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THE NETWORKING INTERVIEW QUESTION AND ANSWER
A backbone network is a centralized infrastructure that is designed to distribute different routes and data to various networks. It also handles management of bandwidth and various channels.
What are routers?
Routers can connect two or more network segments. These are intelligent network devices that store information in its routing table such as paths, hops and bottlenecks. With this info, they are able to determine the best path for data transfer. Routers operate at the OSI Network Layer.
What is anonymous FTP?
Anonymous FTP is a way of granting user access to files in public servers. Users that are allowed access to data in these servers do not need to identify themselves, but instead log in as an anonymous guest.
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.
Describe Network Topology
Network Topology refers to the layout of a computer network. It shows how devices and cables are physically laid out, as well as how they connect to one another.
Briefly describe NAT.
NAT is Network Address Translation. This is a protocol that provides a way for multiple computers on a common network to share a single connection to the Internet.
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 the basis on what materials, connectors and terminations that are applicable for the setup.
What are different ways of securing a computer network?
There are several ways to do this. Install reliable and updated anti-virus programs on all computers. Make sure firewalls are set up and configured properly. User authentication will also help a lot. All of these combined would make a highly secured network.
What is WAN?
WAN stands for Wide Area Network. It is an interconnection of computers and devices that are geographically dispersed. It connects networks that are located in different regions and countries.
How many layers are there under TCP/IP?
There are four layers: the Network Layer, Internet Layer, Transport Layer and Application Layer.
What is the function of the OSI Session Layer?
This layer provides the protocols and means for two devices on the network to communicate with each other by holding a session. This includes setting up the session, managing information exchange during the session, and tear-down process upon termination of the session.
What does 10Base-T mean?
The 10 refers to the data transfer rate, in this case 10Mbps. The word Base refers to base band, as opposed to broad band. T means twisted pair, which is the cable used for that network.
What is NOS?
NOS, or Network Operating System, is specialized software whose main task is to provide network connectivity to a computer in order for it to be able to communicate with other computers and connected devices.
What is OSI and what role does it play in computer networks?
OSI (Open Systems Interconnect) serves as a reference model for data communication. It is made up of 7 layers, with each layer defining a particular aspect on how network devices connect and communicate with one another. One layer may deal with the physical media used, while another layer dictates how data is actually transmitted across the network.
What is the advantage of address sharing?
By using address translation instead of routing, address sharing provides an inherent security benefit. That’s because host PCs on the Internet can only see the public IP address of the external interface on the computer that provides address translation and not the private IP addresses on the internal network.
What is the equivalent layer or layers of the TCP/IP Application layer in terms of OSI reference model?
The TCP/IP Application layer actually has three counterparts on the OSI model: the Session layer, Presentation Layer and Application Layer.
What is the main purpose of OSPF?
OSPF, or Open Shortest Path First, is a link-state routing protocol that uses routing tables to determine the best possible path for data exchange.
Describe star topology
Star topology consists of a central hub that connects to nodes. This is one of the easiest to set up and maintain.
What is the disadvantage of a star topology?
One major disadvantage of star topology is that once the central hub or switch gets damaged, the entire network becomes unusable.
Give some examples of private network addresses.
10.0.0.0 with a subnet mask of 255.0.0.0 172.16.0.0 with subnet mask of 255.240.0.0 192.168.0.0 with subnet mask of 255.255.0.0
What are the functions of a network administrator?
A network administrator has many responsibilities that can be summarized into 3 key functions: installation of a network, configuration of network settings, and maintenance/troubleshooting of networks.
What is a Hybrid Network?
A hybrid network is a network setup that makes use of both client-server and peer-to-peer architecture.
What is the main job of the ARP?
The main task of ARP or Address Resolution Protocol is to map a known IP address to a MAC layer address.
How can you manage a network using a router?
Routers have a built-in console that lets you configure different settings, like security and data logging. You can assign restrictions to computers, such as what resources are allowed access, or what particular time of the day they can browse the internet. You can even put restrictions on what websites are not viewable across the entire network.
What is the use of a default gateway?
Default gateways provide means for the local networks to connect to the external network. The default gateway for connecting to the external network is usually the address of the external router port.
What is the proper termination rate for UTP cables?
The proper termination for unshielded twisted pair network cable is 100 Mbps.
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.
What common software problems can lead to network defects?
Software related problems can be any or a combination of the following: - client server problems - application conflicts - error in configuration - protocol mismatch - security issues - user policy and rights issues
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.
