Tgaq service transaction protocol for andsf discovery service
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Date: 2014-03-19 2. TGaq Service Transaction Protocol for ANDSF Discovery Service. Authors:. Abstract. This is a TGaq Transaction Protocol example showing how a pre-associated STA may access ANDSF Service for WLAN discovery and selection.

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TGaq Service Transaction Protocol for ANDSF Discovery Service

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Tgaq service transaction protocol for andsf discovery service

Date: 2014-03-19

2

TGaq Service Transaction Protocolfor ANDSF Discovery Service

Authors:

Joe Kwak, InterDigital


Abstract

Abstract

This is a TGaq Transaction Protocolexample showing how a pre-associated STA may access ANDSF Service for WLAN discovery and selection.

This builds upon the 11aq draft text in 11-13-1384-03-00aq-service-transaction-protocol and is intended to be the basis for an informative annex in our 11aq draft.

Joe Kwak, InterDigital


Background

Background

  • TGaq develops simple MAC protocol

    • Defines over-the-air messages only (PAM)

  • Meets low level requirements of use cases

  • Other Fora deal with higher layers (L2+)

    • Liaison to other fora of our use cases

  • 3GPP has developed a discovery service for dual mode smartphones and other dual mode (cell/WLAN) devices that uses assistance data to discover and select WLANs suitable for offload.

  • Access Network Discovery and Selection Function (ANDSF) has been specified by 3GPP to provide this assistance data.

  • ANDSF is normally implemented in a server accessible on the internet, and discovered by DNS lookup.

Joe Kwak, InterDigital


Service transaction protocol stp review

Service Transaction Protocol (STP) Review

  • STP is different from ANQP

    • STP is not limited to simple Request/Response mechanism.

    • Using transparent packet containers, STP provides flexible transport for pre-associated STAs to communicate with different existing Upper Layer Protocols (ULPs) for service discovery, bonjour, UPnP, etc.

    • Service/discovery information is transparently encapsulated for transport to a Service Transaction Proxy (STPxy) which implements this protocol for a particular (or set) of discovery ULP.

    • Packets are routed from the pre-associated STA, through the AP, to the STPxy, which acts on behalf of the STA to communicate with the intended discovery protocol server.

    • In other words, STP sets up a short-term tunnel from the STA to the STPxy which proxies for the STA for internet packet exchanges.

Joe Kwak, InterDigital


Service transaction protocol review

Service Transaction Protocol Review

1

  • Part of the PAM (Pre-Association Messages)

  • The TP is implemented as an advertisement protocol enabling it to be carried, over the IEEE 802.11 air interface, by the existing GAS mechanism.

  • Use a new advertisement protocol id “STP” – service transaction protocol (e.g. like RLQP). NOTE: TG has decided to change name to PADP in place of STP

  • Define a new IE for use in Beacon, Probe Response frames to advertise service capabilities.

    [1] Transaction Protocol Review (slides 5-10) from

    11-13-0788-03-00aq-transaction-protocol

Joe Kwak, InterDigital


Service transaction protocol review1

Service Transaction Protocol Review

  • A mobile device requires service information prior to association.

  • The mobile device supports one or more ULP’s

  • The Access Point advertises (in this example using ANQP) service types as well as a list of ULP’s that are supported.

  • An STP Encapsulation message carries the ULP service information request to the AP, which relays the request to the STPxy.

  • The STPxy proxies for the STA to exchange service information using the discovery ULP.

  • The STPxy provides service information in a response that is encapsulated and sent back to the mobile device through the Access Point.

Joe Kwak, InterDigital


Service transaction protocol review2

Service Transaction Protocol Review

  • STP operates between the ULP applications in the pre-associated STA and the Service Transaction Proxy (STPxy).

  • As this ANDSF example shows, the encapsulation mechanism must be transparent to enable this service for ANDSF and perhaps other popular discovery services.

Joe Kwak, InterDigital


Tgaq service transaction protocol for andsf discovery service

Joe Kwak, InterDigital


Service transaction protocol review3

Service Transaction Protocol Review

  • ULP does not need to be standardised within Tgaq

    • deliberately hide the details of the ULP so that we can focus on MAC design

  • When the higher layer ULP responds with another message B, the TXP uses another STP Encapsulation message to transmit message B back to the mobile device including the STP token. If an error occurs in the TXP transaction a Return Code may be alternatively returned to the mobile.

