Data Communications

The term "Data Communication" comprises two words: Data and Communication. Data can be any text, image, audio, video, and multimedia files. Communication is an act of sending or receiving data. Thus, data communication refers to the exchange of data between two or more networked or connected devices. These devices must be capable of sending and receiving data over a communication medium. Examples of such devices include personal computers, mobile, phones, laptops, etc.

Components

Data Communication 5 components-

1. Message
2. Sender
3. Receiver
4. Transmission Medium
5. Set of rules (Protocol)

Sender: A sender is a computer or any such device which can send data over a network. It can be a computer, mobile phone, smartwatch, walkie-talkie, video recording device, etc.

Receiver: A receiver is a computer or any such device which can receive data from the network. It can be any computer, printer, laptop, mobile phone, television, etc. In computer communication, the sender and receiver are known as nodes in a network.

Message: It is the data or information that needs to be exchanged between the sender and the receiver. Messages can be in the form of text, number, image, audio, video, multimedia, etc.

Communication media: It is the path through which the message travels between source and destination. It is also called medium or link which is either wired or wireless. For example, a television cable, telephone cable, ethernet cable, satellite link, microwaves, etc.

Protocols: It is a set of rules that need to be followed by the communicating parties in order to have successful and reliable data communication. You have already come across protocols such as Ethernet and HTTP.

The Intel 4004 is a 4-bit central processing unit (CPU) released by Intel Corporation in 1971.

A Small Network: Bluetooth connection amount computer diagram is below,

Given, Number of computers = 4 then Total Connection = (4 x 2) / 3 = 6

Types of Computer Network

1. PAN (Personal Area Network): It is the network connecting computer devices for personal use within a range of 10 meters.
2. LAN (Local Area Network): It is a collection of computers connected to each other in a small area, for example school, office, or building.
3. WAN (Wide Area Network): A Wide Area Network is a larger area than the LAN. It is spread across the states or countries.
4. MAN (Metropolitan Area Network): A Metropolitan area network is the collection of interconnected Local Area Networks.

Computer Network falls under these broad Categories:

1. Client-Server Architecture:Client-Server Architectureis a type of Computer Network Architecture in which Nodes can be Servers or Clients. Here, the server node can manage the Client Node Behaviour.
2. Peer-to-Peer Architecture:InP2P (Peer-to-Peer) Architecture, there is not any concept of a Central Server. Each device is free for working as either client or server.

Terminologies of Computer Networks

Network:A network is a collection of computers and devices that are connected together to enable communication and data exchange.

Nodes:Nodes are devices that are connected to a network. These can include computers, Servers, Printers,Routers,Switches, and other devices.

Protocol:A protocol is a set of rules and standards that govern how data is transmitted over a network. Examples of protocols includeTCP/IP,HTTP, andFTP.

NAT: A Network Address Translation (NAT) is the process of mapping an internet protocol (IP) address to another by changing the header of IP packets while in transit via a router.

Topology:Network topology refers to the physical and logical arrangement of nodes on a network. The common network topologies include bus, star, ring, mesh, and tree.

Service Provider Networks:These types of Networks give permission to take Network Capacity and Functionality on lease from the Provider. Service Provider Networks include Wireless Communications, Data Carriers, etc.

IP Address: An IP address is a unique numerical identifier that is assigned to every device on a network. IP addresses are used to identify devices and enable communication between them.

DNS:TheDomain Name System (DNS)is a protocol that is used to translate human-readable domain names (such as www.google.com) into IP addresses that computers can understand.

Firewall:Afirewallis a security device that is used to monitor and control incoming and outgoing network traffic. Firewalls are used to protect networks from unauthorized access and other security threats.

Network Devices

Network devices, also known as networking hardware, are physical devices that allow hardware on a computer network to communicate and interact with one another. For example, Repeater, Hub, Bridge, Switch, Routers, Gateway, Brouter, and NIC, etc.

Repeater

A repeater operates at the physical layer of the OSI model.

• A Repeater connects two segments of a network cable.
• Sometimes it regenerates the signals to proper amplitudes and sends them to the other segment.
• If the signal becomes weak, it can copy the signal bit by bit and regenerate it at the original strength.
• It is a 2-port device.

Repeater Symbol

Attenuation: Signal strength decreases with respect to distance

Hub

Hubs work in the physical layer of the OSI model. A hub is a device for connecting multiple Ethernet devices and making them act as a single network segment. It has multiple inputs and output ports in which a signal introduced at the input of any port appears at the output of every port except the original incoming port.

