DBMS Interview Questions and Answers  

1.What is a Database?
Ans: A database is a collection of related data .A database is a logically coherent
collection of data with some inherent meaning.

2. What is DBMS?
Ans: Database Management system is a collection of programs that enables user to create and maintain a database.
Thus a DBMS is a general purposed s/w system that facilitates the process of defining constructing and manipulating a database for various applications. (Defining a data base involves specifying the data types, structures and constraints for the data to be stored in the data database.
Constructing a data base is the process of storing data itself on some storage medium that is controlled by DBMS. Manipulating a database includes such functions as querying the data base to retrieve specific data, updating the database to reflect the changes in the mini-world.

3. What is a Catalog?
Ans: A catalog is a table that contain the information such as structure of each file ,
the type and storage format of each data item and various constraints on the data .
The information stored in the catalog is called Metadata . Whenever a request is
made to access a particular data, the DBMS s/w refers to the catalog to determine
the structure of the file.

4. What is data ware housing & OLAP?
Ans: Data warehousing and OLAP (online analytical processing ) systems are the
techniques used in many companies to extract and analyze useful information
from very large databases for decision making .

5. What is real time database technology?
Ans: These are all the techniques used in controlling industrial and manufacturing
processes.

6. What is program-data independence?
Ans: Unlike in the traditional file sys. the structure of the data files is stored in the
DBMS catalog separately from the access programs . This property is called
program-data independence.i.e. We needn’t to change the code of the DBMS if the
structure of the data is changed .Which is not supported by traditional file sys .

7. What is ORDBMS?
Ans: Object oriented RDBMS is a relational DBMS in which every thing is treated as
objects. User can define operations on data as a part of the database definition.

8. What is program-operation independence?
Ans: An operation is specified in two parts .
1. Interface (operation name and data types of its arguments).
2. Implementation (the code part)
The implementation part can be changed without affecting the interface. This is called
program-operation independence.

9. What is a view?
Ans: A view may be a subset of the database or it may contain virtual data that is
derived from the database files but is not explicitly stored .

10. What is OLTP?
Ans: Online transaction processing is an application that involve multiple database accesses
from different parts of the world . OLTP needs a multi-user DBMS s/w to ensure that concurrent
transactions operate correctly.

11. What is the job of DBA?
Ans: A database administrator is a person or a group responsible for authorizing access to the
database, for coordinating and monitoring its use, and for acquiring s/w and h/w resources as needed.

12. Who are db designer?
Ans: Data base designers are responsible for identifying the data to be stored in the database and for
choosing appropriate structure to represent and store this data .

13. What are different types of end users?
Ans:
1. Casual end-users
2. Naive or parametric end users
3. Sophisticated end users
4. Stand alone users.

14. What are the advantages of using a dbms?
Ans:
1. Controlling redundancy.
2. Restricting unauthorized access.
3. Providing persistent storage for program objects and data structures.
4. Permitting inferencing and actions using rules.
5. Providing multi-user interfaces.
6. Representing complex relationships among data.
7. Enforcing integrity constraints.
8. Providing backups and recovery.

15. What are the disadvantages of using a dbms?
Ans:
1. High initial investments in h/w, s/w, and training.
2. Generality that a DBMS provides for defining and processing data.
3. Overhead for providing security, concurrency control, recovery, and integrity functions.

16. What is a data model?
Ans: It is a collection of concepts that can be used to describe the structure of a database. It provides necessary means to achieve this abstraction. By structure of a database we mean the data types, relations, and constraints that should hold on the data.

17. What are different categories of data models?
Ans:
1. High-level or conceptual data models.
2. Representational data models.
3. Low-level or physical data models.
High level data models provide the concepts that are close to the way many users perceive data.
Representational data models are provide concepts that provide the concepts that may be understood by end users but that are not too far removed from organization of data in the database.
Physical data models describe the details of how data is stored in the computers.

18. What is schema?
Ans: The description of a data base is called the database schema , which is specified during database design and is not expected to change frequently . A displayed schema is called schema diagram .We call each object in the schema as schema construct.

19. What are types of schema?
Ans:
1. internal schema.
2. Conceptual schema.
3. External schemas or user views.

20. What is Data independency?
Ans: Data independency is defined as the capacity to change the conceptual schema without having to change the schema at the next higher level. We can define two types of data independence:
1. Logical data independence.
2. Physical data independence.
LDI is the capacity to change the conceptual schema without having to change external schemas or application programs.
PDI is the capacity to change the internal schema without having to change conceptual (or external) schemas.

