1. CLUE design team meeting
CLUE protocol
CLUE design team meeting
29/05/2014

2. Outline Message structures Versioning and options
Discussion about CLUE protocol updates reflecting changes in
draft-ietf-clue-signaling
draft-ietf-clue-data-channel
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3. A common basis
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4. A common basis Each CLUE message extends the basic CLUE message type
Common info:
protocol: CLUE
v: version
clueId:
the sender’s id within the telepresence system
sequenceNr
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5. Call flow example X Y OPT, sn: Xopt OPT_RES, sn: Yopt
OPT_ACK, sn: Xopt+1
ADV, sn: Xmp
ADV_ACK, sn: Ymc
CONF, sn: Ymc +1
CONF_RES, sn: Xmp+1
X CI
Y CR
ADV, sn: Ymp
X MP
Y MC
CONF+ACK, sn: Xmc
X MC
Y MP
CONF_RES, sn: Ymp+1
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6. Sequence numbers
Each CLUE endpoint manages 3 local sequence number (SN):
1 for the OPTIONS mechanism (before starting the MP and MC state machines) (Xopt, Yopt)
1 for the MP state machine (Xmp, Ymp)
1 for the MC state machine (Xmc, Ymc)
SN are randomly generated and incremented of 1 each time a new message is sent
SN can be used to make reference to the corresponding message within a CLUE dialogue (between a MP and a MC)
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7. Advertisement
The configure request can refer to the sequence number of the advertisement.
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8. Advertisement ACK
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9. Configure
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10. Configure Response
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11. READV A refresh mechanism to retrieve the MP’s current capabilities
lastReceivedAdv: the version number of the last correctly received Adv
0, if no ADV has been delivered yet
If an ADV is malformed, a NACK comes back to the MP
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12. READV Response
The following CONF will use the READV Response sequence number in place of the ADV sequence number
Diff mechanism to be discussed
(introduction of a choice section)
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13. Versioning Imported from the signaling doc:
A version has major and minor components, each a non-negative integer.
Major version changes denote non-interoperable changes
Minor version changes denote schema changes that are backward compatible by ignoring unknown XML elements, or other backward compatible changes.
If a common major version cannot be negotiated, then CLUE MUST NOT be used.
From Paul’s doc:
-Minor versions are always backwards compatible, so support for a
minor version implies support for all smaller minor versions
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14. Options mechanism
The Channel Initiator issues the OPTIONS message with
A boolean flag telling if it is able to act as a MP
<mediaProvider>
A boolean flag telling if it is able to act as a MC
<mediaConsumer>
All the supported versions
All the supported options
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15. OPTIONS
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16. Options mechanism (2 ways)
Current solution: 2 ways
The Channel Reveiver issues an OPTIONS response carrying
A response code telling if an agreement has been found or not
A reason string explaining the response code
<mediaProvider>
<mediaConsumer>
The highest commonly supported version
The common options
If a common version can be found, the MP/MC state machines start
For example, if both parts are able to act only as media providers with each other, the CLUE session should be terminated.
Response code and response string signal the error
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17. OPTIONS Response (2ways)
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18. Options mechanism (3 ways)
Proposal: 3 ways
The Channel Reveiver issues an OPTIONS Response carrying
<mediaProvider>
<mediaConsumer>
All the supported versions
All the supported options
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19. OPTIONS Response (3ways)
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20. Options mechanism (3 ways)
Proposal: 3 ways
The Channel Initiatior send an OPTIONS ACK carrying
A response code telling if the elaboration of the options message is ok or not
A reason string explaining the response code
The highest commonly supported version
The common options
If a common version can be found, the MP/MC state machines start
If we put all the supported things of the CR in the OPTIONS RESPONSE, the OPTIONS ACK would carry the final agreement
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21. OPTIONS ACK (3ways)
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22. Comparison 2 ways: 3 ways:
the Channel Initiator will not know all the supported versions and options of the Channel Receiver, but only the common ones
The matching is up to the Channel Receiver
3 ways:
Both parties know all the capabilities of each other
The matching is up to the Channel Initiator
One message more
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23. Some notes
There is a need for communication between the CLUE stata machine and the SDP negotiation engine
Example:
a CLUE endpoint cannot issue a CONF before the SDP info arrives
State machines need to be updated considering the dependancy between CLUE and SDP
There is no (total) independence
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