Networking

Topic: Networking Class: SSS Three

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Definition of Network and Networking

A computer network consists of a collection of computers, printers, and other equipment that are connected together. This connection allows them to communicate with each other and share resources. It can also be simply defined as a group of two or more computer systems linked together.

Computer Networking is the scientific and engineering discipline that focuses on how these computer systems communicate with each other effectively and efficiently.

Networks can be categorized in several ways, helping us understand their different characteristics and uses. They are commonly grouped by:

1. Scale (Geographical Area Covered)
2. Topology (Physical or Logical Layout)
3. Functional Relationship (e.g., Client-Server, Peer-to-Peer)

Types of Networks According to Scale

Depending on the geographical area they cover, networks are typically classified into the following types:

1. Personal Area Network (PAN): A PAN is a computer network organized around an individual person, typically within a very small range (around 10 meters or less). A PAN can be wired using connections like USB and FireWire, or it can be wireless (WPAN) using technologies such as Infrared Data Association (IrDA) and Bluetooth.
2. Local Area Network (LAN): A LAN is a computer network that covers a small, confined geographical area, such as a single home, office building, or school campus. LANs allow devices within that area to connect and share resources.
3. Metropolitan Area Network (MAN): A MAN is a large computer network that spans a city or a large campus, connecting multiple LANs within that metropolitan area. It's larger than a LAN but smaller than a WAN.
4. Wide Area Network (WAN): A WAN is a computer network that covers a very broad geographical area, often spanning across countries or even continents. The internet is the largest example of a WAN.
5. Internet: The Internet is the ultimate wide area network; it's a global, interconnected network of computer networks that uses standard communication protocols to allow billions of devices worldwide to share information and resources.

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Network Topology

Network topology refers to the arrangement or layout of the various elements (such as links, nodes, and devices) of a computer network. It defines how devices are physically or logically connected and how data flows between them.

The main types of network topologies include:

1. Bus Topology
2. Star Topology
3. Ring Topology
4. Mesh Topology
5. Tree Topology
6. Hybrid Topology

Bus Topology

In a bus topology, all network nodes (like file servers, workstations, and peripheral devices) are connected to a single, continuous cable, often called the backbone or bus. This cable has a terminator at each end to prevent signal reflection. Data travels along this single cable, and each node checks to see if the data is intended for it.

Bus topology was popular in older LANs because it's generally inexpensive and relatively easy to install for small networks.

Advantages of Bus Topology:

• It is inexpensive and simple to implement.
• Requires less cable compared to other topologies.
• Best suited for small networks where devices are few.

Disadvantages of Bus Topology:

• The cable length is limited, which restricts the number of stations that can be connected.
• This topology performs well only for a limited number of nodes; performance degrades with more devices.
• A break in the main cable can take down the entire network.
• Troubleshooting can be difficult as it's hard to isolate a fault.

Ring Topology

Ring topology is a network configuration where the connected devices create a circular path for data to travel. In this setup, each device has exactly two neighbors for communication purposes. Messages travel around the ring in a single direction (either clockwise or counter-clockwise).

A key technology used in ring networks is Token Ring. In this method, a small data packet called a "token" continuously circulates around the network. When a device needs to transmit data, it "grabs" the token, attaches its data packet to it, and sends it around the ring. Only the device holding the token can transmit.

Advantages of Ring Topology:

• It provides orderly access to the network, as devices take turns transmitting (e.g., using a token).
• Easier to manage than a Bus Network, especially in terms of data collisions.
• Can support good communication over long distances.
• Can handle a high volume of traffic efficiently with proper token management.

Disadvantages of Ring Topology:

• The failure of a single node or cable break can disrupt the entire network, as it breaks the loop.
• Adding or removing network nodes requires temporarily shutting down the network, affecting overall performance.
• Troubleshooting can be challenging because a single fault can affect many devices.

Star Topology

In a star topology, each network node (like file servers, workstations, and peripherals) connects individually to a central device. This central device is typically a hub, a switch, or a concentrator. All data on a star network passes through this central device before reaching its destination. The central device manages and controls all functions of the network.

The star topology significantly reduces the chance of overall network failure because individual cable faults only affect the connected device, not the entire network. This is the most common topology used in modern LANs.

Advantages of Star Topology:

• Easy to manage and configure.
• Easy to locate problems (cable or workstation faults) because each connection is separate.
• Easier to expand than bus or ring topologies; new devices can be added without disrupting the existing network.
• Easy to install and wire.
• A fault in one cable or device does not affect the rest of the network.

Disadvantages of Star Topology:

• Requires more cable length than a linear topology like the bus, especially in large areas.
• If the central hub, switch, or concentrator fails, the entire network (or the segment connected to that device) becomes inoperable.
• Can be more expensive due to the cost of the central connecting devices.

Tree Topology

A tree topology (also known as a hierarchical topology) combines elements of both bus and star topologies. It can be visualized as a collection of star networks arranged in a hierarchy, resembling branches of a tree. This structure allows for greater control and easier troubleshooting by organizing links and nodes into distinct levels.

Advantages of a Tree Topology:

• It allows for point-to-point wiring for individual network segments, making it easier to manage connections.
• It's widely supported by various hardware and software vendors.
• Provides good scalability, allowing new segments and devices to be added more easily than simple bus or ring networks.

