802.11u Packet Formats
What is the key enhancement in 802.11u packet formats compared to earlier standards?
802.11u introduces additional Information Elements (IEs) in management frames to support network interworking and discovery.
Which frame types does 802.11u primarily extend?
Management frames such as Beacon, Probe Request/Response, and Association Request/Response.
What are ANQP frames and how do they relate to 802.11u packet formats?
ANQP (Access Network Query Protocol) messages are carried within Generic Advertisement Service (GAS) frames to query network info pre-association.
How does 802.11u use Information Elements (IEs) in packet formats?
It defines new IEs to convey interworking capabilities, network types, and roaming consortium info.
Are control or data frames modified in 802.11u?
No significant changes; 802.11u focuses on management frame extensions.
What role do Beacon frames play in 802.11u packet formats?
Beacons include new IEs advertising interworking and emergency services info.
How does 802.11u handle Probe Requests and Responses?
Probe Responses can carry additional IEs for network discovery and selection based on operator policies.
What is the Generic Advertisement Service (GAS) frame format?
GAS frames encapsulate ANQP queries and responses using a standardized format over existing management frames.
How are Access Network Type IEs structured?
These IEs specify the type of access network (e.g., cellular, WLAN) to assist devices in network selection.
Does 802.11u define new frame subtypes?
No new subtypes, but new IEs are added within existing management frames.
How does the Roaming Consortium IE help in packet formats?
It identifies roaming agreements between network operators to facilitate seamless handoffs.
What is the Emergency Alert IE and how is it formatted?
It is an IE used in management frames to broadcast emergency notifications to devices.
Are 802.11u packet formats backward compatible?
Yes, new IEs are optional and ignored by devices that don’t support 802.11u.
How is information about network capabilities conveyed?
Via extended IEs that include supported authentication types, access network types, and venue info.
Can 802.11u IEs affect the size of management frames?
Yes, the additional IEs increase frame size but remain within standard limits.
How do packet formats support pre-association network discovery?
By enabling devices to query detailed network info before associating using ANQP over GAS.
What is the format of the Access Network Query Protocol (ANQP) message?
ANQP messages have a TLV (Type-Length-Value) structure encapsulated within GAS frames.
How do 802.11u packet formats enhance user experience?
By providing richer network info enabling automatic network selection and seamless roaming.
Where can developers find detailed 802.11u packet format specifications?
In the IEEE 802.11u amendment document and the 802.11 standard clauses on management frames.
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