Top Interview Questions & Answers on Computer Networking
- Posted by: BlogWriter
- Category: Interview_Questions
#1 What are the two types of transmission technology available?
The two types of transmission technology are – broadcast and point-to-point.
#2 What is a ‘subnet’?
A ‘subnet’ is a generic term for a section of a large network, usually separated by a bridge or a router.
#3 What is DNS?
The Domain Name System (DNS) is a central part of the Internet, providing a way to match names (a website you’re seeking) to numbers (the address for the website). Anything connected to the Internet – laptops, tablets, mobile phones, and websites – has an Internet Protocol (IP) address made up of numbers.
#4 Explain ‘hidden shares’.
A hidden or an administrative share is a network share that is not visible when viewing another computer’s shares.
#5 How many layers are there in the OSI model? Name them
There are 7 layers – physical, data link, network, transport, session, presentation, and application.
#6 What is a ‘client’ and ‘server’ in a network?
Clients and servers are separate logical entities that work together over a network to accomplish a task.
#7 What are the different ways to exchange data?
#8 What is a ‘frame relay’ and in which layer does it operate?
A frame relay is a packet-switching technology. It operates in the data link layer.
#9 What is a MAC address?
A MAC (Media Access Control) address is the 48-bit hardware address of a LAN card and is usually stored in the ROM of the network adapter card and is unique.
#10 What are the perquisites to configure a server?
- LAN card should be connected
- Root (partition on which window is installed) should be in NTFS format
- Server should be configured with a static IP address
#11 What is ‘beaconing’?
Beaconing is the process that allows a network to self-repair networks problems.
#12 Differentiate between ‘attenuation’, ‘distortion’, and ‘noise’.
When a signal travels through a medium, it loses some of its energy due to the resistance of the medium. This loss of energy is called attenuation.
When a signal travels through a medium from one point to another, it may change the form or shape of the signal. This is known as distortion.
Noise is unwanted electrical or electromagnetic energy that degrades the quality of signals and data.
#13 What is an IP address?
An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication.
#14 Differentiate between a ‘bit rate’ and ‘baud rate’.
A 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 the no. of bits represented by each signal shift.
#15 What is ‘bandwidth’?
The limited range of frequency of signals that a line can carry is called the bandwidth.
#16 What is Project 802?
It is a project started by IEEE to set standards to enable intercommunication between equipment from a variety of manufacturers.
#17 What is ICMP?
ICMP (Internet Control Message Protocol) is a network layer protocol of the TCP/IP suite used by hosts and gateways to send notification of datagram problems back to the sender.
#18 What are the major types of networks?<
- Server-based network
- Peer-to-peer network
#19 What are the important topologies for networks?
There are three important topologies – Star, Bus and Ring.
#20 Differentiate between static IP addressing and dynamic IP addressing.
In static IP addressing, a computer (or another device) is configured to always use the same IP address, whereas in dynamic IP addressing, the IP address can change periodically and is managed by a centralised network service.
#21 What is a Link?
A link refers to the connectivity between two devices. It includes the type of cables and protocols used in order for one device to be able to communicate with the other.
#22 What is backbone network? Explain different types of backbone network.
The word backbone means the most important part of a system which provides the core support for the rest of the system. Like the backbone of the human body that holds and balances all the body parts together, the same holds true for networks. A backbone network is defined as a network containing a high capacity connectivity infrastructure that forms the main link or backbone to the different parts of the network.
Types of Backbone Networks:-
Serial backbone is the most simple of all backbone architecture and consists of two or more connected devices or nodes. They are linked to each other via a single cable in series, connecting to an extension to the network. Figure 1 demonstrates this Serial backbone architecture.
The Serial backbone is rarely used for enterprise level network topologies because of its high susceptibility to faults and system downtime.
The Distributed backbone network comprises of a hierarchical formation of devices. Devices which are adaptable to multiple connectivity (connect one or more devices) are used to connect devices in hierarchy. Multiple devices are connected to switches for example which forms the intermediary devices connecting to the backbone router and gateway devices seen in Figure
The distributed backbone network, unlike the serial backbone network, is well suited for enterprise wide connectivity. Expanding and troubleshooting the network is simple.
The Collapsed Backbone network makes use of a single but high specification router that serves as the actual backbone or central connection that supports the rest of the network. As the backbone, it is characterized by high computational power to adequately handle the traffic from various networks.
This type of backbone topology is mainly applicable in situation where two different types of sub networks need to be connected and managed effectively.