Bridge

A bridge operates at the data link layer of the OSI model. It can read only the outmost hardware address of the packet but cannot read the IP address. It reads the outmost section of the data packet to tell where the message is going. It reduces the traffic on other network segments. It does not send all the packets. So, a bridge can be programmed to reject packets from a particular network.

Switch

Switches may operate at one or more layers of the OSI model. They may operate in the data link layer and network layer; a device that operates simultaneously at more than one of these layers is known as amultilayer switch.

Router

Routers are small physical devices that operate at the network layer to join multiple networks together.

• A router is a device like a switch that routes data packets based on their IP addresses.
• Routers normally connect LANs and WANs and have a dynamically updating routing table based on which they make decisions on routing the data packets.
• A Router divides the broadcast domains of hosts connected through it.

Gateway

A network gateway can operate at any level of the OSI model. A broadband router typically serves as the network gateway, although ordinary computers can also be configured to perform equivalent functions.

• A gateway is a router or proxy server that routes between networks.
• A gateway belongs to the same subnet to which the PC belongs.

Switch Vs Hub?

Protocol Vs model

OSI Model:OSI stands forOpen Systems Interconnection. It is a reference model that specifies standards for communications protocols and also the functionalities of each layer.The OSI has been developed by the International Organization For Standardization and it is 7 layer architecture. Each layer of OSI has different functions and each layer has to follow different protocols.

Protocol: A protocol is a set of rules or algorithms which define the way how two entities can communicate across the network and there exists a different protocol defined at each layer of the OSI model. A few such protocols are TCP, IP, UDP, ARP, DHCP, FTP, and so on.

Protocols define the format, order of messages sent and received among network entities, and actions taken on message transmission, receipt.

A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.

TCP/IP Vs OSI model Layer

The TCP/IP model refers to the Transmission Control Protocol/Internet Protocol Model. This model is a part of the network domain designed specifically for overseeing efficient and error-free transmission of data.

Layer segregation of TCP/IP Protocol and OSI model-

Difference between OSI Model and TCP/IP Model-

TCP Vs IP

TCP/IP is to transfer the data of a computer from one device to another. The main condition of this process is to make data reliable and accurate so that the receiver will receive the same information which is sent by the sender. To ensure that, each message reaches its final destination accurately, the TCP/IP model divides its data into packets and combines them at the other end, which helps in maintaining the accuracy of the data while transferring from one end to another end.

The Transmission Control Protocol (TCP) is a communication protocol responsible for ensuring that data is transferred reliably and in order between the two devices.

IP is the network layer protocol responsible for routing network traffic.

IP finds the destination of the mail and TCP has the work to send and receive the mail. UDP is another protocol, which does not require IP to communicate with another computer. IP is required by only TCP.

TCP/IP Callback Life Cycle

The TCP/IP protocol suite is the set of communication protocols used to connect hosts on the Internet. TCP/IP allows computers on the same network to identify and communicate with each other. TCP/IP is a two-layer protocol, with the transport layer (TCP) responsible for reliable end-to-end communication and the Internet layer (IP) accountable for routing packets from the host to the host. TCP/IP is a set of standardized rules that allow computers to communicate on a network such as the internet.

• At the transport layer, TCP provides a reliable byte-stream service to applications. TCP guarantees the delivery of data and that data will be delivered in the same order in which it was sent. TCP uses several mechanisms to provide this service, including sequence numbers, acknowledgments, and timeouts.
• At the Internet layer, IP is responsible for routing datagrams (packets) from host to host. IP does not guarantee the delivery of datagrams, but it tries to deliver them as best. If a datagram cannot be delivered, IP will return an error message to the source host.

Top view of TCP/IP layer architecture-

Segment structure for Transport Layer-

Packet structure for Network layer architecture-

FRAME structure for Data Link Layer -

Advantages of TCP/IP

• Scalability: The TCP/IP model is highly scalable and can accommodate small and large networks.
• Reliability: The model is robust and reliable, making it suitable for mission-critical applications.
• Flexibility: It is very flexible, allowing for interoperability between different types of networks.
• Security: The various protocols in the model provide robust security measures.
• Cost-effectiveness: TCP/IP is relatively inexpensive to implement and maintain.

