Question

1) A major function of an operating system is to implement system security and protection. List three common techniques used by an operating system to achieve this function.

2) Assume that all programs spend 1/2 of their time waiting for I/O.

a) If there is one program loaded in memory what fraction of time will the processor be busy?

b) If there are two programs loaded in memory what fraction of time will the processor be busy?

3) Which technology is needed in order to transmit digital signals generated by a computer over a telephone line?

4) We have a greyscale picture with 2000 × 1600 pixels. If each pixel is encoded as 2 bits, how long would it take to send this picture uncompressed via a network at 10 Mbits/second?

5) Bridges and switches are used to connect devices in a local area network (e.g., Ethernet).

a) For each type of device say if the type has a forwarding table.

b) For each type of device say if the type performs error checks before forwarding data.

6) With the OSI reference model, the set of network functions required to deliver high-quality communications is spread across seven different layers.
a) Which layer is in charge of routing data from the source to the destination correctly and efficiently?

  b) Which layer should have a larger number of protocols than other layers?

c) Give one reason for us to use the hierarchical model for carrying out network design and implementation.

Answer 1

1) Authentication, Access control and Firewalls

2) a) 1/2 b)1

3) Telecommunication

4) 1,28,000

5) Trues and False

6) a) Data Link

b)Transport

c) Because it makes the work easier by division