IEEE 802.11u Overview

1. IEEE 802.11u Overview Dave Stephenson April 9, 2009

2. 802.11u Executive Summary • 802.11u – Interworking with External Networks • Purpose: • Interworking with External Networks is a key enabler to allow IEEE 802.11 devices to interwork with external networks, as typically found in hotspots or other public networks irrespective of whether the service is subscription based or free. • Interworking Service aids network discovery and selection, enabling information transfer from external networks, and enabling emergency services. It provides information to the STAs about the networks prior to association. • Interworking Service addresses MAC layer enhancements that allow higher layer functionality to provide the overall end-to-end interworking solution. • Timeline: • Currently in re-circulation Letter Ballot • Expected start of Sponsor Ballot, July 2009 • Final 802.11 working group approval: January 2010 • Final ratification by 802: June 2010

3. 802.11u is of vital importance to WNBU • Provides the basis for data offload service for carriers (e.g., to offload traffic from cellular data network onto Wi-Fi network) • Provides the basis for Concierge Service • Provides the basis for fast network selection solution—Apple Phase 1 partnership project • Provides key technology for wireless QoS (e.g., for video services) • Provides the basis for standards-based handover service (e.g., 802.21)

4. 802.11u Feature Summary • Network discovery and selection (NDS) • Native-GAS (Generic Advertisement Service) and Interworking element in beacon provide lightweight support for network selection • Non-native GAS provides support for higher-layer network discovery, service advertisement and mobility management protocols • Generalized QoS L3  L2 mapping • Service Provider (aka SSPN) Interface • Support for emergency services including Emergency Alert Service (EAS) • Standardized SAP for higher-layer mobility management protocols (only for client devices)

5. Using 802.11u features for Network Discovery and Selection

6. Exemplary Problems Related to Network Discovery and Selection • Terminal powers up in urban setting and scan environment—finds ~100 Wi-Fi networks. How should it select the right network without depleting its battery? • Terminal doesn’t recognize SSID, so it doesn’t know whether it has the proper security credentials • Terminal doesn’t know whether Wi-Fi network provides internet access, so it doesn’t know whether to attempt association • Terminal associates to network, but user’s email doesn’t work (happens with Web-auth/WISPR when user doesn’t launch browser) • Network selection is just too complicated for non-techie users • E.g., network name (SSID) does not match Venue Name (e.g., t-mobile SSID at Starbucks coffee shop)

7. How does Mobile use 802.11u features to autonomously associate to a hotspot? • Mobile Wi-Fi radio wakes up periodically and scans • Mobile actively scans for hotspot and receives: • Internetworking element, identifying AP as 802.11u capable • Network Type = chargeable (SPs use this type to identify their hotspots) • Internet Access bit set • ASRA bit set (indicates AP using Web-auth or supports online sign-up) • Roaming consortium element advertising hotspot owner OUI + top 2 roaming partner’s OUIs • If mobile recognizes OUI, then attempts association using security credentials corresponding to that OUI • Authentication is 802.1x if RSN element received • Authentication is web-auth if no RSN element and ASRA • Note: Each SP must register with IEEE to obtain OUI and OUI must be provisioned into mobile ahead of time

8. How does Mobile use 802.11u features to autonomously associate to a hotspot (cont.)? • If mobile recognizes OUI, it attempts association using security credentials corresponding to that OUI • Authentication is 802.1x if RSN element received • Authentication is web-auth if no RSN element and ASRA=1 • If ASRA=1, mobile transmits native-GAS query to retrieve Network Authentication Type element (authentication details) • If mobile doesn’t recognize OUI, then it transmits a native-GAS query to retrieve: • Roaming consortium list (remainder of OUIs that didn’t fit in beacon element) • NAI Realm List • Hotspot can accept security credentials for these realms • Realms are for hotspot operator or its roaming partners • List also provides supported EAP types • Notes: enterprises can use this capability for initial provisioning

9. How does Mobile use 802.11u features to autonomously associate to a hotspot (cont.)? • If hotspot supports online sign-up (ASRA=1), mobile checks if MSAP supported at hotspot • If so, mobile can sign-up for service (see subsequent slides) • If not, then mobile searches for another hotspot or remains on cellular network • Note: mobile should include chargeable network type in all active scans so that it will only receive responses from APs set to chargeable network type (at least from 802.11u capable APs) • This conserves mobile’s battery energy because it will have far fewer scan responses to stay awake to receive and subsequently process

10. 802.11u details

11. NDS: Interworking element • This element is in beacons and probe responses • Network type: • One of: {private | private with guest access | chargeable | free} • STAs can selectively scan for desired network type • Internet: set to 1 if Wi-Fi network provides internet access • ASRA (additional authentication step required): set to 1 if Web-auth/WISPR configured • EASN (EAS notification): set to 1 if EAS message is currently active (uses CAP, common alerting protocol) • Emergency Service Accessible: set to 1 if emergency services are reachable via the SSID • If network is RSN, then un-authenticated access is provided • May also be an open network

