Questions with Solutions Chapter Two The OSI Model and TCP ...
Transcript of Questions with Solutions Chapter Two The OSI Model and TCP ...
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 1
Questions with Solutions
Chapter Two
The OSI Model and TCP/IP Model
2020/2021
Q1/ List the specific responsibilities of the Physical Layer?
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 Data link 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 Network Layer?
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 Session Layer?
Ans.
a) Managing dialogue control.
b) Graceful close.
c) Token management.
d) Synchronization.
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 2
Q5/ List the specific responsibilities of the Presentation Layer?
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 Application Layer?
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.
Transport layer network layer
logical communication between processes logical communication between hosts
Sender: breaks application messages into
segments (Segment the PDU), and passes to
network layer
Sender:, encapsulates the PDU that it
receives from the Transport layer in the
form of packet PDU and passes to data link
layer
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 3
Q8/ What is the main differences between TCP and UDP Services?
Ans.
Transmission Control Protocol (TCP)
Service
User Datagram Protocol (UDP)
Service
1. Connection-oriented Connectionless
2. Reliable transfer of data. Unreliable Not guaranteed.
3. Segment retransmission and flow
control through windowing
No windowing or retransmission
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
information.
The transmission is faster. Due to the
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 Internet 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: Protocol Data Unit
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
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 4
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 Node to Node Frame 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 protocol stack 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.
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 5
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 TELNET
FTP HTTP SMTP
DHCP 6th Presentation To translate, encrypt, and compress data
5th Session To establish, manage, and terminate
sessions
4th Transport To provide reliable process-to-process
message and error recovery
TCP UDP
3rd Network layer To move packet from source to destination
to provide internetworking
IP ICMP ARP
2nd Data link To organize bits into frames to provide hop
to hop delivery
ETHERNET
Bluetooth 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-Internet Protocol (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)
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 6
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)
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 7
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.- Data link layer
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
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 8
Q21/ What are the main protocols used in application layer and mention the job of each
one.
Ans.
protocols Job Description
DNS (Domain Name System) Matches domain names with IP addresses.
HTTP (Hyper Text Transfer
Protocol)
to transfer data between clients/servers.
SMTP (Simple Mail Transfer
Protocol) & POP3 (Post
Office Protocol version 3)
Used to send email messages from clients to servers over
the internet.
FTP (File Transfer Protocol) Allows the download/upload of files between a
client/server
Telnet Allows users to login to a host from a remote location and
take control as if they were sitting at the machine (virtual
connection).
DHCP (Dynamic Host
Configuration Protocol)
Assigns IP addresses, subnet masks, default gateways,
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
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 9
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
Interconnection.
TCP refers to Transmission Control
Protocol.
2. OSI uses the network layer to define
routing standards and protocols.
TCP/IP uses only the Internet layer.
3. OSI layers have seven layers. TCP/IP has four layers.
4. In the OSI model, the data link layer and
physical are separate layers.
In TCP, physical and data link are both
combined as a single host-to-network layer.
5. Session and presentation layers are a part
of the OSI model.
In TCP/IP application layer equal to
application, presentation and session
Layers in OSI
TCP/IP OSI Reference Model
Application
Transport
Internetwork
Network
Interface
Application
Presentation
Session
Transport
Network
Data Link
Physical
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 10
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- 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)
F / 99 K / 66 T / 44 R /75 LAN 1 LAN 2 LAN 3
A / 50 P / 77 Q / 60
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 11
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: - 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
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 12
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 mac
address ,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
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 13
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
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 14
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
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 15
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
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 16
21. The encapsulation process at the network and Data link layer Through LAN2 If (R)
send a message to (Y) are
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
K / 99 E / 65 V / 45 Q /75 LAN 1 LAN 2 LAN 3
R / 30 W / 80 Y / 50
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 17
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
Alrafidain University College
Assistant Lecturer / Hussain Kassim Ahmad 18
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