Anna University Coimbatore 2009 B.E Electronics

similar to that of signing transactions documents when you do business with a bank.
In network transactions, you can create an equivalent of an electronic or digital
signature by the way you send data.
17. elaborate the advantages & disadvantages of public key encryption?
Advantages:
a) Remove the restriction of a shared secret key ranging from 2 entities. Here every
entity can create a pair of keys, keep the private one, and publicly distribute the
other one.
b) The no. of keys needed is decreased tremendously. For 1 million users to
communicate, only 2 million keys are needed.
Disadvantage:
If you use large numbers the method to be effective. Calculating the cipher text using
the long keys takes a lot of time. So it is not recommended for large amounts of text.
18. elaborate the advantages & disadvantages of secret key encryption?
Advantage:
Secret Key algorithms are efficient: it takes less time to encrypt a message. The
cause is that the key is usually smaller. So it is used to encrypt or decrypt long
messages.
Disadvantages:
a) every pair of users must have a secret key. If N people in world want to use this
method, there needs to be N (N-1)/2 secret keys. For 1 million people to
communicate, a half-billion secret keys are needed.
b) The distribution of the keys ranging from 2 parties can be difficult.
19. describe permutation.
Permutation is transposition in bit level.
Straight permutation: The no. of bits in the input and output are preserved.
Compressed permutation: The no. of bits is decreased (some of the bits are dropped).
Expanded permutation: The no. of bits is increased (some bits are repeated).
20. describe substitutional & transpositional encryption.
Substitutional: A character level encryption in which every character is changed by
a different character in the set.
Transpositional: A Character level encryption in which the characters retain their
plaintext but the position of the character modifications.
PART B
UNIT I
Data communications
1. discuss ISO/OSI reference model. ¾Physical layer ¾Data link layer ¾Network layer ¾Transport layer ¾Session layer ¾Presentation layer ¾Application layer
2. discuss the topologies of the network. ¾Mesh topology ¾Star topology ¾Tree topology ¾Bus topology ¾Ring topology
3. discuss the categories of networks. ¾Local Area Network(LAN) ¾Metropolitan Area Network(MAN) ¾Wide Area Network(WAN)
4. discuss coaxial cable & fiber optics. ¾Coaxial cable ?Coaxial cable standards ?Coaxial cable connectors ¾Fiber optics ?Propagation modes ?Fiber sizes ?Cable composition ?Light sources for optical cable ?Fiber optic connectors ?Advantages & disadvantages of optical fiber
5. discuss line coding (digital to digital conversion). ¾Unipolar
?DC component ?Synchronization ¾Polar ?Non return to zero(NRZ) ?NRZ-L ?NRZ-I ?Return to zero ?Biphase ?Manchester ?Differential Manchester ¾Bipolar ?Alternate Mark Inversion(AMI) ?Bipolar 8-zero substitution(B8ZS) ?High-Density Bipolar 3(HDB3)
UNIT II
Data link layer
1. discuss fault detection and fault correction techniques. ¾Types of errors ?Single bit fault ?Burst fault ¾Error detection ?Vertical redundancy check(VRC) ?Longitudinal redundancy check(LRC) ?Cyclic redundancy check(CRC) ?Checksum ¾Error correction ?Single-bit fault correction ?Hamming code ?Burst fault correction
2. discuss fault control mechanism. ¾Stop and wait ARQ ¾Sliding window ARQ ?Go back-n ?Selective-reject
3. discuss the flow control mechanism ¾Stop and wait ¾Sliding window.
4. discuss the timers and time registers in FDDI.
