Quiz Entry - updated: 2026.07.14
What are the three 802.11 wireless topology modes, and what is the difference between a BSS and an ESS?
The three modes are: Infrastructure (with AP), Ad hoc (peer-to-peer, no AP), and Tethering (hotspot). A BSS is a single AP with its clients; an ESS is multiple BSSs connected by a wired backbone, enabling roaming.
* ESS: multiple BSSs sharing one SSID. — Boberchik, CC BY-SA 4.0, via Wikimedia Commons. *
Topology modes:
- Infrastructure mode: Clients connect through an AP to reach the network — the standard enterprise/home mode
- Ad hoc mode (IBSS): Peer-to-peer — clients communicate directly without an AP (e.g., two laptops sharing files)
- Tethering: A phone/tablet creates a personal hotspot, sharing its cellular data connection via Wi-Fi
BSS vs ESS:
| Concept | BSS (Basic Service Set) | ESS (Extended Service Set) |
|---|---|---|
| Definition | A single AP and all its associated clients | Two or more BSSs interconnected by a wired distribution system |
| Coverage | One AP's radio range (one room/area) | Multiple APs covering a large area (building/campus) |
| Identifier | BSSID = AP's MAC address | ESSID (SSID) = shared network name across all APs |
| Roaming | Not applicable | Clients roam seamlessly between APs in the same ESS |
| Inter-BSS communication | Clients in different BSSs cannot communicate | Clients in different BSSs can communicate through the ESS |
Key terms:
- SSID: The human-readable network name ("CorporateWiFi") — same across all APs in an ESS
- BSSID: The AP's MAC address — uniquely identifies one specific AP
Go deeper:
Service set (802.11 network) (Wikipedia) — diagrams of IBSS/ad-hoc, infrastructure BSS, and ESS with a shared SSID.