Mesh Topology

In a mesh topology, every device has a dedicated point-to-point link to every other device. The term "dedicated" means that the link carries traffic only between the two devices it connects.

Node 1 must be connected to n - 1 nodes, node 2 must be connected to n – 1 nodes, and finally, node n must be connected to n - 1 nodes. We need n (n - 1) physical links.

However, if each physical link allows communication in both directions, the number of links needed is n(n-1)/2.

Advantages

• The use of dedicated links guarantees that each connection can carry its own data load, thus eliminating the traffic problems that can occur when links must be shared by multiple devices.
• A mesh topology is robust. If one link becomes unusable, it does not incapacitate the entire system.
• There is the advantage of privacy or security. When every message travels along a dedicated line, only the intended recipient sees it.
• Point-to-point links make fault identification and fault isolation easy.

Disadvantages

• Amount of cabling and the number of I/O ports required.
• The sheer bulk of the wiring can be greater than the available space (in walls, ceilings, or floors) can accommodate.
• The hardware required to connect each link (I/O ports and cable) can be prohibitively expensive.

Star Topology

In a star topology, each device has a dedicated point-to-point link only to a central controller, usually called a hub.

The devices are not directly linked to one another. Unlike a mesh topology, a star topology does not allow direct traffic between devices. The controller acts as an exchange: If one device wants to send data to another, it sends the data to the controller, which then relays the data to the other connected device.

Advantages

• A star topology is less expensive than a mesh topology.
• In a star, each device needs only one link and one I/O port to connect it to any number of others. This factor also makes it easy to install and reconfigure.
• Far less cabling needs to be housed, and additions, moves, and deletions involve only one connection: between that device and the hub.
• Other advantages include robustness. If one link fails, only that link is affected. All other links remain active.

Disadvantages

• The dependency of the whole topology on one single point, the hub. If the hub goes down, the whole system is inoperative.
• Although a star requires far less cable than a mesh, each node must be linked to a central hub.

Bus Topology

In a bus topology, the preceding examples all describe point-to-point connections. However, a bus topology, on the other hand, is multipoint, where one long cable acts as a backbone to link all the devices in a network.

As a signal travels along the backbone, some of its energy is transformed into heat. Consequently, it becomes weaker and weaker as it travels farther and farther along the cable.

Advantages

• Bus topology offers ease of installation, making it a convenient choice for network setups.
• A bus topology uses less cabling compared to mesh or star topologies, resulting in cost savings and simplified network infrastructure.

Disadvantages

• Reconnecting devices and fault isolation in a bus topology can be challenging when issues arise, potentially leading to network downtime.
• A single fault or break in the bus cable can disrupt all data transmission, even between devices located on the same side of the problem, affecting overall network reliability.

Ring Topology

In a ring topology, each device has a dedicated point-to-point connection with only the two devices on either side of it. A signal is passed along the ring in one direction, from device to device, until it reaches its destination.

Advantages

• A ring topology is relatively easy to install and reconfigure, making it a flexible choice for network setups. Fault isolation is simplified, making it easier to identify and resolve network issues.

Disadvantages

• Unidirectional traffic can be a disadvantage in a ring topology, as data can only travel in one direction around the ring. This limitation can impact network efficiency.
• In a simple ring topology, a break in the ring, such as a disabled station or a cable fault, can disable the entire network. This lack of redundancy can make the network vulnerable to disruptions.

Hybrid Topology

A hybrid topology combines different network topologies within a single network infrastructure. For example, a hybrid network can consist of a primary star topology with each branch connecting several stations in a bus topology.

Advantages

• Hybrid topologies offer greater flexibility in designing and customizing a network to meet specific requirements. They can leverage the strengths of different topologies to optimize network performance.
• By combining topologies, fault tolerance and redundancy can be enhanced. If one part of the network fails, it may not affect the entire system, improving overall network reliability.
• Hybrid topologies can provide scalability, allowing the network to grow and adapt to changing needs without requiring a complete overhaul.

