Interview Quesions

Networking concepts

1.What are the two types of transmission technology available?
(i) Broadcast  and  (ii) point-to-point

2.What is subnet?
A generic term for section of a large networks usually separated
by a bridge or router.

3.Difference between the communication and transmission.
Transmission is a physical movement of information and concern
issues like bit polarity, synchronisation, clock etc.
Communication means the meaning full exchange of information
between two communication media.

4.What are the possible ways of data exchange?
(i) Simplex (ii) Half-duplex (iii) Full-duplex.

5.What is SAP?
Series of interface points that allow other computers to
communicate with the other layers of network protocol stack.

6.What do you meant by “triple X” in Networks? 
The function of PAD (Packet Assembler Disassembler) is described
in a document known as X.3. The standard protocol has been
defined between the terminal and the PAD, called X.28; another
standard protocol exists between hte PAD and the network,called
X.29. Together, these three recommendations are often called
“triple X”.

7.What is frame relay, in which layer it comes?
Frame relay is a packet switching technology. It will operate
n the data link layer.
 
8.What is terminal emulation, in which layer it comes?
Telnet is also called as terminal emulation. It belongs to
application layer.

9.What is Beaconing?
The process that allows a network to self-repair networks
problems. The stations on the network notify the other stations
on the ring when they are not receiving the transmissions.
Beaconing is used in Token ring and FDDI networks.

10.What is redirector?
Redirector is software that intercepts file or prints I/O
requests and translates them into network requests.This comes
under presentation layer.

11.What is NETBIOS and NETBEUI?
NETBIOS is a programming interface that allows I/O requests to
be sent to and received from a remote computer and it hides the
networking hardware from applications.
NETBEUI is NetBIOS extended user interface. A transport protocol
designed by microsoft and IBM for the use on small subnets.

12.What is RAID?
A method for providing fault tolerance by using multiple hard
disk drives.

13.What is passive topology?
When the computers on the network simply listen and receive
the signal, they are referred to as passive because they don’t
amplify the signal in any way. Example for passive topology -
linear bus.

14.What is Brouter?
Hybrid devices that combine the features of both bridges and
routers.

15.What is cladding?
A layer of a glass surrounding the center fiber of glass inside
a fiber-optic cable.

16.What is point-to-point protocol
A communications protocol used to connect computers to remote
networking services including Internet service providers.

17.How Gateway is different from Routers?
A gateway operates at the upper levels of the OSI model and
translates information between two completely different network
architectures or data formats

18.What is attenuation?
The degeneration of a signal over distance on a network cable
is called attenuation.

19.What is MAC address?
The address for a device as it is identified at the Media Access
Control (MAC) layer in the network architecture. MAC address is
usually stored in ROM on the network adapter card and is unique.

20.Difference between bit rate and baud rate.
Bit rate is the number of bits transmitted during one second
whereas baud rate refers to the number of signal units per second
that are required to represent those bits.
baud rate  = bit rate / N
where N is no-of-bits represented by each signal shift.

21.What is Bandwidth?
Every line has an upper limit and a lower limit  on the frequency
of signals it can carry.This limited range is called the bandwidth.

22.What are the types of Transmission media?
Signals are usually transmitted over some transmission media that
are broadly classified in to two categories.
a)Guided Media:
These are those that provide a conduit from one device to another
that include twisted-pair, coaxial cable and fiber-optic cable.
A signal traveling along any of these media is directed and is
contained by the physical limits of the medium. Twisted-pair and
coaxial cable use metallic that accept and transport signals in
the form of electrical current.Optical fiber is a glass or plastic
cable that accepts and transports signals in the form of light.
b) Unguided Media:
This is the wireless media that transport electromagnetic waves
without using a physical conductor. Signals are broadcast either
through air. This is done through radio communication, satellite
communication and cellular telephony.

23.What is Project 802?
It is a project started by IEEE to set standards to enable
intercommunication between equipment from a variety of
manufacturers.
It is a way for specifying functions of the physical layer,the
data link layer and to some extent the network layer to allow for
interconnectivity of major LAN protocols.
It consists of the following:
?802.1 is an internetworking standard for compatibility
of different LANs and MANs across protocols.
?802.2 Logical link control (LLC) is the upper sublayer of the
data link layer which is non-architecture-specific, that is remains
the same for all IEEE-defined LANs.
?Media access control (MAC) is the lower sublayer of the data link
layer that contains some distinct modules each carrying proprietary
information specific to the LAN product being used. The modules are
Ethernet LAN (802.3), Token ring LAN (802.4), Token bus LAN (802.5).
?802.6 is distributed queue dual bus (DQDB) designed to be used in
MANs.

