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33 Cards in this Set
- Front
- Back
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Attenuation |
The weakening of the signal over distance |
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Electromagnetic interference (EMI) |
electronic signals that interfere with the normal data transmission signals normally caused by engines, heavy machinery, radar, etc. Shielding helps to reduce but not eliminate EMI. |
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Eavesdropping |
The ability to detect signals of data transference on a cable which is subject to EMI by detecting the magnetic fields around the cable without physically piercing the cable |
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Crosstalk |
When 2 data transmission cables are close together, the interference of signals between the cables is known as crosstalk
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UTP |
* Usage - used mainly on star network topologies (star)
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Coaxial Cable |
consists of a copper core surrounded by insulation then shielded with shielding also surrounded by insulation Slightly lower attenuation than UTP, allowing for distances up to 250 m Relatively slow less susceptible to EMI due to shielding
Usage - not normally used in networks as bus topologies are a thing of the past. it is still used for tv and satellite |
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Fiber Optic |
Usage - commonly used for broadband internet connections as well as connecting segments in large networks. They are relatively expensive and difficult to install
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Bus Topology |
Uses coax cable Can be considered to be a single line to which a number of nodes are connected If there is a fault on a single node it is difficult to trace and will disrupt the entire network Very simple to set up Designed for LANs of up to 100 nodes |
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Star |
Each node is connected to a central station called a hub with it’s own cable Easy to set up Reliable If one node fails, it usually does not affect the entire network unless that node is a server Easy to troubleshoot Nodes can be added or removed without disrupting the network Uses UTP cabling or fibre-optic Probably the most commonly used topology
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Ring
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Uses fibre optic or coaxial Nodes connected to a central unit known as a MultiStation Access Unit (MSAU) Commonly used for very large networks configuration usually a collapsed ring like a daisy A faulty node can bring down the entire network Nodes cannot be added or removed without disruption of a network. |
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Passive Hubs |
a simple connection box which receives signals and broadcasts them to all other nodes on the network without amplifying or regenerating signals. |
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Active Hubs |
as above, but has the ability when necessary of regenerating or amplifying signals. |
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Intelligent/Switched/Switch Hubs |
Has the ability to amplify or regenerate signals but in addition it also has the ability after receiving a signal to send on to a specific node rather than broadcasting to all nodes thus improving efficiency, reducing traffic, and speeding up the network performance dramatically. Many hubs have the facility for both UTP and fiber optic cabling and occasionally coaxial.
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Repeater |
a device which sits between two segments of a network in order to amplify or regenerate the incoming signal so that it will be strong enough to be read when it reaches its destination. Old school.
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Bridge |
connects two segments of a network in such a way that all messages coming from a segment destined for that same segment is not allowed to cross that bridge while all messages destined for other segments are permitted to cross over. This reduces network traffic dramatically. In addition, bridges also amplify or regenerate signals. Unlike a switch, it sends 47 messages out at once rather than 1.
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Router |
connects LAN segments for different LANs into a WAN(wide area network) while designating the best route between sender and receiver. In order to achieve this, the router is supplied with a routing table. it checks the traffic on each possible route to the destination and selects the best of them.