Disadvantages of TCP/IP

• Complexity: The model is quite complex and requires a certain degree of expertise to configure and maintain.
• Vulnerability: Because of its complexity, it is vulnerable to attack.
• Performance: Performance can be degraded due to network congestion and latency.

Uses of TCP/IP

Here are some of the most valuable uses of TCP/IP models:

• World Wide Web: TCP/IP transfers data between web browsers and servers.
• Email: Applications such as Outlook, Thunderbird, and Gmail use TCP/IP protocols to send and receive emails.
• File Transfer: FTP, SFTP, and other file transfer services rely on TCP/IP to move files from one computer to another.
• Networking: TCP/IP links computers together in a network.
• Virtual Private Networks: VPNs use TCP/IP to encrypt data before it travels across a public or private network.
• Internet of Things: Many smart home devices use TCP/IP to communicate and transfer data.
• Voice Over Internet Protocol: VOIP services such as Skype and Google Voice use TCP/IP to transmit calls over the internet.

Application Layer

The application layer maintains a smooth connection between the application and user for data exchange and offers various features as remote handling of the system, e-mail services, etc.

Application Layer Protocol

Listing all application layer protocols is an extensive task, as there are numerous protocols catering to various services and applications. However, I can provide you with a list of some commonly used application layer protocols:

This is just a sampling, and there are many more application layer protocols designed for specific purposes and services. The landscape is dynamic, and new protocols may emerge over time.

Transport Layer

This layer is responsible for establishing the connection between the sender and the receiver device and also performs the task of dividing the data from the application layer into packets, which are then used to create sequences.

Transport Layer Protocol

Internet Protocols are a set of rules that governs the communication and exchange of data over the internet. Both the sender and receiver should follow the same protocols in order to communicate the data.

1. Transmission Control Protocol (TCP)
2. User Datagram Protocol (UDP)
3. Datagram Congestion Control Protocol (DCCP)
4. Stream Control Transmission Protocol (SCTP)
5. Real-time Transport Protocol (RTP)
6. Reliable Datagram Protocol (RDP)
7. Datagram Delivery Protocol (DDP)
8. Multipath TCP (MPTCP)
9. Reliable User Datagram Protocol (RUDP)

10.Pragmatic General Multicast (PGM)

TCP Vs UDP

Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) both are protocols of the Transport Layer. TCP is a connection-oriented protocol where as UDP is a part of the Internet Protocol suite, referred to as the UDP/IP suite. Unlike TCP, it is an unreliable and connectionless protocol.

Summary difference between TCP vs UDP-

Details difference between TCP (Transmission Control Protocol) and UDP (User Datagram Protocol)

Network Layer

The Network layer performs the task of controlling the transmission of the data over the network modes and enacts protocols related to the various steps related to the transmission of data over the channel, which is in the form of packets sent by the previous layer.

Network Layer protocol

• Internet Protocol (IP): IPv4, IPv6: are the primary protocols for addressing and routing packets across networks.
• Internet Control Message Protocol (ICMP): Used for error reporting and diagnostics, often associated with tools like ping.
• Internet Group Management Protocol (IGMP): Used by hosts and adjacent routers to manage multicast group memberships.
• Routing Information Protocol (RIP): A distance-vector routing protocol used for routing within an autonomous system.
• Open Shortest Path First (OSPF): A link-state routing protocol commonly used within larger networks.
• Intermediate System to Intermediate System (IS-IS): Another link-state routing protocol often used in large, complex networks.
• Border Gateway Protocol (BGP): A path vector protocol used for inter-domain routing on the Internet.
• Internet Protocol Security (IPsec): A suite of protocols that provide security at the Network layer, including authentication and encryption.

Data Link Layer

The datalink layer (also called the link layer, network interface layer, or physical layer) is what handles the physical parts of sending and receiving data using the Ethernet cable, wireless network, network interface card, device driver in the computer, and so on.

Data Link Layer Protocol

• Ethernet (IEEE 802.3): One of the most widely used LAN protocols, operating over various physical media like twisted pair, fiber optics, and coaxial cable.
• Wi-Fi (IEEE 802.11): Wireless LAN protocol providing connectivity over radio frequencies.
• Point-to-Point Protocol (PPP): Used for establishing a direct connection between two nodes, often over serial links.
• High-Level Data Link Control (HDLC): A bit-oriented protocol used for communication over point-to-point and multipoint links.
• Frame Relay: A packet-switching protocol for connecting devices in a Wide Area Network (WAN).
• Asynchronous Transfer Mode (ATM): A protocol used in high-speed networks, often in both LAN and WAN environments.
• LocalTalk: A protocol used in Apple Macintosh networks over a twisted-pair cable.

