Computer networks multiple choice questions with answers 06

Computer networks multiple choice questions with answers, entrance exam quiz questions on computer networks, solved exam questions on computer networks, MCQ in CN

Computer Networks MCQ - SET 06

1. The Domain Name Service (DNS) is an example of a

(a) transaction-oriented application-layer protocol

(b) session-oriented application-layer protocol

(c) transaction-oriented transport-layer protocol

(d) session-oriented transport-layer protocol

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Ans : (a)

Answer: (a) transaction-oriented application-layer protocol Domain name service (DNS) is the application service that translates the IP address into a more recognized and memorable name. Whenever using the Internet, there are millions of DNS servers that translate any uniform resource locator (URL) typed into the location field of any Web browser into a specific IP address. The Domain Name System (or DNS) converts human readable domain names (like: www.google.com) into Internet Protocol (IP) addresses (like: 173.194.39.78).

 

2. Which of the following is an advantage of persistent HTTP connection?

(a) additional RTT's when obtaining multiple Web objects from different Web servers

(b) re-using an existing TCP connection for a Web transfer when it is possible to do so

(c) increased latency on subsequent requests

(d) None of the above

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Ans : (b)

Answer: (b) re-using an existing TCP connection for a Web transfer when it is possible to do so A persistent connection takes 2 RTT for the connection and then transfers as many objects, as wanted, over this single connection. By opening and closing fewer TCP connections, CPU time is saved in routers and hosts (clients, servers, proxies, gateways, tunnels, or caches), and memory used for TCP protocol control blocks can be saved in hosts.

 

3. Which of the following is used by the network application BitTorrent?

(a) the peer-to-peer file sharing and TCP

(b) the peer-to-peer file sharing and UDP

(c) the client-server file sharing and TCP

(d) the client-server file sharing and UDP

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Ans : (a)

Answer: (a) the peer-to-peer file sharing and TCP BitTorrent is a communication protocol for peer-to-peer file sharing (P2P), which enables users to distribute data and electronic files over the Internet in a decentralized manner. Rather than downloading a file from a single source server, the BitTorrent protocol allows users to join a "swarm" of hosts to upload and download from each other simultaneously. Refer Wikipedia.

 

4. In general, the throughput achieved by TCP for a
file transfer is

(a) inversely proportional to the average window size used during the transfer

(b) inversely proportional to the round trip time of the network path

(c) inversely proportional to the TCP segment size used for the transfer

(d) all of the above

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Ans : (b)

Answer: (b) inversely proportional to the round trip time of the network path An important measure of the performance of a TCP connection is its throughput - the rate at which it transmits data from the sender to the receiver.  Clearly, throughput will depend on the value of w (window size). If a TCP sender transmits all w segments back-to-back, it must then wait for one round trip time (RTT) until it receives acknowledgments for these segments, at which point it can send w additional segments. If a connection transmits w segments of size MSS (maximum segment size) bytes every RTT seconds, then the connection's throughput, or transmission rate, is  (w*MSS)/RTT bytes per second.

 

5. For a TCP segment header, the minimum size is

(a) 20 bytes

(b) 25 bytes

(c) 10 – 12 bytes

(d) 16 bits

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Ans : (a)

Answer: (a) 20 bytes The minimum size header is 5 words and the maximum is 15 words thus giving the minimum size of 20 bytes and maximum of 60 bytes, allowing for up to 40 bytes of options in the header.  TCP wraps each data packet with a header containing 10 mandatory fields totaling 20 bytes (or octets). Each header holds information about the connection and the current data being sent.

 

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Related links

 

• Computer Networks MCQ home page

 

What is an advantage of persistent HTTP connection?

What does DNS do?

Domain Name Service is a transaction oriented application layer protocol

How many RTTs a persistent http connection takes

What type of file sharing is done by BitTorrent

How do you relate TCP throughput and Round Trip Time