Computer Network Flashcards
Tell me something about VPN (Virtual Private Network)
VPN or the Virtual Private Network is a private WAN (Wide Area Network) built on the internet. It allows the creation of a secured tunnel (protected network) between different networks using the internet (public network). By using the VPN, a client can connect to the organization’s network remotely.
What are the advantages of using a VPN?
Below are few advantages of using VPN:
- VPN is used to connect offices in different geographical locations remotely and is cheaper when compared to WAN connections.
- VPN is used for secure transactions and confidential data transfer between multiple offices located in different geographical locations.
- VPN keeps an organization’s information secured against any potential threats or intrusions by using virtualization.
- VPN encrypts the internet traffic and disguises the online identity.
What are nodes and links?
Node: Any communicating device in a network is called a Node. Node is the point of intersection in a network. It can send/receive data and information within a network. Examples of the node can be computers, laptops, printers, servers, modems, etc.
Link: A link or edge refers to the connectivity between two nodes in the network. It includes the type of connectivity (wired or wireless) between the nodes and protocols used for one node to be able to communicate with the other.
What do you mean by network topology, and explain types of them
Network topology is the arrangement of nodes and links of a network.
Topologies are categorized as either physical network topology or logical network topology.
The topology of a network is key to determining its performance.
Network topology can be categorized into – Bus Topology, Ring Topology, Star Topology, Mesh Topology, Tree Topology.
What is the DNS?
DNS is the Domain Name System. It is considered as the devices/services directory of the Internet. It is a decentralized and hierarchical naming system for devices/services connected to the Internet. It translates the domain names to their corresponding IPs. For e.g. interviewbit.com to 172.217.166.36. It uses port 53 by default.
What is the use of a router and how is it different from a gateway?
The router is a networking device used for connecting two or more network segments. It directs the traffic in the network. It transfers information and data like web pages, emails, images, videos, etc. from source to destination in the form of packets. It operates at the network layer.
The gateways serve as crucial network point that acts as a entrance and exit point in a network.
What is the SMTP protocol?
SMTP is the Simple Mail Transfer Protocol. SMTP sets the rule for communication between servers. This set of rules helps the software to transmit emails over the internet. It supports both End-to-End and Store-and-Forward methods. It is in always-listening mode on port 25.
OSI Layer
Application, Presentation, Session, Transport, Network, Data Link, Physical
Physical Layer
Responsible for transimission of raw bits in the form of different signals and different transimssion modes like full duplex, half duplex and many more.
Data Link Layer
It is used for transferring the data from one node to another node.
It receives the data from the network layer and converts the data into data frames and then attaches the physical address to these frames which are sent to the physical layer.
It enables the error-free transfer of data from one node to another node.
Functions of Data-link layer:
Frame synchronisation: Data-link layer converts the data into frames, and it ensures that the destination must recognize the starting and ending of each frame.
Flow control: Data-link layer controls the data flow within the network.
Error control: It detects and corrects the error occurred during the transmission from source to destination.
Addressing: Data-link layers attach the physical address with the data frames so that the individual machines can be easily identified.
Network Layer
handles routing and forwarding of data packets between different networks.
Logical addressing (IP addressing)
Path determination and routing
Packet forwarding
Network segmentation and fragmentation
Key Protocols:
Internet Protocol (IP), Internet Control Message Protocol (ICMP)
Transport Layer
Data received from segmentation layer is divided into small units called segments.
Each segment have source and destination port number and a sequence number.
Flow Control - Decide the data trasmission rate.
Error Control
Protocols - TCP, UDP
Session Layer
Session management - Responsible for setting up and managing connections.
Authentication and Authorization are performed by session layer
Presentation
Traslation - Convert asci data to binary data
Data compression - reduce the size of bit before sending to the next layer.
Encrypted/ Decryption before sending to the next layer.
use SSL/TSL protocols for encryption and decryption.
Application
Used by network application like web brower, outlook and skype,
- responsible for file transfer - FTP
- Web surfing - http
- Emails - smtp
- virtual terminal - telnet
application layer provide services for network application with the help of different protocols.
Describe the TCP/IP Reference Model?
It is a compressed version of the OSI model with only 4 layers. It was developed by the US Department of Defence (DoD) in the 1980s. The name of this model is based on 2 standard protocols used i.e. TCP (Transmission Control Protocol) and IP (Internet Protocol).
What are the HTTP and the HTTPS protocol?