#23 What is point to point link?
It refers to a direct connection between two computers on a network. A point to point connection does not need any other network devices other than connecting a cable to the NIC cards of both computers.
#24 What is anonymous FTP?
A method for downloading public files using the File Transfer Protocol (FTP). Anonymous FTP is called anonymous because you don’t need to identify yourself before accessing files. In general, you enter the word anonymous or ftp when the host prompts you for a username; you can enter anything for the password, such as your e-mail address or simply the word “guest”. In many cases, when you access an anonymous FTP site, you won’t even be prompted for your name and password.
#25 What is subnet mask?
A subnet mask is combined with an IP address in order to identify two parts: the extended network address and the host address. Like an IP address, a subnet mask is made up of 32 bits.
#26 What is the maximum length allowed for a UTP cable?
A single segment of UTP cable has an allowable length of 90 to 100 meters. This limitation can be overcome by using repeaters and switches.
#27 What is data encapsulation?
The term “encapsulation” is used to describe a process of adding headers and trailers around some data. For example, when you send an email using your favorite email program (like Outlook or Thunderbird) that email is sent from the Application layer to the Transport layer. The Transport layer encapsulates the data and adds its own header (with its own information, such as which port will be used) and passes the data to the Internet layer, which again encapsulates the received data and adds its own header, usually with information about the source and destination IP addresses. The Internet layer than passes the data to the Network Access layer. This layer is the only layer that adds both a header and a trailer. The data is then sent through a physical network link.
#28 Describe Network Topology
A network topology is the pattern in which nodes (i.e., computers, printers, routers or other devices) are connected to a local area network (LAN) or other network via links (e.g., twisted pair copper wire cable or optical fiber cable).
#29 Types of Network Topology
Network Topology is the schematic description of a network arrangement, connecting various nodes(sender and receiver) through lines of connection.
Bus topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called Linear Bus topology.
Features of Bus Topology
- It transmits data only in one direction.
- Every device is connected to a single cable
Advantages of Bus Topology
- It is cost effective.
- Cable required is least compared to other network topology.
- Used in small networks.
Disadvantages of Bus Topology
- Cables fails then whole network fails.
- If network traffic is heavy or nodes are more the performance of the network decreases.
- Cable has a limited length.
It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbors for each device.
Features of Ring Topology
- A number of repeaters are used for Ring topology with large number of nodes, because if someone wants to send some data to the last node in the ring topology with 100 nodes, then the data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data loss repeaters are used in the network.
- The transmission is unidirectional, but it can be made bidirectional by having 2 connections between each Network Node, it is called Dual Ring Topology.
- In Dual Ring Topology, two ring networks are formed, and data flow is in opposite direction in them. Also, if one ring fails, the second ring can act as a backup, to keep the network up.
Advantages of Ring Topology
- Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data.
- Cheap to install and expand
Disadvantages of Ring Topology
- Troubleshooting is difficult in ring topology.
- Adding or deleting the computers disturbs the network activity.
- Failure of one computer disturbs the whole network.
In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.
Features of Star Topology
- Every node has its own dedicated connection to the hub.
- Hub acts as a repeater for data flow.
- Can be used with twisted pair, Optical Fiber or coaxial cable.
Advantages of Star Topology
- Fast performance with few nodes and low network traffic.
- Hub can be upgraded easily.
- Easy to troubleshoot.
Disadvantages of Star Topology
- Cost of installation is high.
- Expensive to use.
- If the hub fails then the whole network is stopped because all the nodes depend on the hub.
It is a point-to-point connection to other nodes or devices. All the network nodes are connected to each other. Mesh has n(n-1)/2 physical channels to link n devices.
There are two techniques to transmit data over the Mesh topology, they are :
MESH Topology: Routing
In routing, the nodes have a routing logic, as per the network requirements. Like routing logic to direct the data to reach the destination using the shortest distance. Or, routing logic which has information about the broken links, and it avoids those nodes etc. We can even have routing logic, to re-configure the failed nodes.
MESH Topology: Flooding
In flooding, the same data is transmitted to all the network nodes, hence no routing logic is required. The network is robust, and the its very unlikely to lose the data. But it leads to unwanted load over the network.
Types of Mesh Topology
- Partial Mesh Topology: In this topology some of the systems are connected in the same fashion as mesh topology but some devices are only connected to two or three devices.
- Full Mesh Topology: Each and every nodes or devices are connected to each other.
