sscp-context initalization via VTY

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Harald Welte hwelte at sysmocom.de
Thu Jul 6 23:22:05 UTC 2017


Hi Neels and Philipp,

On Thu, Jul 06, 2017 at 03:10:37PM +0200, Neels Hofmeyr wrote:

> Will we ever use osmo_ss7_instance for anything else than SCCP?

no current plans, but completely likely for e.g. ISUP.

> (That's because osmo_sccp_simple_client() accepts a PC argument that is set as
> ss7->cfg.primary_pc. I wonder whether we use a routing indicator of PC in a
> hardcoded way then? Future plans?)

Can you please all get detached from what simple_client() currently
does?  It is nothing less than a crude hack that I introduced so we
(and particularly Philipp) can make quick progress on the higher layers
without having to wait for the then-non-existant ss7 vty code in
libosmo-sccp and the related full configuration, using OsmoSTP, etc.

So whatever that API hack does or doesn't do is not really relevant in
the bigger picture.

> So this is sufficient:
> 
>  msc
>   cs7-inst-a 1
>   cs7-inst-iucs 1

The MSC should point to the address book (by name) and the address book
contains the point code and/or global title, etc. (i.e. the local sccp
address) that it should use, together with the ss7 instance number.

anything else is determined by configuration of the lower layer in
osmo_ss7 vty.

> One more thing: each ss7_instance will only find those address book entries
> defined in its own address book list, right? 

yes.

> If I explore the case of passing the PC directly and using a global SCCP
> address book, the VTY becomes simpler. We don't actually need an cs7-instance
> scope anymore, since all we do in it would be defining an SCCP instance:

Configuration of the SCCP instance and anything below it are not the
concern of the MSC.  Please do not mix the layers.

As analogy: You also don't configure the MAC address and the IP
address, netmask, IP routes, etc. in the system when you crate a TCP socket.

The Ethernet and IP layer configuration (e.g.
MTP/M3UA/ASP/links/linksets/routes/...) is independent of the
application layer, where when you bind a socket, you simply specify one
of many local IP addresses + the respective port number.

The fact that various layers are running within one process, or the fact
that they share one config file / vty doesn't mean those parts are not
separate and have a *very* thin line of interaction:  The SCCP-User-SAP
only.

Regards,
	Harald
-- 
- Harald Welte <hwelte at sysmocom.de>             http://www.sysmocom.de/
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