Basic CS-Networks [3i Infotech Placement]: Sample Questions 66 - 67 of 90

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Question 66

Networks
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Describe in Detail

Essay▾

What is RAID?

Explanation

  • Redundant array of independent disks
  • Data storage virtualization technology combining multiple physical disk drive components into a single logical unit
  • Provides data redundancy, performance improvement or both.
  • Can store the same data in different places on multiple hard disks to protect against drive failures
  • However not all RAID levels provide redundancy.
  • Utilizing redundancy, a RAID array can be reliable than any one disk drive.
  • Also allows data to be read or written in parallel to many physical disk- increasing performance.

How does RAID work?

  • Data is mirrored to one or more disks in the same array, so if one disk fails, the data is preserved.
  • Using technique known as striping, RAID also offers the option of reading or writing to more than one disk at the same time in order to improve performance.

Characteristics of RAID:

  • Fault tolerance
  • Performance
  • Capacity

Question 67

Networks
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Describe in Detail

Essay▾

What is Protocol Data Unit?

Explanation

  • Protocol Data Unit is an open system interconnection term used in telecommunications
  • Refers to a group of information added or removed by a layer of the OSI model.
  • Represents a unit of data specified in the protocol of a given layer- consisting of protocol control information and user data.
  • Term specifically related to the initial four layers of the OSI model.
  • DSAP (Destination Service Access Point) , SSAP (Source Service Access Point) are addresses used by the LLC (Logical Link Control) to identify the protocol stacks on the receiving and sending machines generating and using the data.

PDU for each layer of the OSI model is listed below:

  • Physical layer
    • Raw bits (1s or 0s) transmitted physically via the hardware
  • Data Link layer
    • A frame
  • Network layer
    • A packet that contains the source and destination address
  • Transport layer
    • A segment that includes a TCP header and data
  • Session layer
    • The data passed to the network connection
  • Presentation layer
    • The data formatted for presentation
  • Application layer
    • The data received or transmitted by a software application

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