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2009-02-24 Jacaranda questions 3.1

posted Feb 25, 2009, 2:51 AM by Unknown user   [ updated Apr 10, 2009, 1:45 AM by Eddie Woo ]
1. What are the four elements of communication?
The four elements of communication are the sender, receiver, message, and medium.

2. What is the difference between Baud and bits per second?
Baud is the number of distinct signal events in a second, while bits per second (bps) refers to the number of bits that are sent every second. They are different because one bit is not always equivalent to one signal event.

3. List three error detection methods.
Parity check, Checksum, and CRC (Cyclic Redundancy Check)

5. What strategies do retransmission protocols use to improve their efficiency?
The popular retransmission protocol v.42 forces the sending computer to keep in memory the last 15 blocks of data transmitted. This allows for retransmission even if the original storage device is no longer online, and if the original storage device is online, allows for quicker retransmission. Retransmission protocols also reduce the size of message blocks when errors are detected, so that blocks for retransmission are smaller, hence saving bandwidth by avoiding the retransmission of "healthy" data.

6. How is the sending device made aware that an error has taken place?
The receiving device detects the error through any of the error detection methods aforementioned, and then sends a request for retransmission to the sending device.
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