Features of Mesh Topology
- Fully connected.
- Not flexible.
Advantages of Mesh Topology
- Each connection can carry its own data load.
- It is robust.
- Fault is diagnosed easily..
Disadvantages of Mesh Topology
- Installation and configuration is difficult.
- Cabling cost is more.
- Bulk wiring is required.
It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.
Features of Tree Topology
- Ideal if workstations are located in groups.
- Used in Wide Area Network.
Advantages of Tree Topology
- Extension of bus and star topologies.
- Expansion of nodes is possible and easy.
- Easily managed and maintained.
Disadvantages of Tree Topology
- Heavily cabled.
- If more nodes are added maintenance is difficult.
It is two different types of topologies which is a mixture of two or more topologies. For example if in an office in one department ring topology is used and in another star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology).
Features of Hybrid Topology
- It is a combination of two or topologies
- Inherits the advantages and disadvantages of the topologies included
Advantages of Hybrid Topology
- Reliable as Error detecting and trouble shooting is easy.
- Scalable as size can be increased easily.
Disadvantages of Hybrid Topology
- Complex in design.
#30 What is VPN?
VPN means Virtual Private Network, a technology that allows a secure tunnel to be created across a network such as the Internet. For example, VPNs allow you to establish a secure dial-up connection to a remote server.
#31 How does a network topology affect your decision in setting up a network?
Network topology dictates what media you must use to interconnect devices. It also serves as basis on what materials, connector and terminations that is applicable for the
#32 Briefly describe NAT.
Network Address Translation (NAT) is the process where a network device, usually a firewall, assigns a public address to a computer (or group of computers) inside a private network. The main use of NAT is to limit the number of public IP addresses an organization or company must use, for both economy and security purposes.
#33 What is RIP?
RIP, short for Routing Information Protocol is used by routers to send data from one network to another. It efficiently manages routing data by broadcasting its routing table to all other routers within the network. It determines the network distance in units of hops.
#34 What is NIC?
NIC is short for Network Interface Card. This is a peripheral card that is attached to a PC in order to connect to a network. Every NIC has its own MAC address that identifies the PC on the network.
#35 What does 10Base-T mean?
The 10 refers to the data transfer rate, in this case is 10Mbps. The word Base refers to base band, as oppose to broad band. T means twisted pair, which is the cable used for that network.
#36 What is the advantage of address sharing?
- Low-volume mailers are able to establish a reputation and history with Mailbox Providers
- Seasonal mailers do not need to warm up dedicated IP addresses every year
- Cheap and Inexpensive
#37 What are MAC addresses?
MAC, or Media Access Control, uniquely identifies a device on the network. It is also known as physical address or Ethernet address. A MAC address is made up of 6-byte parts.
#38 What is DHCP?
DHCP (Dynamic Host Configuration Protocol) is a protocol used to provide quick, automatic, and central management for the distribution of IP addresses within a network. DHCP is also used to configure the proper subnet mask, default gateway, and DNS server information on the device.
#39 One way of securing a network is through the use of passwords. What can be considered as good passwords?
Good passwords are made up of not just letters, but by combining letters and numbers. A password that combines uppercase and lowercase letters is favorable than one that uses all upper case or all lower case letters. Passwords must be not words that can easily be guessed by hackers, such as dates, names, favorites, etc. Longer passwords are also better than short ones.
#40 What is the number of network IDs in a Class C network?
For a Class C network, the number of usable Network ID bits is 21. The number of possible network IDs is 2 raised to 21 or 2,097,152. The number of host IDs per network ID is 2 raised to 8 minus 2, or 254.
#41 What is Ping?
Ping is a utility program that allows you to check connectivity between network devices on the network. You can ping a device by using its IP address or device name, such as a computer name.
#42 What is the maximum segment length of a 100Base-FX network?
The maximum allowable length for a network segment using 100Base-FX is 412 meters. The maximum length for the entire network is 5 kilometers.
#43 What can be done to fix signal attenuation problems?
A common way of dealing with such a problem is to use repeaters and hub, because it will help regenerate the signal and therefore prevent signal loss. Checking if cables are properly terminated is also a must.
#44 Describe Ethernet
Definition: Ethernet (pronounced “ether net”) is a computer network technology which is used in different area networks like LAN, MAN, WAN. Ethernet connecting computers together with cable so the computers can share information. Within each main branch of the network, “Ethernet” can connect up to 1,024 personal computers and workstations.