21. What are different DBMS languages?
Ans:
1. DDL (Data definition language)
2. SDL (Storage definition language)
3. VDL (View definition language)
4. DML (Data manipulation language)

22. What are different types of DBMS?
Ans:
1. DBMS
2. RDBMS (Relational)
3. ORDBMS (Object Relational)
4. DDBMS (Distributed)
5. FDBMS (Federated)
6. HDDBMS (Homogeneous)
7. HDBMS (Hierarchical)
8. NDBMS (Networked)

23. What is an entity?
Ans: An entity is a thing in the real world with an independent existence.

24. What are attributes?
Ans: These are the particular properties that describe an entity.

25. What are diff. types of attributes?
Ans:
1. Composite Vs simple attributes.
2. Single valued Vs multi-valued attributes.
3. Stored Vs derived attribute.
4. Null valued attributes.
5. Complex attributes.

26. What is difference between entity set and entity type?

27. What is domain value or value set of an attribute?
Ans: It is the set of values that may be assigned to that attribute for each individual entities .

28. What is degree of a relationship?
Ans: The no of entities participating in that relation .

29. What is recursive relationship?
Ans: It is the relationship where both the participating entities belong to same entity type .

30. What are relationship constraints?
Ans:
1. Cardinality ratio.
2. Participation constraints.

31. What is Cardinality ratio?
Ans: The cardinality ratio for a binary relationship specifies the number of relationship instances that an entity can participate in.

32. What is a Participation constraint?
Ans: The participation constraint specifies whether the existence of an entity depends on its being related to another entity via the relationship type. This is of two types:
1. Total participation.
2. Partial participation.

33. What is a weak entity types?
Ans: The entity types that do not have key attributes of their own are called weak entity types.
Rests are called strong entity types .The entity that gives identity to a weak entity is called owner entity. And the relationship is called identifying relationship. A weak entity type always has a total participation constraint with respect to its identifying relationship.

34. What is an ER Diagram?
Ans:
This data model is based on real world that consists of basic objects called entities and of relationship among these objects. Entities are described in a database by a set of attributes.

35. What is an EER?
Ans:
==

36. What is specialization?
Ans: It is the process of defining a set of subclasses of an entity type where each subclass contain all the attributes and relationships of the parent entity and may have additional attributes and relationships which are specific to itself.

37. What is generalization?
Ans: It is the process of finding common attributes and relations of a number of entities and defining a common super class for them.

38. What are constraints on generalization and specialization?
Ans:
1. disjoint ness constraints.
2. Completeness constraints.
Disjointness constraint specifies that the subclasses of the specialization must be disjoint .i.e. an entity can be a member of at most one of the subclasses of the specialization. The reverse of it is overlapping.
Completeness constraint is a participation constraint which may be
1. Total
2. Partial
Total specialization constraint tells that each entity in the super class must be a member of some subclass in the specialization. And partial specialization constraint allows an entity not to belong to any of the subclasses .Thus we do have the following 4 types of constraints on specialization:
1. Disjoint, total
2. Disjoint, partial
3. Overlapping, total
4. Overlapping, partial

39. What is a ternary relationship?
Ans: A relationship with a degree 3 is called a ternary relationship.

40. What is aggregation and association?
Ans: Aggregation is an abstraction concept for building composite objects from their component objects. The abstraction of association is used to associate objects from several independent classes.

41. What is RAID Technology?
Ans: Redundant array of inexpensive (or independent) disks. The main goal of raid technology is to even out the widely different rates of performance improvement of disks against those in memory and microprocessor. Raid technology employs the technique of data striping to achieve higher transfer rates.

42. What is Hashing technique?
Ans: This is a primary file organization technique that provides very fast access to records on certain search conditions. The search condition must be an equality condition on a single field, called hash field of the file.
1. Internal hashing
2. External hashing
3. Extendible hashing
4. Linear hashing
5. Partitioned hashing

43. What are different types of relational constraints?
Ans:
1. Domain constraints
2. Key constraints
3. Entity integrity constraints
4. Referential integrity constraints
Domain constraints specify that the value of each attribute must be an atomic value from the domain of the attributes.
Key constraints tell that no two tuples can have the same combination of values for all their attributes.
Entity integrity constraint states that no primary key value can be null.
Referential integrity constraints states that a tuple in one relation that refers to another relation must refer to an existing tuple in that relation it is specified between two relations and is used to maintain the consistency among tuples of the two relations.

44. What is difference between a super key, a key, a candidate key and a primary key?
Ans: A super key specifies a uniqueness constrain that no two distinct tuples in a state
can have the same value for the super key. Every relation has at least one default super key.
A key is a minimal super key or the subset of the super key which is obtained after
removing redundancy. A relation schema may have more than one key .In this case
each key is called a candidate key. One of the candidate key with minimum number
of attributes is chosen as primary key.

