Networking Interview questions for Freshers - Part 1

What is NetBIOS Protocol?

NetBIOS protocol utilizes the 802.2 type 1 mode for the purpose of providing the NetBIOS/NetBEUI name service and also the datagram service. It uses 802.2 type 2 modes for the purpose of providing the NetBIOS/NetBEUI session service. Broadcast messages are used widely using NBProtocol which is accountable for its reputation as a chatty interface.

NB Protocol is unroutable. Only for the purpose of communication with devices in the same broadcast domain, NB protocol is used. It can be used with network segments connected with each other through bridges.

Explain the use of IGMP Protocol.

The transmission of datagram to a host group is done in IP multicasting by setting zero or more hosts that are identified by a single IP destination address. The IP multicasting needs the implementation of the Internet Group Management Protocol for allowing a host for creating, joining, and leaving host groups as well as send IP datagram to the host groups.

What is Multicasting? Explain the different types of hosts in Multicasting.

Multicasting is a technology for the purpose of delivering information to a destinations group simultaneously. Multicasting uses efficient strategies for delivering the messages in the network over each link only once.

What are Ping and Tracert?

Ping: Ping is used for verification of IP-Level connectivity. The following are the processes for using ping:

1. To ping the loopback address type ping 127.0.01
2. To ping the IP address of a local computer system to verify whether it is correctly verified or not – ping ipaddress of local host. Ex: c:\>pint 129.29.3.12
3. To ping the IP address of the gateway that is default for verifying the functionality of the gate way = ping ipaddress of default gateway.

Tracert: A route-tracing utility that is used for determining the path of a network from source to destination. The determination of the path that a packet takes on the network tracert is used.

Explain how Tracert works.

An ICMP echo packet to the named host is sent by Tracert. It sends packet with a TTL of 1, then TTL of 2 and so on. Routers send back the message “TTL expired in transit” , after sending the packets by Tracert, until the destination host computer system is reached. Later, it responds with the standard ICMP “echo reply” packet.

Explain the use of RTP and RTCP protocols (Real-Time Transfer Control Protocols).

Real-time Transport Protocol is a standardized packet format. It is used for delivering audio and video over internet. RTP was developed by Audio-Video Transport Working Group of the IETF. The communication and entertainment systems are potential in using RTP , which involves streaming media applications and web based push to talk features. Media streams are carried by H.323,MGCP, Megaco signaling protocols, for performing the streams to carry over network.

Real-time Transfer Control Protocol is used along with RTP. RTP carries audio and video, or out of band signaling, RTCP is utilized for monitoring transmission statistics and quality of service information. With both the protocols conjunction, RTP is originated and received on port numbers that are even, while RTCP uses the port numbers that are next higher odd port numbers.

Explain the concepts of RTP Multiplexing.

RTP multiplexing is a concept used for carrying multiple voice streams between IP telephony gateways, in one RTP packet.

What is RSVP? How it works?

RSVP allocates resources for signaling messages which traverse the network. RSVP is receiver-initiated. In the scenarios of multicast, the PATH message is sent out by application server to multiple receiving computers, so that network bandwidth is conserved. The multiple messages received from receivers are merged by RSVP messages by using the values requested which are maximum. This process takes place when the multicast traffic flows. RSVP is a protocol that is soft-state. It means the reservation must be refreshed periodically or it will expire. The reservation information is called as state. The state is cached in every hop tasked by managing resources. Reservations time out and are dropped, in the situation where the refresh messages are not received.

What is TCP/IP protocol?

The basic communication protocol for internet is TCP/IP. It is also being used as communication protocol in a private network. One copy of TCP/IP program is provided to the computer system which is set up to access internet directly.

Explain the architecture of TCP/IP protocol. - Application Layer, Transport and Internet Layer and Network Interface Layer.

TCP/IP protocol maps four layers namely Application Layer, Transport and Internet Layer and Network Interface Layer.

Application Layer:
Accessibility of other services accessibility by applications is provided by the application layer. Protocol definitions that are used by application for exchanging data is also done by application layer. HTTP, FTP, SMTP, Telnet are some of the application layer protocols for exchanging information. Domain Name System, Routing Information Protocol, Simple Network Management Protocols are used for facilitating the use and management of TCP/IP networks.

Transport Layer:
Session and datagram communications services are provided by transport layer to the application layer. The protocols used for data transmission are TCP and UDP. TCP provides a reliable one-to-one communication service. Establishing TCP connection, sequencing and acknowledgement of sent packets are the responsibilities of TCP. UDP provides one-to-one, one-to-many, connectionless, unreliable communication services. UDP is recommended when the amount of data is small and fit into single packet.