  • When the STP Encapsulation message is received by the mobile terminal the contents are passed back to the service discovery ULP.

Joe Kwak, InterDigital


Service transaction protocol review4

Service Transaction Protocol Review

  • The message sequence is bi-directional and can be initiated by the ULP co-located with the STPxy. The service information is constructed based on the ULP – it does not necessarily execute the ULP protocol over frames transmitted in the pre-associated state

  • IDs of ULP protocols for the STA and the AP infrastructure are required for encapsulation/decapsulation.

  • Possibly need to fragment large ULP frames.

    • GAS already has the capability for fragmentation/reassembly

  • To conserve the medium, using a hash of the service information in the encapsulated STP exchange may be feasible for some applications of STP. (see 13-893r0)

  • Messages could be signed to provide some level of data integrity.

  • Need to do some additional work on defining the ULP ID space and its management

Joe Kwak, InterDigital


Tgaq service transaction protocol for andsf discovery service

ANDSF Example Using 11aq Transaction Protocol

Joe Kwak, InterDigital


3gpp wlan network architecture

3GPP WLAN Network Architecture

  • Both trusted (integrated) and untrusted(over-the-top) interfaces exist

  • The trusted interface involves operator deployed WLAN and is being evolved in 3GPP Release 12

TWAG

Joe Kwak, InterDigital


Tgaq service transaction protocol for andsf discovery service

Normal discovery for 3GPP UE(STA) after association and using IP transport

(Figure 8.5.1-1 from 3GPP TS 23.402)

Joe Kwak, InterDigital


Tgaq service transaction protocol for andsf discovery service

Pre-association discovery for 3GPP UE(STA)

using STPxy with limited IP transport

Joe Kwak, InterDigital


Tgaq service transaction protocol for andsf discovery service

  • A: STPxydecapsulates message and substitutes its own IP add in header to replace dummy IP add from STA

  • B: STPxy substitutes dummy IP add from STA to replace its own IP add in header, then encapsulates and sends to AP

Joe Kwak, InterDigital


Tgaq service transaction protocol for andsf discovery service

  • A: STPxydecapsulates message and substitutes its own IP add in header to replace dummy IP add from STA

  • B: STPxy substitutes dummy IP add from STA to replace its own IP add in header, then encapsulates and sends to AP

Joe Kwak, InterDigital


Discussion and questions

Discussion and Questions

  • Questions on presentation?

  • Should we develop this example into draft text for the informative Annex of the 11aq amendment?

  • Other comments or issues?

  • Joe Kwak will provide draft text for this informative annex at May meeting.

    THANK YOU

Joe Kwak, InterDigital


References listed in order of relevance to this example

  • http://www.3gpp.org/DynaReport/23003.htm3GPP Network Elements: Numbering, Addressing, and Identification –Explains ANDSF discovery mechanism using DNS

  • http://www.3gpp.org/DynaReport/33222.htmGeneric Authentication Architecture and Access to 3GPP Network Using https: --Explains authentication and TLS security for ANDSF connection based on preconfigured or bootstrapped shared key.

  • http://tools.ietf.org/html/rfc2818 HTTP over TLS—General reference for setting up https:

  • http://www.3gpp.org/DynaReport/23234.htmSpecification of 3GPP-WLAN Interworking—Broad reference that provides detail on WLAN-ANDSF interface

  • http://www.3gpp.org/DynaReport/23402.htmSpecification for non-3GPP Access to 3GPP Network—Includes architecture and interworking descriptions for WLAN discovery and connection to ANDSF

  • http://www.3gpp.org/DynaReport/23865.htmStudy of WLAN Selection and Policy Application using ANDSF Information—provides set of illustrative examples showing how STAs use ANDSF Management Object (MO) data to select WLAN.

  • http://www.3gpp.org/DynaReport/234312htmSpecification of ANDSF MO—Complete MO details and structure of WLAN selection policy MO tree.

REFERENCES (listed in order of relevance to this example)

Joe Kwak, InterDigital


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