Wireless Technology Notes

Wireless Networking Topologies

  • WLAN Overview: A wireless local area network (WLAN) enables wireless networking in building or campus environments.
  • 802.11 Standard: The 802.11 wireless standard (specifically 802.11-2020) is ideal for local area applications due to defined range and speeds.
  • Deployment: Most WLAN deployments are in businesses and homes.

802.11 Stations

  • Station (STA): The primary component in an 802.11 network is the station (STA) which can be a radio in an access point (AP) or a client station.
  • Unique MAC Addresses: Each station has a unique Media Access Control (MAC) address.
    • Access Point (AP) MAC: C413E2039F40
    • Client Station MAC: 0C51019C6BFD

Client STA

  • Definition: Non-AP stations are client stations used in various devices such as laptops and smartphones.
  • Association: When connected with an AP, client stations are termed "associated."

Access Point (AP) STA

  • Functionality: AP stations serve as wireless portals that allow communication among connected client stations.
  • Portal Functionality: The distribution system access function (DSAF) allows client communication to wired networks (like Ethernet).

Distribution System (DS)

  • Definition: The 802.11 standard defines a distribution system for interconnecting basic service sets via integrated LANs.
  • Components: Two main components: Distribution System Medium (DSM) for connecting APs, and the Distribution System Service to forward traffic.
  • Common Medium: The DSM typically uses 802.3 Ethernet, which can give power to AP through Power over Ethernet (PoE).

Wireless Distribution System (WDS)

  • Examples: WDS is used in mesh deployments for coverage and in outdoor links for backhaul connectivity.

802.11 Service Sets

  • Types of Topologies:
    • Basic Service Set (BSS)
    • Extended Service Set (ESS)
    • Independent Basic Service Set (IBSS)
    • Personal Basic Service Set (PBSS)
    • Mesh Basic Service Set (MBSS)
    • Quality of Service Basic Service Set (QBSS)

Service Set Identifier (SSID)

  • Definition: The logical name identifying a WLAN; similar to a workgroup name in Windows.
  • SSID Features: Configurable, case-sensitive, may contain up to 32 characters.

Basic Service Set (BSS)

  • Structure: Composed of one AP with multiple client stations and operates on a layer 2 connection.
  • Coverage Area: Basic Service Area (BSA) defines the physical coverage by the AP; clients must maintain signal strength (RSSI).
  • BSSID: The basic service set identifier (BSSID) is the MAC address of the AP's radio, acting as a layer 2 identifier.

Multiple BSSIDs

  • Functionality: An AP can support multiple SSIDs (up to 16), leading to layer 2/3 domains.
  • Performance Consideration: Excessive SSIDs can degrade performance; advised to limit to 3 or 4.

Extended Service Set (ESS)

  • Definition: Composed of multiple BSSs linked by a DSM, usually Ethernet.
  • Seamless Roaming: ESS allows clients to communicate and roam without interruptions.
    • Nomadic Roaming: Clients might lose connectivity when moving between access points.
  • ESSID: An ESS has the same SSID and security settings across APs but unique BSSIDs.

Independent Basic Service Set (IBSS)

  • Structure: Composed solely of client stations without an AP; functions similarly to a wired crossover cable.
  • Communication: Unlike BSS, clients communicate directly with each other without an AP.

Mesh Basic Service Set (MBSS)

  • Purpose: Provides wireless distribution for network traffic through multiple APs functioning in a mesh.
  • Mesh Portal vs. Mesh Point: A mesh portal is connected to upstream wired mediums, while mesh points are not.

QoS Basic Service Set (QBSS)

  • Mechanisms: Quality of Service (QoS) can be implemented in all service sets; commonly supported by enterprise APs.

Configuration Modes - AP

  • Modes:
    • Root Mode (AP mode): Default mode for portals.
    • Mesh Mode: Functions in backhaul for mesh.
    • Sensor Mode: Monitors for intrusion detection systems.
    • Bridge Mode: Provides MAC-layer intelligence for device learning.
    • Workgroup Bridge Mode: Enables wired client connectivity.
    • Client Mode: AP acts as a client for troubleshooting.

Configuration Modes - Clients

  • Infrastructure Mode: Default communication with APs in BSS or ESS.
  • Ad-hoc Mode: Clients communicate directly in IBSS, not supported on all devices.

Wireless AP Feature Sets

  • Key Features: Dual-band support, security features, diversity antennas, WDS support, numerous wireless stations, dynamic rate shifting, adjustable power.

Roaming between WLANs

  • Layer 3 Roaming: New IP addresses are assigned when a user moves between SSIDs.
  • Mobile IP: Allows a host to maintain a single IP address while moving through networks, using home and foreign agents for IP management.