The responsibilities of the OSI Transport layer and some of the responsibilities of OSI session layer are encompassed in the Transport layer.

Internet Layer
The responsibility of addressing, packaging, and routing functions are held by the Internet Layer. The protocols for this layer are IP, ARP, ICMP, and IGMP.

IP addressing, routing and fragmentation and assembling of packets are the responsibilities of IP protocol.Resolution of the Internet layer address to the network interface layer is the responsibility of ARP. Providing diagnostic functions and reporting errors due to the unsuccessful delivery of IP packets is dealt by ICMP. The management of IP multicast groups is the responsibility of IGMP.

Network Interface Layer
Placing TCP/IP packets on the medium of network and receiving TCP/IP packets off the network medium is the responsibility of Network Interface Layer. It was designed as independent of network access method, frame format, and medium. LAN technologies which use Ethernet and Token ring and WAN technologies such as x.25 are connected among them using Network Interface Layer.

Explain TCP header in detail.

TCP headers should perform various tasks. The tasks are performed by various ports as follows:

Source Port: On the sending system, a process is being bounded by the source port. A hash between the IP addresses and destination and source ports is used for uniqueness for binding single application or program.

Destination Port: Destination port was directly bounded to a process at the receiving system.

Sequence Number: A number on every packet of TCP which facilitates the TCP stream properly sequenced. The port can then return an acknowledgement after the packet was properly received.

Acknowledge Number: This number is used when a packet at the host is received.

Data offset: The distance of the TCP header and the location of data part of the packet is indicated by data offset.

Reserved bit: The reserved bits are reserved for future usage.

CWR bit: An added bit to RFC 3268 which is used by ECN. CWR bit is used for sending data to inform the receiving part when the congestion window reduced.

ECE bit: An added bit to RFC 3268 which is used by ECN. TCP/IP stack uses this bit on the receiver host for sending the host that is has received a CE packet.

URG bit: To determine the usage of Urgent Pointer Field, this bit is used. 1 is set as to use Urgent pointer and 0 is set not to use Urgent pointer.

ACK bit: A packet is set by this bit that indicates the reply to another packet that data is received.

PSH bit: To communicate any intermediate hosts for sending data on to the actual user.

RST bit: To indicate to the other end for tearing down the TCP connection, Reset bit is used.

SYN bit: When the connection is initially established, SYN is used. The initial packet and the reply SYN are the two instances of the connection.

FIN bit: The host sends FIN bit which indicates that no more data is left for sending. The other end will respond a FIN when there is no data left.

Window bit: Window bit information is used by the host for informing the sender the volume of data the receiver permits a given point of time.

Checksum bit: It is bit for performing checksum on the whole TCP header. It is a one’s complement of the one’s complement sum of every 16 bit word available in the header. The checksum field is set to zero.

Urgent Pointer bit: A pointer bit that point to the end of the data which is considered as urgent.

Options bit: A variable length field which contains optional headers which may be used. It contains an initial field – the length of options field, second field - informs which options are used.

Padding bit: Until the header ends at a 32-bit boundary, the padding of TCP header takes place. The padding always consists of only zeros to ensure the data part of the packet is not lost.

Explain the concept of CDMA.

CDMA is communication technique which is based on multiple-access scheme. The signal spreads to a wide bandwidth with using unique code which reduces interference and enhances system processing. Time division or frequency for multiple accesses is not required by CDMA. This results in improving the capacity of the communication system.

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.

Difference between MUTEX and Semaphore.

Mutex:
A mutex object allows only one thread among the threads concurrently executed, into a controlled section in a serialized fashion, forcing other threads to wait until the exiting of the first thread from that section.

Semaphore:
The restriction of the number of simultaneous users of a shared resource is performed by a semaphore. Semaphore allows threads to request to the resource and signals the completion of using resources to threads.

Explain Priority Inversion.

Priority inversion is the scenario in scheduling where a task holds shared resources which have lower priority for the higher priority resource, which results in high priority task to be blocked until the lower priority task has released the resources. This results in effectively inverting the relative priorities of the two tasks.

In case, some other task with medium priority, which does not depend on the shared resource, attempts for running in the interim, that task take the precedence over both the lower priority task and the high priority task. Priority inversion causes the reduction of perceived performance of the system.

What are Passive and Active FTPs?

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 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.

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.

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.

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 more.

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.

Define Subnetting.

