IRQ lines allow devices to send interrupt signals to the CPU. IRQ conflicts used to be common when adding devices but plug-and-play specifications have reduced manual configuration. DMA allows hardware subsystems to access memory independently of the CPU to transfer data faster. Modern computers use DMA for devices like hard drives, graphics cards, and sound cards. Firewalls provide security for private networks connected to the internet by allowing only authorized data to pass through based on administrator rules.

1. H/W & N/W Q & A
IRQ :
Abbreviation of interrupt request line, and pronounced I-R-Q. IRQs arehardware lines over which devices can send interrupt signals to
themicroprocessor. When you add a new device to a PC, you sometimes need to set its IRQ number by setting a DIP switch. This specifies which
interrupt line the device may use. IRQ conflicts used to be a common problem when adding expansion boards, but the Plug-and-Play specification has
removed this headache in most cases. In an IBM PC compatible personal computer, an interrupt request (or IRQ) is a hardware signal sent to the
processor that temporarily stops a running program and allows a special program, an interrupt handler, to run instead. Interrupts are used to handle such
events as data receipt from a modem or network, or a key press or mouse movement. The interrupt request level (IRQL) is the priority of an interrupt
request. When working with personal computer hardware, installing and removing devices, the system relies on interrupt requests. There are default
settings that are configured in the system BIOS and recognized by the operating system. These default settings can be altered by advanced users.
Modern plug and play technology has not only reduced the need for concern for these settings, but has virtually eliminated manual configuration.
DMA:
When working with personal computer hardware, installing and removing devices, the system relies on interrupt requests. There are default settings that
are configured in the system BIOS and recognized by the operating system. These default settings can be altered by advanced users. Modern plug and
play technology has not only reduced the need for concern for these settings, but has virtually eliminated manual configuration . Some expansion
boards, such as CD-ROM cards, are capable of accessing the computer's DMA channel. When you install the board, you must specify which DMA
channel is to be used, which sometimes involves setting a jumperor DIP switch.
DMA Direct memory access (DMA) is a feature of modern computers that allows certain hardware subsystems within the computer to access
system memory independently of the central processing unit (CPU).
Without DMA, when the CPU is using programmed input/output, it is typically fully occupied for the entire duration of the read or write operation, and is
thus unavailable to perform other work. With DMA, the CPU initiates the transfer, does other operations while the transfer is in progress, and receives
an interrupt from the DMA controller when the operation is done. This feature is useful any time the CPU cannot keep up with the rate of data transfer, or
where the CPU needs to perform useful work while waiting for a relatively slow I/O data transfer. Many hardware systems use DMA, including disk
drive controllers, graphics cards, network cards and sound cards. DMA is also used for intra-chip data transfer in multi-core processors. Computers that
have DMA channels can transfer data to and from devices with much less CPU overhead than computers without a DMA channel. Similarly, a
processing element inside a multi-core processor can transfer data to and from its local memory without occupying its processor time, allowing
computation and data transfer to proceed in parallel
A DMA controller can generate addresses and initiate memory read or write cycles. It contains several registers that can be written and read by the
CPU. These include a memory address register, a byte count register, and one or more control registers. The control registers specify the I/O port to
use, the direction of the transfer (reading from the I/O device or writing to the I/O device), the transfer unit (byte at a time or word at a time), and the
[1]
number of bytes to transfer in one burst.
To carry out an input, output or memory-to-memory operation, the host processor initializes the DMA controller with a count of the number of words to
transfer, and the memory address to use. The CPU then sends commands to a peripheral device to initiate transfer of data. The DMA controller then
provides addresses and read/write control lines to the system memory. Each time a word of data is ready to be transferred between the peripheral
device and memory, the DMA controller increments its internal address register until the full block of data is transferred.
DMA transfers can either occur one word at a time or all at once in burst mode. If they occur a word at a time, this can allow the CPU to access memory
on alternate bus cycles - this is calledcycle stealing since the DMA controller and CPU contend for memory access. In burst mode DMA, the CPU can be
[2]
put on hold while the DMA transfer occurs and a full block of possibly hundreds or thousands of words can be moved. When memory cycles are much
faster than processor cycles, an interleaved DMA cycle is possible, where the DMA controller uses memory while the CPU cannot.
