computer network

A) The switch (0.5 Marks)

If the switch fails, the whole network will be down.

B) Host 1 (0.5 Marks)

If a connection fails in a host, only that host will be affected, on the other hand the remaining devices still communicate without any problems

2. What is the difference between internet and intranet? (0.5 Marks)

An internet is two or more networks that can communicate with each other.

An Internet is composed of thousands of interconnected networks.

Question Two

1.5 Marks

Learning Outcome(s):

Explain networking principles, models and technologies.

1. What is Multiplexing and De-multiplexing in TCP/IP? (1 Marks)

- Do not provide any drawings in your answers. Otherwise your work is awarded a zero mark.

Because the TCP/IP protocol suite uses several protocols at some layers, multiplexing happens at the source and demultiplexing at the destination.

Multiplexing means that a protocol at a layer can encapsulate a packet from several next-higher layer protocols (one at a time);

Demultiplexing means that a protocol can decapsulate and deliver a packet to several next-higher layer protocols (one at a time).

For example, at the transport layer, either UDP or TCP can accept a message from the application-layer that contains different protocols such as (HTTP, FTP, DNS, and SNMP)

2. Why Multiplexing and De-multiplex is important in networking? (0.5 Marks)

Multiplexing and De-multiplex allows the existence of different protocols at the same layer either at the source of the destination.

In general multiplexing reduces the number of connections for transmission of several signals and allows the share of expensive resources

Question Three

1.5 Marks

Learning Outcome(s):

Clear understanding of the physical layer & associated hardware; integration of internetworking hardware and software.

1. What is the required bit rate to download text document which contains 1000,000 characters (assume one character required 8 bits) and you need to express the answer in megabit per second. (0.5 Marks)

Assume the text document is sent in one second

The bit – rate = 1000 000 character per second = 1000000*8

= 8000000 bits /sec

The bit-rate in megabit per second = 8000000/1000000 = 8 Mbps

2. What is the difference between latency and jitter? (1 Marks)

· The latency defines how long it takes for an entire message to completely arrive at the destination from the time the first bit is sent out from the source.

· The latency consists of four components: propagation time, transmission time, queuing time and processing delay.

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· Jitter is a performance issue related to the delay and it represent the difference in packets delay; it measures the time difference in packet inter-arrival time.

· Jitter is the variation in the packet latency; it’s a problem and can be fixed by using a buffer to adjust the timing between the source and destination.

Question Four

1.5 Marks

Learning Outcome(s):

Outline the physical layer & associated hardware and software integration.

1. List out 2 Advantages and 2 Disadvantages of Optical Fiber over metallic cable. (1 Marks)

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The advantages of Optical Fiber over metallic cable

1. Huge bandwidth up to 250Gbps

2. Higher bit-rates up to 250 Gbps

3. More information carrying capacity with higher rates

4. Greater transmission speed

5. Support extremely high data transmission rates

6. Greater capacity –data rates of hundreds of Gbps

7. Smaller size and lighter weight

8. Reduced size and weight cables

9. Smaller in size and light in weight

10. Small diameter and weight

11. Totally immune to EMI( electromagnetic interference )

12. Electromagnetic isolation –immunity to environmental interference and highly secure due to tap difficulty and lack of signal radiation

13. Less susceptible to noise from other devices

14. Immune to cross talk

15. Immune to static interference

16. No corrosionتأكل , more environment resistive

17. Immune towards environmental hazards and electromagnetic interference

18. Low signal loss ( low attenuation )

19. Lower attenuation

20. Decreased attenuation and increased transmission distance

21. High resistance to eavesdropping

22. More secure, nearly impossible to tap providing for greater security than copper cable

23. Allow greater cable distance without a repeater

24. Cost effective in a long term installation

25. Able to carry significantly more signals than wire

26. Greater repeater spacing – 10s of Km at least

اختر فقط اتنين من العيوب وعدلها باسلوبك

Disadvantage :

1. Initial cost of installation is high

2. Fragile ( easy to be broken )

3. Maintenance and repair more difficult and more expensive

4. Very expensive

5. Difficult to work with

6. Special training required to attach connectors to cables

7. Cost more than twisted pairs and coaxial cable

8. Can be difficult to install and maintain

9. More expensive over short distances

10. Expensive in comparison with conventional electrical cables

11. Expensive and difficult installation

12. Adding additional nodes is difficult

27. Unguided signals can travel from the source to the destination in three ways. Explain only one of them. (0.5 Marks)

- Do not provide any drawings in your answers. Otherwise your work is awarded a zero mark.

اخترنوع واحد فقط وعدلها باسلوبك

In ground propagation :

· Radio waves travel through the lowest portion of the atmosphere, hugging the earth.

· These low-frequency signals (below 2MHz) propagate in all directions from the transmitting antenna and follow the curvature of the planet.

· Distance depends on the amount of power in the signal: The greater the power, the greater the distance.

In sky propagation : (2-30MHz)

· Higher-frequency radio waves radiate upward into the ionosphere (the layer of atmosphere where particles exist as ions) where they are reflected back to earth.

· This type of transmission allows for greater distances with lower output power.

In line-of-sight propagation ( above 30 MHz )

· very high-frequency signals are transmitted in straight lines directly from antenna to antenna.

· Antennas must be directional, facing each other and either tall enough or close enough together not to be affected by the curvature of the earth.