A subnet describes a set of networked computers which have common IP address routing prefix.

Breaking the networking into smaller and more efficient subnets is known as subnets. Subnetting prevents Ethernet packet collision which has excessive rates in a large network. Routers are used to manage the traffic and constitute borders among subnets.

What is the User Datagram Protocol (UDP)?

User datagram protocol allows computer applications to send messages as datagram packets from source to destination on an Internet Protocol, with out using prior communications for setting up special transmission paths. An unreliable service is provided by UDP which makes the datagram packets may arrive irrespective of order. UDP is a better solution for time-sensitive applications due to the reason ‘dropping packets is preferable to use delayed packets’. Its stateless nature makes the server to answer smaller queries to huge number of clients.

Explain TCP Windowing concept.

TCP Windowing is a concept that is used for avoiding congestion in the network traffic. Unacknowledged amount of data that is sent by the sender before the data gets acknowledgment back from the receiver that it has received it is controlled.

What is the Domain Name System (DNS)? What are the advantages of it?

A hierarchical naming system for computer systems, services or for that matter any resource participating in the internet. Various information with domain names is assigned to each of the participants. DNS translates the names of domain into meaningful to humans into binary identifiers that are associated with the equipment of network to locate and address these devices.

Advantages:
More Reliable: Delivers messages to the users with zero downtime.

Faster: DNS are connected well at intersections of internet. Anycast technology enables requests are answered to the next closest node in the case of maintenance or downtime.

Smarter: Automatic corrections of typos.

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.

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 is pulse code modulation?

Pulse Code Modulation: A digital representation of an analog signal. Signal sampling is done with the magnitude of the signal regularly at uniform intervals. Later quantized to a series of symbols in binary form.

PCM is used in digital telephone systems and electronic musical keyboards. It is the standard form for digital audio in computer systems

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 ISDN and ATM.

- ISDN uses circuit switching where as ATM uses packet switching communication
- ISDN is a point to point fixed bandwidth communication, where as ATM is a variable bandwidth communication
- ISDN delivers at minimum two simultaneous connections.

ATM is connection-oriented which establishes a logical connection between 2 end points before the commencement of data exchange.

What is MAC address?

Media Access Control address is an identifier for assigned to most network adapters or Network Interface Cards by the manufacturer for the purpose of identification. MAC address is used in MAC protocol sub layer. MAC address is usually encodes the registered identification number that is registered by the manufacturer. The numbering spaces managed by the IEEE, which are common for formulating a MAC address: MAC-48, EUI-48 and EUI-64.

Difference between the communication and transmission.

The differences between the communication and transmission are:

Physical movement of information and concerning about bit priority, synchronization, clock etc is referred as transmission, where as full exchange of information among media of communication is referred as communication.

Transmission is all about transmitting of data to the destination, where as the dialogue between the source and destination is all about communication.

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.

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.

A Unix/Linux Permissions Refresher

Most people who deal with *nix systems occasionally get confused about file and directory permissions. Sometimes it's the order of the read, write, and execute bits. Other times it's the octal notation, or maybe how to decipher the setuid and sticky bit trickery.

My goal is for this page to serve as an instant UNIX/Linux permissions refresher and/or primer for those who either 1) never quite got it in the first place, or 2) sometimes get tripped up on the details.

Basics

Let's start some output from ls:

# ls -lah // my favorite ls options

-rwxr-xr--  1 daniel consultants  5K  Mar 10 06:55 scanner.rb
-rwxr-xr-x  1 sarah teachers     18M Jul 30 10:07 papers.tar.bz2

• Three Sets Of Three (blue)
  Since we're looking at a file and not a directory, the first character we see starts the nine (9) character string defining three (3) types of permissions for three (3) different access levels (3 x 3 = 9). Remember to count the dashes.


• UGO (Like the car) (blue)
  The way the three sets break down is according to the following order: User, Group, Other. UGO. So the first set of rwx's is for the user, the second is for the group, and the third is for everyone else.


• See Who Owns The File (red)
  You can always see the user and group owners of a file but never the "other". That's because "other" permissions simply apply to those who are not one of the other two.

The Three Numbers

Quite a few people get tripped up when they see the permissions listed as a set of three numbers. There's no cause for alarm. Just remember that this number is simply three binary placeholders, each one holding the number that corresponds to the access level in r, w, x order. Observe the chart:

Permissions on Directories

Also remember that permissions are different on directories than they are on files. On files they're pretty much like you'd expect them: read the file, write/delete the file, and execute the file. But for directories it's a bit less intuitive.

