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Question 1:


For each of the following functions identify the corresponding layer from OSI model.
a. Communicates directly with user’s application program
b. Error correction and retransmission.
c. Mechanical, electrical, and functional interface
d. Responsibility for delivery between adjacent nodes
e. Reassembly of data packets

Answers:
(a) The “application layer” provide the facility to communicate directly with
the user’s application layer.

(b) The task of error correction and retransmission performed by the “data
link layer”.

(c) The task of mechanical, electrical, and functional interface performed by
the “physical layer”

(d) The “network layer” Responsible for delivery between adjacent nodes

(e) The “transport layer” responsible for the Reassembly of data packets


Question 2:
If we have three systems as follows:
1. One in communication from outside city
2. Two systems are within the same city but at different offices not far apart.



Using given scenario, explain the role of following addressing methods for OSI Layers when
Transferring data between systems A, B and C:
1. Service point address
2. Logical address
3. Physical address
Solution

Using given scenario, explain the role of following addressing methods for OSI Layers when transferring data between systems A, B and C:

1. Service point address
Computer A can communicate to Computer B by using TELNET.at a time it can comunicate using FTP. In the TCP/IP architecture, it is unique address process property.
The sending computer is running three process at this time a,b,c. While receiving is running 2 process like p,q. So process 'a' need to communicate with process 'p' using same application of FTP. so it transported data in PACKETS adding two port address sending to network layer.

2. Logical address
As it is necessary for WAN as it has 32-bit address which is uniqe property.HERE each device has a pair of address aw well as one link connection;obviously each router has three pair of address, (separate phisical address for for each connection) one for each connection. DATA encapsulated & framed send over to physical distintion address.

3. Physical address
As it is known as the LINK addresi.e.address of the nod defined by LAN & WAN. As it having authority overthe network(LAN&WAN),hence their formate vary fromnetwork to network. The intendent distination computer(A,B,C) finding a matchb/w the distination addressin the frame &its ownphysical address.
Here frame is checked and decapsulated/delevered to the upper layer.