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

Giovanni Maruzzelli gmaruzz at gmail.com
Wed Nov 29 17:45:58 UTC 2023

Yes, actually there is a difference between 5g and 4g infrastructure, that
actually often involve different interfacing from IMS to it, particularly
pcscf and icscf, eg: the way they interact with hss and pcf/pcrf.
Problem is that 4g infrastructure is different from 5g. When they implement
4g+5g, they implement actually both (so, no problem)

4g+5g is called NSA (not stand alone)

A pure 5g is SA (stand alone) and offer different interfaces from the ones
provided by 4g.

In NSA you (IMS) can behave like it's pure 4g (you use 4g interfaces to do
all things, even for the 5g part)

In SA not at all, you must interface to 5g

The main difference for what ims is concerned is pcf vs pcrf

Let's note that most private networks (enterprise, etc) will be SA

Most carriers will obviously be NSA

answered from mobile, please pardon terseness and typos,

On Wed, Nov 29, 2023, 18:25 Bogdan-Andrei Iancu <bogdan at opensips.org> wrote:

> Hi Johan,
> The lowest point we should address in the whole IMS arch is the P-CSCF, so
> we are agnostic to the actual transport layer below us (like the xG stuff).
> Or am I saying here something wrong and there are some implications to the
> upper layers ?
> Regards,
> Bogdan-Andrei Iancu
> OpenSIPS Founder and Developer
>   https://www.opensips-solutions.com
>   https://www.siphub.com
> On 29.11.2023 18:07, Johan De Clercq wrote:
> In addition, the IMS should be able to handle 4G and 5G calls.
> In my opinion, we should no longer about 2 and 3 G as they are being
> phased out everywhere.
> wkr,
> Op wo 29 nov 2023 om 16:39 schreef Bogdan-Andrei Iancu <
> bogdan at opensips.org>:
>> Hi Giovanni,
>> Thanks for the feedback here, a valuable one as usual :).
>> On the HSS, what you are saying aligns with the my own thoughts - that
>> its functioning logic is somehow outside the our scope here, but we need to
>> pay attention to the interfacing (DIAMETER or HTTP2.0).
>> Now, on the AS side - as I understand, it holds whatever custom logic the
>> operator may have in routing and proving services (included VAS's). So to
>> say, I see it as a highly programmable component. And if so, what we need
>> to provide here is probably a very high level interface / API to allow call
>> manipulation in a very abstract way... :-/ ??
>> Best Regards,
>> Bogdan-Andrei Iancu
>> OpenSIPS Founder and Developer
>>   https://www.opensips-solutions.com
>>   https://www.siphub.com
>> On 29.11.2023 11:11, Giovanni Maruzzelli wrote:
>> First of all:
>> CONGRATULATIONS to the OpenSIPS community !!!
>> (I believe this is the first step of a long and satisfying journey)
>> On the topic:
>> in addition to the CSCF component, I would like to see efforts on the AS
>> (Application Server) component of the IMS infrastructure.
>> The AS is probably way the simplest of it all, it will probably require
>> the least modifications/additions to OpenSIPS.
>> But I would say AS will be crucial to a lot of people/use cases.
>> While for sure there will be a lot of cases for our community to build
>> the voice/video complete IMS infrastructure on top of private 5G networks
>> in enterprises and public administrations, I see as very much relevant also
>> the use case of building infrastructure to provide additional third party
>> services to big carriers, and to big carriers partners.
>> Also, AS is the correct and manageable way to provide additional services
>> even if you build the core IMS infrastructure.
>> About HSS: this is the sancta sanctorum of a carrier/provider
>> Apart from the venerable fraunhofer java implementation, now we can count
>> on the flexible java implementation in
>> https://github.com/nickvsnetworking/pyhss with a lot of features, good
>> performances, and actually built for production.
>> I would say better we concentrate on accessing the various different
>> protocols of HSS (diameter/http2) from the various components (each
>> component in IMS access HSS with a different interface with
>> different vocabularies and actions.
>> MGCF/MGW, if needed, will be a natural extension of our CSCF/AS
>> architecture.
>> Just my two cents, to keep the ball rolling,
>> Congratulation again,
>> -giovanni
>> On Tue, Nov 28, 2023 at 2:02 PM Bogdan-Andrei Iancu <bogdan at opensips.org>
>> wrote:
>>> Hi all,
>>> (disclaimer : cross lists posting is not a good practice - we will do
>>> this only to catch the attention and get momentum with this initial topic)
>>> As a first step here, is to work out the scope of the IMS implementation
>>> in OpenSIPS. IMS is a vast concept, with SIP and non-SIP components, and we
>>> want to understand and agree on which components of IMS may be subject of
>>> work from the OpenSIPS perspective. For example, we do consider the CSCF as
>>> a must here, but we may explore the HSS, AS, MGW or other components.
>>> From the OpenSIPS perspective, we look for IMS components which are SIP
>>> related. At least as a starting point. So, the first obvious candidate is
>>> the *Call Session Control Function (CSCF)*. And here we need to look
>>> into and address the specific functionalities of each sub-component:
>>>     * P-CSCF
>>>     * I-CSCF
>>>     * S-CSCF
>>> Again, these are the pretty obvious components, still may look into and
>>> evaluate (if of an interest of the OpenSIPS IMS implementation) areas as:
>>>     * HSS (from interconnection perspective)
>>>     * MGCF / MGW  (from interconnection perspective)
>>>     * SIP AS
>>>     * others ?
>>> Any feedback (with explanations and arguments) about what we should
>>> consider for our IMS implementation is more the welcome. I set here just a
>>> simple starting point, with no limitations or so. Feel free to contribute
>>> to the topic
>>> Best regards,
>>> --
>>> Bogdan-Andrei Iancu
>>> OpenSIPS Founder and Developer
>>>   https://www.opensips-solutions.com
>>>   https://www.siphub.com
>>> _______________________________________________
>>> Wg-ims mailing list
>>> Wg-ims at lists.opensips.org
>>> http://lists.opensips.org/cgi-bin/mailman/listinfo/wg-ims
>> --
>> Sincerely,
>> Giovanni Maruzzelli
>> OpenTelecom.IT
>> cell: +39 347 266 56 18
>> _______________________________________________
>> Wg-ims mailing list
>> Wg-ims at lists.opensips.org
>> http://lists.opensips.org/cgi-bin/mailman/listinfo/wg-ims
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