Solved question paper for CN May-2018 (BCA 4th)

Question paper 1

1. Section-A

   1.(a) List and explain in brief any two the important user of computer networks.

   Answer:

   1.  

   1. Business application , E-commerce wireless

   B2C= Business to costumer Networking and

   B2B= Business to Business Mobile computing

   C2C= costumer to costumer are often related to

   G2C= government to costumer Mobile Networking

   P2P= peer to oeer is fastest growing

   2. Resource shoring:-It means make all program equipment and data available to anyone on network without regard to the physical location the user.

   3. Communication medium:_ Every company has two or more computers now has email with employees generally used for a great deal of Delhi Communications.

2.  (b) Distinguishing between LAN and WAN on the basis of scale and design issue of each.

   Answer:

   1. Mobile users and home application:-Notebook computers and mobile phone are one of the fast growing segment of the entire computer industry.

   2. 	LAN	WAN
      	it is a local area network	It is wide area network
      speed	Speed is in l a n up to 1 to 10 gbps	Speed is low then 100 mbps
      Components	L a n is a bed using the layer 12 device like switches they are connected to computer	Wn is build using the layer 3 devices routers and multilayer switches.
      Security	More Secured	Less secured
      Technology	Token rings and Ethernet are 2 primary environment	ATM, frame relay are example of WAN.
      Cost	LAN is it less expensive to setup and operate.	more expensive
      Confession	small geographical area like limited to office	It is has extremely large geographical area. It is not linked to one country.
      Example	Network inside an office space.	Internet is the best example of w a n a network

   assessor to remote information person to person communication interactive entertainment and Electronic Commerce are the important use of the internet for the home users.

   All the Wireless networking and mobile computing are often relate. But they are not identical.

3. 2. Enumerate the functions of application transport and network layer in OS I reference model and compare them with the TCP IP model.

   Answer:

   OSI reference model:- it is a logical and conceptual model that define network communication for stock used for communication with other system.

   1. Functions of application layer it helps to determine communication determining resources available.

   It allows user to logon to a remote host

   This player provide various email services.

   This application offer distributed database sound and access for global Information about various object and service.

   2.Transport layer:- it built on the network layer to provide data transport form a process on a source machine to a process on a destination machine.

   Function of transport layers:- it divides into the message received from season layer into segments and number them to make a sequence.

   It also make sure that the entire message arises without any error or else it should be e re transmitted.

   Transport layer make sure that the message is delivered to to tractor process on destination machine.

   3.Network layers:- the layer provide the function and produce means of transferring variable length data sequence from one mode to another connect the different network.

   (I) Routing protocol

   (II) Multi cast group management

   (III) Network layer address assignment and the layer

   management protocol that belong to network layer.

   OIS model	TCP/IP Model
   it provides a clear destination interfaces service and protocols.	It do not offer any clear distinguishing point service interfaces and protocols.
   It uses network layers.	It uses internet layer to define routing and standard protocols.
   Minimum size of the header is 5 bytes	Minimum header size 20 bite.
   Init data link layer and physical are separated layer.	In this data link layer and physical layer are combined as a single host to network layer.

   
    

   
    

4. 3. Enumerate and explain the design issue related to data link layer. How the framing does using bit suffering and physical layer coding violations?

   Answer:

   Design issue related to data link layer:- DLL is the second layer in the model above the physical layer which ensure that the error face data is a transferred the adjacent node in the network.

   Reliability:- network channel and component may be unreliable resulting in a less of bytes white data transfer. Show and enter presented design Ishu is to make sure that the information transfer is is not distorted .

   Scalability:- network size are continuously increasing and leading to Congestion suit design should be done in that the network are scalable.

   Error control:- error in data stream are occur in unreliable channel that are communicated so layers need to agree upon common error detection method.

   Routing:- this way must be multiple Paths from the source to destination but routing involves using an optional Path among all the possible Path

   Security:- this should be adequate mechanism to prevent unauthorised access to data through Cryptography and authorisation.

   So flow control resource allocation statistical multipleing are the major design issues.

   Physical layer coding and is applicator to network ine whitch the encoding on the physical medium contains same redundancy full stop in search code normally a bit 1 bit is a hi Lo pair and a O bit is low pair. The combination of low low and high high which are not used for data may be used for making frame boundaries.

   at the short end of the each name is a flag by consistency of the special bit 0 1 1 1 1 1 10. Whenever the Sanders data link layer encounter 5 consertive is in the data, it automatically straps are zero bit into outgoing bitstream. This technique is called bit suffering.

6. 4. Explain in brief elementary data link layer protocol for flow control.

