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CHAPTER 2: COMPUTER NETWORKING
Unit of learning code: IT/CU/ICT/CR/1/ Related Unit of Competency in Occupational Standard: Perform Computer Networking 2.1 Introduction to the unit of learning This unit specifies the competencies required to perform computer Networking. It involves Identification of network types, Connection of networking devices, configuration of network devices, network testing, configuration of LAN network type and monitoring network connectivity. 2.2 Summary of Learning Outcomes
- Identify network type and components
- Connect network devices
- Configure network devices
- Configure LAN Network type
- Perform Network testing 1.2.1 Learning Outcome 1: Identify Network Type and Components 2.2.1.2 Introduction to the Learning Outcome This learning outcome covers identification of different types of computer networks, identification of Network components, identification of network topologies, identification of transmission media and benefits of computer networking. 2.2.1.3 Performance Standard 2.2.1.3.1 Types of computer networks are identified. 2.2.1.3.2 Network components are identified 2.2.1.3.3 Network topologies are identified. 2.2.1.3.4 Transmission media is identified. 2.2.1.3.5 Benefits of computer Networking are identified.
2.2.1.4 Information Sheet a) Definition of Computer Network A computer network is a group of computers linked to each other that enables the computer to communicate with another computer and share their resources, data, and applications. The most common resource shared today is connection to the Internet. Other shared resources can include a printer or a file server. The Internet itself can be considered a computer network. b) Key terms in Computer Networks Table 1 : Common terms in Networking Terms Definition
- ISO The OSI model is a product of the Open Systems Interconnection project at the International Organization for Standardization. ISO is a voluntary organization.
- OSI Model Open System Interconnection is a model consisting of seven logical layers.
- TCP/IP Model Transmission Control Protocol and Internet Protocol Model is based on four layer model which is based on Protocols.
- UTP Unshielded Twisted Pair cable is a Wired/Guided media which consists of two conductors usually copper, each with its own colour plastic insulator
- STP Shielded Twisted Pair cable is a Wired/Guided media has a metal foil or braided-mesh covering which encases each pair of insulated conductors. Shielding also eliminates crosstalk
- PPP Point-to-Point connection is a protocol which is used as a communication link between two devices.
- LAN Local Area Network is designed for small areas such as an office, group of building or a factory.
- WAN Wide Area Network is used for the network that covers large distance such as cover states of a country
- Active Topology The term active topology describes a network topology in which the signal is amplified at each step as it passes from one computer to the next.
- Aloha Protocol for satellite and terrestrial radio transmissions. In pure Aloha, a user can communicate at any time, but risks collisions with other users' messages. Slotted Aloha reduces the chance of collisions by dividing the channel into time slots and requiring that the user send only at the beginning of a time slot.
- Address Resolution Protocol(ARP) ARP is a used with the IP for mapping a 32-bit Internet Protocol address to a MAC address that is recognized in the local network specified in RFC 826. Network Design and Architecture Network design and architecture refers to the structured planning, layout, and organization of a computer network to ensure efficient communication, reliability, security, and scalability.
1. Network Design
Network design is the process of planning and building a network based on organizational needs. Key Aspects of Network Design
- Requirements Analysis o Number of users and devices o Type of applications (data, voice, video) o Security and performance needs
- Network Topology Selection o Star, bus, ring, mesh, hybrid o Chosen based on cost, reliability, and performance
- Hardware Selection o Routers, switches, servers, access points o Cables (UTP, fiber optic, coaxial)
- IP Addressing and Subnetting o Logical addressing of devices
o Efficient use of IP addresses
- Security Design o Firewalls, encryption, authentication o Access control policies
- Scalability and Redundancy o Ability to expand the network o Backup links and devices
2. Network Architecture
Network architecture is the overall structure and framework that defines how network components interact. Types of Network Architecture a) Client–Server Architecture Central server provides services to multiple clients Used in organizations and institutions Advantages: centralized control, better security b) Peer-to-Peer (P2P) Architecture Devices share resources directly Suitable for small networks Advantages: low cost, easy setup
3. Layered Network Architecture Models
a) OSI Model (7 Layers)
- Physical
- Data Link
- Network
- Transport
- Session
- Presentation
- Application b) TCP/IP Model (4 Layers)
Network topology can be according to logical aspect or on physical aspect. Physical topology describes placement of different components of the network while logical topology describes the data flow within a network instead of physical design. Physical and Logical Topology There are two approaches to network topology: physical and logical. Physical network topology, as the name suggests, refers to the physical connections and interconnections between nodes and the network—the wires, cables, and so forth. Logical network topology is a little more abstract and strategic, referring to the conceptual understanding of how and why the network is arranged the way it is, and how data moves through it. Network topology can be categorize in 2 main categories on the basis of connection: Point to point and multi point. Point to point topology Figure 29: Point to point Topology Point to Point topology is the simplest topology that connects two nodes directly together with a common link. The entire bandwidth of the common link is reserved for transmission between those two nodes. The point-to-point connections use an actual length of wire or cable to connect the two ends, but other options, such as satellite links, or microwaves are also possible. Multipoint: This is a case where more than two specific devices share a single link.