In a bus mastering system, both the CPU and peripherals can be granted control of the memory bus. Where a peripheral can become bus master, it can
directly write to system memory without involvement of the CPU, providing memory address and control signals as required. Some measure must be
provided to put the processor into a hold condition so that bus contention does not occur.
What is firewall?
A firewall is a hardware or software installed to provide security to the private networks connected to the internet. They can be implemented in both
hardware and software, or a combination of both. All data entering or leaving the Intranet passes through the firewall which allows only the data meeting
the administrators’ rules to pass through it.
What are the types of firewalls?
Packet Filtering Firewall : This type of Firewall detects packets and block unnecessary packets and makes network traffic release.

2. Screening Router Firewalls : It's a software base firewall available in Router provides only light filtering.
Computer-based Firewall : It's a firewall stored in server with an existing Operating System like Windows and UNIX.
Hardware base Firewall : Its device like box allows strong security from public network. Mostly used by big networks.
Proxy Server : Proxy server allows all clients to access Internet with different access limits. Proxy server has its own firewall which filters the all packet
from web server.
What is Data encryption?
Data encryption ensures data safety and very important for confidential or critical data. It protect data from being read, altered or forged while
transmission.
What is Ethernet technology?
Ethernet technology is a high speed broadcast bus technology. In this type, all the station shares a single ether channel and receives every single
transmitted signal.
Explain token ring technology.
In this technology, all the devices are arranged in a circle. A token moves around the circular network. A device waits for the token before it sends its
frame. Once it receives token, it initiates transmission of its frame.
What is the difference between TFTP and FTP application layer protocols?
The differences between FTP and TFTP : FTP is connection oriented, where as TFTP is not. TFTP uses error checking and flow control, where as TFTP
does not cause error checking. FTP uses TCP as transport protocol, where as TFTP uses UDP as transport protocol. Authentication is mandatory in
FTP, where as authentication is not needed in TFTP. Just getting and putting application effectively is the design concern of TFTP, where as FTP
provides more control and data connection aspects.
Difference between bit rate and baud rate.
The differences between bit rate and baud rate : Bit rate is measured as number of data bits transmitted / second in communication channel.
Baud rate is measured as number of times a signal state is changed in a communication channel. One change of state can transmit one bit or less than
one bit which depends on modulation technique used. The bit and baud rate have the connection bps = baud / second x the number of bits / per baud
What are NETBIOS and NETBEUI?
Network Basic Input Output System provides session layer of OSI model related services which allows the applications on different computers for
communicating over a LAN. NetBIOS runs over TCP/IP through NetBIOS over TCP/IP (NBT) protocol. This process results in every computer in the
network with NetBIOS name and an IP address that corresponds to a host name.
NetBIOS Extended User Interface is an extended version of NetBIOS. It is a program that allows computers to communicate within a local area network.
NetBEUI forms the frame format which was not a specification of NetBIOS. NetBEUI is the best choice for performing communication within a LAN.
Difference between ARP and RARP.
Address Resolution Protocol is utilized for mapping IP network address to the hardware address that uses data link protocol. Reverse Address
Resolution Protocol is a protocol using which a physical machine in a LAN could request to find its IP address from ARP table or cache from a gateway
server. IP address of destination to physical address conversion is done by ARP, by broadcasting in LAN. Physical address of source to IP address
conversion is done by RARP. ARP associates 32 bit IP address with 48 bit physical address. Allowing a host to discover its internet address after
knowing only its physical address is done by RARP.
What is the difference between POP3 and IMAP Mail Server?
POP3 : All emails are to be downloaded again if used by another desktop PC for checking the email.
May leads to confusion if used for checking email in office and at home pc.
Attachments will be down loaded into desktop while the ‘check new email’ process is in progress.
Mailboxes can be created only on desktop and one mail box exists on the server.
IMAP : There is no need for downloading all email while using another desktop PC for checking email.
Unread mail identification is easier.
Message downloading is possible only when opened for display from its contents.
Multiple mailboxes creation is possible on the desktop PC and also on the server.