#45 Types of Ethernet Networks
There are several types of Ethernet networks, such as Fast Ethernet, Gigabit Ethernet, and Switch Ethernet. A network is a group of two or more computer systems connected together.
- Fast Ethernet
Twisted pair cable
The fast Ethernet is a type of Ethernet network that can transfer data at a rate of 100 Mbps using a twisted-pair cable or a fiber-optic cable. The older 10 Mbps Ethernet is still used, but such networks do not provide necessary bandwidth for some network-based video applications.
Fast Ethernet is based on the proven CSMA/CD Media Access Control (MAC) protocol, and uses existing 10BaseT cabling. Data can move from 10 Mbps to 100 Mbps without any protocol translation or changes to the application and networking software.
- Gigabit Ethernet
Optic fiber cable
The Gigabit Ethernet is a type of Ethernet network capable of transferring data at a rate of 1000 Mbps based on a twisted-pair or fiber optic cable, and it is very popular. The type of twisted-pair cables that support Gigabit Ethernet is Cat 5e cable, where all the four pairs of twisted wires of the cable are used to achieve high data transfer rates. The 10 Gigabit Ethernet is a latest generation Ethernet capable of transferring data at a rate of 10 Gbps using twisted-pair or fiber optic cable.
- Switch Ethernet
Multiple network devices in a LAN require network equipments such as a network switch or hub. When using a network switch, a regular network cable is used instead of a crossover cable. The crossover cable consists of a transmission pair at one end and a receiving pair at the other end.
The main function of a network switch is to forward data from one device to another device on the same network. Thus a network switch performs this task efficiently as the data is transferred from one device to another without affecting other devices on the same network.
The network switch normally supports different data transfer rates. The most common data transfer rates include 10 Mbps – 100 Mbps for fast Ethernet, and 1000 Mbps – 10 GBPS for the latest Ethernet.
Switch Ethernet uses star topology, which is organized around a switch. The switch in a network uses a filtering and switching mechanism similar to the one used by the gateways, in which these techniques have been in use for a long time
#46 You need to connect two computers for file sharing. Is it possible to do this without using a hub or router?
Yes, you can connect two computers together using only one cable. A crossover type cable can be use in this scenario. In this setup, the data transmit pin of one cable is connected to the data receive pin of the other cable, and vice versa.
#47 What are the maximum networks and hosts in a class A, B and C network?
For Class A, there are 126 possible networks and 16,777,214 hosts
For Class B, there are 16,384 possible networks and 65,534 hosts
For Class C, there are 2,097,152 possible networks and 254 hosts
#48 What advantages and disadvantages does fiber optics have over other media?
Advantages of Optical Fiber Cable:
Fiber optic cables have a much greater bandwidth than metal cables. The amount of information that can be transmitted per unit time of fiber over other transmission media is its most significant advantage.
- Low Power Loss
An optical fiber offers low power loss, which allows for longer transmission distances. In comparison to copper, in a network, the longest recommended copper distance is 100m while with fiber, it is 2km.
Fiber optic cables are immune to electromagnetic interference. It can also be run in electrically noisy environments without concern as electrical noise will not affect fiber.
In comparison to copper, a fiber optic cable has nearly 4.5 times as much capacity as the wire cable has and a cross sectional area that is 30 times less.
Fiber optic cables are much thinner and lighter than metal wires. They also occupy less space with cables of the same information capacity. Lighter weight makes fiber easier to install.
Optical fibers are difficult to tap. As they do not radiate electromagnetic energy, emissions cannot be intercepted. As physically tapping the fiber takes great skill to do undetected, fiber is the most secure medium available for carrying sensitive data.
An optical fiber has greater tensile strength than copper or steel fibers of the same diameter. It is flexible, bends easily and resists most corrosive elements that attack copper cable.
The raw materials for glass are plentiful, unlike copper. This means glass can be made more cheaply than copper.
#49What is a Node? What Does a Network Node Do?
A node is any physical device within a network of other devices that’s able to send, receive, and/or forward information. The computer is the most the common node, and is often called the computer node or internet node.
A network node is usually any device that both receives and then communicates something through the network, but might instead just receive and store the data, relay the information elsewhere, or create and send data.
#50 What is Network Topology?
Network Topology is a physical layout of the computer network and it defines how the computers, devices, cables etc are connected to each other.
#51 What are Routers?
The router is a network device which connects two or more network segments. The router is used to transfer information from the source to destination.