Disadvantages of a Tree Topology:

• The overall length of each segment is limited by the type of cabling used.
• If the main backbone line (the central bus) breaks, entire segments of the network will go down.
• More complex to configure and wire than basic topologies like bus or star.
• Can be more expensive due to the additional cabling and networking equipment required.

Mesh Topology

In a mesh topology, every single node in the network is connected to every other node directly. This creates multiple redundant paths for data to travel. While implementing a full mesh topology can be expensive and complex due to the extensive cabling, it offers high reliability. When data travels on a mesh network, it's often automatically configured to reach its destination by taking the shortest route, minimizing "hops" or intermediate connections.

Advantages of Mesh Topology:

• High Reliability/Fault Tolerance: No single point of failure; if one link breaks, data can still find another path.
• No Traffic Problem: Dedicated links between nodes reduce network congestion.
• Easy Fault Identification: Point-to-point links make it easy to pinpoint where a fault is.
• Security: Data travels only on a dedicated link between two devices.

Disadvantages of Mesh Topology:

• High Cabling Cost: Requires a significant amount of cabling, especially for a large number of nodes.
• Complex Installation: Installation is complex as each node needs to be connected to every other node.
• Management Difficulty: A large number of connections can be difficult to manage.
• Expensive: Overall cost is high due to cabling and the need for many network interfaces.

Hybrid Topology

A hybrid topology is a combination of any two or more basic network topologies. It always results when different basic network topologies are connected to form a larger, more complex network. For example, connecting several star networks using a bus backbone creates a hybrid topology.

Advantages of a Hybrid Topology:

• Flexibility: It's extremely flexible, allowing for customized network designs to suit specific needs.
• Reliability: Can be very reliable as it can incorporate the strengths of different topologies (e.g., fault tolerance of a star).
• Scalability: Can be easily expanded without affecting the existing network.

Disadvantages of a Hybrid Topology:

• Expensive: Generally more expensive to implement due to the complexity and multiple types of equipment required.
• Complex Design and Management: Designing and managing a hybrid network can be much more challenging.

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Types of Networks According to Functional Relationship

Networks can also be categorized by the way devices interact and share resources. The two primary functional relationships are Client-Server and Peer-to-Peer models.

Client-Server Network

A client-server network consists of a centralized, powerful computer called a server and other computers, called clients.

• Server: A central computer that manages resources and provides services. Examples include file servers, print servers, web servers, and database servers.
• Client: A computer or device that requests and uses services provided by the server. Most desktop computers and mobile devices act as clients.

Advantages of Client-Server Networks:

• Easier to manage security, data backups, and user accounts.
• More clients and servers can be added to accommodate growth.
• Data is stored and managed on a central server, making it easier to control access and protect information.
• Servers are dedicated to serving requests, leading to better performance for many users.

Disadvantages of Client-Server Networks:

• Requires powerful servers and specialized software, which can be expensive.
• If the server fails, all clients relying on it will lose access to resources.
• Needs dedicated IT staff to manage and maintain the server.

Peer-to-Peer (P2P) Network

In a peer-to-peer (P2P) network, there is no central server. Instead, all connected computers (peers) are equal in terms of functionality and can directly share resources with each other. Each computer can act as both a client and a server, providing resources to and requesting resources from other peers.

Advantages of Peer-to-Peer Networks:

• Lower Cost to set up.
• Relatively simple to set up, especially for small networks.
• If one computer fails, the rest of the network can continue to function.

Disadvantages of Peer-to-Peer Networks:

• Security is difficult to enforce uniformly across all machines.
• Backups and updates must be managed individually on each computer.
• Performance can suffer as the number of peers increases or if many peers are trying to access the same resource simultaneously.
• It Becomes difficult to manage and less efficient as the network grows large.

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Network Devices

Network devices are specialized hardware components that facilitate communication and data transfer between computers and other electronic devices within a network. Here are some common network devices:

Hubs

A hub is a basic networking device that joins multiple computers or other network devices to form a single network segment. It acts as a common connection point. When a hub receives data from one device, it simply broadcasts that data to all other connected devices, without checking the destination. This means all devices on a hub share the same network bandwidth.

Switches

A network switch is a hardware device that connects multiple computer networks or devices within a local area network (LAN). Unlike a hub, a switch is more "intelligent." Switches are capable of inspecting the destination address of data packets they receive. They then forward these packets only to the specific device for which they are intended, rather than broadcasting to all devices. This makes switches more efficient and reduces network congestion.

Modem (MOdulator-DEModulator)

A modem (MOdulator-DEModulator) is an electronic device that converts digital signals from a computer into analog signals that can be transmitted over traditional telephone lines, cable lines, or fiber optic lines, and vice-versa. This conversion allows computers to communicate over various internet service provider (ISP) connections.

Router

Routers are intelligent network devices that connect multiple wired or wireless networks together. Their primary function is to forward data packets between different computer networks, choosing the best path for data to travel to its destination. Routers are essential for connecting your local network to the internet.

Network Interface Card (NIC)

A Network Interface Card (NIC), also known as a network adapter or Ethernet card, is a hardware component (a circuit board or an integrated chip) that is installed in a computer. Its purpose is to enable the computer to connect to a network using a network cable and communicate with other devices on that network. Wireless NICs also exist for Wi-Fi connections.