes on WLANs that transmit data to the other nodes. |
| Characteristic of a BLUETOOTH device | Short-range and low-bandwidth |
| Pneumonic for the Characteristics of Network Operating Software (NOS) | FASSC |
| What does "FASSC" stand for? | File management Administration Security Sharing resources Cross-platform access |
| Characteristics of analgoue & digital signals? | Analogue uses replicated sound waves/pictures Digital is in binary code. |
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