Disadvantages

• Designing and managing a hybrid network can be complex and may require more extensive planning and maintenance compared to single-topology networks.
• The cost of implementing and maintaining a hybrid network can be higher due to the need for different hardware and configurations to support multiple topologies.
• Network troubleshooting and fault isolation may be more challenging in a hybrid topology, as issues can arise from different interconnected topologies.

Connecting Networks: Broadcast and Point-to-Point

After understanding topologies, we delve into different types of network connections.

Broadcast Network

In a broadcast network, all devices share the same communication medium and can send their messages to all other devices on the network. It's like broadcasting a message to everyone.

• Efficient for broadcasting information to all devices simultaneously.
• Prone to congestion as all devices compete for the same channel.
• Security concerns arise as all devices receive all messages.

Point-to-Point Network

In a point-to-point network, devices have dedicated communication links. This type of connection is often seen in a more traditional client-server architecture.

• Offers direct, dedicated communication between devices.
• Enhanced security since only intended recipients receive messages.
• Requires more connections as the network expands.
• Less efficient for broadcasting messages to all devices.

Understanding network topologies aids in deciding which connection type is suitable for different scenarios.

Types of Networks

• LAN (Local Area Network): A network confined to a small geographical area like a single building or campus.
• MAN (Metropolitan Area Network): A larger network that spans across a city or metropolitan area.
• WAN (Wide Area Network): Covers larger distances, often connecting multiple cities or countries.
• Internet: A global network of networks that enables worldwide communication and access to information.

LAN (Local Area Network)

Advantages:

• High data transfer rates, suitable for resource-intensive applications.
  • Having high data transfer rates is like having a super-fast highway for information. It means that data can zoom from one point to another really quickly. This is especially useful for "resource-intensive applications," which are like power-hungry superheroes of the computer world. These applications, such as fancy video editing or intricate 3D graphics, need a lot of computer muscle to do their jobs well. So, when a network boasts high data transfer rates, it's like giving these power-hungry applications the speedway they need to zip through their tasks without slowing down. It's like having a speedy express lane for data, making sure everything runs smoothly for the most demanding jobs in the digital world.
• Low implementation cost as it covers a limited area.
  • Since LANs are designed to connect devices within a confined space, such as a single building, campus, or office floor, the infrastructure required for deployment is relatively contained. This focused coverage allows organizations to establish a network environment without incurring the high costs associated with extensive cabling, networking equipment, and other infrastructure elements needed for larger-scale networks. As a result, LANs provide a cost-effective solution for facilitating seamless communication and resource sharing among connected devices within the specified local area.
• Easy to manage and troubleshoot due to smaller scale.
  • Since it operates on a smaller scale, a notable advantage of this system is its ease of management and troubleshooting. With fewer devices and components to oversee, administrators can more efficiently handle network tasks, monitor performance, and swiftly address any issues that may arise. The reduced complexity associated with a smaller network makes it inherently more manageable, allowing for streamlined operations and a quicker response to potential challenges. This simplicity contributes to a user-friendly environment, where administrators can easily navigate and maintain the network infrastructure, ensuring optimal functionality and minimizing downtime.

Disadvantages:

• Limited coverage area, not suitable for connecting distant locations.
  • Since it has a limited coverage area, a notable constraint of this system is its unsuitability for connecting distant locations. The inherent design of this network restricts its reach to a confined geographic area, such as a building or campus, making it less practical for interconnecting devices across considerable distances. While the system excels in providing localized connectivity, its limitation in terms of coverage renders it less effective for scenarios requiring networking capabilities over extended or remote locations. Organizations seeking to establish connections between geographically distant sites may find alternative network solutions more appropriate for meeting their broader connectivity needs.
• Expensive to expand beyond its initial range.
  • Since expanding beyond its initial range incurs high costs, a significant drawback of this system is its expense when attempting to broaden coverage. The initial deployment of this network may be cost-effective for its intended range, but scaling it to cover a larger area can become financially burdensome. The need for additional infrastructure, such as additional networking equipment, cabling, and other resources, contributes to the increased expenses associated with expansion. As organizations strive to extend network coverage to accommodate growing needs or reach new locations, the financial implications of scaling up this system may necessitate careful consideration of budget constraints and alternative solutions for cost-effective network expansion.

