> On 21 Feb 2017, at 21:40, Keith <keith@rhizomatica.org> wrote:
Hi Keith,
yes for the osmo-sip-connector I have ignored the topic of handover. In
> On the question about SIP re-invite, I am talking about operating
> without rtp_proxy, so that one can have the advantage of BTS<->BTS RTP
> streams at the same time as handover. From what I've read, this is quite
> feasable, as part of the SIP spec.
> I think this is already considered as part of the development of the
> osmo-sip-connector, which is a project I really want to see moving
> forward and hope to find time to contribute to over the next few months.
general I try to see how long I get away with not having to touch the
UDP/RTP streams.
In case of hand-over the new BTS might send from a different src IP,
src Port and will most likely have a new SSRC, timestamp seqno. It is
a bit of a question of how "your" PBX will handle it. I can see a
couple of outcomes.
a.) It has some support for "NAT" handling and will just use the new
stream and return packages to the new src IP/src port. It might go back
and forth but at some point the old bts will stop sending things.
b.) It will accept the new stream but will try to send to the old BTS.
The we would have one-way audio.
c.) It will reject it as it is a unknown src ip/port.
I think for b.) and c.) we will require SIP re-invite but also need
to look at the AoIP spec to see if they say how to handle this
scenario. But that depends on how the PBX handles this as well. So it
means for handover we always need to look at BSC/SIP+PBX and how it is
handling SDP/RTP.