HTTP is the HyperText Transfer Protocol which defines the set of rules and standards on how the information can be transmitted on the World Wide Web (WWW). It helps the web browsers and web servers for communication. It is a ‘stateless protocol’ where each command is independent with respect to the previous command. HTTP is an application layer protocol built upon the TCP. It uses port 80 by default.
HTTPS is the HyperText Transfer Protocol Secure or Secure HTTP. It is an advanced and secured version of HTTP. On top of HTTP, SSL/TLS protocol is used to provide security. It enables secure transactions by encrypting the communication and also helps identify network servers securely. It uses port 443 by default.
What is the TCP protocol?
TCP or TCP/IP is the Transmission Control Protocol/Internet Protocol. It is a set of rules that decides how a computer connects to the Internet and how to transmit the data over the network. It creates a virtual network when more than one computer is connected to the network and uses the three ways handshake model to establish the connection which makes it more reliable.
Protocols like HTTP, FTP, Telnet, SMTP, HTTPS, etc use TCP at the transport layer
What is the UDP protocol?
UDP is the User Datagram Protocol and is based on Datagrams. Mainly, it is used for multicasting and broadcasting. Its functionality is almost the same as TCP/IP Protocol except for the three ways of handshaking and error checking. It uses a simple transmission without any hand-shaking which makes it less reliable.
Protocols like DNS, RIP, SNMP, RTP, BOOTP, TFTP, NIP, etc use UDP at the transport layer
What is the ICMP protocol?
ICMP is the Internet Control Message Protocol. It is a network layer protocol used for error handling. It is mainly used by network devices like routers for diagnosing the network connection issues and crucial for error reporting and testing if the data is reaching the preferred destination in time. It uses port 7 by default.
What do you mean by the DHCP Protocol?
DHCP is the Dynamic Host Configuration Protocol.
It is an application layer protocol used to auto-configure devices on IP networks enabling them to use the TCP and UDP-based protocols. The DHCP servers auto-assign the IPs and other network configurations to the devices individually which enables them to communicate over the IP network. It helps to get the subnet mask, IP address and helps to resolve the DNS. It uses port 67 by default.
What is the ARP protocol?
ARP is Address Resolution Protocol. It is a network-level protocol used to convert the logical address i.e. IP address to the device’s physical address i.e. MAC address. It can also be used to get the MAC address of devices when they are trying to communicate over the local network.
What is the MAC address and how is it related to NIC?
MAC address is the Media Access Control address. It is a 48-bit or 64-bit unique identifier of devices in the network. It is also called the physical address embedded with Network Interface Card (NIC) used at the Data Link Layer. NIC is a hardware component in the networking device using which a device can connect to the network.
What happens when you enter google.com in the web browser?
Check the browser cache first if the content is fresh and present in cache display the same.
If not, the browser checks if the IP of the URL is present in the cache (browser and OS) if not then request the OS to do a DNS lookup using UDP to get the corresponding IP address of the URL from the DNS server to establish a new TCP connection.
A new TCP connection is set between the browser and the server using three-way handshaking.
An HTTP request is sent to the server using the TCP connection.
The web servers running on the Servers handle the incoming HTTP request and send the HTTP response.
The browser process the HTTP response sent by the server and may close the TCP connection or reuse the same for future requests.
If the response data is cacheable then browsers cache the same.
Browser decodes the response and renders the content.
What are Unicasting, Anycasting, Multicasting and Broadcasting?
Unicasting: If the message is sent to a single node from the source then it is known as unicasting. This is commonly used in networks to establish a new connection.
Anycasting: If the message is sent to any of the nodes from the source then it is known as anycasting. It is mainly used to get the content from any of the servers in the Content Delivery System.
Multicasting: If the message is sent to a subset of nodes from the source then it is known as multicasting. Used to send the same data to multiple receivers.
Broadcasting: If the message is sent to all the nodes in a network from a source then it is known as broadcasting. DHCP and ARP in the local network use broadcasting.
What is the firewall?
The firewall is a network security system that is used to monitor the incoming and outgoing traffic and blocks the same based on the firewall security policies. It acts as a wall between the internet (public network) and the networking devices (a private network). It is either a hardware device, software program, or a combination of both. It adds a layer of security to the network.
Modem
Converts digital signals from your network to signals suitable for phone/cable lines.