3. What is a Transaction server?
A transaction server is software that is used for implementing transactions. A transaction comprises of multiple steps that must automatically be
completed. A transaction server consists of a safety providing system and environment where the programs can be written for making use of the
features of guaranteed transactions
Describe the concept of DHCP.
Dynamic Host Configuration Protocol is one of the communication protocol which lets the network administrators manage and assignment of internet
protocol addresses of an enterprise automatically. The IP addresses are assigned uniquely for a specific computer when connected to the internet. In
the absence of DHCP, the ip addresses are to be entered manually when the computer system moves to a new location on the network
Explain the difference between Domain and Workgroup.
In a workgroup : -All computer systems are peers and no computer can not control another computer -Every computer sets user accounts. To make
use of any system, one must have an account on that computer. -The numbers of computer systems are limited to ten or twenty.
-Every computer must be part of the same LAN or subnet.
In a domain : -There will be one or computers are the servers. The security and permissions are controlled by network administrators.
-A user with an account on the domain can log onto any computer system, without having the account on that computer.
-The number of computer systems can be hundreds or thousands of computers.
-The computers can be connected to different local networks
Explain the difference between baseband and broadband.
Baseband:
Digital signals are used
Frequency division multiplexing is not possible
Baseband is bi-directional transmission
Short distance signal travelling
Entire bandwidth of the cable is consumed by a single signal in a baseband transmission.
Broadband:
Analog signals are used
Transmission of data is unidirectional
Signal travelling distance is long
Frequency division multiplexing is possible
The signals are sent on multiple frequencies and allow all the multiple signals are sent simultaneously in broadband transmission.
What is RAID?
The core concept of Redundant Array of Independent Disks is two or more drives are combined together for improvement of performance and fault
tolerance. Improved reliability and large data volumes are offered by combining two or more drives. Data spreads across many disks by RAID and
operating system treats this array as a single disk.
Difference between terminal services and remote desktop.
Terminal service is a client-server environment. In this environment, one computer acts as a server which receives requests from the clients. The
servers can serve in two modes – Application Server mode and Remote Administration mode. The applications on the server are accessed by the
former and the later is utilized for remote administration.
Remote desktop simulates the terminal services of Remote Administration Mode. The difference is there is no client-server environment. Remote
desktop is simply used for the purpose of sharing one computer’s desktop in a network
Explain the problems associated with operating a switched LAN.
The following are the problems in brief in a switched LAN.
Packet sniffing – the ports need to be picked by one and replicate them for monitoring port. All the interfaces and all packets are not segregates actively
in the LAN. Replication of packets is seriously monitors ports which causes inactive watch on all ports without serious switch resource degradation
How do we monitor data in Sockets?
Socket activities are monitored by IP and Socket Monitor tool. Socket monitor is designed for programming using IP and Sockets. Socket monitor
persists and display the socket API calls which are made by the application, like, accept, connect etc. The socket will remain open to handle the data
streamlined to and from terminals.
What are Passive and Active FTPs?

4. Active FTP: A Client connects from a random unprivileged port to the FTP server port 21, using Active FTP. Later the client listens to the port N+1 and
sends the FTP command port N+1 to the FTP server. Then the server connects back to the client’s specified data port from its local data port, 20.
Passive FTP: The client initiates the connections to the server and solving the problem of firewalls filtering the incoming data port connection to the
client from the server is done in passive FTP mode. The client opens two random unprivileged ports locally on opening an FTP connection. The server is
contacted on the first port, 21. Instead issuing a PORT command and allowing the server for connecting back to its data port, the command PASV is
issued by the client. The server opens a random unprivileged port and sends the PORT P command back to the client. The connection from port N+1 to
port P on server to transfer data is initiated by the client.
What is Maximum Transmission Unit (MTU)?
Maximum Transmission Unit is the size of a layer of communication protocols of the largest protocol data unit which it can pass onwards. In association
with a communications interface such as NIC, serial port etc., MTU parameters usually appears. The fixation of MTU can be done by standards like
Ethernet or decided at the time of connection (usually in the case of point-to-point serial links). Greater efficiency is brought by higher MTU as more user
data is carried by each packet while protocol overheads remain fixed. Bulk protocol throughput improvement is referred as high efficiency. However,
large packets can occupy a link that is slow for some time, which causes greater delays for the following packets and increases lag and minimum latency
What is the Ethernet technology?
