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Home , Application layer, Data link layer, Link layer, Presentation layer

Alrafidain University College

Questions with Solutions Chapter Two

The OSI Model and TCP/IP Model 2020/2021 Q1/ List the specific responsibilities of the ? Ans. The specific responsibilities of the Physical Layer: a) Convert the logical 1’s and 0’s coming from layer 2 into electrical signals. b) Transmission of the electrical signals over a communication channel.

Q2/ List the specific responsibilities of the Layer? Ans. a) Error control to compensate for the imperfections of the physical layer. b) Flow control to keep a fast sender from swamping a slow receiver.

Q3/ List the specific responsibilities of the ? Ans. a) Chose the best path from Source-to-destination Packet delivery. b) Routing packets from source to destination. c) Logical addressing. Q4/ List the specific responsibilities of the ? Ans. a) Managing dialogue control. b) Graceful close. c) Token management. d) Synchronization.

Assistant Lecturer / Hussain Kassim Ahmad 1

Alrafidain University College

Q5/ List the specific responsibilities of the ? Ans. a) Data Representation, and Translation. b) Compressing and decompressing data. c) Data compression. d) Data Encryption and decryption. e) Security.

Q6/ List the specific responsibilities of the ? Ans. a) Allows user to interface with the network. b) Provides protocols that are commonly needed.

Q7/ Compare between specific responsibilities of the Transport vs. network layer. Ans. network layer logical communication between processes logical communication between hosts Sender: breaks application messages into Sender:, encapsulates the PDU that it segments (Segment the PDU), and passes to receives from the Transport layer in the network layer form of packet PDU and passes to data

Assistant Lecturer / Hussain Kassim Ahmad 2

Alrafidain University College

Q8/ What is the main differences between TCP and UDP Services? Ans. Transmission Control Protocol (TCP) (UDP) Service Service 1. Connection-oriented Connectionless 2. Reliable transfer of data. Unreliable Not guaranteed. 3. Segment retransmission and flow No windowing or retransmission control through windowing 4. Segment sequencing No sequencing 5. Acknowledge sequencing No acknowledgment 6. Lost data retransmission Feasible Practically, not possible. 7. There is a delay in transfer of The transmission is faster. Due to the information. absence of connection establishment phase,

Q9/ Give the Definition of the Connection-Oriented and Connectionless. Ans. Connection-Oriented: – before data is sent, the service from the sending computer must establish a connection with the receiving computer. (Email is connection-oriented).

Connectionless: – data can be sent at any time by the service from the sending computer.

(Downloading a music file from the is connectionless). Q10/ What does PDU abbreviation stands for in computer networking? Then draw table showing the shape for the PDU for each layer?

Answer:

PDU stands for:

The Layer Shape of data (PDU)

Top three layers (Application layer). Data

Transport layer Segment

Network layer Packets

Data Link layer Frames

Physical layer Bits

Assistant Lecturer / Hussain Kassim Ahmad 3

Alrafidain University College

Q11/ Explain the delivery of data with shapes of data and type of addressing in Layered model? Or

Q11/ Fill the following table of the delivery data in layered model.

layer Type of delivery Shape of data Type of addressing

Ans.

layer Type of delivery Shape of data Type of addressing

Transport End to End Segment Port (socket)

Network Source To Destination Packet Logical (IP)

Data Link to Node Physical (MAC)

Q12/ Define OSI protocol model Encapsulation and the PDU protocol. OR Q20/ Explain with drawing the Encapsulation process and the PDU protocol. Ans.

Encapsulation: As application data is passed down the on its way to be transmitted across the network media, various protocols add information to it at each level.

This is commonly known as the encapsulation process.

The form that a piece of data takes at any layer is called a Protocol Data Unit (PDU). PDU’s are used for peer-to-peer contact between corresponding layers.

Assistant Lecturer / Hussain Kassim Ahmad 4

Alrafidain University College

Q13/ Describe the OSI model and explain each layers function and assign each protocol in the layer.

