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Harald Welte laforge at gnumonks.orgHi Pau,
On Sun, Nov 12, 2017 at 01:56:56PM +0100, Pau Espin Pedrol wrote:
> if I understood correctly: after your patches, osmo-msc can speak SCCPlite
> to osmo-bsc-sccplite (osmo-bsc in openbsc.git)
Not entirely. OsmoSTP can now have signaling links of M3UA and IPA type,
so it can convert between both protocol stackings, passing through the
SCCP and BSSAP/BSSMAP on top.
In theory not much is needed to use libosmo-sigtran with IPA directly
from osmo-msc, but I don't know if it's useful to spend time in this.
In the 3GPP AoIP setup we also require OsmoSTP between BSC + MSC, so
there are reasons to keep the setup as close to the "legacy interop"
one.
> but still cannot communicate with new osmo-bsc in osmo-bsc.git.
No. With current master after my patches, a single osmo-msc instance
will connect via M3UA to osmo-stp. Multiple BSCs can then attach to
osmo-stp via either M3UA or IPA/SCCPlite and talk to that single
instance of OsmoMSC.
> This means if somebody is willing to use osmo-bsc with SCCPlite, the
> older one in openbsc.git must be used. Am I correct?
Yes. We cannot achieve this functionality by using M3UA between BSC and
STP, and then connecting to a SCCPlite MSC from the STP. The reason is
simple: SCCPlite as we know it doesn't contain any addressing
information beyond the SSN, i.e. it is not possible for the MSC to
distinguish from/to which given BSC to send messages. The
differentiator from the BSC side is the underlying TCP connection, so
each BSC must have a separate IPA/SCCPlite connection to the MSC.
If we want to support new osmo-bsc to talk SCCPlite, we need to
1) verify that the existing client-side IPA implementation of
libosmo-sigtran works properly
2) figure out a way how to configure this for the client from the VTY
3) establish direct MGCP interoperability between external MSC and osmo-mgw
I don't have any plans for this for the time being. 1+2 should be
rather easy, the code already exists but is simply not used/tested. '3'
is the more interesting question - but actually also should more or less
"just work" if the AoIP transport IP/Port TLVs are not in the BSSAP,
osmo-bsc simply has to suppress sending MGCP commands for the A-side, but
continue sending MGCP commands for the Abis side.
Regards,
Harald
--
- Harald Welte <laforge at gnumonks.org> http://laforge.gnumonks.org/
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