1. Service discovery architecture for TGaq
April 2013
doc.: IEEE /0796
Nov 2013
Service discovery architecture for TGaq
Date:
Authors:
Ping FANG, Huawei
Ping FANG, Ping FANG, Huawei

2. April 2013
doc.: IEEE /0426
Nov 2013
Abstract
This document presents a service architecture for TGaq. Service indication from AP, network discovery and detailed service information query are described. Possible options and issues are further discussed.
Ping FANG, Huawei
RYU Cheol. ETRI

3. April 2013
doc.: IEEE /0426
Nov 2013
Background
In 13/501r0, a architecture with service registration and service discovery is registered. Per the meeting discussion, the registration can be done in MAC layer or upper layer after association.
In 13/796r0, the procedure on how a STA discovers necessary service information before association is described with a high level 2-step service discovery procedure proposed.
In 13/796r1, more details on service indication are further discussed.
In 13/893r0, different service hash values proposed to be carried in service discovery request and response with public action frame for privacy and security
Ping FANG, Huawei
RYU Cheol. ETRI

4. Overall picture of 11aq Nov 2013 April 2013 doc.: IEEE 802.11-13/0426
Ping FANG, Huawei
RYU Cheol. ETRI

5. Service Indication from AP
April 2013
doc.: IEEE /0426
Nov 2013
Service Indication from AP
Option 1 : new Service Indication IE in Beacon/ Probe Response
Carried in Beacon or Probe Response, no extra overhead
Good for passive scanning to indicate which services are provided or not
Option 2: new Public Action frame
Extra load for AP to broadcast besides Beacon
STA doesn’t know when to receive, broadcast periodically
Assumption:
Proxy in AP caches general service information
Good for scenarios when lots of STA queries
Good to indicate what kind of services are provided or not
Ping FANG, Huawei
RYU Cheol. ETRI

6. Part 2: Service Information
April 2013
doc.: IEEE /0426
Nov 2013
Service Indication IE
Service Indication IE in Beacon/ Probe Response
Service Indication Bitmap
Protocol Part: fixed bits to indicate protocols for services
Service Information Part: Bits used to indicate available services, each bit corresponds to a service/services with hash value
Element ID
Length
Service indication bitmap
1 octet
TBD octet
Part 1: Protocol
Part 2: Service Information
UPnP
Bonjour … … 1 1 1 … …
Bit 1
Bit 2
Bit 3
Hash(“UPnP:Printer”), then set bit 1 value to be 1.
Ping FANG, Huawei
RYU Cheol. ETRI

7. General Service Query General Service Query
April 2013
doc.: IEEE /0426
Nov 2013
General Service Query
General Service Query
To decide whether a service can be provide via AP
Query and response can be relatively shorter
Option 1 : Combine with AP/Network discovery
Carry service hash IE in Probe Request/Response
Different Service hash values can be carried in Probe request/response for privacy
Option 2: New Public Action frame [4]
Carry service hash values in PAM request/response
Different Service hash values be in Probe request/response for privacy
Option 1
Option 2
Ping FANG, Huawei
RYU Cheol. ETRI

8. Public Action Frame vs. Service IE
April 2013
doc.: IEEE /0426
Nov 2013
Public Action Frame vs. Service IE
Option 1: Service IE in Probe Req/Resp
Option 2:New Public Action Frame
Option1 vs. option 2
Element ID
Length
Service Hash Value
Service Capability
1 octet
6 octets
0 or variable
MAC Header
Category(=4)
Public Action
Length
Service Hash Value
Service Capability
28 octet
1 octet
1octet
6 octets
0 or variable
Features
Option 1
Option 2
Help to reduce Probe Response from Legacy APs No
Yes
Overhead
Almost same
Ping FANG, Huawei
RYU Cheol. ETRI

9. Detailed Service Query
April 2013
doc.: IEEE /0426
Nov 2013
Detailed Service Query
Detailed Service Query (Different from general query)
Can provide detailed service information
The query response can be much bigger than that of general query
Option 1 : GAS mechanism for further information query
Mechanism similar to ANQP as carried in GAS
Option 2: new PAM (public action frame)[5]
Carry detailed service query information in PAM between STA and AP
AP may forward the query to backhaul or associated STAs for further detailed information
Option 1
Option 2
Ping FANG, Huawei
RYU Cheol. ETRI