12. NDS: Interworking element (cont.) • Venue information: extensive table of venue groups and venue types to aid client in culling list of candidate networks • Venue Group: {Assembly, Business, Educational, Factory, Mercantile, Residential, etc.} • Venue Type: • {Assembly [Arena, Stadium, Passenger Terminal, Restaurant, Coffee Shop, Bar, etc.], • Business [Attorney’s office, Bank, Doctor’s office, R&D facility, unspecified, etc.] • Mercantile [Grocery Market, Retail store, Shopping Mall, unspecified, etc.] • etc.} • HESSID: Globally unique network identifier—SPs can now uniquely identify each of their networks • Used in conjunction with SSID • SSID can be set by user to anything (e.g., how many “Linksys-g” SSIDs are out there?) • HESSID value is assigned to be one of the MAC addresses of an AP in the network/ESS • EICI: used in conjunction with EASN, incremented when a new EAS message is available

13. NDS: Roaming Consortium element • This element is in beacons and probe responses • Client scans & receives beacon having this element and can quickly determine if there are any Wi-Fi networks for which it has valid security credentials • Each SP or consortium of SPs must register with IEEE to obtain OUI • Element gives OUI for top 3 SPs (or consortium of SPs) having roaming agreements with Wi-Fi access network provider; remainder available via native-GAS query • Number of Native-GAS OUIs provides number of additional OUIs which will be returned on a native-GAS query (see subsequent slide)

14. NDS: Native-GAS • Native-GAS is a query / response protocol used by terminal to discover information about the 802.11 access network and the back-end network • Most important queries supported: • Venue name (multiple languages supported) • Network Authentication Type (Web-auth/WISPR details) • NAI Realm List • List of realm’s for which a terminal having these security credentials should be able to successfully authenticate to the Wi-Fi network • 3GPP Cellular Network information (support for PLMN selection—similar to realm) • Roaming Consortium List • List of identifiers for a single carrier or a consortium of carriers (e.g., iPASS)

15. NDS: Native-GAS (cont.) • Other queries supported: • Domain Name List (domain name(s) supported by Wi-Fi network) • AP Date, Time and Time Zone information (facilitates a client device to re-set it’s clock upon being powered on in a new location—just like cellular system does) • IP Address Type availability (provides whether a public or private IPv4 or IPv6 address can be provided by Wi-Fi network) • AP Civic Location • AP Geospatial Location • Emergency dialing digits (they are location dependent)

16. NDS: Non-native-GAS • Provides transport for higher-layer advertisement protocols • Specific protocol identified using advertisement protocol element (see subsequent slide) • Supports query / response-based protocols in which a client device communicates with a server in the back-end network • AP/WLC proxies the client’s query to the server and buffers the response until the client retrieves it • Non-native GAS will be used for MSAP exchanges

17. NDS: Example Non-native-GAS Message Sequence Chart • Notes: • dtoken = Dialog token, used to correlate requests with responses

18. NDS: Other Beacon elements • Advertisement protocol element • Provides IDs for advertisement protocols supported by the Wi-Fi network • MSAP is an example • Others: 802.21, CAP, LoST • Extended capabilities element • Provides for 802.11u feature negotiation between AP and client

19. Generalized QoS Mapping • Provides QoS Map (DSCP to UP mapping) for consistent packet marking and queuing for all clients in the BSS • Provides for each service to have the proper QoS over the air • There is no standardized mapping of end-to-end QoS (DSCP) to L2 QoS • Voice and Video endpoints can use this information element to provide proper mapping for each flow (e.g., voice, video, signaling) over the air • Hot Spot usage • Multiple service providers can share an AP at a hotspot (e.g., airport hotspot) • Each SP can have their own end-to-end DSCP marking practice and network-specific QoSMap  all will have harmonized L2 QoS on the shared AP

20. SSPN Interface • Permissions received from SP are saved in a MIB and enforced for each client • Provides standardized support for permissions and rate limiting for each QoS level • Maximum data rate permitted for each access category • Maximum data transfer (in bytes) permitted for each access category • Permission to use a specific access category (e.g., voice) • Provides for enforcement of security requirements, location requirements • Forces dis-association of client if hotspot in non-permitted location or cipher too weak • Matches requirements in 3GPP ANDSF

21. 802.11u Provides Access to Emergency Services • Features supporting Emergency Services • Identification of WLANs wherein emergency services are reachable • Provision for access emergency services in an RSN (802.1x network) when client does NOT have valid security credentials • Expedited Bandwidth Request element (technology from CCXv5) • Used with admission control procedures to identify a flow as an emergency call • Support for Emergency Alert Service (EAS) • Uses CAP—common alerting protocol • E.g., Amber alert, severe thunderstorm warning, etc.

22. 802.11u provides support for Mobility Management Protocols • Applies only to client devices • Standardized SAP having MAC primitives to support 802.21 event service and command service (but generic enough to support other mobility management protocols), eg: • Network discovery—tells MIH when a new network is discovered (as opposed to a new AP in the same network) • ESS-Link-going-down—tells MIH when device is leaving the network (as opposed to transitioning away from an AP)