[Type A] Chapter 12 – Sumita Arora Solutions | Class 12 CS/IP

Modulation is the technique in which the feature (Amplitude, frequency) of the base or message signal is change in accordance to the carrier signal.

The need of modulation:
1. To reduce the bandwidth of signal.
2. To reduce the size of antenna.
3. To increase the transmission range of signal.

The two main type of modulation technique:
1. Amplitude Modulation: In this the amplitude of the base signal is change according to the carrier signal.
2. Frequency Modulation: In this the frequency of the base signal is changes in accordance to the carrier signal.

In Amplitude Modulation amplitude of base/message signal is changes in accordance to the carrier signal and frequency is constant while in Frequency Modulation frequency of base/message signal is changes in accordance to the carrier signal and amplitude is constant throughout.

In a half duplex network, a collision is the result of two devices on the same network attempting to transmit data at exactly the same time. The network detects the “collision” of the two transmitted packets and discards them both.

Wired technologies have techniques for collision detection such as CSMA/CD (Carrier Sense Multiple Access/Collision Detection) on 802.3 networks.

Wireless technologies have techniques for collision detection such as CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) on 802.11 networks to overcome hidden node problem.

Carrier-sense multiple access with collision avoidance (CSMA/CA) in computer networking.

CSMA/CA is used in wireless networks to prevent collisions by checking whether the channel is idle before sending a packet. Collisions can still occur in wireless networks, because two devices trying to access the access point at the same time causes a collision when both are authorized to use the same channel.

This is because the two nodes such as (Node A and C) are out of range of each other (and so cannot detect a collision while transmitting). Thus, Carrier sense multiple access with collision detection (CSMA/CD) does not work, and collisions occur.

ACK simply means acknowledge signal which is an indication signal that the send signal received by receiver end.

RTS means Request To Send and indicates to the connected device that it wants to send data.

CTS means Clear to Send and this is also a control signal like RTS which provide indication that receiver is ready to receive.

It  is a network multiple access method in which carrier sensing is used, but nodes attempt to avoid collisions by beginning transmission only after the channel is sensed to be “idle”.

CSMA requires that each station first check the state of the medium before sending.

CSMA/CR is used in controller area networks (CAN), which are mainly used in cars and machines.
CSMA/CA is mainly used in wireless networks.

 CSMA/CA is mainly used in wireless networks, CSMA/CD was developed for Ethernet as for local area network.

Routing is the process of selecting a path for traffic in a network or between or across multiple networks.
The  routing protocols enable routers to build up a forwarding table that correlates final destinations with next hop addresses.

A routing table contains the information necessary to forward a packet along the best path toward its destination.
Each packet contains information about its origin and destination. Routing Table provides the device with instructions for sending the packet to the next hop on its route across the network.

It is like a path tracking for the packet to propagate to final destination through various stops.

An IP addressing is the process of providing an address used in order to uniquely identify a device on an IP network.

The two versions of IP addressing is IP version 4 (IPv4) and IP version 6 (IPv6).

1. IPv4 is 32 bit binary number while IPv6 is 128 bit binary number address.
2. IPv4 address are separated by periods while IPv6 address are separated by colons.
3. IPv4 address considered the primary Internet Protocol and carries 94% of Internet traffic while IPv6 address is being deployed to fulfil the need for more Internet addresses.

The Domain Name System (DNS) is the phone book of the Internet. We simply interact with web by typing www.google.com. Web browsers interact through Internet Protocol (IP) addresses. DNS translates domain names to IP addresses so browsers can load Internet resources.

URL is Uniform Resource Locator and is a reference (an address) to a resource on the Internet such as pages and content of network server.

 A URL has two main components:
Protocol identifier: For the URL http://google.com, the protocol identifier is http.
Resource name: For the URL http://google.com, the resource name is example.com.

A URL is a complete internet address which can locate a complete server network.
A domain name, on the other hand, is a simpler form of a URL, and having definition to an entity. It somehow relates to IP addressing.

The Protocol (IP) plays this role, by defining unique addresses for a network and a host machine that is defines a set of rules through with the host and user side will interact for exchange of information.

Importance of protocol is same as the disciple in real life that means it bound the mean of interaction and involves security.

TCP/IP specifies how data is exchanged over the internet by providing end-to-end communications that identify how it should be broken into packets, addressed, transmitted, routed and received at the destination.
It is the most common protocol for the interaction.