10. New protocol in GAS vs. new Public Action Frame
April 2013
doc.: IEEE /0426
Nov 2013
New protocol in GAS vs. new Public Action Frame
Option 1: New advertisement protocol ID in GAS
Option 2: new Public Action Frame
New advertisement protocol vs. new Public Action Frame
MAC Header
Category(=4)
Public Action (=10)
Dialog Token
Advertisement Protocol element
Query Request length
Query
28 octet
1 octet
1octet
variable 2
MAC Header
Category(=4)
Public Action
Dialog Token
Query Request Length
Query
28 octet
1 octet
1octet 2
variable
Features
Option 1
Option 2
Help to reduce queries
No (for unicast)
Yes (could be multicast)
Overhead
more
less
Ping FANG, Huawei
RYU Cheol. ETRI

11. Discussion on Practice
April 2013
doc.: IEEE /0426
Nov 2013
Discussion on Practice
Service bitmap
For scenario with lots of STAs queries, service bitmap can help to reduce STAs’ queries with passive scanning
When the number of services provided by AP is far less than the length of bitmap, the bitmap can provide useful information to indicate which services are not provided
General service query vs. detailed service query
When there are quite some APs and STAs around, general service query should be used first to reduce channel time
For sparse environment, detailed service query can be used directly to query for detailed service information
Ping FANG, Huawei
RYU Cheol. ETRI

12. Nov 2013
Summary
Overall picture for TGaq is recaptured with service indication from AP, general service query and detailed service query
Service bitmap IE in Beacon/Probe Resp for indication from AP
New Public Action frame carries different service hash values in general service query/response
New Public Action frame carries detailed service query or response of upper layer for detailed service query
Ping FANG, Huawei

13. References IEEE Std 802.11™-2012 11-13-0057-02-00aq-design-options
Nov 2013
References
IEEE Std ™-2012
aq-design-options
aq-service-registration-of-sta-to-an-ap
aq-service-discovery-proposal
aq-transaction-protocol
Ping FANG, Huawei

14. Service Indication Performance Analysis
April 2013
doc.: IEEE /0426
Nov 2013
Service Indication Performance Analysis
Assumption
Number of total service number: k = 5000
Length of Service Hash bitmap: m= 128 bit
Number of services supported by AP: n = 16, 32, 48, 64, 80
Algorithm
Service names are randomly generated with alphabets , digits and phonetic symbols
Services supported by AP are randomly chosen from 5000 services
Service hash values are calculated with SHA256, and then mod(128) to set a corresponding bit in bitmap
Bit value 0 indicate there are no corresponding services
The result is to indicate how many percent of services are not supported by the AP, with the 128 bit service indication bitmap and given the n kind of services supported by the AP
Percentage of no service n
Ping FANG, Huawei
RYU Cheol. ETRI

15. Nov 2013
Straw Polls
Ping FANG, Huawei

16. Straw Polls on Proposed Text to SFD
Nov 2013
Straw Polls on Proposed Text to SFD
Straw Poll-1: add the following sentence to section 5 Frame Formats of TGaq SFD, r1
802.11aq shall define a IE with service hash bitmap for service indication.
Result
Yes No
Need more info
Ping FANG, Huawei

17. Straw Polls on Proposed Text to SFD – con’t
Nov 2013
Straw Polls on Proposed Text to SFD – con’t
Straw Poll-2: add the following sentence to section 5 Frame Formats of TGaq SFD, r1
802.11aq shall define a new public action frame for service query.
Result
Yes No
Need more info
Ping FANG, Huawei

18. Straw Polls on Proposed Text to SFD – con’t
Nov 2013
Straw Polls on Proposed Text to SFD – con’t
Straw Poll-3: add the following sentence to section 7 MLME of TGaq SFD, r1
802.11aq shall define mechanism to provide service indication from AP with service hash bitmap and service protocol bitmap in Beacon and Probe Response
Result
Yes No
Need more info
Ping FANG, Huawei

19. Straw Polls on Proposed Text to SFD – con’t
Nov 2013
Straw Polls on Proposed Text to SFD – con’t
Straw Poll-4: add the following sentence to section 7 MLME of TGaq SFD, r1
802.11aq shall define mechanism to provide general service query for a STA to decide the availability of a service from AP before association.
Result
Yes No
Need more info
Ping FANG, Huawei

20. Straw Polls on Proposed Text to SFD – con’t
Nov 2013
Straw Polls on Proposed Text to SFD – con’t
Straw Poll-5: add the following sentence to section 7 MLME of TGaq SFD, r1
802.11aq shall define mechanism to provide detailed service query for a STA to get the detailed information of a service from AP before association.
Result
Yes No
Need more info
Ping FANG, Huawei

21. Straw Polls on Proposed Text to SFD – con’t
Nov 2013
Straw Polls on Proposed Text to SFD – con’t
Straw Poll-6: add the following sentence to section 8 Security of TGaq SFD, r1
802.11aq shall define mechanism to provide privacy for pre association service queries with different hash values for a service in service query request and response.
Result
Yes No
Need more info
Ping FANG, Huawei