   Answer:

   data link layer protocol for flow control DDL protocol can be broadly divided into two categories depending on whether the transmission channel is a noiseless for noisy.

   Data link protocols

   For noiseless channel		For noisy channel
   	Simplex		Stop and wait ARQ
   	Stop and wait		Go back NARQ
   			Selective repeat AQR

   
    

   Simplex protocol:- it is an hypothetical protocol designed for an directional data transmission over an idea channel for stop it is hypothetical since it does not handle flow control and error control.

   Stop and wait protocol:- it is noiseless channel t o o. It provide an directional data transmission without an error control facilities.

   The Recivers has Finite buffer size with Finite processing speed.

   the sender can send the frame only when it has received indication from the receivers that it is available for for the data processing.

   Stop and wait ARQ:- stop and wait automatic repeat request is a variation of of the above protocols with added error control mechanism for noisy channel.

   Sender keeps a copy of the front frame for stop and wait for the positive acknowledgment from receiver. If lime expired frame is re transmitted and if positive acknowledgment receive then the next frame is sent.

   Go back NARQ:- before receiving to acknowledgment for the first frame go back n a r provide for a sending multiple frames.

   sliding window concept is used so it is called sliding window protocol.

   Frames are frequently number and number of frames are sent.

   Frames are transmitted if the acknowledgment of a frame is not received within the time limit.

   
    

   Selective repeat AQR:- this protocol also provide for the sending multiple frame before receiving the acknowledgement for the first frame.

   So data link layer flow control the number of frames the sender can send before it wait for the acknowledgement from the receivers.

7. Section-B

   5. Distinguishing between static and dynamic routing full stop describe any one dynamic routing algorithm of your choice.

   Answer:

   static and dynamic routing

   static it is ideal for small networks.

   Configuring static routers involve less cost and can be easily maintained by the network administrator. router can't be change until authorised by the network administrator.

   Routers are not updated dynamically in the routing table and hence cart detect inactive rooters.

   Dynamic routing full stop dynamic routing is suitable for large network.

   Dynamic Routing in wall cost in term of CPU processor and brand on the network link.

   Routing protocol find the routers for transaction the packets.

   
    

   Routing protocol update the routing table with update rooters.

   Spf is a dynamic routing protocol used in large to very large IP Network for stop the protocol user a link state database and link state advertisement to map the network topology the topology kal map is used with the link state algorithm to determine the best route available.

   Algorithm used by spf to determine best rooter relies on the link state database and allow us to update its root faster than our IP when a network change is encountered.

   Spf uses to segment the network which health it describes the general size of link step database and consequently speed up network when changes in the network are experience to.

8. 6. What are the congestion control distinguishing between leaky bucket and token bucket algorithm for conjunction control. Which in your opinion is better and why?

   Answer:

   Congestion control:- It is a straight occurring in a network layer when the message traffic is so heavy that it is slow down network response time.

   Leaky Bucket Algorithm:- Following steps are involve Leaky Bucket Algorithm

   • When host want to send up packet and packet is thrown into the bucket.

   • Brishti traffic is covered to uniform traffic by the leaky bucket.

   • In practice the bucket is a finite queue that output at a finite rate.

   Example:- Imaginea bucket with the small hole in the bottom. No matter at what rate water enter the market but outflow is at consistent rate so when bucket is full with water additional water entering spells over the side and is lost.

   
    

   Token pocket Algorithm:-Steps

   1. in regular interval token are thrown into the bucket

   2. the bucket has a maximum capacity . p

   3. If there is a ready packet a token is removed from the bucket and packet is a send.

   4. if there is no talking in the bucket the packetcannot be set a.

   So token bucket is more superior to leaky bucket because it algorithm control the rate at which packet are introduced in the network but very conservative in nature. So some flexibility is introduced in the token bucket algorithm.

9. 7. Decribe the following in the context  of application layer
   (a) Www
   (b) Email

   Answer:

   (a) WWW:- HTTP hypertext transfer protocol is used mainly to assess the data on the world wide web.

   The hypertext transfer protocol the web main application layer protocol all through current browser can assess other types of server

   The respiratory of the information Sahab red all over the world and linked together.

   HTTP protocol transfer data in the form of plain text audio video etc.

   It utilizes TCP connection to send client request and server replies.

   It is a protocol which works by both President and non persistent.

   (b) email protocol are set of rule that helped the client to proper transmit the information to or from the mail server. Following are the various protocols

   1. POP:-It stands for post office protocol. It is generally used to support a single slider. There are several types of variations of POP but the pop 3:00 is current standard

   • It is an application layer internet standard protocol.

