add SGs / CSFB related dot + msc files
Those graphs + message sequence charts are not yet used by any
of our manuals, but they should become used by the OsmoMSC user
manual once SGs interface support is added.
Related: OS#2583
Change-Id: Idfd3a66c18131b5458d183b8e66f62eaaab65991
diff --git a/doc/manuals/images/sgs-imsi_attach_lu.msc b/doc/manuals/images/sgs-imsi_attach_lu.msc
new file mode 100644
index 0000000..e62c2b8
--- /dev/null
+++ b/doc/manuals/images/sgs-imsi_attach_lu.msc
@@ -0,0 +1,15 @@
+msc {
+ UE, MME, VLR [label="MSC/VLR"], HSS [label="HSS/HLR"];
+
+ UE => MME [label="Attach Request"];
+ UE box HSS [label="Steps 3..16 of LTE Attach procedure TS 23.401"];
+ MME box MME [label="Derive VLR Number"];
+ MME => VLR [label="LU Request"];
+ VLR box VLR [label="Create SGs Association"];
+ VLR box HSS [label="MAP/GSUP UL / ISD"];
+ MME <= VLR [label="LU Accept"];
+ UE box HSS [label="Steps 17..16 of LTE Attach procedure TS 23.401"];
+ |||;
+ ...;
+ MME <= VLR [label="Paging Request"];
+}