Lesson Notes By Weeks and Term v5 - Grade 12
Networks, the internet and emerging technologies – Week 6 focus
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Networks, the internet and emerging technologies – Week 6 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Information Technology
Class: Grade 12
Term: 2nd Term
Week: 6
Theme: General lesson support
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This week, we delve deeper into the world of networks, the Internet, and the ever-evolving landscape of emerging technologies. In South Africa, access to reliable internet and understanding how networks function are crucial for participation in the modern economy, accessing education, and connecting with the global community. Understanding these concepts is no longer a luxury but a necessity, as it underpins everything from online banking and e-learning to government services and social interaction. This week’s focus builds upon previous knowledge and introduces more complex networking concepts and considers the impact of emerging technologies.
2.1 Network Topologies A network topology defines the physical or logical arrangement of devices in a network. Understanding different topologies is critical for designing and troubleshooting networks.
Bus Topology: All devices connect to a single cable (the "bus").
Advantages:* Simple and inexpensive to set up.
Disadvantages:* Single point of failure (if the bus breaks, the entire network goes down). Difficult to troubleshoot. Not scalable. Obsolete technology.
South African Relevance:* Rarely used in modern contexts. May exist in older installations but are being replaced by more robust topologies.
Star Topology: All devices connect to a central hub or switch.
Advantages:* Easy to troubleshoot. Failure of one device doesn't affect the rest of the network. Scalable.
Disadvantages:* Central point of failure (if the hub/switch fails, the entire network goes down). Requires more cabling.
South African Relevance:* Widely used in offices, schools, and homes. The hub or switch is the central point controlling data flow. Think of a school computer lab where each computer connects to a central switch.
Ring Topology: Each device connects to exactly two other devices, forming a closed loop.
Advantages:* Data flows in one direction, reducing collisions.
Disadvantages:* Single point of failure (if one device fails, the entire network can go down). Difficult to troubleshoot.
South African Relevance:* Less common, but historically used in some token ring networks. Now mostly superseded by other topologies.
Mesh Topology: Each device connects to multiple other devices.
Advantages:* Highly redundant and reliable. Failure of one device doesn't significantly affect the network.
Disadvantages:* Expensive to implement due to the amount of cabling required. Complex to manage.
South African Relevance:* Used in critical infrastructure and backbone networks where high availability is crucial (e.g., core telecommunications networks).
Hybrid Topology: A combination of two or more topologies.
Advantages:* Flexible and adaptable to different needs.
Disadvantages:* Can be complex to manage.
South African Relevance:* Very common in modern networks. For example, a large office might use a star topology for each department, connected to a central backbone using a mesh topology for redundancy. Think of a university campus where different departments (each with star networks) are connected through a high-speed backbone. 2.2 IPv4 and IPv6 Addressing IP addresses are used to uniquely identify devices on a network.
IPv4: Uses 32-bit addresses, represented in dotted decimal notation (e.g., 192.168.1.1).
Limitations:* Limited address space (around 4.3 billion addresses), leading to address exhaustion. NAT (Network Address Translation) is used to share public IP addresses, but this can cause issues with some applications.
South African Relevance:* Still widely used, but facing increasing pressure due to address exhaustion. Many South African ISPs use NAT to provide internet access to their customers.
Subnetting: Dividing a network into smaller subnetworks. This improves network efficiency and security.
Example: Suppose you have a Class C network 192.168.1.0 with a default subnet mask of 255.255.255.0 (/24). You want to create 4 subnets. You need 2 bits to represent 4 subnets (2 2 = 4). Borrow 2 bits from the host portion of the IP address. The new subnet mask is 255.255.255.192 (/26). (192 is 11000000 in binary).
The subnet ranges are: 192.168.1.0 - 192.168.1.63 192.168.1.64 - 192.168.1.127 192.168.1.128 - 192.168.1.191 192.168.1.192 - 192.168.1.255 The first and last addresses in each subnet are reserved (network address and broadcast address, respectively).
IPv6: Uses 128-bit addresses, represented in hexadecimal notation (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334).
Advantages:* Vast address space, eliminating the need for NAT. Simplified header format, improving routing efficiency. Built-in security features (IPsec).
South African Relevance:* Gradual adoption. Some South African ISPs are deploying IPv6 to prepare for IPv4 address exhaustion. Government initiatives are encouraging IPv6 adoption.
Simplification Rules:* Leading zeroes in a group can be omitted: `2001:0db8:85a3:0000:0000:8a2e:0370:7334` can be written as `2001:db8:85a3:0:0:8a2e:370:7334` One or more consecutive groups of zeros can be replaced with a double colon (::): `2001:db8:85a3:0:0:8a2e:370:7334` can be written as `2001:db8:85a3::8a2e:370:7334` Only one double colon is allowed per address.* 2.3 Networking Devices Hub: A basic device that forwards all data it receives to all connected devices.
South African Relevance:* Obsolete technology. Rarely used in modern networks due to its inefficiency and lack of security.
Switch: A more intelligent device that forwards data only to the intended recipient.
South African Relevance:* Widely used in local area networks (LANs) in offices, schools, and homes. Improves network performance by reducing collisions.