Let's work through this case study step by step, using the CBSE Class 12 Informatics Practices networking concepts.

(i) Topology and cable layout for the Delhi branch

The most suitable topology is the Star topology. Each wing is connected to a central node, which keeps the layout simple and fault-tolerant — if one wing's cable fails, only that wing is affected, not the whole network. The central switch (and the server) is best placed in the Administrative Wing (W1), because W1 has the maximum number of computers (125), so most of the network traffic originates there. Every other wing is then connected to W1:

• W1 to W2: 40 m
• W1 to W3: 85 m
• W1 to W4: 170 m

(ii) Kind of network required

1. W1 with W3 — a LAN (Local Area Network), because both wings are within the same Delhi campus, only 85 m apart.
2. W1 with the Mumbai branch — a WAN (Wide Area Network), because the two locations are in different cities, far apart.

(iii) Placement of devices with justification

(a) Repeater — place a repeater on any cable run longer than 100 m, since a normal twisted-pair Ethernet segment weakens beyond 100 m. Here the W1–W4 link (170 m) is the longest, so a repeater on the W1–W4 cable regenerates the signal so it reaches W4 clearly. …

When a school wants to connect its different wings into a single, efficient network, the first decision is about the physical layout — the topology. Think of topology as the map of how cables run between buildings. The goal is to choose a layout that is reliable, cost-effective (uses the least cable), and easy to manage.

Looking at the distances given, the Administrative Wing (W1) sits at a convenient central point. It is 40 m from W2, 85 m from W3, and 170 m from W4. If we connect every wing directly to W1, we get a Star topology. The total cable length would be: 40 + 85 + 170 = 295 metres. Compare this to a Ring topology (which would require connecting W1→W2→W4→W3→W1, totalling 40 + 25 + 120 + 85 = 270 metres) or a Bus topology (which would run a single long cable past all wings, likely exceeding 300 m). While the Ring uses slightly less cable, the Star is far superior for a school network.

The Star topology also makes it easy to add new wings later, and it centralises network management — all traffic flows through W1, where you can place the main switch and server. This is exactly what a school like ABC International needs.

For the cable layout, the most practical choice today is twisted pair cable (Cat 6 or higher) with RJ-45 connectors, because it supports high speeds (up to 1 Gbps or more) and is affordable. However, note that twisted pair has a maximum segment length of 100 metres. Look at the distances: W1 to W4 is 170 m, and W3 to W4 is 120 m — both exceed 100 m. So for those links, you would need a Repeater (see part iii) or use fibre optic cable, which can run kilometres without signal loss. A practical layout would be: use twisted pair for W1↔W2 (40 m) and W1↔W3 (85 m), and fibre optic for W1↔W4 (170 m) because it is the longest link.

(ii) Kind of network required

1. Administrative Wing (W1) with Middle Wing (W3) — These two wings are on the same campus in Delhi, separated by only 85 metres. They are within the same building or adjacent buildings. This is a classic Local Area Network (LAN). A LAN connects computers within a limited geographical area (like a school, office, or home) and is owned and managed by the organisation itself.
2. Administrative Wing (W1) with the Mumbai branch — Mumbai is in a different city, hundreds of kilometres away. This is a Wide Area Network (WAN). A WAN connects computers across large geographical distances, often using leased telecommunication lines or the public internet. The school would need to subscribe to an internet service provider (ISP) and use technologies like VPN (Virtual Private Network) to securely connect the two campuses.
   Note

   A MAN (Metropolitan Area Network) would cover a city-sized area — say, connecting two schools in different parts of Delhi. But Mumbai is a different city entirely, so it is definitely a WAN.

(iii) Placement of devices with justification

(a) Repeater — A repeater is a device that regenerates a signal, extending the maximum cable length. As noted, twisted pair cable has a 100-metre limit. The distance between W3 and W4 is 120 m, and between W1 and W4 is 170 m. So a repeater is needed on any link that exceeds 100 m. The most critical placement is between W3 and W4 (120 m) or between W1 and W4 (170 m). If using twisted pair for the W1–W4 link, you would place a repeater roughly halfway (around 85 m from W1). If using fibre optic, no repeater is needed because fibre can handle those distances easily. The textbook recommends placing a repeater wherever the cable length exceeds the maximum segment length. …