Chapter 1. Network Models

Chapter 1. Network Models

• OSI Model : Open Systems Interconnection (OSI)

The International Standards Organization (ISO) defined a seven-layer model to standardize networking processes

The seven layers, in order, are as follows:

7. Application

6. Presentation

5. Session

4. Transport

3. Network

2. Data link

1. Physical


Exam Questions


1. Which protocol will allow you to test connectivity through Layer 7?

A. ICMP
B. ARP
C. RIP
D. Telnet

Answer D is the correct answer; Telnet is the only Layer 7 protocol listed. All the others only
operate at Layer 3, so they do not test above Layer 3.

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2. Which answer correctly lists the OSI PDUs in order?

A. Data, Packet, Frame, Segment, Bit
B. Bit, Data, Packet, Segment, Frame
C. Data, Segment, Packet, Frame, Bit
D. Bit, Frame, Segment, Packet, Data

Answer C is the correct answer. "Did Sally Pack for Bermuda?"

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3. Which transport layer protocol provides connection-oriented, reliable transport?

A. TFTP
B. UDP
C. Ethernet
D. TCP
E. Secure Shell

Answer D is the correct answer. TCP is a transport-layer protocol that uses sequencing,
acknowledgments, and retransmission for reliability. Answers A, C, and E are incorrect because
TFTP, Ethernet, and Secure Shell are not transport-layer protocols; Answer B is incorrect because
UDP does not provide reliability.

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4. Which of the following are application layer protocols? Choose all that apply.

A. Ethernet
B. CDP
C. FTP
D. TFTP
E. Telnet
F. ARP
G. ICMP
H. ATM

Answers C, D, and E are correct. Answers A, B, and H are Layer 2 protocols; Answers F and G are
Layer 3 protocols.

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5. Match the protocol with its port number:

FTP 80
Telnet 69
TFTP 20,21
DNS 123
SNMP 25
SMTP 110
NTP 161
POP3 53
HTTP 23

Answer:

FTP 20, 21
Telnet 23
TFTP 69
DNS 53
SNMP 161
SMTP 25
NTP 123
POP3 110
HTTP 80

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