MAN (Metropolitan Area Network)

Advantages:

• Larger coverage area than LAN.
  • One of the notable advantages of this system, is its extended coverage. Operating within the scope of a metropolitan region, such as a city or large campus, a MAN provides a broader network footprint. This expanded coverage allows for connectivity across a more extensive geographical area, facilitating communication and resource sharing for organizations with dispersed locations within the metropolitan vicinity. While a MAN surpasses the confined coverage of LANs, it still retains a regional focus, striking a balance between the localized nature of LANs and the extensive reach of Wide Area Networks (WANs).
• Offers higher data rates than WAN.
  • Another notable advantages of this system, is its enhanced data transfer capabilities. Operating within the intermediate scale between local and wide-reaching networks, a MAN offers faster data rates that surpass those typically achievable in larger-scale WANs. This increased speed in data transmission makes a MAN well-suited for applications that demand more robust and efficient connectivity within a metropolitan area. By delivering accelerated data rates, a MAN addresses the need for swift and reliable communication over a broader regional scope, catering to the connectivity requirements of organizations with distributed locations across a city or large campus.

Disadvantages:

• Installation and maintenance costs.
  • A significant drawback of this system, lies in the financial investments required. The infrastructure necessary for deploying and maintaining a MAN across a metropolitan area, including the installation of networking equipment, cabling, and ongoing maintenance procedures, contributes to elevated costs. Unlike Local Area Networks (LANs), which operate within a confined space, a MAN's intermediate scale introduces complexities that can escalate the initial setup expenses and the long-term maintenance overhead. Organizations considering the implementation of a MAN must carefully weigh the cost implications against the network's intended benefits and operational requirements.
• Not as widely available as LANs.
  • It is not as widely available as Local Area Networks (LANs), a notable limitation of this system, lies in its comparatively narrower availability. While LANs are commonly found in various settings such as homes, offices, and institutions, MANs are less prevalent due to their specific geographic focus on metropolitan areas. The infrastructure requirements and scale of a MAN make its deployment less ubiquitous, limiting its accessibility compared to the more widespread usage of LANs. Organizations seeking network solutions should consider the availability factor, understanding that MANs may not be as readily accessible in all locations as the more pervasive LAN technology.

WAN (Wide Area Network)

Advantages:

• Global coverage, connects remote locations.
  • It offers global coverage and connects remote locations, one of the significant advantages of this system, lies in its expansive reach. Unlike Local Area Networks (LANs) and Metropolitan Area Networks (MANs), which operate within confined areas, a WAN spans across large geographical distances, facilitating connectivity between distant locations worldwide. This global coverage enables organizations with dispersed offices, branches, or facilities to establish seamless communication and data exchange. By connecting remote locations, a WAN plays a crucial role in fostering collaboration and resource sharing on a global scale, making it an essential networking solution for businesses and enterprises with a presence across different regions.
• Facilitates data sharing over long distances.
  • It facilitates data sharing over long distances, one of the notable advantages of this system, lies in its ability to overcome geographic barriers. Unlike Local Area Networks (LANs) and Metropolitan Area Networks (MANs), which operate within confined areas, a WAN excels at extending connectivity over extensive distances. This capability enables seamless data sharing and communication between geographically dispersed locations. Whether for multinational corporations with offices across the globe or for individuals collaborating from different regions, a WAN serves as a vital platform for efficient and reliable data exchange, fostering collaboration and information flow across vast distances.