i. Types of Topology There are five types of topology in computer networks. Hybrid topology is also common Star Bus Ring Tree Mesh Hybrid
1. Star Topology Figure 1 Star topology A star topology, the most common network topology, is laid out so every node in the network is directly connected to one central hub via coaxial, twisted-pair, or fiber-optic cable. Acting as a server, this central node manages data transmission—as information sent from any node on the network has to pass through the central one to reach its destination—and functions as a repeater, which helps prevent data loss. Advantages of Star Topology Star topologies are common since they allow you to conveniently manage your entire network from a single location. Because each of the nodes is independently connected to the central hub,
Figure 2 Bus toplolgy Advantages of Bus Topology Bus topologies are a good, cost-effective choice for smaller networks because the layout is simple, allowing all devices to be connected via a single coaxial or RJ45 cable. If needed, more nodes can be easily added to the network by joining additional cables. Disadvantages of Bus Topology However, because bus topologies use a single cable to transmit data, they’re somewhat vulnerable. If the cable experiences a failure, the whole network goes down, which can be time-consuming and expensive to restore, which can be less of an issue with smaller networks. Bus topologies are best suited for small networks because there’s only so much bandwidth, and every additional node will slow transmission speeds. Furthermore, data is “half-duplex,” which means it can’t be sent in two opposite directions at the same time, so this layout is not the ideal choice for networks with huge amounts of traffic.
3. Ring Topology - Single vs. Dual Ring topology is where nodes are arranged in a circle (or ring). The data can travel through the ring network in either one direction or both directions, with each device having exactly two neighbors. Figure 3 : Ring topology Pros of Ring Topology
Since each device is only connected to the ones on either side, when data is transmitted, the packets also travel along the circle, moving through each of the intermediate nodes until they arrive at their destination. If a large network is arranged in a ring topology, repeaters can be used to ensure packets arrive correctly and without data loss. Only one station on the network is permitted to send data at a time, which greatly reduces the risk of packet collisions, making ring topologies efficient at transmitting data without errors. By and large, ring topologies are cost-effective and inexpensive to install, and the intricate point-to- point connectivity of the nodes makes it relatively easy to identify issues or misconfigurations on the network. Cons of Ring Topology Even though it’s popular, a ring topology is still vulnerable to failure without proper network management. Since the flow of data transmission moves unidirectionally between nodes along each ring, if one node goes down, it can take the entire network with it. That’s why it’s imperative for each of the nodes to be monitored and kept in good health. Nevertheless, even if you’re vigilant and attentive to node performance, your network can still be taken down by a transmission line failure. The question of scalability should also be taken into consideration. In a ring topology, all the devices on the network share bandwidth, so the addition of more devices can contribute to overall communication delays. Network administrators need to be mindful of the devices added to the topology to avoid overburdening the network’s resources and capacity. Additionally, the entire network must be taken offline to reconfigure, add, or remove nodes. And while that’s not the end of the world, scheduling downtime for the network can be inconvenient and costly. Dual-Ring Topology A network with ring topology is half-duplex, meaning data can only move in one direction at a time. Ring topologies can be made full-duplex by adding a second connection between network nodes, creating a dual ring topology.
Figure 5 : Tree topology Pros of Tree Topology Combining elements of the star and bus topologies allows for the easy addition of nodes and network expansion. Troubleshooting errors on the network is also a straightforward process, as each of the branches can be individually assessed for performance issues. Cons of Tree Topology As with the star topology, the entire network depends on the health of the root node in a tree topology structure. Should the central hub fail, the various node branches will become disconnected, though connectivity within—but not between—branch systems will remain. Because of the hierarchical complexity and linear structure of the network layout, adding more nodes to a tree topology can quickly make proper management an unwieldy, not to mention costly, experience. Tree topologies are expensive because of the sheer amount of cabling required to connect each device to the next within the hierarchical layout.
5. Mesh Topology A mesh topology is an intricate and elaborate structure of point-to-point connections where the nodes are interconnected. Mesh networks can be full or partial mesh. Partial mesh topologies are mostly interconnected, with a few nodes with only two or three connections, while full-mesh topologies are—surprise!—fully interconnected.