#52 What is OSI reference model?
Open System Interconnection (OSI) model, an ISO standard for worldwide communication Networks that defines a networking framework for implementing protocols in seven layers. OSI reference model is a logical framework for standards for the network communication. OSI reference model is now considered as a primary standard for internetworking and inter computing. The seven layers can be grouped into three groups – Network, Transport and Application.
- Layer 1, 2 and 3 i.e. physical, data link, and network are network support layers.
• Layer 4, Transport layer provides end to end reliable data transmission.
• Layer 5, 6 and 7 i.e. Session, Presentation, and Application layer are user support layers.
#53 What are the layers in OSI Reference Models? Describe each layer briefly.
In the OSI model, control is passed from one layer to the next, starting at the application layer (Layer 7) in one station, and proceeding to the bottom layer, over the channel to the next station and back up the hierarchy. The OSI model takes the task of inter-networking and divides that up into what is referred to as a vertical stack that consists of the following 7 layers.
- Layer 7 – Application
- Layer 6 – Presentation
- Layer 5 – Session
- Layer 4 – Transport
- Layer 3 – Network
- Layer 2 – Data Link
- Layer 1 – Physical
The Physical layer is also called as the Layer 1. Here are the basic functionalities of the Physical layer:
- Responsible for electrical signals, light signal, radio signals etc.
- Hardware layer of the OSI layer
- Devices like repeater, hub, cables, ethernet work on this layer
- Protocols like RS232, ATM, FDDI, Ethernet work on this layer
Data Link layer
The data link layer is also called as the Layer 2 of the OSI model. Here are the basic functionalities of the data link layer:
- Responsible for encoding and decoding of the electrical signals into bits.
- Manages data errors from the physical layer
- Convers electrical signals into frames
- The data link layer is divided into two sub-layers
- The Media Access Control (MAC) layer
- Logical Link Control (LLC) layer.
- The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it.
- The LLC layer controls frame synchronization, flow control and error checking.
- MAC address is a part of the layer 2.
- Devices like Switch work at this layer
The Network layer is also called as the layer 3 of the OSI model. Here are the basic functionalities of the network layer:
- Switching and routing technologies work here
- Creates logical paths between two hosts across the world wide web called as virtual circuits
- Routes the data packet to destination
- Routing and forwarding of the data packets.
- Internetworking, error handling, congestion control and packet sequencing work at this layer
- Router works at layer three
- Different network protocols like TCP/ IP, IPX, AppleTalk work at this layer
The Transport layer is also called as the layer 4 of the OSI model. Here are the basic functionalities of the Transport layer:
- Responsible for the transparent transfer of data between end systems
- Responsible for end-to-end error recovery and flow control
- Responsible for complete data transfer.
- Protocols like SPX, TCP, UDP work here
The Session layer is also called as the layer 5 of the OSI model. Here are the basic functionalities of the Session layer:
- Responsible for establishment, management and termination of connections between applications.
- The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end.
- It deals with session and connection coordination.
- Protocols like NFS, NetBios names, RPC, SQL work at this layer.
The Presentation layer is also called as the layer 6 of the OSI model. Here are the basic functionalities of the presentation layer:
- Responsible for data representation on your screen
- Encryption and decryption of the data
- Data semantics and syntax
- Layer 6 Presentation examples include encryption, ASCII, EBCDIC, TIFF, GIF, PICT, JPEG, MPEG, MIDI.
The Application layer is also called as the layer 7 of the OSI model. Here are the basic functionalities of the Application layer:
- Application layer supports application, apps, and end-user processes.
- Quality of service
- This layer is responsible for application services for file transfers, e-mail, and other network software services.
- Protocols like Telnet, FTP, HTTP work on this layer.
Explain TCP/IP Model
The most widely used and available protocol is TCP/IP i.e. Transmission Control Protocol and Internet Protocol. TCP/IP specifies how data should be packaged, transmitted and routed in their end to end data communication.
#54 There are four layers as shown in the below diagram:
Given below is a brief explanation of each layer:
- Application Layer: This is the top layer in TCP/IP model. It includes processes which use Transport Layer Protocol to transmit the data to their destination. There are different Application Layer Protocols such as HTTP, FTP, SMTP, SNMP protocols etc.
- Transport Layer: It receives the data from the Application Layer which is above Transport Layer. It acts as a backbone between the host’s system connected with each other and it mainly concerns about the transmission of data. TCP and UDP are mainly used as a Transport Layer protocols.
