ISTM that there is dubious likelihood of success of this is attempted
after the previous connection has already failed. Make-before-break is
safer if you can get some advanced warning. But make-before-break has
its own implications on how you do this so that it doesn't become
break-while-trying-to-make.
Thanks,
Paul
On 7/7/16 12:37 PM, Volkan Hatem wrote:
Hi Dale,
Indeed, INVITE-with-Replaces was the first alternative I could think of as
well.
However, in the case where I implemented the hand-off we could
deterministically bring the SIP-UA to register with its "home" proxy which
holds the current call-leg (dialog). A simple re-INVITE to update the
target address was enough to restore signalling connectivity. This was a
simpler approach in our case due to some other limitations I will not
digress.
I am sure you are aware of RFC 6141 which brings more clarification to
target address update requests.
Of course, there are other issues to tackle as well such as
- NAT traversal, whether ICE or a simpler (always insert a proxy when NAT
detected) mechanisms can be preferred.
- The time it takes to get an IP connectivity, resolve proxy addresses
might complicate it if it takes too long
- Whether it conflicts with other operations requiring re-INVITEs as well
(updating session description to add/remove/modify media)
- Decision to drop or recover unstable calls (before establishing a dialog)
Etc.
Best,
-volkan
2016-07-07 18:49 GMT+03:00 Dale R. Worley <wor...@ariadne.com>:
Is there any generalized technique for "handoff", for moving a SIP
dialog from one interface/medium to another?
My impression is that this problem is most commonly seen switching
between a mobile connection and a WiFi connection, but it can happen in
pure-SIP situations as well.
So far, it seems that a UA could use INVITE-with-Replaces (sent from the
new interface to the other party) to transfer the dialog from its old
interface to its new interface. Has anyone implemented such a
technique?
Dale
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