24.What is Protocol Data Unit?
The data unit in the LLC level is called the protocol data unit
(PDU).The PDU contains of four fields a destination service access
point (DSAP),a source service access point (SSAP),a control field
and an information field. DSAP, SSAP are addresses used by the LLC
to identify the protocol stacks on the receiving and sending machines
that are generating and using the data. The control field specifies
whether the PDU frame is a information frame (I - frame) or a
supervisory frame (S - frame) or a unnumbered frame (U - frame).

25.What are the different type of networking / internetworking
devices?
Repeater:
Also called a regenerator, it is an electronic device that operates
only at physical layer.It receives the signal in the network before
it becomes weak, regenerates the original bit pattern and puts the
refreshed copy back in to the link.
Bridges:
These operate both in the physical and data link layers of LANs of
same type.They divide a larger network in to smaller segments.They
contain logic that allow them to keep the traffic for each segment
separate and thus are repeaters that relay a frame only the side of
the segment containing the intended recipent and control congestion.
Routers:
They relay packets among multiple interconnected networks (i.e. LANs
of different type). They operate in the physical, data link and
network layers. They contain software that enable them to determine
which of the several possible paths is the best for a particular
transmission.
Gateways:
They relay packets among networks that have different protocols
(e.g. between a LAN and a WAN).They accept a packet formatted for
one protocol and convert it to a packet formatted for another
protocol before forwarding it. They operate in all seven layers of
the OSI model.
    
26.What is ICMP?
ICMP is Internet Control Message Protocol, a network layer protocol
of the TCP/IP suite used by hosts and gateways to send notification
of datagram problems back to the sender. It uses the echo test /
reply to test whether a destination is reachable and responding. It
also handles both control and error messages.

27.What are the data units at different layers of the TCP / IP
protocol suite?
The data unit created at the application layer is called a message,
at the transport layer the data unit created is called either a
segment or an user datagram, at the network layer the data unit
created is called the datagram, at the data link layer the datagram
is encapsulated in to a frame and finally transmitted as signals
along the transmission media.

28.What is difference between ARP and RARP?
The address resolution protocol (ARP) is used to associate the 32
bit IP address with the 48 bit physical address, used by a host or
a router to find the physical address of another host on its network
by sending a ARP query packet that includes the IP address of the
receiver.
The reverse address resolution protocol (RARP) allows a host to
discover its Internet address when it knows only its physical
address.

29.What is the minimum and maximum length of the header in the
TCP segment and IP datagram?
The header should have a minimum length of 20 bytes and can have
a maximum length of 60 bytes.  
                    
30.What is the range of addresses in the classes of internet
addresses?
Class A 0.0.0.0  - 127.255.255.255
Class B 128.0.0.0 - 191.255.255.255
Class C 192.0.0.0 - 223.255.255.255
Class D 224.0.0.0 -  239.255.255.255
Class E 240.0.0.0 - 247.255.255.255 

31.What is the difference between TFTP and FTP application layer
protocols?
The Trivial File Transfer Protocol (TFTP) allows a local host to
obtain files from a remote host but does not provide reliability or
security. It uses the fundamental packet delivery services offered
by UDP.
The File Transfer Protocol (FTP) is the standard mechanism provided
by TCP / IP for copying a file from one host to another.It uses the
services offer by TCP and so is reliable and secure.It establishes
two connections (virtual circuits) between the hosts,one for data
transfer and another for control information.

32.What are major types of networks and explain?
?Server-based network
?Peer-to-peer network
Peer-to-peer network, computers can act as both servers sharing
resources and as clients using the resources.
Server-based networks provide centralized control of network
resources and rely on server computers to provide security and
network administration

33.What are the important topologies for networks?
?BUS topology:
In this each computer is directly connected to primary network
cable in a single line.
Advantages:
Inexpensive,easy to install, simple to understand, easy to extend.

?STAR topology:
In this all computers are connected using a central hub.
Advantages:
Can be inexpensive, easy to install and reconfigure and easy to
trouble shoot physical problems.

?RING topology:
In this all computers are connected in loop.
Advantages:
All computers have equal access to network media, installation can
be simple,and signal does not degrade as much as in other topologies
because each computer regenerates it.

34.What is mesh network?
A network in which there are multiple network links between
computers to provide multiple paths for data to travel.

35.What is difference between baseband and broadband transmission?
In a baseband transmission, the entire bandwidth of the cable is
consumed by a single signal. In broadband transmission, signals are
sent on multiple frequencies, allowing multiple signals to be sent
simultaneously.