• Read means you can get a directory listing.
• Write says you can create or delete contents within the directory.
• Execute means you are able to enter the directory, i.e. cd into it.

Setuid, Setguid and Sticky Bits

This is one of the bits (it's British for parts, lol) that gives people the most trouble. No worries.

Setuid

Setuid was designed to solve a very basic problem: user's not having enough permission to run certain programs. The answer was to add an option within files to say, "Regardless of who runs this program, run it as the user who owns it, not the user that executes it."

In today's world this is a lot like getting poked in the eye with a stick. It's just not cool, so don't partake.

Here's the way it looks, though, in case you come across it in the wild:

-rwsr-xr--  1 daniel consultants  5K  Mar 10 06:55 scanner.rb

You see that little "s" in there? It stands for Satan. Notice that it resides where the "x" (execute) would have been for the user: that's because it's setUID, and it relates to execution. Also, it's a lowercase "s" in this example because both the setuid bit and the execute bit are set. If only the setuid bit is set (and the user
doesn't have execute permissions himself) it shows up as a capital "S".

[ Note: This capitalization issue applies to all of the "special" permission bits. The general rule is this: If it's lowercase, that user HAS execute. If it's uppercase, the user DOESN'Thave execute. ]

Setguid

Setguid isn't used nearly as much, but it's the same exact concept applied to the group that the file belongs to instead of the user. Here's how it looks:

-rwxr-Sr-x  1 bjones principals  101K  Aug 16 04:01 grades.xml

Notice that this time the "s" is in the group's set instead of the user's. Also notice that it's a capital "S" instead of a lowercase one. Again, that means that the group (principals in this case) doesn't have execute permissions themselves, but when the program is executed by either bjones or any random user with access to the file, it'll run with the rights of the principles group.

Sticky Bits

The sticky bit had a funky purpose originally, but it's now used to keep people from modifying or deleting the contents of directories that the user or group owns. You can apply it to files as well, but it's usually employed on directories.

An example application of the sticky bit is a school assignment in which you have shared space on a server, with each student having a directory. Using the sticky bit, the administrator could ensure that once a given student created content in their respective folder, no other student could come in and delete it.

Here's how it looks:

drwxr-xr-t  1 alice alice  4.4K  2007-01-01 09:21 Alice

Remember that if "everyone" (other) doesn't have execute permissions on the directory it'll be a capital T instead of lowercase.

Changing Permissions

To change permissions you use the chmod command and simply lay out what you want the permissions to look like on the file directory.

Change the permissions on your web directory to 755.

# chmod 755 web_directory

Change the permissions on your grocery list to 644.

# chmod 644 grocery_list.txt

Assigning Uid, Guid, and Sticky Bits

You can also assign the special properties to a file or directory using chmod.

Set setuid on a script

# chmod 4644 script.rb

Set guid on a script

# chmod 2644 script.rb

Set the sticky bit on a directory

# chmod 1644 myfiles

Exim Academy launches courses in Logistics

EXIM Academy, an accredited member of Chartered Institute of Logistics and Transport (CLIT), U.K., launches its certificate, diploma and advance diploma courses in Logistics and Supply Chain Management. While classes and examinations are conducted in India, the Certification is from CILT. CILT is an international body attained its charter from British Parliament in the year 1919.

After the course completion, students can stay in touch with senior professionals in the industry for inputs.  EXIM Academy will commence classes from mid July 2012 for both regular classes and classes only on Sundays. EXIM Academy plans to empower the under privileged section of the society by providing liberal scholarships to pursue certificate course. Such students and working professionals will attend classes on Sundays.

While tuition and admission fees are waived for these students, they will have to pay CILT student fee out of their stipend earnings. Regular classes from Monday to Friday will be conducted for students after their +2 / degree as the case may be for certificate / diploma programs. The mode of coaching would be through classroom study, group discussions, field visit to ports, airports, SEZ, FTZ and ware housing companies. At the end of the academic course, student will have to do a project by interning with a logistics/SCM company for two months. 

For details, contact 

Exim Academy
No.71/32, Ground Floor,
Race View Towers,
Anna Sala, Guindy,
Chennai—600032

Email: director@eximacademy.in
Phone: +91 44 2250 0057 
Mob: 97908 80601

http://www.eximacademy.in/

Benefits of Hand-On Training

Hands-on training means you get to use your hands and bodies to perform tasks. This training aims to make conditions as realistic as possible, but should not be confused with online training designed for practice using a software program. Although using a mouse and keyboard while interacting with a computer screen involves your hands, it doesn't offer immersion in an authentic setting. An exception is training on the job with a trainer, such as being coached while completing a sales transaction on the sales floor.