- Network or Internet Layer: This layer sends the packets across the network. Packets mainly contain source & destination IP addresses and actual data to be transmitted.
- Network Interface Layer: It is the lowest layer of TCP/IP model. It transfers the packets between different hosts. It includes encapsulation of IP packets into frames, mapping IP addresses to physical hardware devices etc.
#55 What is HTTP and what port does it use?
HTTP is HyperText Transfer Protocol and it is responsible for web content. Many web pages are using HTTP to transmit the web content and allow the display and navigation of HyperText.
It is the primary protocol and port used here is TCP port 80.
#56 What is HTTPs and what port does it use?
HTTPS is a Secure HTTP. HTTPS is used for secure communication over a computer network. HTTPS provides authentication of websites which prevents unwanted attacks.
In a bi-directional communication, HTTPS protocol encrypts the communication so that tampering of the data gets avoided. With the help of a SSL certificate, it verifies if the requested server connection is a valid connection or not. HTTPS uses TCP with port 443.
Disadvantages of Optical Fiber Cable
- Difficult to Splice
The optical fibers are difficult to splice, and there are loss of the light in the fiber due to scattering. They have limited physical arc of cables. If you bend them too much, they will break.
- Expensive to Install
The optical fibers are more expensive to install, and they have to be installed by the specialists. They are not as robust as the wires. Special test equipment is often required to the optical fiber.
- Highly Susceptible
The fiber optic cable is a small and compact cable, and it is highly susceptible to becoming cut or damaged during installation or construction activities. The fiber optic cables can provide tremendous data transmission capabilities. So, when the fiber optic cabling is chosen as the transmission medium, it is necessary to address restoration, backup and survivability.
#57 Distinguish between TCP and UDP.
|TCP stands for Transmission Control Protocol||UDP is stands for User Datagram Protocol or Universal Datagram Protocol|
|Once the connection is setup, data can be sent bi-directional i.e. TCP is a connection oriented protocol||UDP is connectionless, simple protocol. Using UDP, messages are sent as packets|
|The speed of TCP is slower than UDP||UDP is faster compared to TCP|
|TCP is used for the application where time is not critical part of data transmission||UDP is suitable for the applications which require fast transmission of data and time is crucial in this case.|
|TCP transmission occurs in a sequential manner||UDP transmission also occurs in a sequential manner but it does not maintain the same sequence when it reaches the destination|
|It is heavy weight connection||It is lightweight transport layer|
|TCP tracks the data sent to ensure no data loss during data transmission||UDP does not ensure whether receiver receives packets are not. If packets are misses then they are just lost|
#58 What is firewall?
A firewall is a network security device that monitors incoming and outgoing network traffic and decides whether to allow or block specific traffic based on a defined set of security rules.
#59 What is DNS?
Domain Name Server (DNS), in a non-professional language and we can call it as Internet’s phone book. All the public IP addresses and their hostnames are stored in the DNS and later it translates into a corresponding IP address.
#60 What is the difference between a Domain and a Workgroup?
|All computers are peers and no computer has control over another computer||Network admin uses one or more computer as a server and provide all accesses, security permission to all other computers in a network|
|In a Workgroup, each computer maintains their own database||The domain is a form of a computer network in which computers, printers, and user accounts are registered in a central database.|
|Each computer has their own authentication rule for every user account||It has centralized authentication servers which set the rule of authentication|
|Each computer has set of user account. If user has account on that computer then only user able to access the computer||If user has an account in a domain then user can login to any computer in a domain|
|Workgroup does not bind to any security permission or does not require any password||Domain user has to provide security credentials whenever they are accessing the domain network|
|Computer settings need to change manually for each computer in a Workgroup||In a domain, changes made in one computer automatically made same changes to all other computers in a network|
|All computers must be on same local area network||In a domain, computers can be on a different local network|
|In a Workgroup, there can be only 20 computers connected||In a domain, thousands of computers can be connected|
#61 What is full duplex?
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.
#62 What is Asynchronous mode of data transmission?
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.
#63 What is hamming code?
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.
#64 What do you mean by Bluetooth?
It is a wireless LAN technology designed to connect devices of different functions such as telephones, notebooks, computers, cameras, printers and so on.