45. What is a foreign key?
Ans: A key of a relation schema is called as a foreign key if it is the primary key of
some other relation to which it is related to.

46. What is a transaction?
Ans: A transaction is a logical unit of database processing that includes one or more
database access operations.

47. What are the properties of transaction?
Ans:
1. Atomicity
2. Consistency preservation
3. Isolation
4. Durability (permanence)

48. What are the basic data base operations?
Ans:
1. Write_item(x)
2. Read_item(x)

49. What are the disadvantages of not controlling concurrency?
Ans:
1. Lost update problem
2. Temporary update(Dirty read) problem
3. Incorrect summary problem

50. What are serial, non serial?
Ans: A schedule S is serial if, for every transaction T participating in the schedule, all the operations of T is executed consecutively in the schedule, otherwise, the schedule is called non-serial schedule.

51. What are conflict serializable schedules?
Ans: A schedule S of n transactions is serializable if it is equivalent to some serial schedule of the same n transactions.

52. What is result equivalent?
Ans: Two schedules are called result equivalent if they produce the same final state of the data base.

53. What are conflict equivalent schedules?
Ans: Two schedules are said to be conflict equivalent if the order of any two conflicting operations is the same in both schedules.

54. What is a conflict serializable schedule?
Ans: A schedule is called conflict serializable if it is conflict equivalent to some serial schedule.

55. What is view equivalence?
Ans: Two schedules S and S’ are said to be view equivalent if the following three conditions hold :
1. Both S and S’ contain same set of transactions with same operations in them.
2. If any read operation read(x) reads a value written by a write operation or the original value of x the same conditions must hold in the other schedule for the same read(x) operation.
3. If an operation write1(y) is the last operation to write the value of y in schedule S then the same operation must be the last operation in schedule S’.

56. What is view serializable?
Ans: A schedule is said to be view serializable if it is view equivalent with some serial schedule.

57. What are the various methods of controlling concurrency?
Ans:
1. Locking
2. Time stamp
Locking data item to prevent multiple transactions from accessing the item concurrently.
A time stamp is a unique identifier for each transaction, generated by the system.

58. What is a lock?
Ans: A lock is a variable associated with a data item that describes the status of the item with respect to the possible operations that can be applied to it.

59. What are various types of locking techniques?
Ans:
1. a binary lock
2. Shared/Exclusive lock
3. Two phase locking

60. What is a binary lock?
Ans: A binary lock can have two states or values:
1. locked (1)
2. unlocked(0)
If locked it cannot be accessed by any other operations, else can be.

61. What is shared or exclusive lock?
Ans: It implements multiple-mode lock. Allowing multiple accesses for read operations but exclusive access for write operation.

62. Explain two phase locking?
Ans: All the locking operations must precede the first unlock operation in the transaction .It does have two phases:
1. expanding phase (Locks are issued)
2. Shrinking phase (Locks are released)

63. What are different types of two phase lockings (2pl)?
Ans:
1. Basic
2. Conservative
3. Strict
4. Rigorous
this is the basic technique of 2pl described above.
Conservative 2pl requires a transaction to lock all the items it accesses before the transaction begins its execution, by pre-declaring it’s read-set and write-set.
Strict 2pl guarantees that a transaction doesn’t release any of its exclusive locks until after it commits or aborts.
Rigorous guarantees that a transaction doesn’t release any of its locks (including shared locks) until after it commits or aborts.

64. What is a deadlock?
Ans: Dead lock occurs when each transaction T in a set of two or more transactions is waiting for some item that is locked by some other transaction T’ in the set. Hence each transaction is in a waiting queue, waiting for one of the other transactions to release the lock on them.

65. What are triggers?
Ans: Triggers are the PL/SQL blocks definining an action the database should take when some database related event occurs. Triggers may be used to supplement declarative referential integrity, to enforce complex business rules, or to audit changes to data.

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 Networking Interview Questions

1.What do you mean by data communication?
Ans: It is the exchange of data between two devices via some form of transmission medium such as wire cable. The communicating system must be part of a communication system made up of a combination of hardware and software.The effectiveness of a data communication system depends on three fundamental characteristics: delivery, accuracy and timeliness.

2.What is simplex?
Ans: It is the mode of communication between two devices in which flow of data is unidirectional. i.e. one can transmit and other can receive.
E.g. keyboard and monitor.

3.What is half-duplex?
Ans: It is the mode of communication between two devices in which flow of data is bi-directional but not at the same time. ie each station can transmit and receive but not at the same time.
E.g walkie-talkies are half-duplex system.

