1. Virtual Interim CLUE Signalling discussion
Robert Hansen
2014/05/29

2. -01 Document cleanup Revised terminology
Calls are CLUE-enabled or not
Devices are CLUE-capable or not (irrespective of whether call is CLUE-enabled)
Moved encoding information outside of SDP initial offer section
Given draft recommends initial offer does not contain encodings, was a strange place to define them

3. Syntax change Feature tag: ‘sip.telepresence’ changed to ‘sip.clue’
Group syntax: TELEPRESENCE changed to CLUE

4. CLUE group restrictions
CLUE group must have one (and only one) mid related to a data channel
Previously could a CLUE group with no data channel association
Explicitly forbids multiple CLUE groups until someone publishes a way to do it

5. CLUE-controlled media
Restriction on sending media on CLUE-controlled m-lines until negotiated in CLUE as well
Is there a better term for what can’t be sent than ‘media’?
Explicitly mandates that non-media exchanges like DTLS and ICE must be done as normal
No text on RTCP yet – if channel is active should be sent as normal(?)

6. CLUE/SDP state machine interaction
Some changes in call state require CLUE and SDP changes and hence are non-atomic
CLUE and SDP state machines are independent
Participant must cope with transitory states with inconsistent information
CLUE-controlled media unless both CLUE and SDP information available

7. CLUE/SDP state machine interaction
MUST NOT delay ongoing SDP exchange due to CLUE state
MAY delay initiating new SDP exchange
MUST NOT delay any mandatory CLUE transitions (for provider/consumer/participant state machines) due to SDP state
MAY delay “CONF COMPLETED->PREPARING ADV” or “READY TO CONF->TRYING” (send new ADVERTISE or CONFIGURE) based on SDP state

8. CLUE/SDP state machine recommendations
SHOULD ensure that any inconsistencies are transitory
Make this a MUST?
Recommends no ‘speculative’ requests are made
Eg, don’t request anything until details are available in both CLUE and SDP
May require more O/As
Send changes in CLUE before SDP
Minimises SDP O/As needed

9. CLUE/SDP state machine recommendations
Adding stream
Alice
Bob
CLUE ADVERISEMENT
SDP Offer
SDP Answer
May be simultaneous
CLUE CONFIGURE
Media starts

10. CLUE/SDP state machine recommendations
Removing stream
Alice
Bob
CLUE ADVERISEMENT
Media stops
CLUE CONFIGURE
No ordering
recommendation
SDP Offer
SDP Answer