#65 Differences between Hub, Switch and Router?
|Physical Layer Device||Data Link Layer Device||Network Layer Device|
|Simply repeats signal to all ports||Doesn’t simply repeat, but filters content by MAC or LAN address||Routes data based on IP address|
|Connects devices within a single LAN||Can connect multiple sub-LANs within a single LAN||Connect multiple LANS and WANS together.|
|Collision domain of all hosts connected through Hub remains one. i.e., if signal sent by any two devices can collide.||Switch divides collision domain, but broadcast domain of connected devices remains same.||It divides both collision and broadcast domains,|
|by any two devices can collide.||devices remains same.|
#66 What are Unicasting, Anycasting, Multiccasting and Broadcasting?
If the message is sent from a source to a single destination node, it is called Unicasting. This is typically done in networks.
If the message is sent from a source to a any of the given destination nodes. This is used a lot in Content delivery Systems where we want to get content from any server.
If the message is sent to some subset of other nodes, it is called Multicasting. Used in situation when there are multiple receivers of same data. Like video conferencing, updating something on CDN servers which have replica of same data.
If the message is sent to all the nodes in a network it is called Broadcasting. This is typically used in Local networks, for examples DHCP and ARP use broadcasting.
#67 What are layers in OSI model?
There are total 7 layers
1) Physical Layer
2) Data Link Layer
3) Network Layer
4) Transport Layer
5) Session Layer
6) Presentation Layer
7) Application Layer
#68 What is Stop-and-Wait Protocol?
In Stop and wait protocol, a sender after sending a frame waits for acknowledgement of the frame and sends the next frame only when acknowledgement of the frame has received.
#69 What is Piggybacking?
Piggybacking is used in bi-directional data transmission in the network layer (OSI model). The idea is to improve efficiency piggy back acknowledgement (of the received data) on the data frame (to be sent) instead of sending a separate frame.
#70 What happens when you type a URL in web browser?
A URL may contain request to HTML, image file or any other type.
- If content of the typed URL is in cache and fresh, then display the content.
- Else find IP address for the domain so that a TCP connection can be setup. Browser does a DNS lookup.
- Browser needs to know IP address for a url, so that it can setup a TCP connection. This is why browser needs DNS service. Browser first looks for URL-IP mapping browser cache, then in OS cache. If all caches are empty, then it makes a recursive query to the local DNS server. The local DNS server provides the IP address.
- Browser sets up a TCP connection using three way handshake.
- Browser sends a HTTP request.
- Server has a web server like Apache, IIS running that handles incoming HTTP request and sends a HTTP response.
- Browser receives the HTTP response and renders the content.
#71 What is DHCP, how does it work?
- The idea of DHCP (Dynamic Host Configuration Protocol) is to enable devices to get IP address without any manual configuration.
- The device sends a broadcast message saying “I am new here”
- The DHCP server sees the message and responds back to the device and typically allocates an IP address. All other devices on network ignore the message of new device as they are not DHCP server.
In Wi Fi networks, Access Points generally work as a DHCP server.
#72 What is ARP, how does it work?
ARP stands for Address Resolution Protocol. ARP is used to find LAN address from Network address. A node typically has destination IP to send a packet, the nodes needs link layer address to send a frame over local link. The ARP protocol helps here.
- The node sends a broadcast message to all nodes saying what is the MAC address of this IP address.
- Node with the provided IP address replies with the MAC address.
Like DHCP, ARP is a discovery protocol, but unlike DHCP there is not server here.
#73 What is WDM?
WDM is conceptually the same as FDM, except that the multiplexing and demultiplexing involve light signals transmitted through fiber optics channel.
#74 What is TDM?
TDM is a digital process that can be applied when the data rate capacity of the transmission medium is greater than the data rate required by the sending and receiving devices.
#75 What is Synchronous TDM?
In STDM, the multiplexer allocates exactly the same time slot to each device at all times, whether or not a device has anything to transmit.
#76 What is a Linear Block Code?
linear code is an error-correcting code for which any linear combination of codewords is also a codeword. Linear codes are traditionally partitioned into block codes and convolutional codes, although turbo codes can be seen as a hybrid of these two types.
#77 Define Encoder.
An encoder is a device, circuit, transducer, software program, algorithm or person that converts information from one format or code to another, for the purposes of standardization, speed or compression.
#78 What is Framing?
Framing in the data link layer separates a message from one source to a destination, or from other messages to other destinations, by adding a sender address and a destination address. The destination address defines where the packet has to go and the sender address helps the recipient acknowledge the receipt.
#79 Define Decoder.