Ethernet is a LAN architecture, which was developed by Xerox Corporation in cooperation with DEC and Intel. Bus or star topology is used by Ethernet
and supports 10 MBPS data transfer rate. Ethernet specification is the basis for the IEEE 802.3 standard, which specifies physical and software layers.
CSMA/CD access method is used by Ethernet for handling simultaneous demands. Ethernet is a popular LAN standard most widely implemented.
A new version by name 100Base-T or Fast Ethernet will support data transfer rates of 100MBPS. Another newest version, Gigabit Ethernet supports 1
GBPS data transfer rate
What is Ethernet Access Scheme?
Ethernet Access Scheme is called Carrier Sense Multiple Access with Collision Detect (CSMA/CD). The presence of wave in the network is determined
by accessing Ethernet by multiple systems using CSMA. CSMA listens for a message is being transmitted when the interface of has a packet to
transmit. When no transmission is sensed, transmission is started by the host. Each transmission is limited in duration as there is maximum packet size.
Multiple systems can access Ethernet simultaneously and each machine determines whether the network is idle by sensing whether the wave is
present.
What is the token ring technology?
Token ring is a LAN technology that resides at the Data Link Layer of the OSI model. Special three-byte frame is used to travels around the ring. The
token ring frames travel around the loop completely. Token Ring technology was developed by IBM. Token Ring and IEEE 802.5 networks are
compatible, even though minor differences existed in specifications. Token Ring network specifies a star, with all end stations attached to a device called
a multi station access unit. IEEE 802.5 virtually implements the base as a star topology
What is the network segmentation? What is Collision Domain?
Network segment is a portion in a computer network where communication among every device is done using the same physical layer. The networking
segmentation can be either logical or physical.
A collision domain is a logical network segment. In this segment, data packets can collide to each other. Ethernet is the common protocol used when
referring to a collision domain. Collision segment is a group of Ethernet devices in LAN, which runs on CSMA/CD, and is connected through repeaters
for the purpose of competing network access. As data can be transmitted through one device in the same collision domain, the other devices simply
listens in the network in order to avoid data collisions. Carrier Sense Multiple Access/Collision Detection (CDMA/CD) is an efficient way for avoiding
network collisions
Explain the functionality of a hub, a bridge and switch.
Hub: Hub is a device in a network, Data packet from one port is sent to all other ports in a network. The data packet passes through a hub. Hub
transmits the data packet to the destination. Hubs are typically used on small networks where the data transmission is never high.
Bridge: A bridge is similar to hub but one step ahead. It looks for the destination of the packet before transmission of data. A bridge has only one
incoming and one outgoing port. A bridge is used to decide if the message should continue. Bridges are typically used for separating parts of the
network which need not communicate regularly, but obviously needs to be connected.
Switch: A switch is similar to bridge but one step ahead. A packet is determined to which computer the packet is sent. Efficiency is increased in this way
of data packet transmission only to the destined computers but not all. Large networks use switches to connect computers within in the same subnet.
Explain the functionality of a Router.
A packet is like a device or in some cases, a software. A router determines the next network point to which the data packet should be sent towards its
destination. Router is connected to at least 2 networks and determines the way for sending every information packet based on its current understanding

5. of the network state. A router is treated as part of a network switch. The router bounces the packet back, if the packet is going to the LAN. Otherwise,
the packet will be toured based on the routing table. It is usually means out to the internet in a home network.
Explain the functionality of a Gateway.
- A set of data rates are advertised by any gateway server. Some streams can be blocked by a gateway server from reaching the SP, in case the SP is
opted for this service.
- The gateway is associated with a multicast (non-gateway) channel. The gateway needs to listen to the non-gateway channel, and any other SP that is
currently serviced by it.
- A pass-through service is offered by the gateway server in the case of non-crucial data rate control, and a tunnel is established by it and provides the
forwarding service.
What is a MAC address?