What is DNS?
DNS is Domain Name Server. The main function of this network service is to provide host names to TCP/IP address resolution.
What is the difference between a hub and a switch?
A hub acts as a multiport repeater. However, as more and more devices connect to it, it would not be able to efficiently manage the volume of traffic that passes through it. A switch provides a better alternative that can improve the performance especially when high traffic volume is expected across all ports.
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
What protocols fall under the Application layer of the TCP/IP stack?
The following are the protocols under the TCP/IP Application layer: FTP, TFTP, Telnet and SMTP.
What is ipconfig?
Ipconfig is a utility program that is commonly used to identify the address information of a computer on a network. It can show the physical address as well as the IP address.
What is client/server?
Client/server is a type of network wherein one or more computers act as servers. Servers provide a centralized repository of resources such as printers and files. Client refers to workstations that access the server.
When you move the NIC cards from one PC to another PC, does the MAC address get transferred as well?
Yes, that’s because MAC addresses are hard-wired into the NIC circuitry, not the PC. This also means that a PC can have a different MAC address when the NIC card was replaced by another one.
In a network that contains two servers and twenty workstations, where is the best place to install an Anti-virus program?
An anti-virus program must be installed on all servers and workstations to ensure protection. That’s because individual users can access any workstation and introduce a computer virus when plugging in their removable hard drives or flash drives.
What are some drawbacks of implementing a ring topology?
In case one workstation on the network suffers a malfunction, it can bring down the entire network. Another drawback is that when there are adjustments and reconfigurations needed to be performed on a particular part of the network, the entire network has to be temporarily brought down as well.
What is SMTP?
SMTP is short for Simple Mail Transfer Protocol. This protocol deals with all Internal mail, and provides the necessary mail delivery services on the TCP/IP protocol stack.
What is the importance of Encryption on a network?
Encryption is the process of translating information into a code that is unreadable by the user. It is then translated back or decrypted back to its normal readable format using a secret key or password. Encryption help ensure that information that is intercepted halfway would remain unreadable because the user has to have the correct password or key for it.
Explain the importance of authentication.
Authentication is the process of verifying a user’s credentials before he can log into the network. It is normally performed using a username and password. This provides a secure means of limiting the access from unwanted intruders on the network.
What are the different technologies involved in establishing WAN links?
Analog connections – using conventional telephone lines; Digital connections –using digital-grade telephone lines; switched connections – using multiple sets of links between sender and receiver to move data.
When troubleshooting computer network problems, what common hardware-related problems can occur?
A large percentage of a network is made up of hardware. Problems in these areas can range from malfunctioning hard drives, broken NICs and even hardware startups. Incorrectly hardware configuration is also one of those culprits to look into.
How does dynamic host configuration protocol aid in network administration?
Instead of having to visit each client computer to configure a static IP address, the network administrator can apply dynamic host configuration protocol to create a pool of IP addresses known as scopes that can be dynamically assigned to clients.
What is sneakernet?
Sneakernet is believed to be the earliest form of networking wherein data is physically transported using removable media, such as disk, tapes.
What protocols fall under the TCP/IP Internet Layer?
There are 4 protocols that are being managed by this layer. These are ICMP, IGMP, IP and ARP.
What is one basic requirement for establishing VLANs?
A VLAN requires dedicated equipment on each end of the connection that allows messages entering the Internet to be encrypted, as well as for authenticating users.
What is the RSA algorithm?
RSA is short for Rivest-Shamir-Adleman algorithm. It is the most commonly used public key encryption algorithm in use today.
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.
If you are a victim of Denial of Service (Dos) then what do you do?
The function of a denial of service attack is to flood its target machine with too much traffic and prevent it from being accessible to any other requests or providing services.
To prevent DoS attacks the firewall can be configured as a relay; in this approach the firewall responds on behalf of the internal host. During the attack, the firewall responds to the SYN sent by the attacker; since the ACK never arrives, the firewall terminates the connection. By Keeping protocols and Antivirus software up-to-date, we can prevent being a victim of DoS. A regular scanning of the machine is also necessary in order to detect any “anomalous” behavior.Comment on Data Encryption Standard (DES) weakness and strength.The Data Encryption Standard (DES) is a symmetric key block cipher which takes 64-bit plaintext and 56-bit key as an input and produces 64-bit cipher text as output. The DES function is made up of P and S-boxes. P-boxes transpose bits and S-boxes substitute bits to generate a cipher.