Layer layers function Protocols 7th Application To allow access to network DNS 6th Presentation To translate, encrypt, and compress data FTP HTTP SMTP 5th Session To establish, manage, and terminate DHCP sessions 4th Transport To provide reliable process-to-process TCP UDP message and error recovery 3rd Network layer To move packet from source to destination IP ICMP ARP to provide internetworking 2nd Data link To organize bits into frames to provide hop to hop delivery 1st Physical To transmit bits over a medium to provide mechanical and electrical specifications

Q14/ Match of the following responsibilities with the corresponding OSI layer?

1- To allow access to network resource. Ans. (Application laver)

2- Data compression. Ans. (Presentation layer)

3- Token management. Ans. (session laver)

4- Connection-oriented and connectionless services. Ans. (Transport layer)

5- (IP) addressing (Logical addressing). Ans. (Network Layer)

6-Bridges & Switches (multi-port bridges). Ans. (data link laver)

7-Transmission mediums (transmit bits over medium). Ans. (physical laver)

Assistant Lecturer / Hussain Kassim Ahmad 5

Alrafidain University College

Q15/ Match of the following responsibilities with the corresponding OSI model.

1- Provides protocols that are commonly needed. Ans. (Application laver)

2- Data encryption. Ans. (Presentation laver)

3- Managing dialogue control. Ans. (session laver)

4- Provide reliable process to process message delivery & error recovery. Ans. (Transport Laver)

5- Controls the operation of the subnet. Ans. (Network Laver)

6- Error detection and correction methods. Ans. (data link laver)

7- Provide mechanical and electrical specification. Ans. (physical laver)

Q16/ Match of the following responsibilities with the corresponding OSI model?

1- (FTP), (HTTP). (SMTP). (DNS), (DHCP), (Telnet). Ans. (Application laver)

2- Concerned with the syntax and semantics of the information. Ans. (Presentation laver)

3-Allows users on different machines to establish sessions (dialogue) Ans. (Session laver)

4-End-to-end flow control. Ans. (Transport laver)

5-Routing algorithms (Routing packets from source to destination). Ans. (Network Laver)

6-Hop to hop delivery. Ans. (data link laver)

7-Hubs (multi-port repeater). Ans. (physical laver)

Assistant Lecturer / Hussain Kassim Ahmad 6

Alrafidain University College

Q17/ which of the OSI layers handles each of the following functions: 1. Sequencing and reassembling? Ans.- The transport layer

2. Proving best path to reach destination? Ans.- The network layer 3. Dividing the transmitted bit stream into frames? Ans.- 4. Responsible for error detection? Ans.- Data link layer

5. Determining which route through the subnet to use? Ans.- the network layer

6. The layer is closest to the transmission media? Ans.- The physical layer.

7. Reliable process to process data transportation? Ans.- The transport layer.

8.Provides access to the network for end user? Ans.- The application layer.

9.Flow control? Ans.- Data link layer.

Q18/ Which OSI layers is the network support layers? Answer: (Physical, Data link, network layers)

Q19/ Which OSI layers is the user support layers? Answer: (Session, Presentation, Application)

Q20/ Which OSI layer functions as a liaison between user support layers and network support layers? a) Network b) Physical c) Transport d) Application Answer: c) Transport

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Alrafidain University College

Q21/ What are the main protocols used in application layer and mention the job of each one. Ans. protocols Job Description DNS () Matches domain names with IP addresses. HTTP (Hyper Text Transfer to transfer data between clients/servers. Protocol) SMTP (Simple Mail Transfer Used to send email messages from clients to servers over Protocol) & POP3 (Post the internet. Office Protocol version 3) FTP () Allows the download/upload of files between a client/server

Telnet Allows users to login to a from a remote location and take control as if they were sitting at the machine (virtual connection). DHCP (Dynamic Host Assigns IP addresses, subnet masks, default gateways, Configuration Protocol) DNS servers, etc. to users as they login the network.

