📘 01-02: Network Models & Topologies¶
📌 Topology¶
Topology describes how the parts of a network fit and work together.
- Physical topology — the actual hardware layout: devices, cables, and how they physically connect.
- Logical topology — how software controls access and how data logically flows across the network.
Two networks can share the same physical topology but behave differently at the logical level.
📌 Physical Topologies¶
| Topology | Description | Pros | Cons |
|---|---|---|---|
| Star | All nodes connect to a central device (switch) | One cable fault affects one node; easy to manage | Central device is a single point of failure |
| Bus | All nodes share one backbone cable | Cheap, simple (legacy) | One break kills the whole segment |
| Ring | Each node connects to two neighbors in a loop | Predictable performance (legacy) | A break can disrupt the ring |
| Mesh | Nodes interconnect directly (full or partial) | High redundancy/fault tolerance | Expensive, many links |
The star topology dominates modern LANs (every device to a switch). Mesh is common in WAN cores for redundancy.
📌 Hybrid Topologies¶
Real networks combine topologies — e.g., a star-of-stars (hierarchical star) where multiple switches connect up to a core switch. Structured cabling assumes a hierarchical star.
📌 Logical Models Recap¶
- Peer-to-peer — no central control; each host shares its own resources.
- Client-server — a NOS on servers centrally controls access.
(See What Is a Network? for the full comparison.)
Tip
Key idea — Physical topology = the wiring diagram; logical topology = the traffic flow. Modern LANs are physically star (to a switch) and can be logically segmented (e.g., with VLANs — see Virtual LAN (VLAN)).
See also: The OSI Model, Network Hardware Devices
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