Interview Ques Frm DCCN

The Ques genrally asked from Data Communication & Computer Networks:

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

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.

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.

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

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

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.

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.

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.
What is terminal emulation, in which layer it comes
Telnet is also called as terminal emulation. It belongs to application layer.

What is frame relay, in which layer it comes?
Frame relay is a packet switching technology. It will operate in the data link layer.

What do you meant by “triple X” in Networks?
The function of PAD (Packet Assembler Disassembler) is described in a ******** 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”.

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

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

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

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.

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 *******ed 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.

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

What is passive topology?
When the computers 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.

What are the important topologies for networks?
BUS topology:
In this each computer s 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.

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

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