SUA on-link cb?

Harald Welte laforge at gnumonks.org
Mon Apr 4 18:19:39 UTC 2016


Dear Neels and others,

I was confused earlier today.

N-CONNECT is a primitive for a connection oriented SCCP-layer
connection.  You receive it at each time a UE establishes a
connection-oriented SCCP for signalling, and it is what carrie RANAP
InitialUE and related messages.

What you are talking about for the RANAP Reset is the establishment of a
signalling link (underneath SCCP/SUA), so something like the SCTP
connection being established and released underneath.

In the SUA RFC 3868 there are:
* M-SCTP_ESTABLISH confirm
  ASP confirms to LM that it has established an SCTP association with its peer
* M-SCTP_ESTABLISH indication
  SUA informs LM that a remote ASP has established an SCTP association.
"LM" is the "Layer Manager".  This is not the SCCP user, so no luck
here.

However, Q.711 / Q.714 contain a N-STATE.indication, which can be sent
to a local SCCP user to inform it about the subsystem status.

FRrom 5.3.6.2:

"The local broadcast procedure provides a mechanism to inform local
 allowed concerned subsystems of any related SCCP/subsystem/signalling
 point status information received. [...] SCCP management then informs
 local allowed concerned SCCP subsystems about the subsystem status by
 invoking N-STATE indication primitive with "User-out-of-service"
 information."

So once we loose the signalling link, all SCCP users should receive
N-STATE.ind with "User-out-of-service".

When the signalling link is (re-)established, all SCCP users should
receive N-STATE.ind with "User-in-service".  This should then be the
trigger to send a N-UNITDATA.req() with a RANAP Reset inside.

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