# Q7(b) · Four network topologies

Subject: Computer Networks

Exam: TEE

Reader: https://deep-learning-study-room.vercel.app/cn/#tee/papers/paper-2024-feb-reexam/q7b

Canonical: https://deep-learning-study-room.vercel.app/read/cn/tee/papers/paper-2024-feb-reexam--q7b/

Actual paper; 100 marks attempted. Current-syllabus alignment is stated per question.

### Q7(b). Define network topology. Compare various network topologies (any 4) with the advantages and disadvantages of each. Draw diagram to illustrate each topology. [10 marks]

### Answer

**Topology** is the arrangement of nodes and links. Physical topology describes actual links; logical topology describes how data flows. A switch-centred physical star is different from a shared collision-domain bus.

Swipe across the diagram to read its labels ↔

![Four physical network topologies](https://deep-learning-study-room.vercel.app/cn/fig/tee-topologies.d9e18f041b.svg)

Diagram: Four physical network topologies. Labels: Four physical network topologies | Four physical network topologies | Star | Bus | Ring | Full mesh: 4 nodes, 6 links | S | Links show arrangement. Actual access rules are a separate concept.

Star, bus, ring and full mesh; edges depict physical connections.

| Topology | Structure | Benefit | Limitation |
| --- | --- | --- | --- |
| Bus | Devices share a common backbone | Simple small shared-medium layout | Backbone fault affects segment; collisions possible on classic shared bus |
| Star | Each device connects to a central switch/hub | Easy expansion and fault isolation | Central-device failure affects star; more cabling |
| Ring | Each node connected to two neighbours in a ring | Structured traversal; token-based variants coordinate access | Simple single-ring break can disrupt operation unless protected |
| Full mesh | Every pair has a direct link | Redundant paths and direct connectivity | Expensive ports/cabling: n(n−1)/2 undirected links |
| Tree/hybrid | Hierarchical stars or combined topologies | Scales into buildings/floors | Upper-level faults affect dependent branches |

#### Practical example

A lab normally uses a switch-centred star: unplugging one workstation cable isolates that workstation. A failed central switch can stop the whole lab unless redundancy is provided.

**Yaad rakho:** Layout draw karo, then one strength and one failure case.

### Two advantages and two disadvantages of each topology

| Topology / example | Advantage 1 | Advantage 2 | Disadvantage 1 | Disadvantage 2 |
| --- | --- | --- | --- | --- |
| Star: switched computer laboratory | A device can be added on a spare central port without rebuilding the whole topology | A single access-cable fault normally isolates only its attached device | Central-switch failure affects all attached devices unless redundant | A separate cable and switch port are needed per device |
| Bus: legacy coaxial Ethernet | Uses little cable in a small linear layout | No central switch is required in the simple shared-bus design | A backbone fault can disable the segment | Shared bandwidth, contention and fault diagnosis become difficult as it grows |
| Ring: token-based ring | Controlled token access avoids data collisions among compliant stations | Token rotation gives stations an organized opportunity to transmit | A break can interrupt an unprotected single ring | Adding/removing a node can disrupt a simple ring |
| Mesh: redundant router backbone | Alternate links preserve connectivity after some link failures | Direct pairwise links can carry separate exchanges without a shared central bottleneck | A full mesh needs n(n−1)/2 links and many ports | Configuration, cabling and maintenance become complex |

The ring benefits above assume token-controlled access; physical ring wiring alone does not guarantee fairness or collision avoidance. The failure disadvantages describe simple layouts without protection/redundancy.