   • It is offline access to message so it requires less internet usage time.

   • Pop does not allow search facility.

   2. Simple mail transfer protocol:-It is a standard protocol used for sending email efficiently and reliability over the internet for stop

   • SMTP is an application level protocol.

   • It is connection oriented protocol.

   • It is a test based protocol

   • Incase message cant send error send to sender so it is reliable protocol

   3. IMAP:-It is a standard for internet mail access protocol it allowed the client program to manipulate the email message on the server without downloading them on the local computer.

11. 8. How is network security achieved using the following.
    (a)Public key algorithm

    Answer:

    Network security:- Public Key Algorithms:- it is an eryptoimphic system that used to ki public key known as everyone and private key known as only to the recipient of the message.

    • Public key can be used to encrypt message and only to corresponding private key can be used to descript them

    • It is Virtually impossible to the private key if you know the public key.

    Public key system such as PT good private are popular for transmitting information via the internet.

    • They are extremely secure and comparatively simple to use.

    • One of the only difficult way to public key system is that you need to know the receptance public key to encrypt the message for him or her.

    Example:- Vijay wants to send a secure message to Malaya hi use Vijesh public key to encrypt the message.

12. (b) Digital signature

    Answer:

    Digital signature:- It is a process that guarantee that the contents of a message have not been Ultra in transit. When you the server digitally sign a document you add a one-way wash of the message content using public and private key pair.

    Integrity authentication and non reproduction. The digital signature is used to achieve about aspects.

    1. Integrity:- It preserves the integrity of of a message become if any e attack Intercept a message and particularly all total changes it then the descriptive message would be impossible.

    2. Authentication:- We can use the following reason to show how the message and 8

    Encryption with its private key and description with a public key result in garbage value.

    3. Non- Repudiation:- If the sender device sending the message then her private key corresponding to her public-key is tested on the plaintext.

    If the descriptive message is same as the original message then we know that the sender has sent the message.

13. Section C

    9. Answer any five of the following question in brief
    (i) What do you mean by protocols, interfaces and service and network architecture

    Answer:

    Protocols, Interfaces & Services:- networks work piggy packing a number of different protocol on the top of each other. In this way one piece of data can be transmitted using multiple protocol encapsulate within one another.

    Services Interfaces:-Interfaces are networking communication point for your computer each interface associated with a physical or virtual networking device fullstop in computing a network interface is a software or hardware interface two pieces of equipment and protocol layer in a computer network.

    A typical Tower model is between 15 to 25 inches High.

14. (ii) What are the functions of presentation layer of OSI reference model

    Answer:

    Presentation Layer:-

    1. Translation:-Presentation layer is responsible for converting various formats into required format of the recipient.

    2. Encryption:- Data encryption and decryption is a done by presentation layer for security

    3. Compression and Decompression:- Data topi transfer compressed while sending and dwara while receiving for reducing time of transmission.

16. (iii) Describe one error detection technique used in networks

    Answer:

    Error Detection Technique:- Single site error:- the Only One byte of given data unit is changed from 1 to 0 from 0 to 1.

    0 0 0 0 1 0 1 0

    0 0 0 0 0 0 1 0

    
     

    • The message which is sent to corrupted as a single byte . Bite is changed to 1.

    • Single bit error does not appear more likely in serial data transmission.

    • Mainly occur in parallel data transmission.

    With digital signature for given messages

    Be practical some digital signature in storage.

17. (iv) Explain the design issue of network layer.

    Answer:

    Design issues of the network layer:- Store and forward packet switching.

    • service provided to the transport layer

    • implementations of connectionless service

    • implementation of of connection oriented service

    • comparison of virtual circuit and

18. (v) How is the namespace organised in a DNS

    Answer:

    DNS:- Name Space Organisation a namespace is a context with which the names of all objects must be unambiguously resolvable.

    For example:- The internet is a single DNS namespace within which all network devices with our DNS name can be resolved to particular address.

    For example:- domain name .sub. secondry.. Com . .com is the top lavel domain. Secondry I identify the secondary domain name and sub identify a subdomain with a layer network entry DNS domain structure is called DNS Namespace.

19. (vi) What is transposition cipher?

    Answer:

    Transposition cipher:- It is it to reverse the order of the letter in a plain text.

    Example:- ELPMAXE reverse Of example.

    In transposition cypher there is no substitution of of directors instead there location change. At character is a first position of plaintext May appear in the tenth position of ciphertext tractor in the eighth position may appear in the first position. another position word trans position Cypher recorded the symbol in block of symbols.