Figure 6 : Mesh topology The web-like structure of mesh topologies offers two different methods of data transmission: routing and flooding. When data is routed, the nodes use logic to determine the shortest distance from the source to destination, and when data is flooded, the information is sent to all nodes within the network without the need for routing logic. Advantages of Mesh Topology Mesh topologies are reliable and stable, and the complex degree of interconnectivity between nodes makes the network resistant to failure. For instance, no single device going down can bring the network offline. Disadvantages of Mesh Topology Mesh topologies are incredibly labor-intensive. Each interconnection between nodes requires a cable and configuration once deployed, so it can also be time-consuming to set up. As with other topology structures, the cost of cabling adds up fast, and to say mesh networks require a lot of cabling is an understatement.
6. Hybrid Topology Hybrid topologies combine two or more different topology structures—the tree topology is a good example, integrating the bus and star layouts. Hybrid structures are most commonly found in larger
1. Personal Area Network (PAN) A personal area network, or PAN, is a computer network that enables communication between computer devices near a person. It is a computer network organized around an individual for personal use only. PANs can be wired, such as USB or FireWire, or they can be wireless, such as infrared, ZigBee, Bluetooth and ultra-wideband. The range of a PAN typically is a few meters. Examples of wireless PAN, or WPAN, devices include cell phone headsets, wireless keyboards, wireless mice, printers, bar code scanners and game consoles. Wireless PANs feature battery-operated devices that draw very little current. Sleep modes commonly are used to further extend battery life.
- Local Area Network (LAN) A Local Area Network (LAN) is a group of computers and other devices that are connected together over a network and are all in the same location, within a single building like an office or home. On a typical home or small office LAN, you might find a modem that provides an internet connection (and a basic firewall against intrusion from the internet), a router that lets other devices share that connection and connect to one another, and a Wi-Fi access point that lets devices access the network wirelessly. Sometimes, those functions are combined into a single device.
- Wireless Local Area Network (WLAN) Functioning like a LAN, a WLAN provides wireless network communication over short distances using radio signals instead of traditional network cabling. Typically, a wireless local area network (WLAN) extends an existing wired local area network to devices not connected to the LAN.
- Metropolitan Area Network (MAN) These types of networks are larger than LANs but smaller than WANs – and incorporate elements from both types of networks. MANs span an entire geographic area (typically a town or city, but
sometimes a campus). Ownership and maintenance is handled by either a single person or company (a local council, a large company, etc.).
- Wide Area Network (WAN) A wide-area network (or WAN) is a computer network that connects smaller networks. Since WANs are not tied to a specific location, they allow localized networks to communicate with one another across great distances. They also facilitate communication and the sharing of information between devices from anywhere in the world. WANs allow organizations to create unified networks so that employees, customers, and other stakeholders can work together online, regardless of location. Though WANs cover a large area, connections can be either wired or wireless. Wired WANs usually consist of broadband internet services and multiprotocol label switching (MPLS), which is a form of data-forwarding technology used to control traffic flow and speed up connection, while wireless WANs normally include 4G/5G and Long-Term Evolution (LTE) networks. e) Computer Network Components Computer networks components comprise both physical parts as well as the software required for installing computer networks. Some important physical network components are NIC , switch , cable , hub , router , and modem. Depending on the type of network that we need to install, some network components can also be removed. For example, the wireless network does not require a cable. Following are the major components required to install a network: 1. NIC NIC stands for Network Interface Card is an adapter card that plugs into the system bus of a computer and allows the computer to send and receive signals on a network. A network interface card (NIC) is also known as a network adapter card or simply a network card.
Figure 9 : Computer Network hub
3. Switch A switch is a hardware device that connects multiple devices on a computer network. A Switch contains more advanced features than Hub. The Switch contains the updated table that decides where the data is transmitted or not. Switch delivers the message to the correct destination based on the physical address present in the incoming message. A Switch does not broadcast the message to the entire network like the Hub. It determines the device to whom the message is to be transmitted. Therefore, we can say that switch provides a direct connection between the source and destination. It increases the speed of the network. Figure 10 : A Network Switch
- Router A router is a hardware device which is used to connect a LAN with an internet connection. It is used to receive, analyze and forward the incoming packets to another network. A router works in a Layer 3 (Network layer) of the OSI Reference model. A router forwards the packet based on the information available in the routing table. It determines the best path from the available paths for the transmission of the packet. Advantages of Router: Security: The information which is transmitted to the network will traverse the entire cable, but the only specified device which has been addressed can read the data. Reliability: If the server has stopped functioning, the network goes down, but no other networks are affected that are served by the router. Performance: Router enhances the overall performance of the network. Suppose there are 24 workstations in a network generates a same amount of traffic. This increases the traffic load on the network. Router splits the single network into two networks of 12 workstations each, reduces the traffic load by half.
