data communication 2 assignment solution fall 2010

[Xpert]

Marks: 20
Question 1: [5]
How do the layers of the Internet model correlate to the layers of the OSI model?
Question 2: [5]
Match the following to one or more layers of the OSI model:
a. Format and code conversion services
b. Establishes, manages, and terminates sessions
c. Ensures reliable transmission of data
d. Log-in and log-out procedures
e. Provides independence from differences in data representation
Question 3: [5]
What is the difference between a port address, a

[Xpert]

Q1.
How do the layers of the Internet model correlate to the layers of the OSI model?

ANS.
The Internet Model is a subset of OSI model.

OSI model consist of 7 layers.
7. Application Layer
6. Presentation Layer
5. Session Layer
4. Transport Layer
3. Network Layer
2. Data Link Layer
1. Physical Layer

But the Internet model consist of only 4 layers , where the 6th (Presentation Layer) and 5th(Session Layer) are combined with the Application Layer and finally the 1st (Physical Layer) and 2nd (Data Link Layer) are merged into a new NETWORK INTERFACE Layer.

4. Application Layer
3. Transport Layer
2. Network Layer
1. Network Interface Layer.


The Internet model is also called TCP/IP model.





Q2.
Match the following to one or more layers of the OSI model:
a. Format and code conversion services
b. Establishes, manages, and terminates sessions
c. Ensures reliable transmission of data
d. Log-in and log-out procedures
e. Provides independence from differences in data representation




ANS
Match the following to one of the seven OSI layers:
a. format and code conversion services.- Presentation (6)
b. establishes, manages, and terminates sessions.- Session (5)
c. ensures reliable transmission of data – Transport (4)
d. log-in and log-out procedures – Application (7)
e. provides independence from differences in data representation – Presentation (6)

Q3.

What is the difference between a port address, a logical address, and a physical address? How and at which layer they are used


Port address
Port address is used for each process from client to server and it depends on the transport layer.
Physical Address

Transferring data from A,B and C there needs a addressing called physical address. Physical address is added to define the physical address of sender and receiver.


Logical Address

While transferring data from A, B and C then physical addressing is not that enough for this kind of transformation and logical address is needed in the data to help distinguish source and destination systems.

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Logical address: Network Layer

Physical adress: either Physical Layer or Data Link Layer.

Port address: Transport Layer

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Logical Address: An IP address of the system is called logical address. This address is the combnation of Net ID and Host ID. This address is used by network layer to identify a particular network (source to destination) among the networks. This address can be changed by changing the host position on the network. So it is called logical address.

Physical address: Each system having a NIC(Network Interface Card) through which two systems physically connected with each other with cables. The address of the NIC is called Physical address or mac address. This is specified by the manficture company of the card. This address is used by data link layer.


Port Address: There are many application running on the computer. Each application run with a port no.(logically) on the computer. This port no. for application is decided by the Karnal of the OS. This port no. is called port address.


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