COMPUTER NETWORKS QUESTIONS AND ANSWERS - I

PART B

UNIT  I

1. Explain in detail the error detection and error corrections.(UQ)
2. Discuss in detail about the layers of OSI model. (UQ)
3. Discuss in detail about HDLC.
4. Discuss in detail about SONET.
5. Explain the different approaches of framing in detail.
6. Write the Sliding Window Algorithm and explain it in detail.
7. Compare Stop and Wait ARQ scheme with sliding window ARQ scheme.
8. Write in detail about the flow control mechanisms.

UNIT II

COMPUTER NETWORKS QUESTIONS AND ANSWERS - V

UNIT-IV

1. Explain the main idea of UDP?

             The basic idea is for a source process to send a message to a port and for the destination process to receive the message from a port.

2. What are the different fields in pseudo header?

·       Protocol number

·       Source IP address

·       Destination IP addresses.

3. Define TCP?

               TCP guarantees the reliable, in order delivery of a stream of bytes. It is a full-duplex protocol, meaning that each TCP connection supports a pair of byte streams, one flowing in each direction.

4. Define Congestion Control?

               It involves preventing too much data from being injected into the network, thereby causing switches or links to become overloaded. Thus flow control is an end to an end issue, while congestion control is concerned with how hosts and networks interact.

5. State the two kinds of events trigger a state transition?

·       A segment arrives from the peer.

·       The local application process invokes an operation on TCP.

6. What is meant by segment?

               At the sending and receiving end of the transmission, TCP divides long transmissions into smaller data units and packages each into a frame called a segment.

7.  What is meant by segmentation?

               When the size of the data unit received from the upper layer is too long for the network layer datagram or data link layer frame to handle, the transport protocol divides it into smaller usable blocks. The dividing process is called segmentation.

8. What is meant by Concatenation?

              The size of the data unit belonging to single sessions are so small that several can fit together into a single datagram or frame, the transport protocol combines them into a single data unit. The combining process is called concatenation.

9. What is rate based design?

            Rate- based design, in which the receiver tells the sender the rate-expressed in either bytes or packets per second – at which it is willing to accept incoming data.

10. Define Gateway.

A device used to connect two separate networks that use different communication protocols.

11. What is meant by quality of service?

            The quality of service defines a set of attributes related to the performance of the connection. For each connection, the user can request a particular attribute each service class is associated with a set of attributes.

12.  What are the two categories of QoS attributes?

            The two main categories are,

·       User Oriented

·       Network Oriented

13.  List out the user related attributes?

            User related attributes are SCR – Sustainable Cell Rate PCR – Peak Cell Rate MCR- Minimum Cell Rate CVDT – Cell Variation Delay Tolerance.

14. What are the networks related attributes?

The network related attributes are, Cell loss ratio (CLR) Cell transfer delay (CTD) Cell delay variation (CDV) Cell error ratio (CER).    

15. What is RED?

            Random Early Detection in each router is programmed to monitor its own queue length and when it detects that congestion is imminent, to notify the source to adjust its congestion window.

16. What are the three events involved in the connection?

          For security, the transport layer may create a connection between the two end ports. A connection is a single logical path between the source and destination that is associated with all packets in a message. Creating a connection involves three steps:

·       Connection establishment

·       Data transfer

·        Connection release

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COMPUTER NETWORKS QUESTIONS AND ANSWERS - IV

UNIT-III

1. Define packet switching?

            A packet switch is a device with several inputs and outputs leading to and from  the hosts that the switch interconnects.

2. What is a virtual circuit?

            A logical circuit made between the sending and receiving computers. The connection is made after both computers do handshaking. After the connection, all packets follow the same route and arrive in sequence.

3. What are data grams?

In datagram approach, each packet is treated independently from all others. Even when one packet represents just a place of a multi packet transmission, the network treats it although it existed alone. Packets in this technology are referred to as datagram.

4. What is meant by switched virtual circuit?

Switched virtual circuit format is comparable conceptually to dial-up line in circuit switching. In this method, a virtual circuit is created whenever it is needed and exits only for the duration of specific exchange.

5. What is meant by Permanent virtual circuit?

Permanent virtual circuits are comparable to leased lines in circuit switching.  In this method, the same virtual circuit is provided between two uses on a continuous basis. The circuit is dedicated to the specific uses.  

COMPUTER NETWORKS QUESTIONS AND ANSWERS - III

UNIIT-II

1. What are the functions of MAC?

            MAC sub layer resolves the contention for the shared media. It contains synchronization, flag, flow and error control specifications necessary to move information from one place to another, as well as the physical address of the next station to receive and route a packet.

2. What are the functions of LLC?

The IEEE project 802 models take the structure of an HDLC frame and divides it into 2 sets of functions. One set contains the end user portion of the HDLC frame – the logical address, control information, and data. These functions are handled by the IEEE 802.2 logical link control (LLC) protocol. 

3. What is Ethernet?

            Ethernet is a multiple-access network, meaning that a set of nodes send and receive frames over a shared link.

4. Define the term carrier sense in CSMA/CD?

            All the nodes can distinguish between idle and a busy-link and “collision detect” means that a node listens as it transmits and can therefore detect when a frame it is transmitting has interfered (collided) with a frame transmitted by another node.

5. Define Repeater?

            A repeater is a device that forwards digital signals, much like an amplifier forwards analog signals. However, no more than four repeaters may be positioned between any pairs of hosts, meaning that an Ethernet has a total reach of only 2,500m.