doc.: ieee 802.11-05/0499r1 submission may 2006 srinivas sreemanthulaslide 1 tgu proposal: network...
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May 2006
Srinivas SreemanthulaSlide 1
doc.: IEEE 802.11-05/0499r1
Submission
TGu Proposal: Network Selection
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Date: 2006-05-015
Name Company Address Phone email Srinivas Sreemanthula
Nokia Irving, TX USA
+1 972 894 5000
Eleanor Hepworth Siemens Roke Manor
Research
Romsey, Hampshire, SO51 0ZN,
UK
+44 1794 833146
Stefano Faccin [email protected]
Authors:
May 2006
Srinivas SreemanthulaSlide 2
doc.: IEEE 802.11-05/0499r1
Submission
Abstract
• This proposal addresses all mandatory requirements in the network selection cluster (R9N1, R9N2, R9N3 and R9N4).
• The slides are related to following documents – 802.11-06/0648r00
– 802.11-06/0649r00
May 2006
Srinivas SreemanthulaSlide 3
doc.: IEEE 802.11-05/0499r1
Submission
Motivation
• To enable the STA to identify the availability of a desired network service and indicate a desire to use it.– Requirement identified by deployment issues associated with
public access hotspots, but could be extended for use in Enterprise
• Currently networks selected based on SSID and guesswork– If unsuccessful, other networks are associated with on a trial and
error basis
• The aim of this proposal is to improve user interactions with the network, for example, by providing roaming agreement information to user devices.
May 2006
Srinivas SreemanthulaSlide 4
doc.: IEEE 802.11-05/0499r1
Submission
Proposed Solution Framework
• The proposal is divided into two parts– Passive Discovery: which provides information to the STA in
beacon/probe responses
– Active Discovery: which supports a query/response exchange between STA and AP, allowing the STA to request additional information from the network
• Finally, associating with the Network: providing a means for the STA to indicate which SSPN it is interested in accessing.
May 2006
Srinivas SreemanthulaSlide 5
doc.: IEEE 802.11-05/0499r1
Submission
Passive Discovery: ESSID
• The scheme is based on– an expanded definition of SSID and the introduction of a new IE called ESSID, to
be carried in beacon, probe responses and neighbour reports– the station asserting the selected ESSID at association
• The ESSID contains three types of data:– An identifying name (ESS Name)
• human readable name to identify the group of APs, can be the same as the SSID• USED to inform the user about which ESS they are connecting to
– A unique identifier (ESS Address)• It ensures there will not be a collision between the ESSID values of two groups of APs• set to the BSSID value of one of the APs in the group; the use of the BSSID guarantees
that the ESSID as a whole is globally unique
– One or more External Network Identifiers• used to enable the station to select between multiple possible back-end networks• each External Network Identifier is advertised by adding a SSPN id for each
May 2006
Srinivas SreemanthulaSlide 6
doc.: IEEE 802.11-05/0499r1
Submission
ESSID
• Use of ESSID removes some of the observed weaknesses of SSID:– Deprecates SSID to be general network identifier– It encourages the assignment of a unique identifier to groups of APs– It has a method to ensure uniqueness of each AP as manufactured– It provides discrimination between access point groups in cases where
SSID has been overloaded with the service provider’s identity• The scheme introduces a new feature not previously available:
– The ability to discriminate between multiple networks behind the AP• E.g. Handle forwarding of EAP to specific SSPN
– A station can use the ESSID to gather more accurate information about the connectivity and compatibility of an access point before an association/ transition
• Format is left to the implementers or other organizations– Formatted NAI as in 3GPP, NAI with domain name etc.
May 2006
Srinivas SreemanthulaSlide 7
doc.: IEEE 802.11-05/0499r1
Submission
Passive DiscoveryTechniques to reduce beacon bloating
• Layered Beacon– Include ESSID related IE to current beacons under low load conditions
– Implementation decides what to do when load increases
• Hashing– Basic: External Network Identifier value can be hashed and truncated
whose length can be varied based on load conditions
– Diverse: An AP with diverse hashing capability chooses one of the truncations from the calculated hash value to reduce hash collision
May 2006
Srinivas SreemanthulaSlide 8
doc.: IEEE 802.11-05/0499r1
Submission
Passive versus Active Discovery
• Thanks to the additional Unadvertised Service IDs bit, the STA knows whether the whole list of services is advertised in the beacon or not
• In case the STA does not discover the desired service advertised in the beacon (passive discovery), it can perform an active discovery (e.g. through a query).
• Passive discovery is also applicable to TGr when deciding where to perform the fast transition, in order to give assurance that the AP will support connectivity to the selected SSPN/service upon transition.