Disadvantages:

• Higher costs due to long-distance infrastructure.
  • It involves higher costs attributed to long-distance infrastructure, a significant disadvantage of this system, lies in the financial implications associated with its extensive reach. The infrastructure required to establish and maintain connectivity over long distances, including the deployment of networking equipment, cabling, and other resources, contributes to elevated costs. Unlike Local Area Networks (LANs) and Metropolitan Area Networks (MANs), which operate within more confined spaces, the scale of a WAN introduces complexities that can escalate both the initial setup expenses and ongoing maintenance overhead. Organizations considering the implementation of a WAN must carefully assess and manage the associated higher costs against the network's intended benefits and operational requirements."
• Slower data transfer rates compared to LAN.
  • It entails slower data transfer rates compared to Local Area Networks (LANs), a notable disadvantage of this system, lies in its reduced speed of data transmission. While LANs offer fast and efficient communication within localized environments, the expansive nature of WANs introduces latency and bandwidth limitations. The longer distances involved in connecting remote locations contribute to delays in data transfer, making WANs less suitable for applications that demand rapid and real-time data exchange. Organizations relying on WANs should be mindful of the potential trade-off between the network's extended reach and the comparatively slower data transfer rates, ensuring that it aligns with their specific communication needs and operational requirements.

Differences Between Network Types

Internet

Advantages:

• Unlimited access to information and resources.
• Global communication and collaboration.

Disadvantages:

• Security and privacy concerns.
• Potential for misinformation and cyber threats.

Parallel Transmission

Multiple data bits sent simultaneously using separate lines.

• Faster data transfer than serial transmission.
• Requires more wires, suitable for short distances.

The main advantages of parallel transmission overserial tranmission are:

• It is easier to program
• And data is sent faster

Although parallel transmission can transfer data faster, it requires more transmission channels than serial transmission. that means expensive.

Serial Transmission

Data bits sent one after another over a single line.

• Slower data transfer compared to parallel transmission.
• Requires fewer wires, suitable for long distances.

Advantages: It requires only one transmission channel, that means economical.

Disadvantages: Data is sent slower.

Serial Transmission Types

1. Synchronous Transmission
2. Asynchronous Transmission
3. Isochronous Transmission

Some protocols:

• TCP/IP (Transmission Control Protocol/Internet Protocol): The foundation of the internet and most modern networks. TCP handles reliable, connection-oriented data transmission, while IP provides the addressing and routing of data packets.
• HTTP (Hypertext Transfer Protocol): Used for web communication, allowing the transfer of web pages and resources between a web server and a web browser.
• FTP (File Transfer Protocol): Used for transferring files between a client and a server on a network or the internet.
• SMTP (Simple Mail Transfer Protocol): Used for sending and receiving email messages between email servers.
• DNS (Domain Name System): Converts human-readable domain names (e.g., www.example.com) into IP addresses, enabling users to access websites using domain names.

Some standards:

• IEEE (Institute of Electrical and Electronics Engineers): Known for creating standards related to networking, such as IEEE 802.11 (Wi-Fi) and IEEE 802.3 (Ethernet).
• ITU (International Telecommunication Union): Focuses on global telecommunication standards, including those for modems and telecommunications networks.
• ISO (International Organization for Standardization): Develops international standards for various industries, including networking.
• IETF (Internet Engineering Task Force): Responsible for developing and promoting internet standards, protocols, and related documents.

Link Layer / Network Access Layer

• The Link Layer, also known as the Network Access Layer, deals with the physical transmission of raw data bits over a physical medium, such as copper wires, optical fibers, or wireless frequencies. It defines the electrical, mechanical, and procedural details for transmitting data between devices.
• At this layer, TCP/IP doesn't define any specific protocol but is designed to support a wide range of standard and proprietary protocols that operate at these layers. This flexibility allows TCP/IP to adapt to different network technologies and environments. A TCP/IP internetwork can incorporate various types of networks, whether they're local-area networks (LANs) or wide-area networks (WANs). This adaptability is one of the strengths of TCP/IP, as it enables networks of different scales and types to interconnect seamlessly while utilizing the appropriate protocols for their specific requirements.