4.What is full duplex?
Ans: It is the mode of communication between two devices in which flow of data is bi-directional and it occurs simultaneously. Here signals going in either direction share the capacity of the link.
E.g. telephone

5.What is a network?
Ans: It is a set of devices connected by communication links. A node can be a computer or any other device capable of sending and/or receiving data generated by other nodes on the network.

6.What is distributed processing?
Ans: It is a strategy in which services provided by the network reside at multiple sites.

7.What is point to point connection?
Ans:It provides a dedicated link between two devices. The entire capacity of the link is reserved for transmission between the two devices
e.g. when we change the TV channels by remote control we establish a point to point connection between remote control and TV control system.

8.What is multipoint connection?
Ans: In multipoint connection more than two specific devices share a single link.
Here the capacity of the channel is shared either separately or temporally.

9.What is a topology?
Ans: Topology of a network is defined as the geometric representation of the relationship of all the links and linking devices (node) to one another.Four basic topologies are star, bus, ring and mesh.
Star – Here each device has a dedicated point to point link only to a central controller called hub.
Bus -It is multipoint. One long cable acts as a backbone to link all the devices in the network.
Ring -Here each device has a dedicated point to point connection only with the two devices on either side of it.
Mesh -Here every device has a dedicated point to point link to every other device.

10.Define LAN, MAN and WAN.
Ans: LAN- A local area network (LAN) is a privately owned and links the devices in a single office, building or campus.
It allows resources to be shared between personal computers and work stations.
MAN- A metropolitan-area network (MAN) spreads over an entire city.
It may be wholly owned and operated by a private company, eg local telephone company.
WAN – A wide area network (WAN) provides long distance transmission of data, voice, image and video information over large geographic areas that comprise a country, a continent or even whole world.

11.Define internet?
Ans: It is a network of networks.

12.What is a protocol?
Ans: It is a set of rules that governs data communication. A protocol defines what is communicated, how it is communicated, and when it is communicated. The key elements of protocol are syntax, semantics and timing.

13.What is TCP/IP protocol model?
Ans: It is a five layered model which provides guidelines for the development of universally compatible networking protocols.
The five layers are physical, data link, network, transport and application.

14.Describe the functions of five layers?
Ans: Physical- It transmits raw bits over a medium. It provides mechanical and electrical specification.
Data link- It organizes bits into frames. It provides hop to hop delivery.
Network-It moves the packets from source to destination.It provide internetworking.
Transport-It provides reliable process to process message delivery and error recovery.
Application-It allows ti access to network resources.

15.What is ISO-OSI model?
Ans: Open Systems Interconnection or OSI model was designed by the International Organization for Standardization (ISO) .It is a seven layer model. It is a theoretical model designed to show how a protocol stack should be implemented.
It defines two extra layers in addition to TCP/IP model.
Session -It was designed to establish, maintain, and synchronize the interaction between communicating system.
Presentation-It was designed to handle the syntax and semantics of the information exchanged between the two systems. It was designed for data translation, encryption, decryption, and compression.

16. What is multiplexing?
Ans: Multiplexing is the process of dividing a link, the phycal medium, into logical channels for better efficiency. Here medium is not changed but it has several channels instead of one.

16.What is switching?
Ans: Switching in data communication is of three types
Circuit switching
Packet switching
Message switching

17.How data is transmitted over a medium?
Ans: Data is transmitted in the form of electromagnetic signals.

18. Compare analog and digital signals?
Ans: Analog signals can have an infinite number of values in a range but digital signal can have only a limited number of values.

19.Define bandwidth?
Ans: The range of frequencies that a medium can pass is called bandwidth. It is the difference between the highest and lowest frequencies that the medium can satisfactorily pass.

20.What are the factors on which data rate depends?
Ans: Data rate ie.how fast we can send data depends upon
i) Bandwidth available
ii) The levels of signals we can use
iii) The quality of the channel (level of noise)

21.Define bit rate and bit interval?
Ans: Digital signals are aperiodic.so instead of using period and frequency we use bit interval and bit rate respectively.Bit interval is the time required to send one single bit.Bit rate is the number of bit intervals per second.

22.What is Nyquist bit rate formula?
Ans: For a noiseless channel, the Nyquist bit rate formula defines the theoretical maximum bit rate
Bitrate=2* Bandwidth*log2L
Where Bandwidth is the bandwidth of the channel
L is the number of signal level used to represent the data
Bitrate is the bit rate in bits per second.

23.Define Shannon Capacity?
Ans: Shannon Capacity determines the theoretical highest data rate foe a noise channel.
Capacity= Bandwidth * log2 (1+SNR)
Bandwidth is the bandwidth of the channel.
SNR is the signal to noise ratio, it is the statical ratio of the power of the signal to the power of the noise.
Capacity is the capacity of the channel in bits per second

24.What is sampling?
Ans: It is the process of obtaining amplitude of a signal at regular intervals.