Strength- The strength of DES lies on two facts:
The use of 56-bit keys: 56-bit keys are used in encryption, there are 256 possible keys. A brute force attack on such a number of keys is impractical. The nature of algorithm: Cryptanalysts can perform cryptanalysis by exploiting the characteristic of DES algorithm but no one has succeeded in finding out the weakness.
Weakness- Weakness has been found in the design of the cipher:
Two chosen inputs to an S-box can create the same output. The purpose of initial and final permutation is not clear.
What are Brute Force Attacks?
Brute forcing is a mechanism which is used by an attacker to break the encryption of data by applying a set of various keys. Cryptanalysts have a set number of keys and apply them one by one to the encryption algorithm until he get the right key.
How do you use RSA for both authentication and secrecy?
RSA is a public key encryption algorithm. The RSA algorithms are based on the mathematical part that it is easy to find and multiply large prime numbers together, but it is extremely difficult to factor their product.For authentication: One can encrypt the hash (MD4/SHA) of the data with a private key. This is known as digital signature.For Secrecy: Secrecy/confidentiality is achieved by encrypting the data with public key and decrypting with private key.
Can you differentiate among encoding, encryption and hashing?
Encoding: Basically encoding is used to protect the integrity of data as it crosses through a communication network to keep its original message upon arriving. It is primarily an insecure function because it is easily reversible.
Encryption: Encryption is basically designed for confidentiality and data integrity and reversible only if you have the appropriate key.
Hashing: With hashing the operation is one-way i.e. non-reversible. It takes an input (or ‘message’) and returns a fixed-size string, which is called the hash value.
If you have to generate a hash function then what characteristics are needed in a secure hash function?
A secure hash function should have the following characteristics:
i. The output generated by a hash function should be of a fixed length.
ii. It should be very easy to find out a hash function for a given message.
iii. If a hash value is given to a message then it is almost impossible to get that message.
iv. The two different messages should not have the same hash value; it is against the hash function property.
What is digital signature? Differentiate between Physical and Digital Signature
A digital signature is an electronic analogue of a written signature; the digital signature can be used to provide assurance that the claimed signatory signed the information. Digital signature is used to detect the integrity of signed data. We can differentiate between physical and digital signature as:
i. Physical signature is just writing on paper but digital signature includes crucial parameters of identification.
ii. Physical signatures can be copied but it is impossible to copy a digital signature.
iii. Physical signature does not give any privacy to content but digital signature enables encryption and thus privacy.
What is Authentication Header and how does it provide protection to IP header?
Basically Authentication Header protects IP header and provides complete authenticity to the IP packets.AH may work in two ways: transport mode and tunnel mode.In tunnel mode; AH protects the IP header using two IP header layers inner and outer. The inner IP header is used to contain the source and destination addresses, and the outer IP header is used to contain the security gateway information.
Explain SSL Protocol. How does it protect internet users from various threats?
The SSL protocol (Secure Socket Layer protocol) was originally developed by Netscape, to ensure security of data transported and routed through HTTP, LDAP or POP3 application layer.SSL uses TCP as a communication layer to provide a reliable end-to-end secure and authenticated connection, which helps internet users to protect from various threats. SSL Record protocol is used to ensure the data security and integrity.
What is PIX firewall security? How does it differ from a firewall?
PIX (Private Internet Exchange)
It is a popular IP firewall and NAT (Network Address Translation) appliance.
PIX firewall security is developed by Cisco Systems.
PIX firewall is used to protect your network with a stateful packet filtering firewall.
A firewall is a part of a computer system or network that is designed to block unauthorized access while permitting authorized communications.
What is Malware? Explain different types of Malware?
Malware is a software program which is developed to destroy a computer system. These programs run in the victim's computer without any information to the victim, i.e. the victim does not know that someone hacked his system.
Different types of malware are: worm, Trojans Horse, Rootkits.
Worm: Worm is a computer program which makes its copy again and again in the victim’s computer. They damage the network by using a lot of bandwidth.
Trojan Horses: Trojan horse consists of two parts, server and client. Server is an executable file which runs on the victim's computer and the attacker may take full control of the victim’s computer.
Rootkits: Rootkits are used to hide the malicious processes from active process
What are replay attacks? Give an example of replay attack
Replay attacks are the network attacks in which an attacker spies the conversation between the sender and receiver and takes the authenticated information e.g. sharing key and then contact to the receiver with that key. In Replay attack the attacker gives the proof of his identity and authenticity.
