Re: [rtcweb] JSEP-06: How to create the second offer where only the port numbers are changed?

Christer Holmberg <> Mon, 03 March 2014 13:48 UTC

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From: Christer Holmberg <>
To: Justin Uberti <>
Thread-Topic: JSEP-06: How to create the second offer where only the port numbers are changed?
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Date: Mon, 03 Mar 2014 13:48:27 +0000
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Subject: Re: [rtcweb] JSEP-06: How to create the second offer where only the port numbers are changed?
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As specified in BUNDLE, before the remote peer has indicated support of BUNDLE, all m- lines (including those within to a bundle group) must have unique port numbers.
Then, when the remote peer has indicated support of BUNDLE, a second offer (called the BAS offer) needs to be sent, in which the same port number is assigned to all m- lines within a bundle group.
My question is: how do I create the BAS offer? I don’t want to change anything – I just want to get an SDP with the BUNDLE port assigned to all m- lines. Is there a flag in createOffer() for that?
The implementation knows that any offers that are created after the BUNDLE answer should have the same port numbers. So, the app could push the createOffer button once it receives the answer if it wanted to ensure this happened immediately. Otherwise, there will be an onnegotiationneeded event once ICE completes, and the offer sent at that time will have the updated ports.
When I call createOffer(), can I be ensure that only the port values will change?

No. Why would this be necessary?

Because the only thing I want to do is to send a new offer, with the same port number in each m- line. I don’t want anything else to change.