UGC NET COMPUTER SCIENCE SOLVED PAPERS 2017-19 - UGC NET Computer Science November 2017 Paper 3

26. Quadrature Amplitude Modulation means changing both:

  • Option : C
  • Explanation :
    Quadrature Amplitude Modulation means changing both amplitude and phase of the carrie. So, option (C) is correct.
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27. If a file consisting of 50,000 characters takes 40 seconds to send, then the data rate is __________.

  • Option : D
  • Explanation :
    50,000 character takes 40 seconds
    ie 50,000 * 8 = 40 seconds. (each character is of 8 bits)
    In one second → (50,000 * 8)/40 bits / second.
    10,000 bits / second.
    ie. 10 Kbps.
    So, option (D) is correct.
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28. Match the following:

List - IList -II
(a) Data link layer(i) Encryption
(b) Network layer(ii) Connection control
(c) Transport layer(iii) Routing
(d) Presentation layer(iv) Framing
 code:
 (a)(b)(c)(d)
(1)(iv) (iii)(i)(ii)
(2)(iii)(iv)(ii)(i)
(3)(iv)(ii)(iii)(i)
(4)(iv)(iii)(ii)(i)

  • Option : D
  • Explanation :
    1. Framing of data occured in data link layer.
    2. Network layer is responsible for end to end communication so routing takes place here.
    3. connection control is regulated by transport layer
    4. Encryption of data takes place at presentation layer.
    So, option (D) is correct.
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29. The address of a class B host is to be split into subnets with a 6 - bit subnet number. What is the maximum number of subnets and maximum number of hosts in each subnet?

  • Option : A
  • Explanation :
    Maximum number of subnets = 2^6-2 =62.
    Note that 2 is subtracted from 2^6. The RFC 950 specification reserves the subnet values consisting of all zeros (see above) and all ones (broadcast), reducing the number of available subnets by two.
    Maximum number of hosts is 2^10-2 = 1022.
    2 is subtracted for Number of hosts is also. The address with all bits as 1 is reserved as broadcast address and address with all host id bits as 0 is used as network address of subnet.
    In general, the number of addresses usable for addressing specific hosts in each network is always 2^N – 2 where N is the number of bits for host id.
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30. Which of the following statements are true?
(a) The fragmentation fields in the base header section of IPv4 have moved to the fragmentation extension header in IPv6.
(b) The authentication extension header is new in IPv6.
(c) The record route option is not implemented in IPv6.

  • Option : D
  • Explanation :
    The fragmentation fields in the base header section of IPv4 have moved to the fragmentation extension header in IPv6:
    Nov17 cs
    So, given statement is correct. Authentication header (protocol 51) is identical in both IPv4 and IPv6, but authentication extension header is new in IPv6. So, given statement is correct. In the IPv6 specifications [IPv6], no record route function is defined, and the record route function for IPv4 is less flexible and has scalability problems. So, given statement is correct. Although, RR6 (Record Route for IPv6) mechanism is redesigned to establish an optimized record route mechanism for IPv6 and fix the problems of the record route function for IPv4 using Hop-by-Hop Option Extension. Hence, option (D) is correct.
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