Example: Suppose in the communication of two parties A and B; A is sharing his key to B to prove his identity but in the meanwhile Attacker C eavesdrops on the conversation between them and keeps the information which are needed to prove his identity to B. Later C contacts B and proves its authenticity.
If you have to ‘encrypt’ as well as ‘compress’ data during transmission then which would you do first and why?
Data should be transmitted over any communication network in such a way that the data integrity and authenticity should be maintained, for this first compress the data and then encrypt the data.
The reason behind it is; if you encrypt first you will have nothing but random data to work with, which will destroy any potential benefit from compression.
What is the goal of Information Security in an organization?
Mainly there are three Information security goals in an organization: Confidentiality, Integrity and Availability.
Confidentiality: Confidentiality means maintaining secrecy during transmission of information.
Integrity: Integrity means changes made in the stored information need to be done only by authorized entities and through authorized mechanisms.
Availability: Information is useless if it is not available. Availability means information created and stored should be available to authorized entities.
What is Symmetric-Key cryptography and Asymmetric-Key cryptography?
Symmetric-Key Cryptography: Symmetric-key cryptography uses a single key for both encryption and decryption. Encryption and decryption algorithms are inverse of each other.
Example:To create the ciphertext from the plaintext John uses an encryption algorithm and a key. To create the plaintext from ciphertext, Bob uses the decryption algorithm and the same key.
Asymmetric-Key cryptography: It is also called public key cryptography. In public key cryptography two keys: a private key and a public key is used. Encryption is done through the public key and decryption through private key. Receiver creates both the keys and is responsible for distributing its public key to the communication community.
Example:The sender (say John) uses the public key to encrypt the plaintext into ciphertext and the receiver (say Bob) uses his private key to decrypt the ciphertext.Explain the services provided by IP (Internet Protocol) - Addressing, Fragmentation, Packet timeouts and options
1. Addressing: For the purpose of delivering data-gram 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 on the 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 for the 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 the 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: 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 account 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 192-223. 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 the 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 purposes. 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 use unicast messaging.
Broadcast: A term used for describing communication that sends 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 a network address and the host address. The first two numbers represent the network address and the second two numbers represent the host of the network.Define Subnetting.A subnet describes a set of networked computers which have a 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, without 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 using delayed packets’. Its stateless nature allows the server to answer smaller queries to a huge number of clients.
Explain TCP Windowing concept.
TCP Windowing is a concept that is used for avoiding congestion in the network traffic. An unacknowledged amount of data that is sent by the sender before the data gets acknowledgment back from the receiver that it has received 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 domains meaningful to humans into binary identifiers that are associated with the equipment of the 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 the internet. Any cast technology enables requests to be answered to the next closest node in the case of maintenance or downtime.Smarter: Automatic corrections of typos.
What is the TTL (Time to Live)? Why is it required?
TTL is a value in a 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 a 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 the 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.
What is the use of IGMP protocol
Internet Group Management Protocol: - It allows internet hosts to participate in multicasting. The IGMP messages are used to learn which hosts are part of which multicast groups. The mechanism also allows a host to inform its local router that it wants to receive messages.
What are Ping and Tracert?
Ping and tracert are the commands used to send information to some remote computers to receive some information. Information is sent and received by packets. Ping I particularly used to check if the system is in network or not. It also gives packet lost information. In windows ping command is written as ping ip_address Tracert is called as trace route. It is used to track or trace the path the packet takes from the computer where the command is given until the destination. In windows ping command is written as tracert ip_address
Explain RSVP. How does it work?
Resource Reservation protocol is used to reserve resources across a network. It is used for requesting a specific Quality of Service (QoS) from the network. This is done by carrying the request (that needs a reservation of the resource) of the host throughout the network. It visits each node in the network. RSVP used two local modules for reservation of resources. Admission control module confirms if there are sufficient available resources while policy module checks for the permission of making a reservation. RSVP offers scalability. On a successful completion of both checks RSVP uses the packet classifier and packet scheduler for the desired Qos requested.
Explain the concept of DHCP.
Dynamic Host Configuration Protocol is used to assign IP addresses to computers in a network. The IP addresses are assigned dynamically. Certainly, using DHCP, the computer will have a different IP address every time it is connected to the network. In some cases the IP address may change even when the computer is in the network. This means that DHCP leases out the IP address to the computer for some time. A clear advantage of DHCP is that the software can be used to manage IP addresses rather than the administrator.
