IT 420 Spring 2019 Homework 1 Solutions

IT 420

Spring 2019

Homework 1 Solutions

Note:  Where applicable, units of the solution must be correct for full credit.

1. Answer the following questions concerning chapter 1:

• As an arriving message moves from the network interface layer up to the application layer, headers are ______ .

1. added b. removed c. rearranged   d. modified

   1.2  Which are peer layers?

1. The application layer in the sender and the transport layer in the sender
2. The application layer in the receiver and the transport layer in the receiver
3. The application layer in the sender and the transport layer in the receiver
4. The application layer in the sender and the application layer in the receiver

1.3  If the unit exchanged at the network interface layer (layer 2) is called a frame and the unit exchanged at the internet layer (layer 3) is called a packet,

1. frames encapsulate packets b.  packets encapsulate frames
2. both a and b d.  neither a nor b

2. Choose which layer each of the following phrases describes:

1. Application b.  Transport    c.  Internet       d.  Network Interface  e.  Physical

___B___  Process to process communication

                 

___E___  Media              

__  A___ Interacts with the user  

___E____ Encodes data using physical phenomena, such as changing voltage 

___C___  Host to host communication

___D____Sends a frame through a single local area network

___D___  Uses physical (MAC) addresses          in the header

     

___C___  Uses IP addresses in the header          

___B___  Uses protocol ports in the header

3. Assume a five layer TCP/IP model. There are A bytes of application data. A B byte header is added at the transport layer, a C byte header is added at the internet layer and a D byte header is added at the network interface layer.  The network interface layer also adds an E byte trailer. Express the answers to the questions below in terms of A, B, C, D, and E.

1. How many total bytes are sent to the physical layer?

Physical Layer Bytes = A + B + C + D + E

1. What percentage of the bytes sent to the physical layer is overhead?

% overhead =      number bytes overhead data in physical layer     * 100%

                                    total number of physical layer bytes

                    =  ((B + C + D + E) /( A + B + C + D + E )) * 100%

1. How many total bytes are in the transport layer packet?

Transport Layer Packet  = A +  B 

1. What percentage of the bytes in the transport layer packet is overhead?

% overhead = number bytes overhead data in transport layer     * 100%

                             total number of transport layer bytes

                      =  (B/( A + B)) * 100%

4. In the five-layer networking model, data sent to the physical layer consists of the application data, network interface layer header, network interface layer trailer, internet layer header, and transport layer header. In the diagram of data sent to the physical layer below, label each part using one of the terms above. (Order matters.)
5. Answer the following questions concerning chapter 6:

5.1   A signal has 100 possible levels.  This signal is

1. analog digital         c.  neither        d.  cannot be determined

   5.2  As the period of a sine wave increases, the frequency __________________ .

1. decreases         b.  increases     c. remains the same     d. doubles

   5.3  A possible unit for analog bandwidth is bits per second.

1. true                         b.  false

   5.4  A simple sine wave is created by adding multiple composite signals together.

1. true             b.  false

6. Match the terms concerning sine waves with their definitions

1. Period   frequency               c.  amplitude               d.  analog bandwidth

__D____  The difference  between the high frequency and the low frequency

__B____  The number of cycles per second

__C____  The absolute value of the peak value

__A_____ The time for one cycle

7. Write the equation for a sine wave with an amplitude of 3, a frequency of 5, and a phase of π/2.

s(t) =3sin(2π5t + π/2)

8. Draw the following sine wave in the time domain, showing amplitude and phase:

 s(t) = 4sin (2πt + π)

9. What is the phase of each sine wave shown below?

Top:  3π/2

Middle:  0

Bottom:  π

10. What is the period of a 5 MHz sine wave?

   T =  1 /  f                      

       =       1     =             1                =        0.2 x 10^-6 sec       =  0.2µsec

            5 MHz       5 x10⁶ cycles/sec               cycle

11. A sine wave has a period of 4 msec. What is the frequency?

f  =      1 /  T               

   =       1 cycle         =    1  cycle        =  0.25 x 10³ cycles   =   0.25 KHz

             4 msec            4 x 10^-3sec                  sec

12. Consider the following composite signal.

f(t) = 2sin(2π5t) + 3sin(2π7t) + 4sin(2π9t)

1. Graph this in the frequency domain, showing amplitude and frequency
2. Assuming the frequency is in Hertz, what is the analog bandwidth for this signal?

BW = high frequency – low frequency

              = 9 - 5

              = 4 Hz

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