Packet

Data Link layer PACKET Architecture:

Packet: In networking, a packet is a small segment of a larger message. Data sent over computer networks, such as the Internet, is divided into packets. These packets are then recombined by the computer or device that receives them.

The packet architecture at the Data Link Layer includes the following components:

Frame Header:

• Preamble: A series of bits used for synchronization and to alert the receiving device of an incoming frame.
• Start Frame Delimiter (SFD): Indicates the start of the frame and helps the receiver identify the frame boundaries.
• Destination MAC Address: The hardware address of the intended recipient device.
• Source MAC Address: The hardware address of the sender device.

Frame Body:

• Carries the actual data being transmitted, including the payload or user data.

Frame Footer:

• Frame Check Sequence (FCS): Contains error-checking information, such as a CRC (Cyclic Redundancy Check), to ensure the integrity of the frame during transmission.

Physical Layer

Links: Physical Media

In Computer Network, the transmission media is a channel between sender and receiver. The data from sender is sent to receiver through transmission media.

The transmission media is categorized in following two types:

1. Guided media: Guided media is also called wired communication or bounded transmission media. There are three types of Guided media:
   • Twisted pair: 100 Mbps, 1 Gbps Ethernet
   • Coaxial cable: 100's Mbps per channel
   • Optical fiber cable: transmission (10's-100's Gbps)
   • UnGuided media: The unguided media is also called wireless communication or unbounded transmission media.

• Microwave Transmission: 1 GHz to 300 GHz
• Radio Transmission: 3 kHz to 300 GHz
• Infrared Transmission: 300 GHz to 430 THz
• X-Ray: 30 petahertz (PHz) to 30 exahertz (EHz)
• γ Ray: Greater than 30 EHz
• Ultraviolet Ray: 750 THz to 30 PHz
• Cosmic Ray: Extremely variable; spans a wide range of frequencies, often associated with high-energy particles from space.

Radio link types:

• Wireless LAN (WiFi): 10-100's Mbps; 10's of meters
• wide-area (e.g., 4G cellular): 10's Mbps over ~10 Km
• Bluetooth: cable replacement: short distances, limited rates
• Terrestrial microwave: point-to-point; 45 Mbps channels
• Satellite: up to 45 Mbps per channel, 270 msec end-end delay

Switching

Packet-Switching: Queueing occurs when work arrives faster than can be serviced.

Packet queuing and loss: if arrival rate (in bps) to link exceeds transmission rate (bps) of link for some period of time.

• packets will queue, waiting to be transmitted on output link
• packets can be dropped (lost) if memory (buffer) in router fills up

Circuit Switching:

Circuit switching is a connection-oriented network technique (much like transmission control protocol or TCP), while packet switching is a connectionless network switching method. This means that for circuit switching, there must be an actual creation of the network path through which information will pass.

Frequency Division Multiplexing (FDM): optical, electromagnetic frequencies divided into (narrow) frequency bands

Time Division Multiplexing (TDM): time divided into slots, each call allocated its own band, can transmit at max rate of that narrow band. Each call allocated periodic slot(s), can transmit at maximum rate of (wider) frequency band (only) during its time slot(s).

Network Identifiers

Hostname: Each device in the network is associated with a unique device name known as Hostname in Application Layer. Type “hostname” in the command prompt(Administrator Mode) and press ‘Enter’, this displays the hostname of your machine.

DNS Server:DNS stands forDomain Name System.DNS is basically a server that translates web addresses or URLs (ex: www.google.com) into their corresponding IP addresses. It's working in Application Layer.

We don't have to remember all the IP addresses of each and every website.The command nslookup gives you the IP address of the domain you are looking for. This also provides information on our DNS Server.\

Port:A port can be referred to as a logical channel through which data can be sent/received to an application in Transport Layer. Any host may have multiple applications running, and each of these applications is identified using the port number on which they are running.

HTTP: 80, HTTPS: 443, FTP request: 21, FTP Data: 20, SMTP: 26, POP: 110

Number of ports: 65,536
Range: 0 to 65535
Type netstat -a in the command prompt and press "Enter", this lists all the ports being used.

