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| Information presented in a form that is agreed upon by the parties creating and using the data |
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| exchange of data between two devices via some form of transmission medium such as a wire cable |
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| the information to be communicated, (text, picture, video) |
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| the pyshical path by which a message travels |
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| a set of rules that govern data communications |
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| Direction of data only going one way |
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| Direction of data going two different ways but not at the same time (walkie talkie) |
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| Data going two directions at all times |
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| a set of devices connected by communication links |
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| Point to point and Multi point |
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Definition
| Point to point is one station connected to another. Multipoint has multiple stations on the same link |
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| All nodes are connected to all other nodes on the network |
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| All nodes connect to a central hub |
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All nodes connect along a central line or bus* that has two ends One long cable, backbone
Ease of installation
Difficult reconnection and fault isolation; break in cable, fails network |
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Definition
| Easy to install and reconfigure; IBM introduced it; less popular now |
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| Star and bus topologys mixxed together |
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| Open Systems Interconnection model. Introduced in the late 70's by the ISO |
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| Seven layers of the OSI model |
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Definition
| Physical - Data Link - Network - Transport - Session - Presentation - Application |
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Definition
| Responsible for movements of individual bits from one hop (node) to the next. |
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Definition
| Responsible for moving frames from one hop (node) to the next. |
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Definition
| Delivery of frames from the data link level of one node to the data link layer of another node. |
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| Responsible for the delivery of individual packets from the source host to the destination host. |
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| Source to destination delivery |
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Definition
| Delivery of packets from the network layer of the sender to the network layer of the reciever not just including the hops along the way but the entire path. |
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Definition
| responsible for the delivery of a message from one process to another. |
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| 4 levels of addressing used in TCP/IP |
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Definition
| Physical, Logical, Port, Specific |
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| the rate of change with respect to time (Change in short span means high freq, long span means low freq) |
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Definition
| Means a loss of energy caused by resistance of the medium |
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Definition
| The shannon capacity gives us the upper limit; the Nyquist formula tells us how many signal levels we need. |
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Definition
| Amplitude of the carrier signal is varied to create signal elements. Both frequency and phase remain constant while the amplitude changes. |
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Definition
| The frequency of the carrier signal is varied to represent data. Both peak amplitude and phase remain constant for all signal elements. |
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Definition
| The phase of the carrier is varied to represent two or more different signal elements. Both peak amplitude and frequency remain constant as the phase changes. |
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Definition
| When the bandwidth of a medium linking two devices is greater than the needed bandwith it can be shared. Multiplexing is techniques taht allow the simultaneous transmission of multiple signals across a single data link. |
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Term
| Frequency Division Multiplexing |
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Definition
| FDM is an analog multiplexing technique that combines analog signals |
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| Wavelength division multiplexing |
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Definition
| WDM is an analog multiplexing technique to combine optical signals. It is designed to use the high data rate capablity of fiber optic cable |
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Term
| Synchrounous Time Division Multiplexing |
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Definition
| TDM is a process that allows several connections to share the high bandwidth of a link. Instead of sharing a portion of a bandwidth as in FDM, time is shared |
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Definition
| Combine signals from differennt sources to fit into a larger bandwidth but goals are to prevent eavesdropping and jamming by using redundancy. |
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Definition
| means that 2 or more bits in the data unit have changed |
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Definition
| the hamming distance between two words is the number of differences between corresponding bits |
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Term
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Definition
| a k-bit dataword is changed to a n-bit codeword where n=k+1. The extra bit called the parity b it is selected to make the total number of 1's in the code even or odd. |
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Definition
| the sum of data is sent along with the data, the reciever adds all the original numbers and compares with the sum. if it equals the sum it assumes no errors. |
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Definition
| The data link layer needs to pack bits into frames so that each frame is distinguishable from another. Like putting a letter into an envelope. |
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