Internet Layer

• The Internet Layer, also known as the Network Layer, handles routing and forwarding of data packets across networks. It's primarily based on the Internet Protocol (IP), which is responsible for addressing, routing, and fragmenting data for transmission.
• Within the Internet Layer, there are four essential supporting protocols:
  • Internet Protocol (IP): IP is the backbone of the TCP/IP protocols, responsible for transmitting data across networks. It operates as an unreliable and connectionless protocol, providing a best-effort delivery service. This 'best effort' approach means that IP doesn't perform error checking or tracking and assumes the underlying layers are not perfect, aiming to get data to its destination without guarantees.
  • Address Resolution Protocol (ARP): ARP associates a logical address with a physical address, aiding in finding the physical address when the Internet address is known.
  • Reverse Address Resolution Protocol (RARP): RARP helps a host discover its Internet address when it only knows its physical address, often used when a computer is connected to a network for the first time.
  • Internet Control Message Protocol (ICMP): ICMP is used for hosts and gateways to send notifications about datagram issues back to the sender, handling query and error reporting messages.
• These protocols working together within the network layer of TCP/IP play a crucial role in ensuring effective communication, managing issues, and enabling specific types of transmissions.

Transport Layer

• The Transport Layer manages end-to-end communication and data flow between two devices. It offers two main protocols:
  • Transmission Control Protocol (TCP): TCP provides reliable and ordered data transmission with connection setup. It ensures that data is delivered accurately and in the correct order. TCP operates as a connection-oriented protocol, establishing a connection before data transmission.
  • User Datagram Protocol (UDP): UDP offers fast, connectionless data transmission without reliability guarantees. It is suitable for applications where speed is prioritized over reliability. UDP adds basic port addresses, checksum error control, and length information to the upper-layer data.
• Additionally, a newer protocol called Stream Control Transmission Protocol (SCTP) has been introduced to cater to the needs of certain modern applications, combining features of both TCP and UDP.
• These protocols within the transport layer play a critical role in managing how data is delivered, ensuring reliability, and accommodating various communication needs.

Application Layer

• The Application Layer in TCP/IP serves a role equivalent to the combined Session, Presentation, and Application Layers in the OSI model. This layer is home to numerous protocols that facilitate various functionalities.
• The Application Layer in TCP/IP is the topmost layer and plays a crucial role in enabling communication between software applications and the underlying network. It's responsible for providing application-specific services and protocols that allow different programs to communicate with each other over a network.
• Key functions and tasks of the Application Layer in TCP/IP include:
  • Data Formatting and Translation: The Application Layer handles the formatting, structure, and presentation of data in a way that is understandable by both the sender and the receiver.
  • User Interface and Interaction: Providing user interfaces for applications, allowing users to interact with software and handling user authentication and security.
  • Application Protocols: Defining various protocols that applications use to exchange data, such as HTTP (for web browsing), SMTP (for email), FTP (for file transfer), and DNS (for domain name resolution).
  • Data Encryption and Security: Implementing security features and encryption methods to ensure the confidentiality, integrity, and authenticity of data being transmitted.
  • Resource Sharing and Remote Access: Enabling resource sharing and remote access to files, printers, and other devices on a network.
  • Error Handling and Recovery: Implementing error-checking and recovery procedures to ensure the reliable transfer of data.
  • Support for Different Applications: Accommodating a wide range of applications, from simple text-based communication to complex multimedia and real-time applications.

Multiplexer (MUX):

• Multiplexing is achieved by using a device called Multiplexer (MUX).
• A multiplexer (MUX) is a device that combines 'n' input lines to generate a single output line.
• Multiplexing follows a many-to-one approach, with 'n' input lines and one output line.

Demultiplexer (DEMUX):

• Demultiplexing is achieved using a device called a Demultiplexer (DEMUX), typically available at the receiving end.
• DEMUX separates a signal into its component signals, following a one-to-many approach, with one input and 'n' outputs.

Purpose of Multiplexing:

• The transmission medium can only handle one signal at a time, necessitating multiplexing when multiple signals need to share it.
• To divide the medium's available bandwidth so that each signal gets its share. For example, if there are 10 signals and 100 units of bandwidth, each signal gets 10 units.
• Prevents collisions when multiple signals share a common medium.
• Helps save on expensive transmission services.