Practice

The biggest benefit of hands-on training is the opportunity for repeated practice. It doesn't matter how much natural talent a worker has, he can still improve in a skill by practicing. Training programs are more beneficial when they provide many opportunities for practicing a skill. The ultimate test is when a worker returns to his job and whether he feels confident to perform a skill learned in training.

Prevention

In some workplaces, it's necessary to provide hands-on training that approximates real work conditions while avoiding the risks associated with a novice employee's mistakes. An example is when a trainer sets up a workstation with similar equipment and procedures, but an employee can learn to perform a skill at her own pace without impeding the work tasks of co-workers or creating unsafe conditions for everyone in the workplace.

Self-Critique and Peer Review

Some jobs, such as financial advisor and customer service representative, hinge on the transaction with the client. It is helpful to offer hands-on training in a similar environment so that learners can role-play what they would say to clients in different scenarios. This training, if recorded or observed, is quite useful. If an employee's training performance is recorded, he can critique himself and get feedback from peers also watching the recording. If a trainer observes his performance, she can offer expert feedback. A learner can improve rapidly over a few days by implementing feedback from himself and others.

Learning Styles and Application

Trainers also recognize that people have different learning styles. Auditory and visual learners may learn better in a classroom or by watching an expert trainer perform a task. Kinesthetic learners do better when they can move around and perform activities. Hands-on training can meet the needs of these the styles because there are chances to watch and listen as well as performance tasks. When performance is required, learners can apply a skill.

Cloud Computing Interview Questions - Part 1

1. What is cloud computing?

The cloud computing is the computing which is completely based on the Internet. It can also be defined as the next stage in the evolution of the Internet. The cloud computing uses the cloud (Internet) that provides the way to deliver the services whenever and wherever the user of the cloud needs. Companies use the cloud computing to fulfill the needs of their customers, partners, and providers. The cloud computing includes vendors, partners, and business leaders as the three major contributors. The vendors are the one who provide applications and their related technology, infrastructure, hardware, and integration.

The partners are those who offer cloud services demand and provide support service to the customers. The business leaders are the ones who use or evaluate the cloud service provided by the partners. The cloud computing enables the companies to treat their resources as a pool and not as independent resources.

2. What is a cloud?

A cloud is a combination of hardware, networks, storage, services, and interfaces that helps in delivering computing as a service. It has broadly three users which are end user, business management user, and cloud service provider. The end user is the one who uses the services provided by the cloud. The business management user in the cloud takes the responsibility of the data and the services provided by the cloud. The cloud service provider is the one who takes care or is responsible for the maintenance of the IT assets of the cloud. The cloud acts as a common center for its users to fulfill their computing needs.

3. What are the basic characteristics of cloud computing?

The four basic characteristics of cloud computing are given as follows:

• Elasticity and scalability.
• Self-service provisioning and automatic de-provisioning.
• Standardized interfaces.
• Billing self-service based usage model.

4. What is a Cloud Service?

A cloud service is a service that is used to build cloud applications. This service provides the facility of using the cloud application without installing it on the computer. It reduces the maintenance and support of the application as compared to those applications that are not developed using the cloud service. The different kinds of users can use the application from the cloud service, which may be public or private application.

5. What are main features of cloud services?

Some important features of the cloud service are given as follows:

• Accessing and managing the commercial software.
• Centralizing the activities of management of software in the Web environment.
• Developing applications that are capable of managing several clients.
• Centralizing the updating feature of software that eliminates the need of downloading the upgrades.

6. How many types of deployment models are used in cloud?

There are 4 types of deployment models used in cloud:

1. Public cloud
2. Private cloud
3. Community cloud
4. Hybrid cloud

7. What is the AppFabric component?

The AppFabric component is used to create access control and distribute messages across clouds and enterprises. It has a service-oriented architecture, and can be considered as the backbone of the Windows Azure platform. It provides connectivity and messaging among distributed applications. It also has the capabilities of integrating the applications and the business processes between cloud services and also between cloud services and global applications.

The AppFabric component provides a development environment that is integrated with Visual Studio 2010.TheWindows Communication Foundation (WCF) services built in VS 2010 can be published on cloud from the Visual Studio design environment.

