Support of AoverIP (AOIP) in osmo-bsc

historical

Hi Harald,

> With a limited set of resources available, I would always rather spend the resources on making the BSC and BSSAP/BSSMAP more complete, than spend time on a new M3UA implementation - which doesn't add >new functionality, as an existing external signalling gateway could do the SUA-M3UA translation with no R&D involved.

We went through the OsmoSS7 Erlang code base and the webpage " https://projects.osmocom.org/news/30", we see no activity done on osmo-ss7 for 3 years.
Considering the use of osmo-ss7 as the signaling gateway for SUA to SCCP/M3UA translation, we have following concerns: 
a. Is osmo-ss7 compliant to latest specifications of SCCP and M3UA?
b. Does osmo-ss7 implement the complete functionality of the signaling gateway.
c. Is osmo-ss7 inter-op tested with 3rd party 3GPP compliant MSC and osmo-BSC.
d. After upgrading SUA and the BSSAP, can the osmo-bsc be tested with 3rd party MSC by using the osmo-ss7 as signaling gateway? Do you see some changes on OsmoSS7 codebase?
e. If osmo-ss7 does the complete functionality of the signaling gateway  that is translation from SUA to SCCP/M3UA then why to upgrade the SCCP and implement M3UA in osmo-bsc  even in future.

Regards,
Bindhu

-----Original Message-----
From: OpenBSC [mailto:openbsc-bounces at lists.osmocom.org] On Behalf Of Harald Welte
Sent: Tuesday, March 15, 2016 7:28 PM
To: Bindhu Anjaneya <Bindhu.Anjaneya at radisys.com>
Cc: openbsc at lists.osmocom.org
Subject: Re: Support of AoverIP (AOIP) in osmo-bsc

Hi Bindhu,

On Tue, Mar 15, 2016 at 11:33:01AM +0000, Bindhu Anjaneya wrote:
> Though the above approach is the simplest way, this implementation 
> will not be in compliance with 3GPP specification, this would also 
> introduce a hop between BSC and MSC on the A-Interface.

I don't think the extra hop would be a problem.  It reduces the implementation complexity and a SUA-capable BSC is an initial, functional implementation that could already be deployed.  Real M3UA support could be a second, incremental step at a later point.

We prefer to do development in smaller, more easily digestable chunks rather than having a too large scope for a task from the beginnign.

Also, on the BSSAP/BSSMAP level, the A interface exposed by OsmoBSC is also limited in many ways.  It only implements Intra-BSC hand-overs, and no Inter-BSC hand-overs at that point.

With a limited set of resources available, I would always rather spend the resources on making the BSC and BSSAP/BSSMAP more complete, than spend time on a new M3UA implementation - which doesn't add new functionality, as an existing external signalling gateway could do the SUA-M3UA translation with no R&D involved.

> So my suggestion is for Osmo-bsc to be 3GPP compliance, the SIGTRAN 
> stack BSSAP/SCCP/M3UA/SCTP/IP need to be implemented in Osmo-bsc.
> To achieve this:-
> Existing SCCP - need to be upgraded if needed

It will definitely need to be, as there is no code for connection-oriented SCCP at all.  libosmo-sccp only contans code for encoding/decoding some SCCP frames.

> M3UA - need to be developed may be as a separate library

should be part of libosmo-netif, as is the current SUA code.

The applications should all simply use the sccp-user-sap that we already offer and use from the IuCS/IuPS side, and not worry about the underlying protocol stack.  This way we ensure that later on, any added M3UA or other SIGTRAN protocol stack will not require modifications to the applications on top.

> We can introduce a compile time flag if we need to differentiate 
> between the support for SCCP/M3UA and SUA.

We don't like that.  When supporting multiple protocol stacks, we introduce one common/shared interface abstraction and we switch at run-time based on configuration.  For example, osmo-gbproxy supports NS-over-IP as well as NS-over-FR-over-GRE as two alternative stacks.

-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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