History of Multiplexing:

• Multiplexing has a long history:
• Originated in telegraphy in the early 1870s.
• Widely used in telecommunications, where multiple telephone calls are carried through a single wire.
• George Owen Squier's development of telephone carrier multiplexing in 1910 was a significant milestone.

Concept of Multiplexing:

• The 'n' input lines are transmitted through a multiplexer, and the multiplexer combines the signals to form a composite signal.
• The composite signal is passed through a Demultiplexer, and the demultiplexer separates a signal into component signals and transfers them to their respective destinations.

Advantages of Multiplexing

• Efficient Resource Utilization: Multiplexing optimizes the use of network or communication resources, ensuring efficient allocation and sharing among multiple data streams or devices.
• Increased Bandwidth Efficiency: It maximizes the utilization of available bandwidth, allowing multiple data streams to be transmitted simultaneously over the same communication channel.
• Cost-Effective Communication: By enabling multiple signals or data streams to share a common medium, multiplexing helps reduce the cost of establishing and maintaining separate communication channels for each source.
• Prevention of Collisions: Multiplexing helps prevent collisions in shared communication channels, ensuring that data can be transmitted without interference or data loss.
• Flexible Data Transmission: It offers flexibility in accommodating various types of data streams, including voice, video, text, and application data, within the same network infrastructure.
• More than one signal can be sent over a single medium.
• The bandwidth of a medium can be utilized effectively.

Multiplexing Techniques

Why Switching?

• Whenever we have multiple devices, we have the problem of how to connect them to make one-to-one communication possible.
• Point-to-point and star topologies are impractical for large networks due to inefficiency and excessive infrastructure requirements.
• A better solution is switching, which involves interlinked nodes known as switches capable of creating temporary connections.

Classification of Switching Techniques

• Circuit Switching:
• Establishes a dedicated path between sender and receiver.
• Requires a complete end-to-end path before communication.
• Used in public telephone networks for voice transmission.
• Fixed data can be transferred at a time in circuit switching technology.
• Message Switching:
• Messages are transferred as complete units, routed through intermediate nodes, and stored and forwarded.
• No establishment of a dedicated path between sender and receiver.
• Dynamic routing based on message content.
• Treats each message as an independent entity.
• Packet Switching:
• Message divided into packets, each with unique identification and routing information.
• Packets travel across the network independently, reassembled at the receiving end.
• Used in modern data networks, including the Internet.
• Supports variable-sized data.

Circuit Switching

• Circuit Establishment:
• A complete end-to-end path must exist before communication takes place.
• Request signal is sent to the receiver, followed by acknowledgment, before data transfer.
• Used in public telephone networks and for voice transmission.
• Circuit Disconnect:
• Once the dedicated path is established, data transmission occurs with minimal delay.
• Long connection setup time (approx 10 seconds) with no data transmission during this period.
• Inefficient if the path remains idle.
• Space Division Switches:
• Space Division Switching uses physically separate cross points for a single transmission path.
• Includes crossbar switches and semiconductor-based switches.
• Offers high speed, high capacity, and no blocking.

Packet Switching

• Packet Structure:
• Messages divided into smaller packets with unique identification and routing information.
• Packets travel independently, reassembled at the receiving end.
• Header contains source address, destination address, and sequence number.
• Advantages of Packet Switching:
• Cost-effective, as switching devices do not require massive storage.
• Reliable and efficient use of available bandwidth.
• Supports simultaneous use by many users.
• Disadvantages of Packet Switching:
• Not suitable for applications requiring low delay and high-quality services.
• Complex protocols and high implementation cost.
• Retransmission of lost packets may lead to information loss.

Message Switching

• Message Transmission:
• Messages transferred as complete units, stored at intermediate nodes, and forwarded to the next node.
• Dynamic routing based on message content.
• Each node stores and forwards the entire message.
• Advantages of Message Switching:
• Efficient use of data channels and available bandwidth.
• Traffic congestion can be reduced due to message storage at nodes.
• Supports message priority and variable message sizes.
• Disadvantages of Message Switching:
• Nodes must have sufficient storage for message storage and forwarding.
• Potential for long delays due to message storage and forwarding.