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The Islamic University of Gaza
Faculty of Engineering
Computer Engineering Department
Data Communications ECOM 4314
Assignment # 1
(Chapter 2)
Dr. Hasan Qunoo
Eng. Wafaa Audah
Eng. Waleed Mousa
Question 1: Choose the correct answer
(10 Marks)
1. As the data packet moves from lower to upper layers, headers are
a. added
b. subtracted
c. rearranged
d. modified
2. Suppose your network is connected to another network via a router. Which OSI
model layer provides the information necessary to direct data between the two
a. Network layer
b. Physical layer
c. Data Link layer
d. Session layer
3. Which of the following would be found in a Data Link layer header?
a. The packet’s fragmentation offset
c. The packet’s sequence number
b. The source’s logical address
d. The source’s physical address
4. When data are transmitted from device A to device B, the header from A's layer 4
is read by B's _______ layer.
a. Physical
b. Transport
c. Application
d. None of the above
5. The_____ address identifies a process on a host.
b. IP
c. port
d. specific
6. What is a primary function of the trailer information added by the data link layer
a. Supports error detection
c. Identifies the devices on the local network
b. Ensures ordered arrival of data
d. Provides delivery to correct destination
7. Which of the following is an application layer service?
a. Remote login
b. File transfer and access
8. Which of the following is a transport layer protocol?
a. DNS
c. TCP
9. The data link layer attempts to make control
a. Source to destination delivery
b. Process-to-process delivery
c. Mail service
d. All the above
d. ARP
c. Hop-to-hop delivery
d. None of above
10. Which of the following is/are correct about physical layer
a. The sender and receiver must use the same bit rate.
b. Sender and receiver can have different clocks (bit level) at their communication.
c. The sender and the receiver clocks must be synchronized.
d. Bit rate at the sender must be larger than a bit rate at the receiver.
Question 2: Match the following to one or more layers of the OSI model (10 Marks)
1. Reliable process-to-process message delivery
Transport Layer
2. Defines frames
Data link layer
3. Error correction and retransmission
Data link and Transport layers
4. Transmission of bit stream across physical medium
Physical layer
5. Communicates directly with user's application program
Application Layer
6. Provides user services such as e-mail and file transfer
Application Layer
7. Responsibility for carrying frames between adjacent nodes
8. Establishes, manages, and terminates sessions
9. Route selection
Data link layer
Session layer
Network Layer
10. Specifies the characteristics of the transmission medium
Question 3: Explain the meaning of the following terms
Physical layer
(5 Marks)
1. “peer-to-peer communication”
The communication or process on two or more devices communicating at a same layer
2. “encapsulation”
The process of adding headers and trailers by lower layers at the sender.
3. “logical address”
Universal address in which each host can be identified uniquely, regardless of the
underlying physical network. It is necessary for universal communication
4. “error control”
End to end rather than across a single link. Sending transport layer makes sure that the
entire message arrives at the receiving transport layer without error (damage, loss, or
duplication, one of the responsibilities of transport layer)
5. “segmentation”
Dividing data into segments having sequence number (one of the responsibilities of
transport layer)
Question 4: answer the following questions
1. Draw the OSI model that represents the layers with their order.
(5 Marks)
2. Draw the TCP/IP protocol architecture that represents the layers with their order.
Question 5: answer the following questions
(10 Marks)
Each of the previous addresses is added to data as a header at layered model; give the
following for each one:
The layer that add this header (address)
Physical: Data link layer
Logical: Network layer
Port: Transport layer
Specific: Application layer
2. Size of the address (how long in bits)
Physical: 48-bit
Logical: 32-bit
Port: 16-bit
Specific: variable
3. The format of the header (give an example: how it is represented)
 Physical:
Source and destination for the next link
(D S)
 Logical:
Final source and destination addresses (end systems)
(S D)
 Port: 16-bit
Source and destination for the end systems process port numbers.
(S D)
For example: