[WG-IMS] Scope of IMS in OpenSIPS - RFC

[Giovanni Maruzzelli]

On Tue, Dec 5, 2023 at 11:23 AM Bogdan-Andrei Iancu <bogdan at opensips.org>
wrote:

> I did some reading about this NSA vs SA and as I understand, this will not
> impact the actual functionalities we need, but more the logic and
> interfacing with other components (HSS or PC(R)F).
>
>
Maybe I gave the impression it is a problem of formal requirements (and
that's not), actually in my view it is a problem of (open source)
implementations.

One of the problems is that in 5G (let's call it NR, NewRadio), Open5GS
implemented a different interface in PCF vs the one implemented in PCRF.

So, while in LTE (4G) Open5GS uses Diameter for interfacing, in NR (5G) it
has only implemented HTTP2.
Then, we need HTTP2 and NR specific logic for implementing VoNR (Voice over
New Radio) using Open5GS as NR core.

More or less, from OpenSIPS perspective, we need the same set of features,
> but the scripting will differ (as logic and DIAMETER messages).
>
>
Yep, definitely: if all specs would have been implemented, VoNR would have
*both* diameter and http2, so, it would be a superset of VoLTE with added
http2 and some more things, and you can decide to interface it from IMS
(that's us) via diameter (like in VoLTE) or via HTTP2 (VoNR specific). But
Open5GS does not implement diameter in NR.

Yes, as Carlsten said, we may implement a network function of a translator
between diameter and http2, no idea if that is easier than implementing
http2 into (x)CSCF.
Maybe (just maybe) with kubernetes and all these deployment environments
mainly tailored to web, they will heavily push with http2 for additional
services.

Or maybe in near future Open5GS will implement diameter in NR.

Without Open5GS interfacing us (IMS)  we'll not be able to actually test
real implementation with actual 5G phones (and devil is always in details,
simulations are nice, but...)

-giovanni
--
Sincerely,

Giovanni Maruzzelli
OpenTelecom.IT
cell: +39 347 266 56 18
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