25.Define pulse amplitude modulation?
Ans: It is an analog to digital conversion method which takes analog signals, samples it and generates a series of pulse based on the results of the sampling. It is not used in data communication because the series of pulses generated still of any amplitude. To modify it we use pulse code modulation.

26.Define pulse code modulation?
Ans: Pulse code Modulation modifies pulses created by PAM to create a completely digital signal.
For this PCM first quantizes the PAM pulse. Quantization is the method of assigning integral values in a specific tange to sampled instances.PCM is made up of four separate processes: PAM, quantization, binary encoding and line encoding.

27.What is Nyquist Theorem?
Ans: According to this theorem, the sampling rate must be at least 2 times the highest frequency of the original signal.

28.What are the modes of data transmission?
Ans: Data transmission can be serial or parallel in mode
In parallel transmission, a group of bits is sent simultaneously, with each bit on a separate line.In serial transmission there is only one line and the bits are sent sequentially.

29.What is Asynchronous mode of data transmission?
Ans: It is a serial mode of transmission.
In this mode of transmission, each byte is framed with a start bit and a stop bit. There may be a variable length gap between each byte.

30.What is Synchronous mode of data transmission?
Ans: It is a serial mode of transmission.In this mode of transmission, bits are sent in a continuous stream without start and stop bit and without gaps between bytes. Regrouping the bits into meaningful bytes is the responsibility of the receiver.

31.What are the different types of multiplexing?
Ans: Multiplexing is of three types. Frequency division multiplexing and wave division multiplexing is for analog signals and time division multiplexing is for digital signals.

32.What is FDM?
Ans: In frequency division multiplexing each signal modulates a different carrier frequency. The modulated carrier combines to form a new signal that is then sent across the link.
Here multiplexers modulate and combine the signal while demultiplexers decompose and demodulate.
Guard bands keep the modulating signal from overlapping and interfering with one another.

32.What is TDM ?
Ans: In TDM digital signals from n devices are interleaved with one another, forming a frame of data.
Framing bits allow the TDM multiplexer to synchronize properly.

33.What are the different transmission media?
Ans: The transmission media is broadly categorized into two types
i)Guided media(wired)
i)Unguided media(wireless)

34.What are the different Guided Media?
Ans: The media which provides a conduct from one device to another is called a guided media. These include twisted pair cable, coaxial cable, and fiber-optic cable.

35.Describe about the different Guided Medias.
Ans: Twisted pair cable consists of two insulated cupper wires twisted together. It is used in telephone line for voice and data communications.
Coaxial cable has the following layers: a metallic rod-shaped inner conductor, an insulator covering the rod, a metallic outer conductor (shield), an insulator covering the shield, and a plastic cover.Coaxial cable can carry signals of higher frequency ranges than twisted-pair cable.
Coaxial cable is used in cable TV networks and Ethernet LANs.Fiber-optic cables are composed of a glass or plastic inner core surrounded by cladding, all encased in an outer jacket.Fiber-optic cables carry data signals in the form of light. The signal is propagated along the inner core by reflection. Its features are noise resistance, low attenuation, and high bandwidth capabilities.
It is used in backbone networks, cable TV nerworks, and fast Ethernet networks.

36.What do you mean by wireless communication?
Ans: Unguided media transport electromagnetic waves without using a physical conductor. This type of communication is referred as wireless communication.
Here signals are broadcaster through air and thus available to anyone who has a device to receive it.

37.What do you mean by switching?
Ans: It is a method in which communication devices are connected to one another efficiently.
A switch is intermediary hardware or software that links devices together temporarily.

38.What are the switching methods?
Ans: There are three fundamental switching methods: circuit switching, packet switching,
And message switching.In circuit switching, a direct physical connection between two devices is created by space division switches, time division switches or both.
In packet switching data is transmitted using a packet switched network. Packet switched network is a network in which data are transmitted in independent units called packets.

39.What are the duties of data link layer?
Ans: Data link layer is responsible for carrying packets from one hop (computer or router) to the next. The duties of data link layer include packetizing, adderssing, error control, flow control, medium access control.

40.What are the types of errors?
Ans: Errors can be categorized as a single-bit error or burst error. A single bit error has one bit error per data unit. A burst error has two or more bits errors per data unit.

41.What do you mean by redundancy?
Ans: Redundancy is the concept of sending extra bits for use in error detection. Three common redundancy methods are parity check, cyclic redundancy check (CRC), and checksum.

42.Define parity check.
Ans: In parity check, a parity bit is added to every data unit so that the total number of 1s is even (or odd for odd parity).Simple parity check can detect all single bit errors. It can detect burst errors only if the total number of errors in each data unit is odd.In two dimensional parity checks, a block of bits is divided into rows and a redundant row of bits is added to the whole block.