The two important services of AppFabric are as follows:

• Access Control Service (ACS) - Allows rules-driven and claims-based access control for distributed applications. These claims-based rules and authorization roles can be defined in the cloud for accessing on-premise and cloud services. The claim can be a user or application attribute, which the service application expects, such as e-mail address, phone number, password, and role, for appropriate access control. When any application wants to use the Web service, it sends the required claims to ACS for requesting a token. ACS converts the input claims into output claims by following the rules of mapping. These rules are created during the configuration of ACS. The ACS issues a token containing the output claims for the consumer application. This application uses this token in the request header and sends to the Web service. This service validates the claims in the token and gives suitable access to the user.
• Service bus - Provides messaging between cross-enterprise and cross-cloud scenarios. It provides publish/subscribe, point-to-point, and queues message patterns for exchange of messages across distributed applications in the cloud. It integrates with the Access Control service to establish secure relay and communication.

8. Why does an organization need to manage the workloads?

The workload can be defined as an independent service or a set of code that can be executed. It can be everything from a data-intensive workload to storage or a transaction processing workload and does not rely upon the outside elements. The workload can be considered as a small or complete application.

The organization manages workloads because of the following reasons:

• To know how their applications are running.
• To know what functions they are performing.
• To know the charges of the individual department according to the use of the service.

9. Which services are provided by Window Azure operating system?

Windows Azure provides three core services which are given as follows:

• Compute
• Storage
• Management

10. Explain hybrid and community cloud.

The hybrid cloud consists of multiple service providers. This model integrates various cloud services for Hybrid Web hosting. It is basically a combination of private and public cloud features. It is used by the company when a company has requirements for both the private and public clouds. Consider an example when an organization wants to implement the SaaS (Software as a Service) application throughout the company. The implementation requires security that can be provided by the private cloud used inside the firewall. The additional security can be provided by the VPN on requirement. Now, the organization has both the private and public cloud features.

The community cloud provides a number of benefits, such as privacy and security. This model, which is quite expensive, is used when the organizations having common goals and requirements are ready to share the benefits of the cloud service.

11. Explain public and private cloud.

The public cloud (or external cloud) is freely available for access. You can use a public cloud to collect data of the purchasing of items from a Web site on the Internet. You can also use public cloud for the reasons, which are given as follows:

• Helps when an application is to be used by a large number of people, such as an e-mail application, on the Internet.
• Helps when you want to test the application and also needs to develop the application code.
• Helps when you want to implement the security for the application.
• Helps when you want to increase the computing capacity.
• Helps when you are working on the projects in collaboration.
• Helps when you are developing the project on an ad-hoc basis by using PaaS.

The private cloud allows the usage of services by a single client on a private network. The benefits of this model are data security, corporate governance, and reliability concerns. The private cloud is used by the organization when it has a huge, well-run data center having a lot of spare capacity. It is also used when an organization is providing IT services to its clients and the data of organization is highly important. It is best suited when the requirements are critical.

The characteristics of this model are given as follows:

• Provides capability to internal users and allows provision of services.
• Automates the tasks of management and provides the billing of consumption of a particular service.
• Offers a well-managed environment.
• Enables the optimization of computational resources, such as servers.
• Manages the workload of the hardware.
• Offers self-service based provisioning of hardware resources and software.

12. Give a brief introduction of Windows Azure operating system.

The Windows Azure operating system is used for running cloud services on the Windows Azure platform, as it includes necessary features for hosting your services in the cloud. It also provides runtime environment that consists of Web server, computational services, basic storage, queues, management services, and load balancers. The operating system provides development. Fabric for development and testing of services before their deployment on the Windows Azure in the cloud.

13. What are the advantages of cloud services?

Some of the advantages of cloud service are given as follows:

• Helps in the utilization of investment in the corporate sector; and therefore, is cost saving.
• Helps in the developing scalable and robust applications. Previously, the scaling took months, but now, scaling takes less time.
• Helps in saving time in terms of deployment and maintenance.

Network Security Interview questions for freshers - Part 1

What is Symmetric Cryptosystems and Asymmetric Cryptosystems?

Symmetric Cryptosystems: The same key is used for both encryption and decryption. The key need to be kept as private key, hence the SC can also be called as private key cryptography. The secure distribution of keys is the major challenge that is associated with symmetric key cryptosystems. Data Encryption Standard and Advanced Encryption Standards are the algorithms which uses common cryptosystems.

The reliability of security of exchange is based on the security of the symmetric key. A new cipher text can be created by an attacker’s interpretation which uses the symmetric key after reading the cipher text.