A Media Access Control address is a unique identifier that is assigned to the network adapters or NICs by the manufacturers for the purpose of
identification and used in the Media Access Control protocol sub layer. It is a 12 digit hexadecimal number. A MAC address usually encodes the
registered identification of the manufacturer, if the address is assigned by the manufacturer. It some times also called as Ethernet Hardware Address /
physical address/ adapter address.
Explain Spanning-Tree protocols.
Spanning Trees are a standard technique implemented in LAN connections. On a mesh topology, a set of spanning tree algorithms were developed for
prevention of redundant transmission of data along intermediate hops between a source and a destination host. In the absence of spanning trees, a
mesh network is flooded and rendered unusable by messages by circulating within a loop that is infinite, between hosts. An algorithm used in
transparent bridges which determines the best path from source to destination to avoid bridge loops.
At the time of STP initialization in a network, its first action is to utilize the Spanning Tree Algorithm for selection of a root bridge and a root port. The root
bridge is the ne which has lowest-value bridge identifier. All the switches on the network use Bridge Protocol Data Units to broadcast the bridge IDs to
the other switches in that network. Soon after selection of the root bridge, determination of the root ports on all other bridges is done.
ATM technology vs. Ethernet technology.
Ethernet technology:
- Delivers high bandwidth to high-speed server connections.
- Familiar technology and relatively inexpensive
- The traffic to deliver an effective Class of service cannot be prioritized
- It limits jitter to deliver Quality of Service can not be delivered
ATM technology:
- Designed for the purpose of integrating telephony, data, voice and video traffic on a single network for both LANs and WANs
- ATM technology accommodates a variety of different bit rates.
- Real-time traffic is supported by limiting jitter and latency across the networks.
- End-to-End congestion and flow control are provided by using indictors which are able to inform a transmitting station for slowing down its transmission
due to a congested path.
- It is high cost compared to Ethernet.
What is the use of VPN technology?
A Virtual Private Network is a private data network which is used for public telecommunication infrastructure, privacy maintenance through the use of a
tunneling protocol and security procedures. A VPN can be used by private community / company with owned or leased lines which can only be used by
one company. The purpose of VPN is to provide the facilities and capabilities to the company as private leased lines with much lower cost with the help
of public infrastructure. Because of these advantages, companies are looking to use VPNs for both extranets and wide-area intranets
Public vs. Private IP addresses.
Private IP Address: An IP address is private if the number is within a specific range which is reserved for private uses by Internet Standards group. The
range is 10.0.0.0 through 10.255.255.255.
Public IP address: With a pubic IP address, other users can know about and access one’s computer system / server, like a website.
MAC address vs. IP address.
MAC Address: A MAC address is a digital name of interface. Each and every network interface has a unique MAC address with unique ones. It is a
hexadecimal number of 12 or 16 digits length. These addresses uniquely identify Ethernet network cards. Although all the computers in the network use
Ethernet, not all connections are made over Ethernet.

6. IP Address: An address that is assigned for connecting the PC or Laptop to the router or to the default gateway of network. Computer systems on the
same local subnet, share part of their IP addresses. Like 192.168.6.121 and 192.168.6.130.
What is the use of Address Resolution Protocol?
Address Resolution Protocol is used for networks that support hardware broadcast. An ARP will not work on x.25 network. The ARP’s responsibility is to
convert the higher-level protocol addresses to physical network addresses. ARP functionality is broadcasting a packet to the hosts that are attached to
an Ethernet. The packet has IP address of the sender. The target machine identifies and recognizes that the IP address in the data packet matches its
own, and returns an answer.
What is the Reverse Address Resolution Protocol (RARP)?
Reverse Address Resolution Protocol (RARP) is a link layer networking protocol that is used by a host computer system which obtain its IP address
once it has available its link-layer address, like Ethernet address. RARP needs one or more servers to host for maintaining a database or mappings from
link layer address to protocol address. Serving only IP address was the limitation of RARP. An RARP can be used at startup of a diskless machine for
finding its IP address.
What is the TTL (Time to Live)? Why is it required?