43. Define cyclic redundancy check (CRC).
Ans: C RC appends a sequence of redundant bits derived from binary division to the data unit. The divisor in the CRC generator is often represented as an algebraic polynomial.

44. What is hamming code?
Ans: The hamming code is an error correction method using redundant bits. The number of bits is a function of the length of the data bits. In hamming code for a data unit of m bits, we use the formula 2r >= m+r+1 to determine the number of redundant bits needed. By rearranging the order of bit transmission of the data units, the hamming code can correct burst errors.

45.What do you mean by flow control?
Ans: It is the regulation of sender’s data rate so that the receiver buffer doesn’t become overwhelmed.i.e. flow control refers to a set of procedures used to restrict the amount of data that the sender can send before waiting for acknowledgement.

46.What do you mean by error control?
Ans: Error control refers primarily to methods of error detection and retransmission. Anytime an error is detected in an exchange, specified frames are retransmitted. This process is called automatic repeat request (ARQ).

47.Define stop and wait ARQ.
Ans: In stop and wait ARQ, the sender sends a frame and waits for an acknowledgement from the receiver before sending the next frame.

48.Define Go-Back-N ARQ?
Ans: In Go-Back-N ARQ, multiple frames can be in transit at the same time. If there is an error, retransmission begins with the last Unacknowledged frame even if subsequent frames arrived correctly. Duplicate frames are discarded.

49.Define Selective Repeat ARQ?
Ans: In Selective Repeat ARQ, multiple frames can be in transit at the same time. If there is an error, only unacknowledged frame is retransmitted.

50.What do you mean by pipelining, is there any pipelining in error control?
Ans: The process in which a task is often begun before the previous task has ended is called pipelining. There is no pipelining in stop and wait ARQ however it does apply in Go-Back-N ARQ and Selective Repeat ARQ.

51.What is HDLC?
Ans: It is a bit oriented data link protocol designed to support both half duplex and full duplex communication over point to point and multi point links.HDLC is characterized by their station type,configuration and their response modes.

52.What do you mean by point to point protocol?
Ans: The point to point protocol was designed to provide a dedicated line for users who need internet access via a telephone line or a cable TV connection. Its connection goes through three phases: idle, establishing, authenticating, networking and terminating.
At data link layer it employs a version of HDLC.

53. What do you mean by point to point protocol stack?
Ans: Point to point protocol uses a stack of other protocol to use the link, to authenticate the parties involved, and to carry the network layer data. Three sets of protocols are defined: link control protocol, Authentication protocol, and network control protocol.

54.What do you mean by line control protocol?
Ans: It is responsible for establishing, maintaining, configuring, and terminating links.

55.What do you mean by Authentication protocol?
Ans: Authentication means validating the identity of a user who needs to access a set of resources.
It is of two types
i)Password Authentication Protocol(PAP)
ii)Challenge Handshake Authentication Protocol(CHAP)
PAP is a two step process. The user sends a authentication identification and a password. The system determines the validity of the Information sent.CHAP is a three step process. The system sends a value to the user. The user manipulates the value and sends the result. The system Verifies the result.

56.What do you mean by network control protocol?
Ans: Network control protocol is a set of protocols to allow the encapsulation of data coming from network layer protocol that requires the services of PPP.

57. What do you mean by CSMA?
Ans: To reduce the possibility of collision CSMA method was developed. In CSMA each station first listen to the medium (Or check the state of the medium) before sending. It can’t eliminate collision.

58.What do you mean by Bluetooth?
Ans: It is a wireless LAN technology designed to connect devices of different functions such as telephones, notebooks, computers, cameras, printers and so on. Bluetooth LAN Is an adhoc network that is the network is formed spontaneously? It is the implementation of protocol defined by the IEEE 802.15 standard.

59.What is IP address?
Ans: The internet address (IP address) is 32bits that uniquely and universally defines a host or router on the internet.
The portion of the IP address that identifies the network is called netid. The portion of the IP address that identifies the host or router on the network is called hostid.

60.What do you mean by subnetting?
Ans: Subnetting divides one large network into several smaller ones. It adds an intermediate level of hierarchy in IP addressing.

61.What are the advantages of fiber optics cable ?
Ans: The advantages of fiber optics cable over twisted pair cable are Noise resistance-As they use light so external noise is not a factor. Less signal attenuation-fiber optics transmission distance is significantly greater than that of other guided media.Higher bandwidth-It can support higher bandwidth.

62.What are the disadvantages of fiber optics cable?
Ans: The disadvantages of fiber optics cable over twisted pair cable are
Cost-It is expensive Installation/maintenance-Any roughness or cracking defuses light and alters the signal Fragility-It is more fragile.