Q22/ Classify the following protocol with their uses in each layer in the TCP/IP reference model. TCP, IP, HTTP, UDP, ETHERNET, ICMP, FTP, TELNET, SMTP, DHCP Ans. Layer Protocols Application HTTP TELNET FTP SMTP DHCP Transport TCP UDP Internet IP ICMP Network access (Host-to-network) ETHERNET

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Alrafidain University College

Q23/ What are the main differences between TCP/IP and OSI 7-layers model? Ans. The main differences between TCP/IP and OSI 7-layers model? OSI Model TCP/IP Model 1. OSI refers to Open Systems TCP refers to Transmission Control Interconnection. Protocol. 2. OSI uses the network layer to define TCP/IP uses only the . routing standards and protocols. 3. OSI layers have seven layers. TCP/IP has four layers. 4. In the OSI model, the data link layer and In TCP, physical and data link are both physical are separate layers. combined as a single host-to-network layer. 5. Session and presentation layers are a part In TCP/IP application layer equal to of the OSI model. application, presentation and session Layers in OSI

TCP/IP OSI Reference Model

Application Application

Presentation

Session

Transport Transport

Internetwork Network

Data Link Network

Interface Physical

Assistant Lecturer / Hussain Kassim Ahmad 9

Alrafidain University College

Q24/ Show the encapsulation process at the network and Data link layer at each node in the following cases:

a- If A send a message to Q b- If P send a message to Q

A / 50 P / 77 Q / 60

R /75 T / 44 K / 66 F / 99 LAN 1 LAN 2 LAN 3

a- Answer. Through LAN1 (from A/50 to R/75)

Through LAN2 (from T/44 to K/66)

Through LAN3 (from F/99 to Q/60)

b- Answer. Through LAN2 (from P/77 to K/66)

Through LAN3 (from F/99 to Q/60)

Assistant Lecturer / Hussain Kassim Ahmad 10

Alrafidain University College

Q25: What are the types of connecting devices are used to connect a network or multiple networks together and cite each device in which layer are used. Ans.

There are two types of connecting devices: a. Networking Devices:

1) Repeater: - Repeaters is a Layer 1 device. 2) Hub: - is a Layer 1 device. 3) Bridge: - A bridge is a Layer 2 device 4) Switch: - A switch is a Layer 2 device b. Internetworking Devices.

5) : - Router is a Layer 3 device. choose the best path for them through the network. 6) Gateway: Gateway is a Layer 7 device. الشكل للتوضيح

Assistant Lecturer / Hussain Kassim Ahmad 11

Alrafidain University College

Q26: What is the addresses are used in an internet employing the TCP/IP protocols, and cite each address in which layer are used. Ans. Four levels of addresses are used in an internet employing the TCP/IP protocols:

1-Physical Addresses: The physical address, also known as the link address or ,it is the address used in physical layer.

2-Logical Addresses (IP): Logical addresses are necessary for network to network communication A logical address in the Internet is currently a 32-bit, and it is used in the network layer.

3- Port Addresses: It is implemented in transport layer as process to process delivering, and it is used in the transport layer.

4- Specific Addresses: it is used in the application layer.

الرسم للتوضيح

Assistant Lecturer / Hussain Kassim Ahmad 12

Alrafidain University College

Q27/ Choose the correct answer from the following:

1. The ______is responsible for delivering data units from one station to the next without errors. a. Network Layer b. Transport Layer c. Data link Layer e. Physically layer Answer: (c). Data link Layer

2. Web and Mail services are provided by ______. a. Session Layer b. Presentation Layer c. Application Layer e. Physically layer Answer: (c). c. Application Layer

3. The TCP/IP ______layer is equivalent to the combined session, presentation, and application layers of the OSI model. a. application b. network c. data link d. physical Answer: (a).application

4. ______is responsible for process to process delivery. a. network layer b. transport layer c. session layer d. data link layer Answer: (b). transport layer

5. ______provides the services to user. a. application layer b. session layer c. presentation layer d. none of the mentioned Answer: (a).application layer

6. The functionalities of presentation layer includes ______. a. Data compression b. Data encryption. c. Data description. d. All of the mentioned Answer: (d).All of the mentioned

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Alrafidain University College

7. In the OSI model, as a data packet moves from the lower to the upper layers, headers are ______. a. Added b. Removed c. Rearranged d. None of the mentioned Answer: (b).Removed

8. The ______layer is responsible for the source-to-destination delivery of a packet across multiple network links. a. transport b. Network c. data link d. physical Answer: (b).network

9. In OSI model dialogue control and token management are responsibilities of ______. a. Session Layer b. Network layer c. Transport layer d. Data link layer Answer: (a).Session Layer