IP Address (Internet Protocol address): Also known as the Logical Address, the IP Address is the network address of the system across the Network Layer.To identify each device in the world-wide-web, the Internet Assigned Numbers Authority (IANA) assigns an IPV4 (Version 4) address as a unique identifier to each device on the Internet.The length of an IPv4 address is 32 bits, hence, we have 2³²IP addresses available. The length of an IPv6 address is 128 bits.
Type "ipconfig" in the command prompt and press "Enter", this gives us the IP address of the device.

IPV4 (32 bits) => Number of Address 2^32 = 4.3 billion

Range (Decimal) 0:0:0:0 to 255:255:255:255

IPV6 (128 bits) => Number of Address 2^128 = 340 Undecillion

Range (Hexadecimal): 0000:0000:0000:0000:0000:0000:0000:0000 to FFFF: FFFF: FFFF: FFFF: FFFF: FFFF: FFFF: FFFF

IPV4 Private/Public (NAT), Subnet Mask

Classful/Classless Address

IP = Logical Address, Changeable

Socket:The unique combination of IP address and Port number together is termed a Socket.

MAC Address (Media Access Control address):Also known as physical address, theMAC Addressis the unique identifier of each host and is associated with itsNIC (Network Interface Card) for Data Link Layer.A MAC address is assigned to the NIC at the time of manufacturing.The length of the MAC address is: 12-nibble/ 6 bytes/ 48 bitsType "ipconfig/all" in the command prompt and press "Enter", this gives us the MAC address.

Range (Hexadecimal): 00:00:00:00:00:00 to FF:FF:FF:FF:FF:FF

First 24 bits is Manufacturer ID, and next 24 bits are Product ID. For example,

Question: If a company has manufacturer ID A1:B2:C3 then what is the number of products they can assign?

Answer: Next 24 bits are product ID, so number of products can be assigned = 2²⁴ = 16,777,216.

MAC address is Physical Address, Fixed

Section 1.1: What is the internet?

Internet: The Internet is a global or wide area network of billions of computers and other electronic devices. With the Internet, it's possible to access almost any information, communicate with anyone else in the world, and do much more.

Internet Structure

At center: small # of well-connected large networks

tier-1 commercial ISPs (e.g., Level 3, Sprint, AT&T, NTT), national & international coverage

Content provider networks (e.g., Google, Facebook): private network that connects its data centers to Internet, often bypassing tier-1, regional ISPs

Host: A host is acomputer that is accessible over a network. It can be a client, server, or any other type of computer. Each host has a unique identifier called a hostname that allows other computers to access it.

Server: A server is a computer program or device that provides a service to another computer program and its user, also known as the client.

End System: a computer, phone, or internet of things device connected to a computer network is sometimes referred to as an end system or end station, because it sits at the edge of the network. The end user directly interacts with an end system that provides information or services.

End systems, packet switches, and other pieces of the Internet run protocols that control the sending and receiving of information within the Internet. The Transmission Control Protocol (TCP) and the Internet Protocol (IP) are two of the most important protocols on the Internet.

Types of end systems:

• Personal Computer Systems.
• Workstations.
• Web Servers.
• E-mail Servers.
• Personal Digital Assistant (PDA)
• Television.
• Mobiles.
• Internet connected devices and many others.

Question: Is a Web server an end system?

No, a web server is typically not considered an end system. End systems are devices like computers, laptops, smartphones, etc., that are the source or destination of data in a network. Web servers, on the other hand, are infrastructure components that provide services to end systems by hosting websites and serving web pages.

Question: How to connect end systems to edge router?

End systems (such as computers, servers, or other devices) are typically connected to an edge router through a local area network (LAN) or a broadband connection. Here are common methods of connecting end systems to an edge router:

• Ethernet Connection
• Wireless Connection (Wi-Fi)
• Broadband Connection (DSL, Cable, Fiber, etc.)
• Cellular Connection
• Satellite Connection
• Point-to-Point Connection

Question: The word protocol is often used to describe diplomatic relations. How does Wikipedia describe diplomatic protocol?

Wikipedia describes diplomatic protocol as a set of formal rules and customs governing interactions between representatives of different countries, facilitating diplomatic relations and ensuring proper conduct in international affairs.

Question: Why are standards important for protocols?

Standards are important for protocols because they ensure uniformity and interoperability, allowing different systems and devices to communi