Transcript 21-07-0238-00-0000-Initial_NetSel_in_WLAN

 IEEE 802.21 MEDIA INDEPENDENT HANDOVER
 DCN: 21-07-0238-00-0000
 Title: Initial Network Selection in WLAN
 Date Submitted: June, 2007
 Presented at IEEE 802.21 session in ETRI
 Authors or Source(s):
Vivek Gupta, Stephen McCann, Dave Stephenson
 Abstract: This provides an update on initial Network Selection
procedures/flow in 802.11 network using 802.21 services.
21-07-0238-00-0000
•
•
•
IEEE 802.21 presentation release statements:
This document has been prepared to assist the IEEE 802.21 Working Group. It is offered
as a basis for discussion and is not binding on the contributing individual(s) or
organization(s). The material in this document is subject to change in form and content
after further study. The contributor(s) reserve(s) the right to add, amend or withdraw
material contained herein.
The contributor grants a free, irrevocable license to the IEEE to incorporate material
contained in this contribution, and any modifications thereof, in the creation of an IEEE
Standards publication; to copyright in the IEEE’s name any IEEE Standards publication
even though it may include portions of this contribution; and at the IEEE’s sole discretion
to permit others to reproduce in whole or in part the resulting IEEE Standards publication.
The contributor also acknowledges and accepts that this contribution may be made public
by IEEE 802.21.
The contributor is familiar with IEEE patent policy, as outlined in Section 6.3 of the IEEESA
Standards
Board
Operations
Manual
<http://standards.ieee.org/guides/opman/sect6.html#6.3> and in Understanding Patent
Issues
During
IEEE
Standards
Development
http://standards.ieee.org/board/pat/guide.html>
21-07-0238-00-0000
Comment 5583 in LB-1d
Add this in Annex H8 in Draft D5.1:
Network Selection in 802.11 (WLAN) using
MIH Protocol:
21-07-0238-00-0000
Network Selection in WLAN with 802.11u & 802.21: Fig-1
21-07-0238-00-0000
Use Case: Query SSPN List: Fig-2
STA
AP
802.21 IS
802.21 IS
(802.11u-capable)
(802.11u-capable)
(local Access Network)
(“home” SSPN)
Pre-configuration
• Advertising protocol ID (APID) = IS
• Maximum acceptable length (LEN) for
query responses
Pre-configuration
Beacon (Interworking IE, GAS:APID)
Probe Request
Probe Response (Interworking IE,
GAS:APID)
Relay MIH frame (with query content)
Transport method: (1) 802.3, (2) IP
Comeback delay
(optional – STA to PS mode)
GAS initial request (request IE, APID)
Query content (“list of SSPNs?”)
GAS Initial Response (Query ID, Dialog
Token, comeback delay)
COLOR KEY
MIH Response (transaction ID,
answer information); may be delayed
until answer is ready
GAS Comeback Request (Query ID)
GAS Comeback Response (Query ID,
answer information)
21-07-0238-00-0000
Out of scope
802.11
802.21
Steps in Network Selection
Fig-1 shows the general topology of WLAN network with 802.21 IS.
The steps in Network selection as shown in Fig-2 are as follows:
1) Pre-configuration: The AP is preconfigured with advertising protocol identifier (APID) of choice and
is pre-configured to use 802.21 MIIS. The AP may discover the MIIS through a variety of different
mechanisms that are outside the scope of specification. The maximum length of response
messages from MIIS is also set. The AP may communicate with MIIS at L2 or at L3 using a
protocol defined elsewhere.
2) Discover AP/Access Network Capabilities: The AP sends out beacon with Inter-working IE set and
APID set to GAS (Generic Access Protocol). The STA may discover access network capabilities
by listening to beacons or it could also send a probe request and discover access network
capabilities through the probe response.
3) Query list of SSPNs: The STA sends out a query asking for list of available SSPNs? The query is
defined using 802.21 specific MIH frame. The MIH frame is then relayed by the AP to the MIIS.
Meanwhile the AP sends out the initial GAS response to the STA with initial delay (comeback
delay)
4) GAS response: The MIIS interprets the query and retrieves the response either from local or remote
repository. It then packs the response in appropriate MIH frame and sends it to the AP.
Subsequently when the STA sends the GAS comeback request to the AP, the AP responds with
the available information in the MIH frame. The STA then retrieves the information out of the MIH
frame and gets the answer to the query.
21-07-0238-00-0000
Backup
21-07-0238-00-0000
Questions and notes
• What is the AP-to-IS communication?
– What is the protocol used? Is it direct L2 connection, MIPSHOP,
RADIUS/DIAMETER, or something else entirely?
• Potential resolution: 802.21 needs to create an IP-based transport protocol.
– Is a query ID necessary to match STA query to IS responses?
• Potential resolution: AP assures that 802.21 Transaction ID is unique on a
per-STA basis for a reasonable time interval, and rewrites Transaction ID if
necessary for uniqueness
• This works as a long as transactions are not integrity protected. There is no
security in state 1, so this may not be a big drawback. Does the STA need
to refrain from using integrity protection in state 1?
• How much interpretation does AP do of MIH requests?
– If none, then will any claimed frame from STA be relayed to IS?
– How much of the MIH packet does the AP need to understand? Query
and response should be opaque. How much of the header is
necessary?
21-07-0238-00-0000