Solution. Assignment # 1. (Chapter 2) Dr. Hasan Qunoo. The Islamic University of Gaza. Faculty of Engineering. Computer Engineering Department

Transcription

1 The Islamic University of Gaza Faculty of Engineering Computer Engineering Department Data Communications ECOM 4314 Assignment # 1 (Chapter 2) Solution Dr. Hasan Qunoo Eng. Wafaa Audah Eng. Waleed Mousa

2 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 networks? 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. physical b. IP c. port d. specific 6. What is a primary function of the trailer information added by the data link layer encapsulation? 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 c. Mail service b. File transfer and access d. All the above 8. Which of the following is a transport layer protocol? a. DNS b. HTTP c. TCP d. ARP 9. The data link layer attempts to make control a. Source to destination delivery c. Hop-to-hop delivery b. Process-to-process delivery d. None of above 2

3 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 and file transfer Application Layer 7. Responsibility for carrying frames between adjacent nodes Data link layer 8. Establishes, manages, and terminates sessions Session layer 9. Route selection Network Layer 10. Specifies the characteristics of the transmission medium Physical layer Question 3: Explain the meaning of the following terms (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 3

4 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 (5 Marks) 1. Draw the OSI model that represents the layers with their order. 4

5 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: 1. The layer that add this header (address) Physical: Data link layer Logical: Network layer Port: Transport layer Specific: Application layer 5

6 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: Physical Logical port 6