What are the differences between a domain and a workgroup?
In a domain, one or more computers can be a server to manage the network. On the other hand in a workgroup all computers are peers having no control on each other. In a domain, a user doesn’t need an account to logon on a specific computer if an account is available on the domain. In a work group the user needs to have an account for every computer. In a domain, Computers can be on different local networks. In a work group all computers need to be a part of the same local network.
Explain how NAT works.
Network Address Translation translates an IP address used in a network to another IP address known within another network. A NAT table is maintained for global to local and local to mapping of IP’s. NAT can be statically defined or dynamically translated from a pool of addresses. The NAT router is responsible for translating traffic coming and leaving the network. NAT prevents malicious activity initiated by outside hosts from reaching local hosts by being dependent on a machine on the local network to initiate any connection to hosts on the other side of the router.
What is PPP protocol? Explain PPP packet format.
Point to Point protocol helps communication between 2 computers over a serial cable, phone line or other fiber optic lines. E.g. Connection between an Internet Service Provider and a host. PPP also provides authentication. PPP operates by sending Request packets and waiting for Acknowledge packets that accept, reject or try to change the request. The protocol is also used to negotiate on network address or compression options between the nodes.
Packet format:- Flag field: 1 byte: - Indicates frames beginning or end Address field: 1 byte: - Used for broadcast address (destination address) Control field: 1 byte: - Used as a control byte Protocol field: - 1 or 2 bytes: - Setting of protocol in information field (of datagram) Information: - 0 or more bytes: - Datagram (whether it contains data or control information) Padding: - 0 or more bytes: - optional padding FCS: - 2 or more bytes: - error check sum
What is IP Spoofing and how can it be prevented?
IP spoofing is a mechanism used by attackers to gain unauthorized access to a system. Here, the intruder sends messages to a computer with an IP address indicating that the message is coming from a trusted host. This is done by forging the header so it contains a different address and making it appear that the packet was sent by a different machine.
Prevention:-Packet filtering: - to allow packets with recognized formats to enter the network Using special routers and firewalls. Encrypting the session
What is an application gateway?
An application gateway is an application program that runs on a firewall between two networks. An application gateway is used for establishing connection between client programs and destination service. The client negotiates with the gateway to communicate with the service of destination. Here, gateway can be called as a proxy. Hence, two connections are made. One between client and proxy; other, between proxy and destination service. Connections take place behind the firewall.
What is 'Gateway Of Last Resort'?
A Gateway of Last Resort or Default gateway is a route used by the router when no other known route exists to transmit the IP packet. Known routes are present in the routing table. Hence, any route not known by the routing table is forwarded to the default route. Each router which receives this packet will treat the packet the same way, if the route is known, the packet will be forwarded to the known route.
What is Router? Explain components of Routers.
The way switches connect multiple computers, a router connects multiple networks. Routers comprise of data consisting of large tables of networks and addresses. Routers use algorithms to determine the shortest route to an address in a network.
Explain different layers in the OSI model.
Application Layer:Closest to the end user Interact directly with the software application.
Presentation Layer:Translates application to network format, and vice versa Works to transform data into the form that the application layer can accept Formats and encrypts data to be sent across a network
Session Layer: Controls the connections between computers Establishes, manages and terminates the connections between the local and remote application. Provides full-duplex, half-duplex, or simplex operation Establishes checkpointing, adjournment, termination, and restart procedures
Transport Layer: Provides transparent transfer of data between end users Providing reliable data transfer services to the upper layers Controls the reliability of a given link through flow control, segmentation /desegmentation, and error control.
Network Layer: Provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks Performs network routing functions Performs fragmentation and reassembly, and reports delivery errors.
Data Link Layer: Provides the functional and procedural means to transfer data between network entities Detects and corrects errors that occur in the Physical Layer.
Physical Layer: Defines the electrical and physical specifications for devices.
What is IP Multicasting?
It is an IP address that identifies a particular group of hosts in a network. This group of hosts is called a multicast group.
What is Subneting? Explain the advantages of using Subnetting.
Subnetting is dividing a network into several subnets. This is usually done for the following purposes: Reducing network traffic by decreasing the number of broadcasts Exceeding the limitations in a local area network Enabling people to connect to the network remotely without opening the entire network.
What is VLSM, Variable length subnet masking?
VLSM is a means of allocating IP addressing resources to subnets according to their individual need rather than some general network-wide rule.