TTL is a value in data packet of Internet Protocol. It communicates to the network router whether or not the packet should be in the network for too long
or discarded. Usually, data packets might not be transmitted to their intended destination within a stipulated period of time. The TTL value is set by a
system default value which is an 8-bit binary digit field in the header of the packet. The purpose of TTL is, it would specify certain time limit in seconds,
for transmitting the packet header. When the time is exhausted, the packet would be discarded. Each router receives the subtracts count, when the
packet is discarded, and when it becomes zero, the router detects the discarded packets and sends a message, Internet Control Message Protocol
message back to the originating host.
Explain the use of Internet Control Message Protocol (ICMP).
Internet Control Message Protocol is one of the important protocols in the Internet Protocol suite. It is mainly used in operating system of networked
computers, for the purpose of sending error messages, for example, a requested service is unavailable or the host could not be reached. It is not
directed by the network applications. ICMPs are utilized by routers, hosts for communicating the updates or error information to other routers.
Explain the services provided by IP (Internet Protocol) - Addressing, Fragmentation, Packet timeouts and options.
1. Addressing: For the purpose of delivering datagram packets, IP needs to know about the address of the destination. By including the host addressing,
this task is carried out by IP. As IP operates in an internet, its systems are designed to accept the addressing of devices which are unique.
2. Fragmenting: The datagram packets are sent to the data link layer for the purpose of transmission on the network. The physical network frame size
that uses IP may be different. To resolve this, IP fragments the datagram into certain pieces. So that, each piece can be carried on the network. The
receiving systems use these pieces and reassemble the whole IP datagram again.
3. Packet timeouts: A timeout packet is the time for waiting next instruction from the command station. If the command is not sent by the station, it shuts
down
Explain the classes of IP address.
IP addresses are organized into classes. For convenience of humans, IP addresses are expressed in the decimal format. Every number in each class is
represented as binary to computers.
The four numbers in an IP address are known as ‘octets’. Each of them has eight bit positions. The octets are divided into two sections: Net and Host.
The first octet represents Net for identifying the network and the Host contains the last octet. There are five IP classes.
Class A: The class A is used for very large networks. There are 1 to 126 are part of this class. That means there are 126 Class A networks. Class A
networks accounts for half of the total available IP addresses.
Class B: It is used for medium size networks. The IP address with a first octet from 128 to 191 is part of this class. Class B networks have a first bit
value of 1 and a second bit value of 0 in the first octet.
Class C: Class C is used for small to middle size networks. IP address with a first octet starts from 102-223. Class C networks have a first bit value of 1,
second bit value of 1 and a third bit value of 0 in the first octet.
Class D: It has first, second and third bit value as 1 and the fourth bit as 0. The other 28 bits are used for identifying the group of computers which is
intended for multicast messages.
Class E: Class E is used for identification purpose. The four bits value is 1. The other 28 bits are used for identifying the group of computers which is
intended for multicast messages.
Define Broadcast, Unicast and Multicast.

7. Unicast: A term used in communication to describe a piece of information to send from one point to another. There are only sender and receiver. All
LANs support unicast transfer mode and most applications that employ TCP transport protocol uses unicast messaging.
Broadcast: A term used for describing communication that is sent a piece of information from one point to all other points. There is one sender and
multiple receivers. All LANs support broadcast transmission.
Multicast: A term described in communicating a piece of information sent from one or more points to a set of other points. The senders and receivers
are one or mor
What is Network Mask?
A network mask is used for determination of what subnet an IP address belongs to. An IP address has network address and the host address. The first
two numbers represents the network address and the second two numbers represents the host of the network.
What are data encoding and modulation? How do they differ from one another?
Data Encoding: A technique that requires the polar change in the line level after each bit. To gain the control circuitry that ensures consistent level
discrimination, a level is used. The encoding is involved in inverting the polarity of alternating bits, filtering al odd harmonics, transmitting and receiving
the waveform, and decoding the demodulated wave form. This is done by comparing absolute value of the halt-cycle peak-to-peak voltage gain to a
predetermined table.
Modulation: Character varying process of a periodic wave with external signals is known as modulation. Information bearing signal over distances is sent
by modulation.
Differences: Encoding is the way in which the data is represented and modulation is to alter the characteristic of a message signal.
Explain What is Packet Switched, Cell Switched and Circuit Switched Technology.
