MIS 6316

							                                     MIS 6316
                                    Final Exam
                                        7/24/04


True/False (Answer to the left with T or F)
         Only a software or firmware upgrade is required when implementing TKIP.
             True
         802.11i is the ultimately wireless security solution because it provides mutual
             authentication, improved data encryption and stronger data integrity. True
         MPLS stands for Multi Protocol Linkage Switching. False
         The OSI Architecture is famous for its five layer design. False
         TCP/IP uses a five layer architecture. True
         TCP is the only protocol that rides on top of IP. False
         MPLS is inefficient because it combines Layer 2 Switching with Layer 3
             Routing. False
         VPNs provide little privacy or security. False
         There are two kinds of data that pass over networks: analog and digital. True
         Data communications will be at least 1000 times faster in ten years. True
         Streaming data communications has no practical applications. False
         On the Internet, Firewalls are used to backup large data servers. False
         3G is a Cell Phone voice technology. False
         W-CDMA and cdma2000 are the dominant 3G standards. True
         Music requires less bandwidth than speech. False
         3G will be too slow for video applications. True
         Internet2 uses the same IP protocol as the Internet. False
         Grid computing only applies to supercomputers. False
         AM radio uses a much higher frequency than FM. False
         IPv6.0 uses the same addressing as IPv4.0. False
         Switched networks can handle much more traffic than unswitched ones. True
         Switching happens in layer 2. True
         Routing happens in layer 3. True
         X.25 is a telephone switching protocol. False
         ATM uses extra large packets for efficiency. False
         Regular voice telephones are full-duplex. True
         Amplitude modulation and Frequency modulation are the only two ways
             analog data can be put on a radio frequency carrier. False
         Synchronous data transmission means we don’t have to worry about timing.
             False
         The binary number 1011 Exclusive OR’d with 1101 would yield 0100. False
         Flow control can keep a data source from overwhelming a receiver. True
         Multiplexing is no longer needed because data transmission lines are so fast.
             False
         Frequency and Wavelength Division Multiplexing are really the same thing
             but are used for rf data comm. and optical data comm. respectively. True
     Frequency division multiplexing uses different sub bands for different data
          streams. True
     It is possible to transmit a single side band and still transmit all of the data.
          True
     The wavelength of visible light is much greater than infrared light. True
     Statistical TDM uses time divisions that vary according to loads. False
     Dalton’s group at the University of Washington is concerned with electo-
          optical molecular devices for switching light. True
     Data communications are doubling in speed every 9 months. True
     Gordon Moore’s law says that LSI device densities will double every 18
          months. True
     DSL to the home requires fiber optic connections to each house. False
     RFID is an advanced technology which could replace bar code readers and
          grocery store checkers. True
     There is a critical shortage of optical fiber data lines in the USA. False
     Wireless data services will compete with DSL and phone service to the home.
          True

Short Answer Questions:
     Briefly explain adaptive routing.

 Adaptive routing is when routing decisions change as conditions of traffic and the
 status of nodes on the network change. One reason that can impact a routing
 decision is failure of a node or trunk in the network. Another reason could be
 traffic congestion due to heavy traffic. Although adaptive routing can help, it also
 adds processing burden on the network nodes.

     Briefly explain multiplexing.

 Multiplexing is a way to enable two or more sources share a common circuit
 thereby providing better utilization of circuit capacity. A multiplexer can have n
 possible sources or channels of data that are combined by the multiplexer and
 transmitted on to a higher capacity data link. There is generally a demultiplexer
 at the other end which accepts the multiplexed data, separates out the various
 sources and delivers them to the appropriate output lines. This is shown in the
 diagram below:


                    Multiplexer                                   De -
                                                                  Multiplexer
                                         1 link with n channels
     What are the advantages of using fiber optics instead of twisted pairs or
       coaxial cables?

     The main advantages of Optical fiber are:
         Smaller size and weight
         Greater capacity – data rate can be 100 GBPS plus
         Lower attenuation
         Electromagnetic isolation
         Less number of repeater requirements – repeaters can be 30-50 km
           apart as there is less loss

     What is the future of data communications?

     In the future Wireless communication is expected to dominate the growth in
     the data communications. Next-generation wireless gadgets connected by a
     wireless Web, will permeate our life and will be seen everywhere. Data
     communication technologies like WLAN, Ultra-Wideband, RFID and
     Bluetooth technology will all dominate future interest.

     Data security will be another area of interest. In today’s world where so much
     sensitive data is traveling over networks, there is a need to secure data and
     development of encryption algorithms to maintain privacy is highly critical.

     There will also be a lot of interest in effort towards increased data
     transmission rates over current infrastructure so that videos, music etc. can
     be downloaded to consumers faster.

Bonus Questions: (Answer below and on the back.)
     Explain how CDMA and other similar technologies allow many people to
         share the same physical area and bandwidth.
     CDMA or Code division Multiple Access is a multiplexing Technique used
     with spread spectrum. In CDMA each user is assigned a fixed unique pattern
     called the User’s code. Each bit transmitted from User is broken into k chips
     based on the user code. So, if the user has a data signal rate D, then after
     codification the new channel has data rate kD. Typically if the user wants to
     send 1, the User code is transmitted while if the user wants to send 0,
     complement of the Users code is transmitted. As the decoder at the base
     station knows the user code, it ignores other sources when using this
     particular user’s code for decoding. The user codes are orthogonal in nature
     thereby making the base station receivers capable of filtering out unwanted
     users. This feature of unique user code helps the same physical area and
     bandwidth to be shared by several users without interference.

     Explain the difference between time division multiplexing and frequency
        division multiplexing.
Time-Division Multiplexing (TDM) divides time into equal parts and
interleaves portions of various input signals in time. Fixed time slots are
assigned to sources and are allocated even if no data is available for
transmission from that particular source. The interleaving can be at bit level
or in blocks of bytes. Time slots do not have to be evenly distributed amongst
sources. This is possible whenever input signals have lower data rate than the
transmission media being used.

Frequency-Division Multiplexing (FDM) is used whenever useful bandwidth
of medium exceeds required bandwidth of channel. For FDM, each source
signal is modulated to a different carrier frequency with the carrier
frequencies separated so signals do not overlap. The frequency channel is
allocated even if no data is available for transmission from that source.

Explain the difference between the time domain and the frequency domain.
Time Domain: Any signal whether analog or digital is said to be represented
in the time domain when the signal is represented as the variation of
amplitude or signal strength with the variation of time. This can be best shown
below with the Y axis representing amplitude while the X axis representing
time:




                        Time
Frequency Domain: Any signal whether analog or digital is said to be
represented in the frequency domain when the signal is represented as the
variation of amplitude or signal strength with the variation of frequency.
Signal usually made up of many frequencies with component sine waves. This
can be best shown below with the Y axis representing amplitude while the X
axis representing time:
             Frequency


The speed of light is 3 x 108 Meters per second. The wavelength of a
   particular color of light is 300 x 10-9 Meters. What is the frequency of this
   light (in cycles per second)?

We know Wavelength = Velocity/Frequency
Hence Frequency = Velocity/Wavelength
                = 3 * 108/(300 * 10 -9 )
                = 10 15 Hz

What are the fastest growing segments of the Telecomm business?

Some of the fastest growing segments of the Telecom Industry are:

   Wireless communication
   Cellular telephony
   Technology related to data Communication and transmission rate
    increase. Also, technology related to better utilization of available
    infrastructure
   Data Security related technology like encryption
   Consumer devices related to music, video downloads, streaming etc.