Asymmetric Cryptosystems: Both private key and public key are used in Asymmetric cryptosystems. One key is used for data encryption and another for data decryption. Asymmetric cryptography is used in solving the challenge of secure distribution of the secret keys. Asymmetric cryptography solves the challenge of secure distribution of secret keys. Authentication is another feature of Asymmetric Cryptosystems.

 

Disadvantages of Symmetric Cryptosystems.

The following are the disadvantages of Symmetric Cryptosystems:

- Key transportation is one disadvantage of Symmetric Cryptosystems. From the sending system to the receiving system the secret key is to be transmitted before the actual message transmission. Electronic communication, in every means is insecure as it is not guarantee that no tapping communication channels can be tapped. Personal exchanging of key exchange is the only source.

- repudiate digital signatures can not be provided

Disadvantages of Asymmetric Cryptosystems.

The following are the disadvantages of Asymmetric Cryptosystems:

-The encryption speed is the disadvantage of Asymmetric Cryptosystems. Popular secret-key encryption methods are available which are significantly faster than public-key encryption

- The sizes of keys must be larger than symmetric cryptosystems for the purpose of achieving the protection of the same level.

Explain the concept of PKI, Public Key Infrastructure.

Public Key Infrastructure: A set of hardware, software, people, policies and procedures comprises the Public Key Infrastructure (PKI) and digital certificates are revoked. The arrangement of public key binding with respective of identification of users by means of a Certificate Authority , is done in PKI. Every certificate authority should have a unique user identity. The registration and issuance process that is depending on the level of assurance is involved in binding, which may be carried out be software at a CA. The binding assurance portrayed by PKI is known as Registration Authority. The public key certificates issued by the CA are comprised unforgettable user identity, public key and their binding, validity conditions and other attributes.

Explain the different components of PKI - PKI Client, Certification authority (CA), Registration authority, Certificates, Certification distribution systems.

PKI Client: PKI Client is software which enables the USB of eToken operation and implementation of eToken solutions which are PKI based. Certificate-based strong two-factor authentication, encryption and digital signing are included in eToken solution. It is secure, portable and secure by using PKI client.

Certificate Authority: CA is an entity used for the purpose of issuing digital certificates which are used by the other parties. Many public key infrastructure schemes are used in characterizing CAs. The matching private key is available publicly. This key is kept under secret by the end user who is the generator of the key pair.

Registration Authority: A registration Authority verifies the requests of users for a digital certificates and communicates to the certificate authority to issue the certificate. RA is a part of PKI.

Certificates: Certificates are utilized for authentication of network access as strong security for authentication is provided by them for users and computers. Less secure password-based authentication methods are eliminated by the certificates.

Explain the concepts of digital certificates.

A digital certificate is a credential which validates the certificate owner’s identity. The information provided by the digital certificate is known as ‘the subject distinguished name’. Certificate Authority issues the digital certificates to the users or the organizations. The trust in the certificate as a valid credential is provided as the foundation by the Certificate Authority.

What is Tunneling?

A way in which data is transmitted between networks in a secured manner. The complete data is segmented into packets and then transmitted through the tunnel. Each packet passed through tunnel is encrypted with additional layer with tunneling encryption and is used for the purpose of routing the data packets to the right direction. The encapsulation is reverted for decryption at the receiving node.

What is VPN Tunneling Packets?

VPN Tunneling Packets are packets to transmit over VPN in a specific VPN protocol format. These packets are encapsulated within some other base or carrier protocol followed by transmission between VPN client and VPN server. Finally, at the receiving side, de-encapsulation takes place.

Explain the concept of Voluntary and Compulsory Tunnels.

Voluntary Tunnel: The user creates a voluntary tunnel model. This model is typically uses a L2TP enabled client. An L2TP packet is sent by user to the Internet Service Provider which will in turn forward them on to LNS. The support of L2TP support is not needed by ISP. The L2TP tunnel initiator resides on the same system effectively playing as a remote client.

Compulsory Tunnel: The tunnel creation in compulsory tunnel, no action from the user and without allowing the user any choice is performed. Internet service provider access concentrator receives a point-to-point protocol packets from the user. The encapsulation of packets in L2TP and sending them through a tunnel to the L2TP network server is performed by the ISP. It is mandatory that the ISP is L2TP-capable.

What are Static and Dynamic Tunnels?

Static Tunnel: The manually created tunnels are called Static Tunnels. Static tunnels creation is the only choice when global discovery of hosts and tunnel partners are disabled by enhancing Xpress tunnels into manually created tunnels. The priority is higher when compared with static tunnel.

