2 Comments

1. 

   AYESHA MUMTAZ on February 8, 2019 at 12:44 pm

   What is the difference between guided and unguided media?
   Answer: Click here for detail
   Guided Media are those media that provide a conduit from one device to another. Guided
   Transmission Media uses a “cabling” system that guides the data signals along a specific path while
   Unguided Transmission Media consists of a means for the data signals to travel but nothing to guide
   them along a specific path. It passes through a vacuum; it is independent of a physical pathway.
   Write Commercial advantage and characteristics of token bus
   Answer: (Page 232)
    Other LANs are not suitable for this purpose
    Token Bus has no commercial application in data communications
    Token Ring allows each station to send one frame per turn
    Access method: Token passing
   What is the difference between FDM and TDM
   Answer: Click here for detail
   1) FDM-Frequency division multiplexing where as TDM mean Time division
   Multiplexing.
   2) In FDM spectrum is divided into frequency whereas in TDM divided into time slot.
   3) FDM is used in 1st generation analog system whereas TDM is used in 2nd generation analog
   system.
   Write the types transmission noise
   Answer: (Page 143)
   Thermal Noise: Due to random originally sent by TX
   Induced Noise: Comes from sources like Motors and Appliances
   Crosstalk: Effect of one wire on another
   Impulse Noise: Spike (A signal with high energy in a very short period of timepower lines, lightening
   etc.
   What is power bandwidth
   Answer: Click here for detail
   The power bandwidth of an amplifier is sometimes taken as the frequency range (or, rarely, the
   upper frequency limit) for which the rated power output of an amplifier can be maintained (without
   excessive distortion) to at least half of the full rated power.
   OR
   Power Bandwidth
   Answer: (Page 67)
   Frequency band in which 99% of the total power resides.
   What does the CRC generator append to data unit? [2]
   Answer: (Page 175)
   Appending it to the end of the data must make the resulting bit sequence exactly divisible
   by the divisor

2. 

   AYESHA MUMTAZ on February 8, 2019 at 12:45 pm

   Which one has more overhead, a repeater or a bridge? Explain your answer. [3]
   Answer:
   A bridge has more overhead than a repeater. A bridge processes the packet at two layers; a repeater
   processes a frame at only one layer. A bridge needs to search a table and find the forwarding port as
   well as to regenerate the signal; a repeater only regenerates the signal. In other words, a bridge is also a
   repeater (and more); a repeater is not a bridge
   Define high frequency [HF] and super high frequency [SHF], which devices uses these
   frequencies [3]
   Answer: Page 135 and 136
   High frequency.
   HF uses ionospheric propagation. These frequencies move into the ionosphere where the density
   difference reflects them back on earth.
   It is used for Citizen’s Band Radio, International Broadcasting, Military Communication, Telephone,
   Telegraph and Fax
   Super high frequency.
   SHF waves are TX using mostly line-of-sight and some Space propagation.
   It is used for Terrestrial and Satellite Microwave and Radar Communication devices.
   Write all steps of checksum method. [3]
   Answer: (Page 179)
   o The sender subdivides data units into equal segments of ‘n’ bits(16 bits)
   o These segments are added together using one’s complement
   o The total (sum) is then complemented and appended to the end of the original data unit as redundancy bits
   called CHECKSUM
   o The extended data unit is transmitted across the network
   o The receiver subdivides data unit as above and adds all segments together and complement the result
   o If the intended data unit is intact, total value found by adding the data segments and the checksum field
   should be zero o If the result is not zero, the packet contains an error & the receiver rejects it
   Differentiate internet and the internet? [3]
   Answer: (Page 240)
   INTERNET
   o An internet is a generic term used to mean an interconnection of individual networks
   o To create an internet, we need networking devices called routers and gateways
   o An internet is different from the Internet
   o Internet is the name of a specific worldwide network
   What is the differences in between bit oriented and character oriented protocols [5]
   Answer: (Page 206)
   Character – Oriented Protocols
   o Also called Byte- Oriented Protocol
   o These protocols interpret a transmission frame or packet as a succession of characters,
   each usually composed of one byte
   o All control information is in the form of an existing character encoding system
   Bit – Oriented Protocols
   o Character –Oriented Protocols are not as efficient as bit – oriented protocols and are seldom used
   o They are easy to comprehend and employ the same logic as bit-oriented protocols
   o Their study will provide the basis for studying the other data link layer protocols
   o IBN’s BSC is the best known character oriented protocol