Feature #1842

Full M3UA SIGTRAN variant in libosmo-sccp

Added by laforge 4 months ago. Updated about 1 month ago.

Start date:
Due date:
% Done:


Spec Reference:


The M3UA+SCCP variant of SIGTRAN is used for spec-compliant AoIP and IuCS/IuPS interfaces. Osmocom libosmo-sccp currently only implements the SUA variant, and thus is not fully compatible with the lower protocol stacking of those standard interfaces.

Related issues

Related to libosmo-sccp - Feature #1930: Clean up and merge the Iu branch (SUA and SCCP User primitives) In Progress 01/28/2017


#1 Updated by laforge 4 months ago

  • Target version deleted (120)

#2 Updated by laforge 4 months ago

  • Project changed from Cellular Infrastructure to OpenBSC
  • Target version set to A-over-IP interface as per 3GPP

#3 Updated by laforge 2 months ago

  • Assignee set to laforge

#4 Updated by laforge 2 months ago

  • Priority changed from Normal to High

#5 Updated by laforge about 2 months ago

  • Related to Feature #1930: Clean up and merge the Iu branch (SUA and SCCP User primitives) added

#6 Updated by laforge about 1 month ago

  • % Done changed from 0 to 50

see gerrit patches till for some preparatory work. The actual M3UA and SCCP code is following up to that, currently in a laforge/sigtran branch of libosmo-sccp.git (see

The general idea is:
  • use osmo_prim to formally implement the SAP specified between protocol layers, e.g. MTP-SAP between M3UA and SCCP, or SCU-SAP between SCCP User and application
  • use osmo_fsm to implement the state machines, e.g. ASP and AS FSM of M3UA
  • use osmo_fsm to implement SCCP SCOC (connection oriented) per-connection state machine
  • migrate existing SUA code to new SCOC FSM
  • use parsed SUA (struct xua_msg) representation by default in all code, transcode from SCCP wire format to this for incoming messages, and from xua_msg to SCCP on outgoign messages. This helps keep the code more simple.
Various bits and pieces already exist in my branch
  • untested but fairly complete osmo_fsm for SCOC
  • definition for MTP SAP
  • xUA ASP and AS osmo_fsm implementation
  • SCCP <-> SUA transcoding with preliminary unit tests

More work is needed to pull the strings together and fix missing gaps.

Also available in: Atom PDF