Dynamic Tunnel: The tunnels that are auto-discovered are known as dynamic tunnels. Dynamic tunnels are created quickly and automatically after the Packet Shaper is reset. At the time of preventing automatic tunnel, dynamic tunnels are allowed to setup the situation.

What is PPP Protocol?

Point-to-Point Protocol is known as data link protocol. This protocol is most commonly for establishment of direct connection among network nodes, usually between 2 nodes. Authentication of connection, privacy for transmission encryption and compression are provided by Point-to-Point Protocol. It has three fields – Protocol field, to indicate the type of payload packet. Information field contains the PPP payload, and a Padding field, if at all a particular protocol can be padded to distinguish information from padding.

Explain PPP Packet Format.

The following are the fields in the format of PPP packet. The fields transmission is from left to right.

Code Field: The code field is one octet, which identifies the kind of LCP packet. A code-reject packet is transmitted, when a packet is received with an unknown code field. In the most recent Assigned Numbers RFC, the LCP code field’s up-to-date field values are specified.

Identifier: The identifier field supports as an aid for matching requests and responses. When an invalid identifier field is available in a received packet, the packet discarding occurs without affecting the automation silently.

Length: It has two octets which indicate the length of the LCP packet, including the Code, Identifier, and Data fields. The length is not supposed to exceed the MRU of the specified link. On reception, the octets outside the range of the Length field are treated as padding and are ignored.

Data: It has zero or more octets. This was indicated by the Length field. The Code field identifies the format of Data field.

Explain Point-To-Point Tunneling Protocol, PPTP.

PPTP is one of the methods to implement Virtual Private Networks. Confidentiality or encryption does not provided by PPTP. The reliability of PPTP is being tunneled for the purpose of providing privacy. PPTP works by sending Point-to-Point Protocol to the peer with the Generic Encapsulation protocol. Because of its easy way of configuration, it is most popular protocol used in VPNs. It was the first protocol for VPNs and was supported by Dial-up network of Microsoft.

What is GRE (Generic Routing Encapsulation) in PPTP?

Generic Routing Encapsulation is a protocol for Point-to-Point Protocol. The encapsulation of a variety of network layer protocol packet types inside IP tunnels is done by GRE. This is done by creating virtual point-to-point link to routers which are pointed over an IP internetwork. It is completely stateless protocol based. Soon after it is configured, the GRE tunnel interface comes up and stays up until a valid tunnel resource address or interface is up.

What is CHAP (Challenge-Handshake Authentication protocol)?

Challenge-Handshake Authentication Protocol authenticates to an authenticating entity of a user or network. The entity can be an Internet access provider. CHAP is used by Point-to-Point Protocol that servers for the validation of identifying of remote clients. The identity of the client is verified by CHAP periodically with the use of a three-way handshake. This situation occurs when an initial link is established and maybe repeated after at any time. The shared secret is the base for verification. CHAP protection to play back attack by the peer. This is done by using an incrementally changing identifier and of a variable challenge-value. Both client and server need to know about the plain text of secret which uses CHAP.

What is PAP (Password Authentication Protocol)?

Password Authentication Protocol is one of the simple authentication protocols which are used for the purpose of authenticating a user to a network access server. This is used by Internet service providers. Point-to-Point Protocol uses PAP. Validating a user is the process of authenticating a user to access the server resources. The remote servers of network operating system remote servers support PAP. Unencrypted ASCII passwords are transmitted by Password Authentication Protocol over a network and are treated as insecure. In case of non-supporting a stronger authentication protocol, like CHAP, the PAP is used for the purpose of authentication.

What is Authentication header (AH) protocol?

Data origin authentication, data integrity and replay protection are provided by the Authentication Header protocol. Data confidentiality is not provided by Authentication Header. Data integrity with checksum which is a message authentication code is ensured by AH protocol. A secrete shared key is included by AH protocol for the purpose of ensuring data origin authentication. AH protocol uses a sequence number field for ensuring replays protection, within the header of AH protocol.

What is ESP (Encapsulating Security Payload)?

Encapsulating Security Payload is a protocol for the inter security architecture. It is the key protocol, which is targeted to provide a mixed service of security in IPv4 and IPv6. The ESP seeks for providing confidentiality and integrity by implementing protecting data using encryption and places this data in the portion that is assigned for data of IP ESP. The same mechanism can be used based on the requirements of security of the user. The process can be utilized for encrypting either a transport-layer segment or an entire IP datagram. The protected data encapsulation is used for providing necessary confidentiality for the entire original datagram.