A device or program that translates encoded data into its original format (e.g., it decodes the data).
#80 What is Brouter?
A brouter is a device that functions as both a bridge and a router. It can forward data between networks (serving as a bridge), but can also route data to individual systems within a network (serving as a router)..
#81 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.
#82 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.
#83 What is traffic shaping?
Traffic shaping is a way to help increase network performance by controlling the amount of data that flows into and out of the network. Traffic is categorized, queued, and directed according to network policies.
#84 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.
#85 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.
#86 What is BGP (Border Gateway Protocol)?
It is a protocol used to advertise the set of networks that can be reached within an autonomous system. BGP enables this information to be shared with the autonomous system. This is newer than EGP (Exterior Gateway Protocol).
#87 What is Proxy ARP?
Proxy ARP is a technique by which a device on a given network answers the ARP queries for an IP address that is not on that network. The ARP proxy is aware of the location of the traffic’s destination, and offers its own MAC address as (ostensibly final) destination.
#88 What is source route?
In computer networking, source routing, also called path addressing, allows a sender of a packet to partially or completely specify the route the packet takes through the network.
#89 Which are the different factors that affect the reliability of a network?
The following factors affect the reliability of a network:
- Frequency of failure
- Recovery time of a network after a failure
#90 What are the different types of networks?
Networks can be divided on the basis of area of distribution. For example:
- PAN (Personal Area Network): Its range limit is up to 10 meters. It is created for personal use. Generally personal devices are connected with this network. For example: computers, telephones, fax, printers etc.
- LAN (Local Area Network): It is used for a small geographical location like office, hospital, school etc.
- HAN (House Area Network): It is actually a LAN that is used within a house and used to connect homely devices like personal computers, phones, printers etc.
- CAN (Campus area Network): It is a connection of devices within a campus area which links to other departments of the organization within the same campus.
- MAN (Metropolitan Area Network): It is used to connect the devices which spans to large cities like metropolitan cities over a wide geographical area.
- WAN (Wide Area Network): It is used over a wide geographical location that may range to connect cities and countries.
- GAN (Global Area Network): It uses satellites to connect devices over global are.
#91 What is the maximum length allowed for a UTP cable?
The maximum length of UTP cable is 90 to 100 meters.
#92 What are the perquisites to configure a server?
- LAN card should be connected
- Root (partition on which window is installed) should be in NTFS format
- Server should be configured with a static IP address
#93 Differentiate between static IP addressing and dynamic IP addressing.
|BASIS FOR COMPARISON||STATIC IP ADDRESS||DYNAMIC IP ADDRESS|
|Provided by||ISP (For external IP address)||DHCP|
|Change acquirement||Once static IP is assigned, it doesn’t change.||Dynamic IP changes each time when a user connects to a network.|
|Security||Risk is high.||More secure than static IP address.|
#94 Differentiate between a ‘bit rate’ and ‘baud rate’.
|BASIS FOR COMPARISON||BIT RATE||BAUD RATE|
|Basic||Bit rate is the count of bits per second.||Baud rate is the count of signal units per second.|
|Meaning||It determines the number of bits traveled per second.||It determines how many times the state of a signal is changing.|
|Term usually used||While the emphasis is on computer efficiency.||While data transmission over the channel is more concerned.|
|Bandwidth determination||Can not determine the bandwidth.||It can determine how much bandwidth is required to send the signal.|
|Equation||Bit rate = baud rate x the count of bits per signal unit||Baud rate = bit rate / the number of bits per signal unit|
#95 What is Round Trip Time?
The duration of time it takes to send a message from one end of a network to the other and back, is called RTT.
#96 What is Pipelining?
In networking and in other areas, a task is often begun before the previous task has ended. This is known as pipelining.
#97 What is simplex?
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.
#98 What is half-duplex?
It is the mode of communication between two devices in whiata 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.
#99 Define parity check
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.
#100 Define cyclic redundancy check (CRC).
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.
#101 What do you mean by ALOHA ?
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
#102 What is Bridges?
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 physical and data link layer of OSI model.
#103 Compare Error Detection and Error Correction:
The correction of errors is more difficult than the detection. In error detection, checks only any error has occurred. In error correction, the exact number of bits that are corrupted and location in the message are known. The number of the errors and the size of the message are important factors.
#104 What are the protocols in application layer?
The protocols defined in application layer are
#105 What are the protocols in transport layer?
The protocols defined in transport layer are
#106 What do you mean by client server model?
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.