36.Explain 5-4-3 rule?
In a Ethernet network, between any two points on the network ,there
can be no more than five network segments or four repeaters, and of
those five segments only three of segments can be populated.

37.What MAU?
In token Ring , hub is called Multistation Access Unit(MAU).

38.What is the difference between routable and non- routable
protocols?
Routable protocols can work with a router and can be used to build l
arge networks. Non-Routable protocols are designed to work on small,
local networks and cannot be used with a router

39.Why should you care about the OSI Reference Model?
It provides a framework for discussing network operations and design.

40.What is logical link control?
One of two sublayers of the data link layer of OSI reference model,
as defined by the IEEE 802 standard. This sublayer is responsible
for maintaining the link between computers when they are sending data
across the physical network connection.

41.What is virtual channel?
Virtual channel is normally a connection from one source to one
destination, although multicast connections are also permitted.
The other name for virtual channel is virtual circuit.

42.What is virtual path?
Along any transmission path from a given source to a given
destination, a group of virtual circuits can be grouped together
into what is called path.

43.What is packet filter?
Packet filter is a standard router equipped with some extra
functionality. The extra functionality allows every incoming or
outgoing packet to be inspected. Packets meeting some criterion
are forwarded normally. Those that fail the test are dropped.

44.What is traffic shaping?
One of the main causes of congestion is that traffic is often busy.
If hosts could be made to transmit at a uniform rate, congestion
would be less common. Another open loop method to help manage
congestion is forcing the packet to be transmitted at a more
predictable rate. This is called traffic shaping.

45.What is multicast routing?
Sending a message to a group is called multicasting, and its routing
algorithm is called multicast routing.

46.What is region?
When hierarchical routing is used, the routers are divided into what
we will call regions, with each router knowing all the details about
how to route packets to destinations within its own region, but
knowing nothing about the internal structure of other regions.

47.What is silly window syndrome?
It is a problem that can ruin TCP performance. This problem occurs
when data are passed to the sending TCP entity in large blocks, but
an interactive application on the receiving side reads 1 byte at a
time.

48.What are Digrams and Trigrams?
The most common two letter combinations are called as digrams.
e.g. th, in, er, re and an. The most common three letter combinations
are called as trigrams. e.g. the, ing, and, and ion.

49.Expand IDEA.
IDEA stands for International Data Encryption Algorithm.

50.What is wide-mouth frog?
Wide-mouth frog is the simplest known key distribution center
(KDC) authentication protocol.

51.What is Mail Gateway?
It is a system that performs a protocol translation between
different electronic mail delivery protocols.

52.What is IGP (Interior Gateway Protocol)?
It is any routing protocol used within an autonomous system.

53.What is EGP (Exterior Gateway Protocol)?
It is the protocol the routers in neighboring autonomous systems
use to identify the set of networks that can be reached within or
via each autonomous system.

54.What is autonomous system?
It is a collection of routers under the control of a single
administrative authority and that uses a common Interior Gateway
Protocol.

55.What is BGP (Border Gateway Protocol)?
It is a protocol used to advertise the set of networks that can be
reached with in an autonomous system. BGP enables this information
to be shared with the autonomous system. This is newer than EGP
(Exterior Gateway Protocol).

56.What is Gateway-to-Gateway protocol?
It is a protocol formerly used to exchange routing information
between Internet core routers.

57.What is NVT (Network Virtual Terminal)?
It is a set of rules defining a very simple virtual terminal
interaction. The NVT is used in the start of a Telnet session.

58.What is a Multi-homed Host?
It is a host that has a multiple network interfaces and that
requires multiple IP addresses is called as a Multi-homed Host.

59.What is Kerberos?
It is an authentication service developed at the Massachusetts
Institute of Technology. Kerberos uses encryption to prevent
intruders from discovering passwords and gaining unauthorized
access to files.

60.What is OSPF?
It is an Internet routing protocol that scales well, can route
traffic along multiple paths, and uses knowledge of an Internet’s
topology to make accurate routing decisions.

61.What is Proxy ARP?
It is using a router to answer ARP requests. This will be done
when the originating host believes that a destination is local,
when in fact is lies beyond router.
62.What is SLIP (Serial Line Interface Protocol)?
It is a very simple protocol used for transmission of IP datagrams
across a serial line.

63.What is RIP (Routing Information Protocol)?
It is a simple protocol used to exchange information between the
routers.

64.What is source route?
It is as sequence of IP addresses identifying the route a datagram
 must follow. A source route may optionally be included in an IP
datagram header.