Network Security Subcategories

Networking Overview I	Network Hardware
Freshers	Socket Secure Layer I
Network Security	Classful Addressing
Experienced	Secure Shell I
Designing Subnets I

In an IP packet, the value of HLEN is 516 and the value of the total length field is 002816.What is the efficiency of this datagram?

A. 0.8
B. 0.5
C. 0.66
D. 0.75

Explanation: Total number of bytes in the header = 5 x 4 = 20 bytes. Total length = 0028_16 = 40 bytes. Data carried by the packet = (40 – 20) = 20 bytes. Efficiency = payload length / total length = 20/40= 50%.

An IP packet has arrived with the first 8 bits as 01000010. What is the version?

A. 3
B. 4
C. 5
D. 6

Explanation: The first 4-bits show the version i.e. 0100 -> version 4.

An IP packet has arrived with the first 8 bits as 01000010. What is the header length?

A. 4
B. 8
C. 12
D. 16

Explanation: The right 4-bits multiplied by 4 is the header length (0010=2). 2 x 4 = 8.

In an IP packet, the value of HLEN is 1000 in binary. How many bytes of options are being carried by this packet?

A. 16
B. 64
C. 32
D. 8

Explanation: HLEN = 1000 = 8. 8 x 4 = 32 bytes.

In an IP packet, the value of HLEN is 5_16 and the value of the total length field is 0028_16. How many bytes of data are being carried by this packet?

A. 10
B. 40
C. 60
D. 20

Explanation: Total number of bytes in the header = 5 x 4 = 20 bytes. Total length = 0028_16 = 40 bytes. Data carried by the packet = (40 – 20) = 20 bytes.

An IP packet has arrived with the first few hexadecimal digits as shown below: 45000028000100000102 . . . How many hops can this packet travel before being dropped?

A. 2
B. 5
C. 3
D. 1

Explanation: In an IPv4 header, the TTL is the 9th byte (or the 17th and 18th hexadecimal digits) which is one when counted from right to left. (or the 17th and 18th hexadecimal digits).

Convert the following binary notation to dotted-decimal notation – 10000000 00001011 00000011 00011111

A. 128.11.5.32
B. 128.11.3.31
C. 127.11.3.32
D. 127.12.5.31

Explanation: Converting the binary value to their respective decimal values yields 128.11.3.31.