Time registers ?Synchronous allocation(SA) ?Target token rotation time(TTRT) ?Absolute maximum time(AMT) ¾Timers ?Token rotation timer(TRT)
?Token holding timer(THT)
5. discuss about Ethernet. ¾Access method :CSMA/CD ¾Addressing ¾Electrical specification ¾Frame format ¾Implementation: ?10 base five :Thick Ethernet ?10 base two :Thin Ethernet ?10 base T :Twisted-pair Ethernet ?1 base five :Star LAN
6. discuss the frame format for token ring and token bus. ¾Access method: Token passing ?Priority and reservation ?Time limits ?Monitor stations
7. discuss about HDLC. ¾Station types: ?Primary station ?Secondary station ¾Configurations: ?Unbalanced configuration ?Symmetrical configuration ?Balanced configuration ¾Modes of communication: ?Normal Response Mode(NRM) ?Asynchronous Response Mode(ARM) ?Asynchronous Balanced Mode(ABM) ¾Frames : ?Flag field ?Address field ?Control field ?Information field ?FCS field
UNIT III
Network layer
1. discuss the 2 approaches of packet switching techniques. ¾Datagram approach ¾Virtual circuit approach ?Switched virtual circuit(SVC) ?Permanent virtual circuit(PVC) ¾Circuit – switched connection versus virtual – circuit connection ?Path versus route ?Dedicated versus shared
2. discuss IP addressing method. ¾Internetwork protocol (IP) ¾Datagram ¾Addressing ?Classes ?Dotted decimal notation ?A sample internet
3. describe routing & discuss distance vector routing and link state routing. ¾Distance vector routing ?Sharing info ?Routing table ?Creating the table ?Updating the table ?Updating algorithm ¾Link state routing ?Information sharing ?Packet cost ?Link state packet ?Getting info about neighbors ?Initialization ?Link state database
4. describe bridge and discuss the kind of bridges. ¾Bridges ¾Types of bridges ?Simple bridge ?Multiport bridge ?Transparent bridge
5. discuss subnetting ¾Subnetting ¾Three levels of hierarchy ¾Masking ?Masks without subnetting ?Masks with subnetting ¾Finding the subnetwork address ?Boundary level masking ?Non-boundary level masking
6. Write short notes about repeaters, routers and gateways. ¾Repeaters ¾Routers ?Routing concepts ?Least-cost routing ?Non adaptive routing ?Adaptive routing ?Packet lifetime ¾Gateways
UNIT IV
Transport layer
1. discuss the duties of transport layer.
End to end delivery
Addressing
Reliable delivery
· fault control
· Sequence control
· Loss control
· Duplication control
Flow control
Multiplexing
2. discuss socket in detail.
· Introduction
· Explanation
· program
3. discuss UDP & TCP. ¾User Datagram Protocol(UDP) ?Source port address ?Destination port address ?Total length ?Checksum ¾Transmission Control Protocol(TCP) ?Source port address ?Destination port address ?Sequence number ?Acknowledgement number ?Header length ?Reserved ?Control ?Window size ?Check sum ?Urgent pointer ?Options and padding
4. discuss about congestion control. ¾Congestion avoidance ?BECN ?FECN ?Four situations ¾Discarding
5. discuss leaky bucket and token bucket algorithm ¾Leaky bucket algorithm ?Leaky bucket ?Switch controlling the output rate ?Flowchart
UNIT V
Application Layer
1. discuss the functions of SMTP.
· System for sending messages to other computer users based on e-mail
addresses. SMTP provides mail exchange ranging from users on the identical
or various computers.
· User Agent
· Mail Transfer Agent
· Multipurpose Internet Mail Extensions
· Post Office Protocol
2. Write short notes on FTP.
· Transfer a file from 1 system to a different.
· TCP connections
· Basic model of FTP
3. discuss about HTTP.
· HTTP transactions
· HTTP messages
· URL
4. discuss the WWW in detail.
· Hypertext & Hypermedia
· Browser Architecture
· Categories of Web Documents
· HTML
· CGI
· Java
5. discuss the kind of encryption/decryption method.
Conventional Methods:
· Character-Level Encryption: Substitutional & Transpositional
· Bit-Level Encryption: Encoding/Decoding, Permutation, Substitution,
Product, Exclusive-Or & Rotation
Public key Methods
6. discuss about RSA algorithm.
· Public key Encryption technique.
· Encryption algorithm
· Decryption algorithm
· Security in RSA
7. discuss about secret key encryption algorithm.
· Data Encryption Standard
· Algorithm
· Sub key generation

Earning:   Approval pending.