Suppose all four SS7 trunks of one 3G
Gateway are connected to one switch, as
indicated in the connection schematic to the
right.
In this example the Originating Point Code
(OPC) of the 3G Gateway equals 99, and the
Destination Point Codes (DPCs) for all trunks
equal 100.
Both OPC and DPC are provided by the
telephone network operator.
These settings can be seen in the schematic
and in the screen shot of the SS7 window
below right. All trunks can carry a maximum
of 30 calls, i.e. 30 data time slots.
Each data time slot is identified uniquely by
its OPC, DPC and Circuit Identification Code
(CIC). The “absolute” CIC consist of a CIC
“base address”, which has to be defined
for each trunk in the SS7 window, i.e. in
this case 0, 32, 64 and 96, and a relative
address. The latter is a number between 0
and 31 and depends on the choice of the
framing time slot and signalling time-slot
numbers.
Since one time slot is reserved for framing,
in this case set to time slot 0 by default, and
one time slot has to be defined for signalling
(16 in this example), 30 time slots are left
to transport call related data, i.e. time slots
with relative addresses 1–15 and 17–31,
see the table in the schematic.
For signalling fail-over purposes a maximum
of 2 SS7 trunks, also called links, can be
defined to take care of the SS7 signalling of
all 4 trunks in the 3G Gateway,
In this case trunks 1 and 2 are used for SS7
signalling. Since there is a direct connection
between the 3G Gateway and the switch,
both links are defined in the same link set
with the DPC of the switch, i.e. 100. Since
fail-over has been arranged within one link
set, no routes can be defined.

SS7 Configuration – Example 1