In this exercise we will use a simplified mathmatical model to analyze the trade

Question

In this exercise we will use a simplified mathmatical model to analyze the trade-off between connection-oriented communication and connectionless communication. Explain your answer.

On a certain network both forms of communication are provided:

-Using connection-oriented communication, it takes 50 seconds to establish a connection, after which a packet of up to 10 characters can be sent in 1.0 seconds over the connection, in either direction.

-Using connectionless communication, a packet of up to 10 characters can be sent 1.2 seconds (the sending of each packet takes slightly longer than in the connection-oriented case, since each packet must find its way to the receiver).

Suppose processes A and B exchange messages on this network. A initiates the communication and sends to B a message of 100 characters, which are partitioned into 10 packets. In reply, B sends a message of 50 characters, which are partitioned into 5 packets.

Assuming that there is no delay other than the time it takes for establishing a connection (in the connection-oriented case) and for packet transmission:

a. How long does the session between A and B last, using connection-oriented communication? Explain.

b How long does the session between A and B last, using connectionless communication? Explain.

c. How much data (in number of characters) must be exchanged between A and B in order for the connection-oriented communication to yield a shorter session than the connectionless communication? Explain.

Explanation / Answer

Solution:

Explanation of connection-oriented communication:

In a connection-oriented communication, a connection is first established between the sender and the receiver. The transport layer protocol ( in general TCP) of both sender and receiver make a logical connection between them.The connection is made between sender and receiver in such a way that the data are seemed to be transfered through a imaginary tube that carries the data in the form of stream of bytes.One of the important services of Connection-oriented communication involves stream-delivery of data.

Explanation of connectionless communication:

In a connectionless communication, no connection is made previously before transferring of data. A path with minimum distance is found in the presense of source and destination IP address( required at network layer) and MAC address ( required at data-link layer) by routing protocols. For this reason connectionless communication takes more time than connection-oriented communication because for each packet a path is required to be found.

Question (a):

How long does the session between A and B last, using connection-oriented communication? Explain.

Explanation:

As explained earlier, in case of connection-oriented communication, a connection is first made between sender and receiver. Here it takes 50 seconds to make this connection (as given in the question).

A packet of 10 characters takes 1.0 second to be transmitted in either side. Here in this question after initiating the connection A sends 10 packets each containing 10 characters. Therefore 10 packets need a total of 10*1.0 = 10.0 seconds.

In a reply B sends 5 packets each containing 10 characters. Therefore 5 packets need a total od 5*1.0 = 5.0 seconds.

As a result the connection-oriented communication takes (50 + 10.0 + 5.0) seconds = 65.0 seconds to initiate the connection, sending 10 packets from A to B and sending 5 packets from B to A respectively.

Therefore the connection-oriented communication lasts for 65.0 seconds ( there is no delay as mentioned in the question ).

Question (b):

How long does the session between A and B last, using connectionless communication? Explain.

Explanation:

A packet of 10 characters takes 1.2 seconds to be transmitted in either side.  A sends 10 packets each containing 10 characters. Therefore 10 packets need a total of 10*1.2 = 12.0 seconds.

In a reply B sends 5 packets each containing 10 characters. Therefore 5 packets need a total od 5*1.2 = 6.0 seconds.

As a result the connectionless communication takes (12.0 + 6.0) seconds = 18.0 seconds sending 10 packets from A to B and sending 5 packets from B to A respectively.

Therefore the connectionless communication session lasts for 18.0 seconds( there is no delay as mentioned in the question ).

Question (c):

How much data ( in number of characters ) must be exchanged between A and B in order for the connection-oriented communication to yield a shorter session than the connectionless communication? Explain.

Explanation:

In this problem, connectionless communication takes 18.0 seconds to transmit 100 characters from A to B and 50 characters from B to A and the connection-oriented communication takes 65.0 seconds to transmit 100 characters from A to B and 50 characters from B to A.

Connection establishment and connection termination are important services for connection oriented communication. Here in this problem connection establishment takes maximum time ( 50 seconds). The data transmission for connection-oriented communication takes (10 * 1.0 + 5 * 1.0)seconds = 15 seconds < time taken to transmit data for connectionless communication.

Therefore, 100 characters of data is transmitted in connection-oriented communication in 15 seconds where as 100 characters of data is transmitted in connectionless communication in 18 seconds.

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