Data Communications I, Autumn 2000
Problems for Exercise 1 (18.-22.9.2000)
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Try to find, from web or other sources, answers to the following questions about networks. PLEASE, do not bother the network maintenance people!
- What logical networks are provided for students to use at the Computer Science
Department, at the University of Helsinki, for all students in Finland by FUNET
(Finnish University Net)?
- What kind of technology is used in these networks? Here it is enough just to give names
or terms. It is not necessary to understand the technology.
- What kind of services do these networks provide for the students?
- Connection oriented, connectionless
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What is the main difference between connectionless and connection oriented data communications.
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Can a service be connectionless, though the network is circuit switched. Or
connection oriented when the network is packet switched? Give
reasons and examples.
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How is it possible that a message in a data communication network can
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totally disappear
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multiply
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pop up to a receiver much later than many of its followers (in principal even many days later?
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The capacity of a communication line is 1 Mbps and the transfer
rate of data is 100 Kbps. Users typically first fetch data from the
Internet and then read it. On average reading takes 90% of the time
and data transfer only 10%
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If circuit switching is used how many users can, at the same time, use the line?
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What is the probability that all the users are really transferring data
at the same time?
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What indications do these results give you about the efficiency of circuit
switching and
packet switching?
- Reference models
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What are the two reasons for using layered protocols?
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List two ways in which the OSI Reference model and the TCP/IP reference
model are the same. Now list two ways in which they differ.
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Which of the OSI layers handles each of the following?
* Breaking the transmitted bit stream into frames.
* Determining which route through the network to use.
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Search the Web to find answers to the following questions.
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How many Internet standards exist?
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Find RFC 791. What is it about? When was it published?
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What companies and organizations of your home country are participating in the ATM Forum?
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Where can you find WAP standards WAP 191 and WAP 203. What do
these standards standardize?
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What is IMT-2000?
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What does the ISO committee JTC 1/SC 6 standardize?