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Signaling System Number Seven
Signalling System Number 7 (SS#7) is the
protocol used by the telephone companies
for interoffice signalling. In the past,
in-band signalling techniques were used
on interoffice trunks. This method of
signalling used the same physical path
for both the call-control signalling and
the actual connected call. This method
of signalling is inefficient and is
rapidly being replaced by out-of-band or
common-channel signalling techniques.
A network utilizing common-channel
signalling is actually two networks in
one:
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First there is the circuit-switched
"user" network which actually
carries the user voice and data
traffic. It provides a physical path
between the source and destination.
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The second is the signalling network
which carries the call control
traffic. It is a packet-switched
network using a common channel
switching protocol.
The original common channel interoffice
signalling protocols were based on
Signalling System Number 6 (SS#6). Today
SS#7 is being used in new installations
worldwide. SS#7 is the defined
interoffice signalling protocol for
ISDN. It is also in common use today
outside of the ISDN environment.
The primary function of SS#7 is to
provide call control, remote network
management, and maintenance capabilities
for the inter- office telephone network.
SS#7 performs these functions by
exchanging control messages between SS#7
telephone exchanges (signalling points
or SPs) and SS#7 signalling transfer
points (STPs).
The switching offices (SPs) handle the
SS#7 control network as well as the user
circuit-switched network. Basically, the
SS#7 control network tells the switching
office which paths to establish over the
circuit-switched network. The STPs route
SS#7 control packets across the
signalling network. A switching office
may or may not be an STP.
For expert help in converting to or
implementing Signaling System Number
Seven please contact us for a
professional presentation.
info@teralight.com
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