63.What are the propagation type of radio wave ?
Ans: Radio wave propagation is dependent upon frequency.There are five propagation type.
i)surface propagation
ii)Tropospheric propagation
iii)Ionospheric propagation
iv)Line of sight propagation
v)space propagation

64.What do you mean by Geosynchronous Satellites ?
Ans: Satellite communication uses a satellite in geosynchronous orbit to relay signals.The Satellite must move at the same speed as the earth so that it seems to remain fixed above a certain spot..Only one orbit can be geosynchronous.This orbit occurs at the equatorial plane and is approximately 22,000 miles from the surface of earth.

65.What are the factors for evaluating the suitability of the media ?
Ans: The factors are cost,throughput,attenuation,Electromagneric interference(EMI),securtty.

66.What do you mean by medium access control(MAC) sublayer.
Ans: The protocols used to determine who goes next on a multi-access channel belong to a sublayer of the data link layer is called the multi-access channel(MAC) sublayer.It is the buttom part of data link layer.

67.What do you mean by ALOHA ?
Ans: It is the method used to solve the channel allocation problem .It is used for:
i)ground based radio broadcasting
ii)In a network in which uncoordinated users are competing for the use of single channel.
It is of two types:
1.Pure aloha
2.Slotted aloha

68.What is pure ALOHA?
Ans: It lets users transmit whenever they have data to sent.Collision may occur but due to feedback property sender can know the status of message.conflict occur when at one time more bits are transmitted.The assumptions are :
i)all frame size is same for all user.
ii)collision occur when frames are transmitted simultaneously
iii)indefinite population of no of user.
iv)N=number of frames/frame time
iv)it obeys poisson’s distribution if N>1 there will be collision 0<1

69.What is slotted ALOHA?
Ans: In this method time is divided into discrete intervals,each interval corresponding to one frame.It requires user to agree on slot boundaries.Here data is not send at any time instead it wait for beginning of the next slot.Thus pure ALOHA is tuened into discrete one.

70.What do you mean by persistent CSMA(carrier sense multiple access) ?
Ans: When a station has data to send,it first listens to the channel to see if anyone else is transmitting at that moment.If channel is busy it waits until the station becomes idle. When collision occurs it waits and then sends.It sends frame with probability 1 when channel is idle.

71.What do you mean by non persistent CSMA(carrier sense multiple access) ?
Ans: Here if no one else is sending the station begins doing so itself.However if the channel is already in use,the station does’t continuously sense it rather it waits for a random period of time and then repeats.It leads better channel utilization but longer delay.

72.What do you mean by p persistent CSMA(carrier sense multiple access) ?
Ans: It applies to slotted channels.when a station becomes ready to send,it senses the channel.If it is idle it transmits with a probability P,with a probability Q=P-1
It defers until the next slot.If that slot is also idle,it either transmits or defers again with probability P and Q.The process is repeated until either the frame has been transmitted or another station begins transmitting.

73.What is FDDI?
Ans: It is high performance fiber optic token ring LAN running at 100Mbps over distance up 1000 stations.FDDI access is limited by time.A FDDI cabling consist of two fiber rings.
i)one transmitting clockwise
ii)one transmitting counterclockwise

74.What is Firewalls?
Ans: It is an electronic downbridge which is used to enhance the security of a network. It’s configuration has two components.
i)Two routers
ii)Application gateway
the packets traveling through the LAN are inspected here and packets meeting certain criteria are forwarded and others are dropped.

75.What is Repeaters ?
Ans: A receiver receives a signal before it becomes too weak or corrupted,regenerates the original bit pattern,and puts the refreshed copy back onto the link.It operates on phycal layer of OSI model.

76.What is Bridges?
Ans: They divide large network into smaller components.They can relay frames between two originally separated LANs.They provide security through partitioning traffic.They operate on phycal and data link layer of OSI model.

77.What is Routers ?
Ans: Router relay packets among multiple interconnected networks.They receive packet from one connected network and pass it to another network.They have access to network layer addresses and certain software that enables them to determine which path is best for transmission among several paths.They operate on phycal,data link and network layer of OSI model.

78.What is Gateway ?
Ans: It is a protocol converter.A gateway can accept a packet formatted for one protocol and convert it to a packet formatted for another protocol.It operates on all the seven layers of OSI model.

79.What do you mean by Data Terminal Equipment(DTE) ?
Ans: It is any device that is source of or destination for binary digital data.At phycal layer it can be a terminal computer. They generate or consume information.