May 2006
Srinivas SreemanthulaSlide 9
doc.: IEEE 802.11-05/0499r1
Submission
Active Discovery
• Active discovery allows the STA to query the network to find out whether particular services are available
• Supported through the definition of two new Action Frame formats– Service Request: indicates the external network identity (SSPN) the
STA would like to discover. The information is sent as a string of up to 256 bytes.
– Service Response: • includes an indication as to whether the requested service is supported, and
the SSID and a Supported ESSID IE containing the information to be used to connect to the network
• the ESSID (and the SSPN id, if provided) will be verified when the user attempts to connect to the network.
• In addition, the Query ID and ComeBackDelay IEs may be included to support the ComeBack mechanism to enable power saving advantages.
May 2006
Srinivas SreemanthulaSlide 10
doc.: IEEE 802.11-05/0499r1
Submission
Active Service Query
STA APBacken
d
Service Request (IE1, IE2, IE3)
“Come-back” Service Request ([QueryID])
Service Response (resp-IE2, resp-IE3)
“Come-back” Service Response
(resp-IE1, [QueryID], [ComeBackDelay])
AP cannot provide response to IE2 and IE3
Retrieve info for IE2 and IE3
Resp-IE2, Resp-IE3
Typically
>>
5ms
< 5ms
< 5ms
Delay =
ComeBackDelay
[X] : optional IE
Not defined in TGu
May 2006
Srinivas SreemanthulaSlide 11
doc.: IEEE 802.11-05/0499r1
Submission
Data-frame based Solution
• Relies on providing a transparent protocol solution using 802.11 data frames with a defined Ethertype
• Argument for media independence, but– Essentially this is a WLAN network selection
– Speculation that this can be extended to other 802 technologies
• AP or 802.11 MAC is not involved in this solution (except for capability adv)– Protocol defined elsewhere
– dependency on other protocols for WLAN network selection
• Data-frame solution considerations– Power management issues
– Security issues are same as active discovery mechanisms e.g. DoS attacks
May 2006
Srinivas SreemanthulaSlide 12
doc.: IEEE 802.11-05/0499r1
Submission
Summary and Assessment
• R9G1: Minimize battery consumption (not applicable to data frame solution)– Extended passive discovery is not expected to impact battery
consumption.
– Active discovery battery concerns have been addressed by the ComeBack mechanism.
– Association modifications only affect the contents of the message, so only have a trivial impact on battery life.
– The improved selectivity of the passive discovery process reduces the number of failed association attempts, thereby improving battery life even further.
May 2006
Srinivas SreemanthulaSlide 13
doc.: IEEE 802.11-05/0499r1
Submission
Summary and Assessment
• R9G2: Security Impacts– Additional information included for passive discovery is treated in
the same way as existing information; it is not believed that new threats are introduced.
– Finer granularity of information may mitigate rogue AP attacks.
– Active discovery introduces some new DoS attacks.
• R9G3: Legacy STAs– Legacy STAs are still able to use existing SSID IE and can ignore
ESSID information.
May 2006
Srinivas SreemanthulaSlide 14
doc.: IEEE 802.11-05/0499r1
Submission
Supporting PartiesName Company Address Phone email
Andrew McDonald Siemens Roke Manor Research
Roke Manor, Old Salisbury Lane,
Romsey, Hampshire, SO51 0ZN, UK
+44 1794 833833
Srinivas Sreemanthula Nokia Cambridge, UK +44 1353 648567
Jari Jokela Nokia Tampere, Finland +358 718060445 [email protected]
Yang Sook Hyun LG Electronics, Inc. 16 Woomyeon-dong
Seocho-gu Seoul Korea
+82 2 526 4198 [email protected]
Ronny Yongho Kim LG Electronics, Inc.
533 Hogye-ldong Dongan-gu Anyang-
shi Kyongki-do Korea
+82 31 450 1879 [email protected]
Sabine Demel T-Mobile Vienna, Austria [email protected]
Jouni Korhonen TeliaSonera P.O.Box 970, 00051
Sonera, Finland +358 40534445 [email protected]
Frans Hermodsson TeliaSonera
Isbergs gata 2, SE-205 21 Malmo,
Sweden +46 406618658 [email protected]
Wolfgang Groeting BenQ
Neutorplatz 3-4, 46395 Bocholt,
Germany +49 2842 95
2142 [email protected]
Stefan Berg BenQ
Neutorplatz 3-4, 46395 Bocholt,
Germany +49 2842 95
1781 [email protected]
Farooq Bari Cingular Wireless
+1 425 580 5526 [email protected]
Andrew Myers BT
First Floor PP8, Orion Building, Adastral Park, Ipswich, UK
+44-7802 791440
Marion Rudolf Interdigital Canada