Explain the concepts and capabilities of IP Datagram.
Data transmitted over an internet using IP is carried in messages called IP datagrams. Like all network protocol messages, IP uses a specific format for its datagrams.
The IPv4 consists of the following fields: Version: the version of IP used to generate the datagram. For IPv4, this is of course the number 4 Internet Header Length: Specifies the length of the IP header, in 32-bit words. Type of service: information to provide quality of service features Total Length Identification: it can be used if the datagram must be fragmented by a router during delivery and then for reassembling. Flags: (Don’t Fragment, More Fragment) Fragment Offset: When fragmentation of a message occurs, this field specifies the offset, or position. Time to Live: specifies how long the datagram is allowed to “live” Protocol: ICMP, TCP, UDP, etc Header Checksum: to provide basic protection against corruption in transmission. Source Address Destination Address Options Padding: if number of bits used for options is not a multiple of 32, then padding is added Data
What is a MAC address?
Media Access Control address is an identifier 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 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.
Explain the function of Transmission Control Block
Hort for a trusted computing base. TCB refers to the totality of protection mechanisms (hardware, firmware and software) that provide a secure computing environment. The TCB includes everything that must be trusted --access control, authorization and authentication procedures, cryptography,firewalls, virus protection, data backup, and even human administration -- in order for the right level of security to work.
Difference between bit rate and baud rate?
Bit rate is no. of bits transmitted during one second. baud rate is max. no of times the signal is changed per second.
What is the difference between a tree and forest?
A tree starts whenever you install the first domain controller and a tree may consist of a single domain or multiple domain arranged in structure called child or grand child which will inherit name from its parent. When we install the first domain controller, a new domain ,a new tree and a new forest begins.In a new forest you can have a single tree or multiple tree.
What are NETBIOS and NETBEUI?
NETBIOS: basic input and output system.It is a non-routable protocol. NETBEUI: Netbeui is the protocol that is responsible for data transport.does handle all the frame formatting that is not handled by netbios.
What is RIP (Routing Information Protocol)?
Rip (routing information protocol) there are two type .class full and classless protocol.is a distance vector protocol selecting nearest best path count a hope 0 to 15.
What is the difference between TFTP and FTP application layer protocols?
FTP is connection oriented, whereas TFTP is not. TFTP uses error checking and flow control, whereas TFTP does not cause error checking.
FTP uses TCP as transport protocol, whereas TFTP uses UDP as transport protocol. Authentication is mandatory in FTP, whereas authentication is not needed in TFTP.
Just getting and putting application effectively is the design concern of TFTP, whereas FTP provides more control and data connection aspects.how drivers are selected and implemented for various network components. Drivers are selected for Network components as per their performance and capacity to carry the signals across the network and it also depends on the performance of the drivers of Networks selected, that should be robust and easy to implement and secure.
What is the difference between baseband and broadband transmission?
In a base-band transmission, the entire bandwidth of the cable is consumed by a single signal. In broadband transmission, signals are sent on multiple frequencies, allowing multiple signals to be sent simultaneously
What is piggy backing?
The technique of temporarily delaying outgoing acknowledgement so that it can be hooked on to the next outgoing data frames is called piggybacking.. The advantage of using piggybacking is the better utilization of available channel bandwidth.
Define IP ?
Ans: Internetwork protocol (IP) is the transmission mechanism used by TCP/IP protocol.It is an unreliable and connectionless datagram protocol.It provides no error checking and tracking.
What is the information that a computer attached to a TCP/IP internet must possess?
Ans: Each computer attached to TCP/IP must possesses the following information • Its IP address • Its subnet mask • The IP address of the router. • The Ip address of the name server.
What is TELNET ?
Ans: TELNET is a client –server application that allows a user to log on to a remote machine,giving the user access to the remote system. TELNET is an abbreviation of terminal Network.
What is Network Virtual Terminal ?
Ans: A universal interface provided by TELNET is called Network Virtual Terminal(NVT) character set.Via this interface TELNET translates characters (data or command) that come from local terminal into NVT form and delivers them to the network
What is Hypertext Transfer Protocol(HTTP) ?
Ans: It is the main protocol used to access data on the World Wide Web .the protocol transfers data in the form of plain text,hypertext,audio,video,and so on. It is so called because its
What is the URL ?
Ans: It is a standard for specifying any kind of information on the World Wide Web
What is HTML?
Ans: Hypertext Markup Language (HTML) is a language for creating static web pages