80.What do you mean by Data Terminating Equipment (DCE) ?
Ans: Data circuit terminating equipment includes any functional unit that transmit or receives data in the form of an analog or digital signal through a network.DTE generates digital data and passes them to a DCE ,the DCE converts the data to a form acceptable to the transmission media and sends the converted signal to another DCE on the network.

81.What do you mean by protocol stack ?
Ans: The list of protocols used by certain system ,one protocol per layer is called protocol stack.

82.What do you mean by peer ?
Ans: Entities comprising the corresponding layers on different machines are called peers.It may be
• hardware device.
• processes
• human being
peers communicate by using protocol.

83.What do you mean by broadcasting ?
Ans: Broadcast system allow addressing a packet to all destination by using a special code in address field.when packet is transmitted it is received and processed by every machine on the network.

84.What are the advantages of broadcast network.
Ans:
• a single communication channel is shared by all computers.
• packets are transmitted and received by all the computer.
• address field is attached to whom it is intended.
• multicasting is used in network.

85.What do you mean by point to point network?
Ans: Point to point network consist of many connections between individual pair of machines.large networks are point to point.Routing algorithm plays an important in point to point network.It uses stored ad forword technique.It is a packet switching network.

86.What are the design issue of layers ?
Ans: The design issue of layer are
• Addressing technique.ie source and destination address
• Types of communication
• Error control
• Order of message.
• Speed matching
• Multiplexing and demultiplexing.

87.What are the protocols in application layer ?
Ans: The protocols defined in application layer are
• TELNET
• FTP
• SMTP
• DNS

88.What are the protocols in transport layer ?
Ans: The protocols defined in transport layer are
• TCP
• UDP

89.Define TCP ?
Ans: It is connection oriented protocol.It consist byte streams oeiginating on one machine to be delivered without error on any other machine in the network.while transmitting it fragments the stream to discrete messages and passes to interner layer.At the destination it reassembles the messages into output stream.

90.Define UDP ?
Ans: It is unreliable connectionless protocol.It is used for one-shot,client-server type,requesr-reply queries and applications in which prompt delivery is required than accuracy.

91.Define IP ?
Ans: Internetwork protocol (IP) is the transmission mechanism used by TCP/IP protocol.It is an unreliable and connectionless datagram protocol.It provides no error checking and tracking.

92.What do you mean by client server model ?
Ans: In client server model ,the client runs a program to request a service and the server runs a program to provide the service.These two programs communicate with each other. One server program can provide services to many client programs.

93.What are the information that a computer attached to a TCP/IP internet must possesses ?
Ans: Each computer attached to TCP/IP must possesses the following information
• Its IP addesss
• Its subnet mask
• The IP addesss of the router.
• The Ip address of the name server.

94.What is domain name system(DNS)?
Ans: Domain Name System (DNS )is a client server application that identifies each host on the internet with a unique user friendly name.

95.What is TELNET ?
Ans: TELNET is a client –server application that allows a user to log on to a remote machine,giving the user access to the remote system. TELNET is an abbreviation of terminal Network.

96.What do you mean by local login and remote login ?
Ans: When a user logs into a local time-sharing system ,it is called local login. When a user wants to access an application program or utility located on a remote machine,he or she performs remote login.

97.What is Network Virtual Terminal ?
Ans: A universal interface provided by TELNET is called Network Virtual Terminal(NVT) character set.Via this interface TELNET translates characters (data or command) that come from local terminal into NVT form and delivers them to the network.

98.What do you mean by Simple Mail Transfer Protocol ?
Ans: The TCP/IP protocol that supports electronic mail on the internet is called Simple Mail Transfer Protocol.SMTP provides for mail exchange between users on the same or different computer and supports Sending a single message to one or more recipient Sending message that include text, voice,video,or graphics.Sending message to users on network outside the internet.

99.What is Hypertext Transfer Protocol(HTTP) ?
Ans: It is the main protocol used to access data on the World Wide Web .the protol transfers data in the form of plain text,hypertext,audio,video,and so on. It is so called because its efficiency allows its use in a hypertext environment where there are rapid jumps from one document to another.

100.What is URL ?
Ans: It is a standard for specifying any kind of information on the World Wide Web.

101. What is World Wide Web ?
Ans: World Wide Web is a repository of information spread all over the world and linked together.It is a unique combination of flexibility,portability,and user-friendly features .The World Wide Web today is a distributed client-server service,in which a client using a browser can access a service using a server.The service provided is distributed over many locations called web sites.

102.What is HTML ?
Ans: Hypertext Markup Language (HTML) is a language for creating static web pages.

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Posted By Sundeep aka SunTechie

Sundeep is a Founder of Youth Talent Auzzar, a passionate blogger, a programmer, a developer, CISE and these days he is pursuing his graduation in Engineering with Computer Science dept.

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