Transcript 11-13-0788-01-00aq-transaction-protocol.ppt

September 2013
doc.: IEEE 802.11-13/0788r1
TGaq Transaction Protocol (update)
Date: 2013-07-16
Authors:
Name
Company
Michael Montemurro
BlackBerry
Stephen McCann
BlackBerry
Submission
Address
4701 Tahoe Blvd
Mississauga, ON, Canada
L4W0B4
200 Bath Road, Slough,
Berkshire, SL1 3XE, UK
Slide 1
Phone
email
+1-905-629-4746
x14999
[email protected]
+44 1753 667099
[email protected]
Michael Montemurro, BlackBerry
September 2013
doc.: IEEE 802.11-13/0788r1
Abstract
Transaction Protocol for TGaq
Submission
Slide 2
Michael Montemurro, BlackBerry
September 2013
doc.: IEEE 802.11-13/0788r1
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
Submission
Slide 3
Michael Montemurro, BlackBerry
September 2013
doc.: IEEE 802.11-13/0788r1
Transaction Protocol
• 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)
• New bit in AP extended capability IE
Submission
Slide 4
Michael Montemurro, BlackBerry
September 2013
doc.: IEEE 802.11-13/0788r1
Transaction Protocol
• STP is different from ANQP
– Not a request/response mechanism
• Allows unsolicited push messages from the STA
– Messages can carry information from non-AP STA to AP
– ANQP is a network oriented protocol. STP is not for network
discovery. Separate rules are needed.
– STP can use broadcast.
Submission
Slide 5
Michael Montemurro, BlackBerry
September 2013
doc.: IEEE 802.11-13/0788r1
Network
Service Query Messages
AP2
Local Access
Network
Service
Transaction Proxy
(TPX)
AP1
Pre-association Messages
STA
Submission
Slide 6
Michael Montemurro, BlackBerry
September 2013
STA
doc.: IEEE 802.11-13/0788r1
Service
Transaction
Proxy
AP
1) Initialisation
2) Request (token, “3D Printer”)
3) Response (token, “available”, destination_address)
Submission
Slide 7
Michael Montemurro, BlackBerry
September 2013
doc.: IEEE 802.11-13/0788r1
Transaction Protocol
• A service discovery ULP within the mobile device
wishes to send a message A to the LAN or external
network (e.g. to discover a service).
• Mobile device may need to discover BSS architecture
– Send STP to AP, or to a proxy?
• An STP Encapsulation message carries the ULP
message A to the TXP. In turn the TXP passes the
message to the co-located service discovery ULP. As
the STP element type is STP Encapsulation the TXP
recognises that no analysis is required. It merely
forwards the message to the higher layer.
Submission
Slide 8
Michael Montemurro, BlackBerry
September 2013
doc.: IEEE 802.11-13/0788r1
Transaction Protocol
• STP operates between the ULP entities within itself and
that of the Service Transaction Proxy (TXP).
• The ULP is not tunnelled, as this may require a proxy
for multicast DNS.
– More detail required.
• Thoughts on possible Push mode:
– Push mode could be troublesome during the discovery/scanning
phase
– Need some state on STA to do push mode (potentially after 802.11
Authentication or potentially during Association sequence)
Submission
Slide 9
Michael Montemurro, BlackBerry
September 2013
Upper Layer
Protocol
(ULP)
doc.: IEEE 802.11-13/0788r1
STA
AP
TXP / ULP
1) ULP message A
2) Encapsulation (token, “ULP message A”)
3) Encapsulation (token, “ULP message B”)
4) ULP message B
Submission
Slide 10
Michael Montemurro, BlackBerry
September 2013
doc.: IEEE 802.11-13/0788r1
Transaction Protocol
• 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.
Submission
Slide 11
Michael Montemurro, BlackBerry
September 2013
doc.: IEEE 802.11-13/0788r1
Transaction Protocol
• The message sequence is bi-directional and can be initiated by the
ULP co-located with the TXP. Additionally STP does not need to
“answer” Message A with a Message B, as it has no knowledge of
how the ULP operates.
• May require some IDs of ULP protocols and associate it with the
encapsulation.
• Possibly need to fragment large ULP frames.
– Could just use GAS fragmentation
• Possibly use a hash of a large ULP frame. (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
Submission
Slide 12
Michael Montemurro, BlackBerry
September 2013
doc.: IEEE 802.11-13/0788r1
Possible IE
Octets:
Submission
ID
Length
Token ID
ULP ID
ULP payload
2
2
2
1
variable
Slide 13
Signature Length
(optional)
Signature
(optional)
2
variable
Michael Montemurro, BlackBerry
September 2013
doc.: IEEE 802.11-13/0788r1
Data Integrity
• Signature may be useful for data integrity, not security.
Submission
Slide 14
Michael Montemurro, BlackBerry