[MMUSIC] Empty candidate lists in ice-sip-sdp offers and answers

[Roman Shpount <[e-mail]>]

Hi All,

One more topic for discussion regarding the changes proposed in ice-sip-sdp
pull request ( https://github.com/suhasHere/ice-sip-sdp/pull/1 )

Since it is legal for the ICE agent to reject all the candidates due to
unsupported connection address type or due to FQDN not being resolvable, I
thought it makes sense to allow both offers and answers with no candidates.
It was never explicitly stated in RFC 5245 that such offers are illegal, so
I added the following notes to the Offer/Answer procedures to explicitly
allow them.

In the Sending the Initial Offer section I have added the following note:

NOTE: It is valid for an offer "m=" line to include no SDP candidate
attributes and default destination correspond to IP address values
"0.0.0.0"/"::" and port value of "9". This implies that offering agent is
only going to use peer reflexive candidates or that additional candidates
would be provided in subsequent signaling messages.


In the Sending the Initial Answer section I have added the following:

NOTE: It is valid for an answer "m=" line to include no SDP candidate
attributes and default destination correspond to IP address values
"0.0.0.0"/"::" and port value of "9". This implies that answering agent is
only going to use peer reflexive  candidates or that additional candidates
would be provided in subsequent signaling messages.

NOTE: Since it is possible that no candidates were provided in the offer,
or that all candidates in the offer where skipped due to unsupported
address type or FQDN name resolution failure, ICE nomination process can
start with no remote candidates. This, however, does not indicate an
immediate ICE nomination failure. See <<draft-holmberg-ice-pac>> for more
details.


In the Receiving the Initial Answer section I have added the following:

NOTE: Since it is possible that no candidates were provided in the answer,
or that all candidates in the answer where skipped due to unsupported
address type or FQDN name resolution failure, ICE nomination process can
start with no remote candidates. This, however, does not indicate an
immediate ICE nomination failure. See <<draft-holmberg-ice-pac>> for more
details.


I wanted to get the group's opinion regarding:

1. Allowing offers and answers with no candidates
2. Adding a reference to draft-holmberg-ice-pac regarding how such session
descriptions or session descriptions where all candidates were rejected are
handled.

Regards,
___________________________________________
Roman Shpount | CTO | Cell: [phone]
4905 Del Ray Ave, Suite 300 | Bethesda, MD 20814
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