Change in osmo-ttcn3-hacks[master]: msc: inter-MSC HO test: use CGI cell ID, not LAI

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neels gerrit-no-reply at
Fri Jul 2 15:14:30 UTC 2021

neels has uploaded this change for review. ( )

Change subject: msc: inter-MSC HO test: use CGI cell ID, not LAI

msc: inter-MSC HO test: use CGI cell ID, not LAI

Fixes inter-MSC handover tests: in the inter-MSC 'Handover Required', do
not send a LAI cell identifier, but a CGI one.

This is analogous to the fix applied to inter-BSC HO in


As explained in OS#5188, 3GPP TS 48.008 allows a LAI identification only
in the Cell Identifier List IE, but not in the single Cell Identifier

In the inter-MSC HO test's Handover Required message, we so far send a
LAI identifier in a List IE to osmo-msc. And so far, osmo-msc simply
echos that in the Handover Request message's single Cell Id IE.

The LAI is, as actually defined in the spec, omitted from the single IE
in deps/titan.ProtocolModules.BSSMAP/src/BSSAP_Types.ttcn, and when
osmo-msc sends the non-standard LAI Id, ttcn3 fails to parse the BSSMAP
Handover Request message: the Cell Identifier IE gets wrong values, and
all remaining IEs are parsed as 'omit' even though they are present on
the wire. So as long as osmo-msc sends back a LAI Id, we cannot sanely
verify the Handover Request received from the MSC.

The CGI identifier type is supported in both IEs. So when the test sends
a CGI identifier in the Handover Required, osmo-msc will also reflect a
CGI identifier in the Handover Request, and ttcn3 parsing works.

Related: OS#5188 SYS#5324
Change-Id: I525b5deaa9634fcdb63fbd2c97c767aff045767c
M msc/MSC_Tests.ttcn
1 file changed, 1 insertion(+), 1 deletion(-)

  git pull ssh:// refs/changes/27/24827/1

diff --git a/msc/MSC_Tests.ttcn b/msc/MSC_Tests.ttcn
index e548c5c..a165d5c 100644
--- a/msc/MSC_Tests.ttcn
+++ b/msc/MSC_Tests.ttcn
@@ -5985,7 +5985,7 @@
 	var BssmapCause cause := enum2int(cause_val);
 	var template BSSMAP_FIELD_CellIdentificationList cil;
-	cil := { cIl_LAI := { ts_BSSMAP_CI_LAI('017'H, '017'H, 1) } };
+	cil := { cIl_CGI := { ts_BSSMAP_CI_CGI('017'H, '017'H, 1, 1) } };
 	/* old BSS sends Handover Required */
 	BSSAP.send(ts_BSSMAP_HandoverRequired(cause, cil));

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Gerrit-Project: osmo-ttcn3-hacks
Gerrit-Branch: master
Gerrit-Change-Id: I525b5deaa9634fcdb63fbd2c97c767aff045767c
Gerrit-Change-Number: 24827
Gerrit-PatchSet: 1
Gerrit-Owner: neels <nhofmeyr at>
Gerrit-MessageType: newchange
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