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CSMA/CD |
(carrier sense multiple access/ collision detection)
This is the most common access method used by star and bus topologies with ethernet. A device that requires a signal to be sent listens for a transmission on the line (carrier sense). If the line is clear, the message is sent. If not, a random length of time is waited and then another attempt at sending is made. At the same time, other stations might send messages because the line is clear (multiple access). If a collision of signals is detected, the stations all wait random length of time before resending. This continues until all signals are successfully sent. *
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FDDI |
FDDI(fiber distributed data interface) An electronic token is sent around the ring from workstation to workstation. If a workstation needs to send a message it waits for the token and if the token is free it attaches its message with its own address, the address of the recipient and changes the status of the token to busy. The token continues from node to node and if another workstation needs to send a message, it takes the token sees that its busy, and releases it. When the token reaches the destination the message is stripped, a received is added and the token continues until it reaches the sending workstation. The sending workstation strips the acknowledgment and the addresses from the token and changes its status to free before sending it on. This is repeated until all workstations have sent all messages. In FDDI more than one token is sent at the same time with all tokens travelling in the same direction. If a section of the ring is faulty FDDI will bypass that section by using the second ring and will then return to the original. Used in dual riing topologies |
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Gateway |
While routers have the ability of connecting LAN and Wan Segments using different protocols, these protocols still have to be of the same type e.g. pc - pc. In fact modern switches are also capable of the functions. However, in order to connect completely different protocols and platforms e.g. pc - mainframe, gateways are essential. Generally speaking, the gateway is set up at the firewall access point |
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GAN |
A global area network (GAN) refers to a network composed of different interconnected networks that cover an unlimited geographical area. The term is loosely synonymous with Internet, which is considered a global area network |
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World Wide Web |
The World Wide Web, or simply Web, is a way of accessing information over the medium of the Internet. It is an information-sharing model that is built on top of the Internet. The Web uses the HTTP protocol, only one of the languages spoken over the Internet, to transmit data. Web services, which use HTTP to allow applications to communicate in order to exchange business logic, use the the Web to share information. The Web also utilizesbrowsers, such as Internet Explorer or Firefox, to access Web documents called Web pages that are linked to each other via hyperlinks. Web documents also contain graphics, sounds, text and video. |
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Circuit/ Line switching
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This method relied on a dedicated circuit or line being established between sender and receiver for the duration of the data transmission. This method allows for the sending of any type of data including live video, and audio. The system does not make good use of resources as the user has to allow for the maximum amount of bandwidth required at any stage as a permanent resource.(essentially, the amount used does not flex with usage, it must be at the maximum the whole time)
This method is fairly expensive but it is extremely reliable as well as fast.
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Packet switching |
Data is broken up into smaller units called packets. Each packet, in addition to the data contains the senders address, the receiver's address, and the packet sequence number. At no stage during transmission is a set circuit or line set up between the 2 points. Packets can be sent along different routes and as a result they might arrive out of sequence. Once all the packets have arrived at their destination they are ordered into sequence and are reassembled. Packet switching makes excellent use of resources and is one of the most cost effective methods of transmitting data however it cannot be used for live audio or video transmission
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Cell switching |
This technology uses a combination of circuits and packet switching, data is divided into small packets called cells of the same length (43 bytes). During data transmission, a connection is setup between sender and receiver for the duration of the sending of a single packet, the connection is then terminated and a new dedicated line is set up for the next packet. This method makes exceptionally efficient use of resources and even if packets are sent along different routes, they always arrive in sequence. As a result, cell switching allows for any type of data without necessitating continuous high bandwidth.
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TCP |
transfer control protocol - governs the sending of data between nodes in a network |
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POP3 |
post office protocol) - allows us to download email from an email/exchange server |
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IMAP |
IMap has similar properties to POP3 but mirrors/synchronises email with the server stored email. (it also stores it on the service providers server). The two places are mutually exclusive (either both there or both not- action in one location mirrors in the other) |
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WEP |
encryption protocol, fairly difficult to configure and due to the fact that it has a 40 bit or 104 bit encryption key it is quite easy to break. |
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WPA |
(WIFI protected access) - A WIFI security standard which uses a pre-shared key (PSK). It uses the temporal key/integrity protocol (TKIP) for encryption. Every packet that is sent has a dynamically generated new 128 Bit key [Harder to break] |
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WPA2 |
Backward compatible with WPA with a level of assurance that only authorised users can access their networks. [ 2 versions- 1) password or 2.) corporate server authenticated (which is an extra step {you connect, then the server authenticates you based on separate credentials})]
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node |
workstations, network printers, servers, etc. |
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(NiC) |
Network Interface Card allows for the physical connection of the node to the network as well as converting from the node signal to the network signal (always needed) |
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NOS |
Network Operating System most modern OS on desktop platforms as well as on portable devices include basic network capabilities as an integrated function. A number of OS, such as linux, unix, apple osx do not differentiate between client and server NOS whereas with OS such as windows, there is a clear distinction between client and server OS
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