SCALANCE W1750D UI
Configuration Manual, 02/2018, C79000-G8976-C451-02
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Hotspot Profiles
33
33.1
Understanding Hotspot Profiles
Hotspot 2.0 (Passpoint Release 1) is a Wi-Fi Alliance specification based on the 802.11u
protocol, which allows wireless clients to discover hotspots using management frames (such
as beacon, association request, and association response), connect to networks, and roam
between networks without additional authentication.
Hotspot 2.0 provides the following services:
●
Network discovery and selection—Allows the clients to discover suitable and available
networks by advertising the access network type, roaming consortium, and venue
information through the management frames. For network discovery and selection,
Generic Advertisement Service (GAS) and Access Network Query Protocol (ANQP) are
used.
●
QOS Mapping—Provides a mapping between the network-layer QoS packet marking and
over- the-air QoS frame marking based on user priority.
When a hotspot is configured in a network:
●
The clients search for available hotspots using the beacon management frame.
●
When a hotspot is found, the client sends queries to obtain information about the type of
network authentication and IP address, and IP address availability using the Generic
Advertisement Service (GAS) action frames.
●
Based on the response of the advertisement server (response to the GAS Action
Frames), the relevant hotspot is selected and the client attempts to associate with it.
●
Based on the authentication mode used for mobility clients, the client authenticates to
access the network.
Generic Advertisement Service (GAS)
GAS is a request-response protocol, that provides L2 transport mechanism between a
wireless client and a server in the network prior to authentication. It helps to determine an
802.11 infrastructure before associating clients and allows clients to send queries to multiple
802.11 networks in parallel.
An AP can include its SP Organization Identifier (OI) indicating the identity of the SP in
beacons and probe responses to clients. When a client recognizes an AP's OI, it attempts to
associate to that AP using the security credentials corresponding to that SP. If the client
does not recognize the AP’s OI, the client sends a Generic Advertisement Service (GAS)
query to the AP to request more information about the network before associating. A client
transmits a GAS Query using a GAS Initial Request frame and the AP provides the query
response or information on how to receive the query response in a GAS Initial Response
frame. To transmit a GAS query for any advertisement protocol, the advertisement protocol
ID must include the advertisement protocol information element (IE) with details of the
advertisement protocol and its corresponding advertisement control.