Connects your local network to the internet via ISP
Like a translator between your network and internet service
Example: Cable/DSL modem from your internet provider
Repeater
Amplifies network signals to extend range
No data processing, just signal boosting
Like a megaphone for network signals
Example: WiFi extenders in large homes
Gateway
Translates communication between different types of networks
Acts as entrance/exit point between networks
Like a translator between people speaking different languages
Example: Internet gateway connecting your local network to the internet
Bridge
Connects two network segments together
Simpler than a switch but smarter than a hub
Like a bridge connecting two islands
Example: Connecting two floors in a building network
Hub (Legacy Device)
Simple device that copies incoming data to all connected devices
No intelligence in data forwarding
Like shouting in a room - everyone hears everything
Example: Old office networks (rarely used now)
Router
Connects different networks together and directs traffic between them
Uses IP addresses to find best path for data
Like a postal service that knows how to send packages between cities
Example: Your home internet router connecting you to the internet
Switch
A device that connects multiple devices within a network
Uses MAC addresses to send data only to intended device
Like a smart traffic controller that knows exactly which road to send data
Example: Office computers connecting to each other
What is the firewall?
The firewall is a network security system that is used to monitor the incoming and outgoing traffic and blocks the same based on the firewall security policies. It acts as a wall between the internet (public network) and the networking devices (a private network). It is either a hardware device, software program, or a combination of both. It adds a layer of security to the network.
What is a subnet?
A subnet is a network inside a network achieved by the process called subnetting which helps divide a network into subnets. It is used for getting a higher routing efficiency and enhances the security of the network. It reduces the time to extract the host address from the routing table.
Bandwith
Data transfer capacity of a computer network in bits per second.
What is DNS, DNS forwarder, NIC, ?
DNS:
1. DNS is an acronym that stands for Domain Name System.DNS was introduced by Paul Mockapetris and Jon Postel in 1983.
2. It is a naming system for all the resources over the internet which includes physical nodes and applications. It is used to locate resources easily over a network.
3. DNS is an internet which maps the domain names to their associated IP addresses.
4. Without DNS, users must know the IP address of the web page that you wanted to access.
DNS Forwarder : A forwarder is used with a DNS server when it receives DNS queries that cannot be resolved quickly. So it forwards those requests to external DNS servers for resolution. A DNS server which is configured as a forwarder will behave differently than the DNS server which is not configured as a forwarder. NIC stands for Network Interface Card. It is a peripheral card attached to the PC to connect to a network. Every NIC has its own MAC address that identifies the PC on the network. It provides a wireless connection to a local area network. NICs were mainly used in desktop computers.
What is a subnet?
A subnet is a network inside a network achieved by the process called subnetting which helps divide a network into subnets. It is used for getting a higher routing efficiency and enhances the security of the network. It reduces the time to extract the host address from the routing table.
Server-side load balancer
All backend server instances are registered with a central load balancer. A client requests this load balancer which then routes the request to one of the server instances using various algorithms like round-robin. AWS ELB(Elastic Load Balancing) is a prime example of server-side load-balancing that registers multiple EC2 instances launched in its auto-scaling group and then routes the client requests to one of the EC2 instances.
Advantages of server-side load balancing:
Simple client configuration: only need to know the load-balancer address.
Clients can be untrusted: all traffic goes through the load-balancer where it can be looked at. Clients are not aware of the backend servers.
RSA Algorithm
RSA algorithm is an asymmetric cryptography algorithm. Asymmetric actually means that it works on two different keys i.e. Public Key and Private Key. As the name describes, the Public Key is given to everyone and the Private key is kept private.
An example of asymmetric cryptography : A client (for example browser) sends its public key to the server and requests for some data. The server encrypts the data using the client’s public key and sends the encrypted data. Client receives this data and decrypts it. Since this is asymmetric, nobody else except the browser can decrypt the data even if a third party has the public key of the browser.
What is HTTP and HTTPS protocol ?
HTTP is the HyperText Transfer Protocol which defines the set of rules and standards on how the information can be transmitted on the World Wide Web (WWW). It helps the web browsers and web servers for communication. It is a ‘stateless protocol’ where each command is independent with respect to the previous command. HTTP is an application layer protocol built upon the TCP. It uses port 80 by default. HTTPS is the HyperText Transfer Protocol Secure or Secure HTTP. It is an advanced and a secured version of HTTP. On top of HTTP, SSL/TLS protocol is used to provide security. It enables secure transactions by encrypting the communication and also helps identify network servers securely. It uses port 443 by default.