10. The layer of OSI model which is responsible about data compression and encryption is ______. a) Session layer b) Presentation layer c) Application layer d) None of above

Answer: a) Presentation layer

11. Which type of address is used in an internet layer of TCP/IP model? a) Physical address b) Port address c) Specific address d) Logical address

Answer: d) Logical address

12. The process to process delivery is the responsibility of______. a) Network layer b) Transport layer c) Session layer d) Data link layer

Answer: b) Transport layer

13. Layer that is used to deal with Transmission mediums is______. a) Data Link Layer b) Network Layer c) Physical Layer d) Transport Layer

Answer: c) Physical layer

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Alrafidain University College

14. The layer which is responsible about node to node communication is ______. a) Application layer b) Session layer c) Physical layer d) None of above

Answer: d) None of above

15. The operation of switch is depends on ______. a) Port address b) Physical address c) Logical address d) None of above

Answer: b) Physical address

16. The frame trailer include information about ______. a) Flow control b) Frame size c) Frame type d) Error control

Answer: d) Error control

17. The layer which allows access to network resource is ______. a) Physical layer b) Transport layer c) Application layer d) Data link layer

Answer: c) Application layer

18. The main function of transport layer ______. a) Find the best route to destination.

b) Receives data from upper layers and segments it into packets.

c) Give logical address to the segment

d) None of all

Answer: b) Receives data from upper layers and segments it into packets. 19. Which one of the following is a transport layer protocol used in internet? a) TCP b) UDP c) Both (A) and (B) d) None of the mentioned

Answer: c) Both (A) and (B)

20. In transport layer, a message is normally divided into transmittable ______. a) Segments b) Signals c) Networks d) Frames

Answer: a) Segments

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Alrafidain University College

21. The encapsulation process at the network and Data link layer Through LAN2 If (R) send a message to (Y) are

R / 30 W / 80 Y / 50

Q /75 V / 45 E / 65 K / 99 LAN 1 LAN 2 LAN 3

a- Upper layer Data Network layer R Y Data Data link layer 65 45 R Y Data T b- Upper layer Data Network layer V E Data Data link layer 65 45 V E Data T c- Upper layer Data Network layer R Y Data Data link layer 30 50 R Y Data T

d- Upper layer Data Network layer V E Data Data link layer 30 50 R Y Data T

Answer: a Upper layer Data Network layer R Y Data Data link layer 65 45 R Y Data T

22. UDP is considered as a connectionless protocol because ______. a) There is no connection establishment and no connection termination is performed.

b) No flow control is needed. c) Segments Delivered out-of-order.

d) All of the mentioned

Answer: d) All of the mentioned

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Alrafidain University College

23. The Layer which Convert the logical 1's and O's coming from layer 2 into electrical signals is: a. Physical layer b. Network layer c. Transport layer d. TCP layer

Answer: a. Physical layer

24. Downloading a music file from the Internet is: a. connection- less b. Connection-oriented c. forwarding d. routing

Answer: a. connection- less 25 In no handshaking between sender and receiver. a. UDP b. TCP c. both TCP and UDP d. DNS

Answer: a. UDP

26. Which protocol is used to transfer web page from server to client; a. DNS b. SMTP c. FTP d. HTTP

Answer: d. HTTP

27. Which protocol is used to send email messages from clients to servers over the internet. a. DNS b. SMTP c. FTP d. HTTP

Answer: b. SMTP

28. Which protocol allows the download/upload of files between a client/server. a. DNS b. SMTP c. FTP d. HTTP

Answer: c. FTP

29. Which protocol allows users to login to a host from a remote location and take control as if they were sitting at the machine (virtual connection). a. DNS b. SMTP c. Telnet d. HTTP Answer: c. Telnet

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Alrafidain University College

30. Which protocol Assigns IP addresses, subnet masks, default gateways, DNS servers, etc. to users as they login the network. a. DHCP b. DNS c. SMTP d. Telnet Answer: a. DHCP

31. Which protocol Matches domain names with IP addresses. a. DHCP b. DNS c. SMTP d. Telnet Answer: b. DNS

Assistant Lecturer / Hussain Kassim Ahmad 18