Computer Networks



What is piggybacking ?
Piggybacking on Internet access is the practice of establishing a wireless Internet connection by using another subscriber's wireless Internet access service without the subscriber's explicit permission or knowledge. It is a legally and ethically controversial practice, with laws that vary by jurisdiction around the world. While completely outlawed or regulated in some places, it is permitted in others.


Name the two sub layers of Data link layer. Specify their protocols.
1.  Logical link control(LLC)
Protocols : SDLC, NetBIOS, NetWare
2.  Media access Control (MAC)
Protocols : CSMA/CA, Slotted-ALOHA, CDMA, OFDMA


How we arrived 7 layers of OSI reference model? Why not less than 7 or more than 7 ?
The ISO looked to create a simple model for networking. They took the approach of defining layers that rest in a stack formation, one layer upon the other. Each layer would have a specific function, and deal with a specific task. Much time was spent in creating their model called "The ISO OSI Seven Layer Model for Networking". In this model, they have 7 layers, and each layer has a special and specific function.


 Why network standardization is done ?

Computer networking is a great way of connecting the computers and sharing data with each other.  There are many vendors that produce different hardware devices and software applications and without coordination among them there can be chaos, unmanaged communication and disturbance can be faced by the users. There should be some rules and regulations that all the vendors should adopt and produce the devices based on those communication standards. 

Difference between unacknowledged connection less services and acknowledged connection less services ?
 Unacknowledged connectionless service consists of having the source machine send independent frames to the destination machine without having the destination machine acknowledged. Most LAN's use this service. 
Acknowledged connectionless service in this service there are no logical connections used but each frame sent individually acknowledged. In this way the sender knows whether a frame has arrived correctly. It is useful on wireless systems

What is frame ?
In computer networking and telecommunication, a frame is a digital data transmission unit or data packet that includes frame synchronization, i.e. a sequence of bits or symbols making it possible for the receiver to detect the beginning and end of the packet in the stream of symbols or bits.


 What is bit stuffing?
Ans: Bit stuffing is the insertion of one or more bits into a transmission unit as a way to provide signaling information to a receiver. The receiver knows how to detect and remove or disregard the stuffed bits.


 What is encryption and decryption ?
Ans: Encryption is an algorithm which converts the message into a form that is unreadable known as scrambled message and decryption is the process which converts the encrypted message into readable form known as unscrambled message. Actually this is a method to transfer message from one side to other in a secure manner.


What are the various types of key used in cryptography ?
Ans: here are two main types of cryptography:
  • Secret key cryptography
  • Public key cryptography
Secret key cryptography is also known as symmetric key cryptography. With this type of cryptography, both the sender and the receiver know the same secret code, called the key. Messages are encrypted by the sender using the key and decrypted by the receiver using the same key.
Public key cryptography  also called asymmetric encryption, uses a pair of keys for encryption and decryption. With public key cryptography, keys work in pairs of matched public and private keys.