TCP (Transmission Control Protocol) is a standard that defines how to establish and maintain a network conversation through which application programs can exchange data.

In the Internet protocol set of rules, for routing and addressing packets of data so that they can travel across networks and arrive at the correct destination

TCP uses a congestion window in the sender side to do congestion avoidance.

The congestion window indicates the maximum amount of data that can be sent out on a connection without being acknowledged. 
TCP detects congestion when it fails to receive an acknowledgement i.e. ACK signal for a packet within the estimated timeout.

This phase continues until the congestion window size reaches the slow start threshold. 
Threshold = Maximum number of TCP segments that receiver window can accommodate / 2 = (Receiver window size / Maximum Segment Size) / 2.

(i) In computing, traceroute  are computer network diagnostic commands for displaying destination point.

(ii) Ping is a basic Internet program that allows a user to verify that a particular IP address exists and can accept requests.

(iii) Ipconfig displays all current TCP/IP network configuration values and refreshes Domain Name System (DNS) settings.

(iv) Nslookup is a command-line administrative tool for testing and troubleshooting DNS servers. 

(v) Whois  is a query and response protocol that is widely used for querying databases that store the registered users Internet resource.

The  Protocol (IP) plays this role, by defining unique addresses for a network and a host machine that is defines a set of rules through with the host and user side will interact for exchange of information.

Importance of protocol is same as the disciple in real life that means it bound the mean of interaction and involves security.

(i) HTTP: Hypertext Transfer Protocol (HTTP) is an application-layer protocol for transmitting hypermedia documents, such as HTML.

(ii) FTP: File Transfer Protocol (FTP) is a client/server protocol used for transferring files to or exchanging files with a host computer.

(iii) SCP: SCP is a network protocol, based on the BSD RCP protocol, which supports file transfers between hosts on a network. SCP uses Secure Shell (SSH) for data transfer.

(iv) SSH: SSH is typically used to log into a remote machine and execute commands, but it also supports tunnelling, forwarding TCP ports.

(v) POP: POP (Post Office Protocol) mail refers to email software on your computer that sends and receives mail via a shared computer’s electronic post office.

(vi) IMAP: IMAP (Internet Message Access Protocol) is a standard email protocol that stores email messages on a mail server, but allows the end user to view and manipulate the messages as though they were stored locally on the end user’s computing device.

(vii) SMTP: Simple Mail Transfer Protocol, a protocol for sending e-mail messages between servers. Most e-mail systems that send mail over the Internet use SMTP to send messages from one server to another.

(viii) VoIP: VoIP technology enables traditional telephony services to operate over computer networks. VoIP is the technology that converts your voice into a digital signal, allowing you to make a call directly from a computer,

(ix) NFC: Near Field Communication (NFC) is a short-range wireless connectivity standard that uses magnetic field induction to enable communication between devices when they’re touched together.

Hypertext Transfer Protocol (HTTP) is an application-layer protocol for transmitting hypermedia documents, such as HTML. It was designed for communication between web browsers and web servers. It uses TCP for the communication.

 Your email client transfers the message to your email server. Through the working and set condition of protocol like POP and SMTP. Queries the Server (email address verification and if email address exists) it then proceeds to start process of opening connection to the Recipient mail server to send mail.

Mail Exchange (MX) records are DNS records that are necessary for delivering email to your address. In simple an MX record is used to tell the world which mail servers accept incoming mail for your domain and where emails sent to your domain should be routed to.

Hyper Text Transfer Protocol Secure (HTTPS) is the secure version of HTTP, the protocol over which data is sent between your browser and the website that you are connected to. The ‘S’ at the end of HTTPS stands for ‘Secure’. It means all communications between your browser and the website are encrypted.

Encryption is the process through which data is encoded so that it remains hidden from or inaccessible to unauthorized users. It helps protect private information, sensitive data, and can enhance the security of communication between client apps and servers.

Data without encryption to third party “hello what’s going on”.
Data with encryption to third party “!@#f%^D5f5”.

Secure Sockets Layer (SSL) is a standard security technology for establishing an encrypted link between a server and a client-typically a web server (website) and a browser.

It enhances the Security and neglect to involvement and interruption of third party involvement.

Remote desktop is a program or an operating system feature that allows a user to connect to a computer in another location, it allows access to someone else system from remote location.

A login that allows a user terminal to connect to a host computer via a network or direct telecommunications link.