Packet Switching: A method of transmitting data group with the concern of content, type or structure into suitably-sized blocks. Data packets are
shared in a shared network which route each packet independently from others. The core objective of packet switching is to optimize the usage of
available link capacity and robustness of communication improvement.
Cell Switching: The process of packet switching is resembles in cell switching. The difference is the packets length is fixed. ATM technology is popular
for packet switching.
Circuit Switching: Resembles the same process that of cell switching and difference is the process of setting up the circuit itself is the part of the
process. Between two parties, the channel is setup, through which the data is transmitted and the channel is torn down soon after the data transmission.
Circuit switching technology is familiar to use in CCNA candidates in ISDN.
Explain what POP3 is. How does is differ from POP?
POP3 is a protocol that is used for downloading email from an ISP to the recipient mail program. POP3 allows mail retrieval by a workstation for
receiving mail which is held by the server. Among stations, POP3 transmissions appear as data messages.
POP was designed for the purpose of supporting ‘offline’ mail processing. Mail is delivered to a server. A PC uses invokes the ail client program
periodically which connects to the server and all pending mails is delivered to users own machine.
Why we need IP address over Mac address?
IP address is a logical address of a computer system, where as MAC address is the physical address of a computer system that is usually persisted in
network card.
The data link layer creates frames by writing MAC address in to the header of the message. This process ensures the exact destination receives the
message.
IP address is used for transferring information over the networks, where as MAC address is used for information distribution.
What is a hardware loopback plug?
A hardware loopback pug is a simple device for redirecting the outgoing transmissions from a system directly back into it. They are used in conjunction
with software that diagnoses transmission problems. Loop back plugs are available both as serial ports and parallel ports. A hardware loop back plug
loops the outgoing data signal wires back into the system on the signal line which has incoming signal
What do you mean by Twisted-pair Cabling?
A twisted pair is a cable in which the cables are twisted at regular distances. Twisted pairs are used for transferring signals with high frequency, instead
of coax cable. The twisted pair is a balanced system, which anti phase signals are being transmitted on a pair of wires. Certain sophisticated twisted
pairs allow the transferring of certain signals, like audio and 2 video channels.

8. What is the use of Kerberos protocol?
Kerberos is an authentication protocol in a compute network that makes the nodes communicates over a non-secure network for providing their
identification to one another in most secure manner. The protocol design is aimed at a client-server model, which provides the mutual authentication –
the identification of both users and the client verifies each other’s identity. The messages that are handled by Kerberos protocol are protected against
‘eavesdropping’ and ‘replay attacks’. Kerberos was built on symmetric key cryptography and it needs a trusted third party
Difference between bit rate and baud rate.
The differences between bit rate and baud rate:
Bit rate is measured as number of data bits transmitted / second in communication channel.
Baud rate is measured as number of times a signal state is changed in a communication channel.
One change of state can transmit one bit or less than one bit which depends on modulation technique used. The bit and baud rate have the connection:
bps = baud / second x the number of bits / per baud
What are NETBIOS and NETBEUI?
Network Basic Input Output System provides session layer of OSI model related services which allows the applications on different computers for
communicating over a LAN. NetBIOS runs over TCP/IP through NetBIOS over TCP/IP (NBT) protocol. This process results in every computer in the
network with NetBIOS name and an IP address that corresponds to a host name.
NetBIOS Extended User Interface is an extended version of NetBIOS. It is a program that allows computers to communicate within a local area network.
NetBEUI forms the frame format which was not a specification of NetBIOS. NetBEUI is the best choice for performing communication within a LAN.
Difference between ARP and RARP.
The differences between ARP and RARP:
Address Resolution Protocol is utilized for mapping IP network address to the hardware address that uses data link protocol.
Reverse Address Resolution Protocol is a protocol using which a physical machine in a LAN could request to find its IP address from ARP table or cache
from a gateway server.
IP address of destination to physical address conversion is done by ARP, by broadcasting in LAN.
Physical address of source to IP address conversion is done by RARP.
ARP associates 32 bit IP address with 48 bit physical address.
Allowing a host to discover its internet address after knowing only its physical address is done by RARP
S.N.College , Gadhinglaj.