U1T1.2 - Networks Flashcards Preview

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Flashcards in U1T1.2 - Networks Deck (46)
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What is TCP/IP?

Transmission Control Protocol/Internet Protocol. Most common general purpose standard protocol which allows any networked comps to communicate. Specifies how signals sent across network + provides transport + routing for data. Used by most networking systems so reduced special gateways to convert signals into diff protocols. Splits data into small packets. How info packaged, sent, routed + received.
Defines how split + how sent + received.


What is the TCP layer?

Supports file transfer between comp systems + controls security. Also splits data into packets + allocates address to each.


What is the IP layer?

Transfers data packets from node to node by forwarding each using its address. Responsible for verifying correct delivery + detecting errors/lost data.


What is ethernet?

Fast + robust. Hard wired network, 802.3 standard (IEEE). Network protocol + hardware. Deals with physical (hardware) + transport (data movement) layers of OSI. Systems using it to communicate divide data streams into frames. Provides services up to data link layer. How data sent over LAN.


What is a frame?

Short piece of a data stream used when communicating by ethernet. Each contains source + destination address + error checking data so damaged frames detected + discarded. Higher layer protocols trigger retransmission of lost frames.


What are the parts of communication protocol?

How to set up + end connection, start + end message, deal with corrupted data + format data being sent.


What is CSMA/CD?

Carrier Sense Multiple Access with Collision Detection. Used by ethernet.


Describe CSMA/CD.

Method of data traffic management on LAN. Protocol for implementing below on ethernet LANs. Network interface on each comp is responsible for waiting for network to be free before sending message. If 2 sent at same time, collision occurs. Collision detected by all participating stations + messages resent when free. If another collision occurs, time intervals from which random waiting time is selected are increased.


What is a token ring network?

A ring network in which info is sent around ring as variable sized data packets, containing data, source + destination address.


What is a token?

Signal (series of bits) which passes round network (packet carrier). Packet attaches to it so it can travel network. Helps to avoid collisions. Systems rules in protocol specs dictate how long device may keep token, transmit for + how to generate new token if none circulating.


What is wi-fi?

Wireless fidelity. Digital comms protocol through which devices can comm without cables. IEEE committee for 802 standards which manages networking protocols among electronic devices created extension 802.11 which works on wireless mode. Can be open (no password) or closed (password).


What do you need for wifi to work?

Wireless transmitter. Receives info from internet via home broadband connection. AKA WAP. Converts info into radio waves + emits it, creating small WLAN around itself, device can receive this if it has a wireless adapter. Signals don't travel far. When you send info to internet, process works in reverse (device sends radio to wap which converts signal + sends back via broadband). Can buy broadband dongle to connect to wifi.



Wireless Local Area Network.


What is bluetooth?

Uses radio waves to connect. 2 devices must pair to communicate. Short-range on piconets. Aimed at simplifying connections + data synchronisation among enabled devices. Devices must be qualified + pass interoperability testing by Bluetooth Special Interest Group prior to release. Can't pass through solid objects.


What is a piconet?

Ad hoc network. Network of devices connected using bluetooth. One device becomes master whilst others act as slaves. Established dynamically + automatically as bluetooth devices enter + leave radio proximity.


What is VoIP?

Voice over Internet Protocol. Allows phone calls to be made over digital comp networks (internet). Converts analogue signals into digital data packets supports realtime 2 way convo transmission using IP. e.g. Skype


What is RFID?

Radio-frequency Identification. Use of radio waves to read + capture info stored on tag attached to object. Can be read from several feet away + doesn't need to be in direct line of sight of reader to be tracked. Tag contains data programmed into small comp chip activated by radio waves emitted from RFID reader. Sends data stored in memory to reader. Can be used in active (own power supply) + passive (activated by reader) systems. Doesn't require human intervention.


What is bandwidth?

Measure of capacity of data which can travel along channel in given time. Range of frequencies channel can handle. May be given as frequency (range/3kHz) or transmission rate/line speed (bps/63kbps) Determined by transmission medium + need to prevent electrical interference. High bw lines cost more than low bw lines.


What does capacity mean?

Maximum amount.


What is broadband?

Transmission channel with wide bandwidth over 3 kHz. For practical network applications, should be over 300MHz. Coaxial, fibre optic, radio or TP. Use DSL. Always on, faster than dial up.


Give 6 types of transmission media.

Coaxial cable, twisted pair, fibre optic, infrared, microwave + satellite.


Describe coaxial cable as a type of transmission media.

Made to variety of specs. Used for connecting tv aerial to tv. Has 2 conductors. 1 wire down centre, single strand, insulated by second, made of many strands braided round insulation for inner wire.


Describe TP cable.

Commonly used for data transmission (phone lines). Pair of copper wires twisted together, surrounded by copper braid + external insulation. Some made of multiple twisted pairs surrounded by overall (earthed) braid screen. Another form involves twisted copper in pairs with earth wire. Pairs may be grouped to form single multi connected cable. Minimum interference data transmission. Twist reduces signal loss.


Describe fibre optic cable.

Fine glass strand allowing rapid data transmission using modulated light beams. Covered in cladding which insulates it. Many strands in single cable, each capable of carrying 1+ data signals. Provides interference free, secure data transmission + no corrosion. Fibres are unidirectional so 2 used (1 to send, 1 to receive) Requires repeaters over long distances.


Describe infrared comms.

Uses same systems as domestic remote control tvs. Requires direct unobstructed line of sight between transmitter + receiver.


Describe microwave comms.

Used as method of comms within public phone services. Many organisations use private installations to transmit data between key sites. Use highly directional transmitters + receivers with dish aerials.


Describe satellite comms.

Satellite links are used for international comms by many providers of public phone services. Unlike satellite broadcast systems, they use highly directional, narrow beam, 2 way transmissions. Single channel capable of simultaneously carrying large num of separate transmissions.


Volume of data transfer:
Coaxial, TP, fibre optic, wifi + bluetooth.

Up to 10mbps, depends on category (<100kbps - 100mbps+), 100mbps - 2gbps, up to 250mbps, up to 25mbps.


Coaxial, TP, fibre optic, wifi + bluetooth.

Moderately high, low, v.high, high, low.


Coaxial, TP, fibre optic, wifi + bluetooth.

Fair, low, high, low, low (improving).