Page 442 - Handbook of Modern Telecommunications

Network Management and Administration 3-233

Internet Partner

Gateway Gateway
SS7 SS7

Core Core
Switch Switch
Switches Switches

Core Core
Switch Switch
Edge Routers Edge Routers

Data Center 1 Data Center 2

= Signaling data collection point – SS7
= Signaling data collection point – SIGTRAN

FIGu RE 3.9.6 Deploying signaling-based sensor networks.
SS7 network and control protocol suite. In the emerging IP-based world, there are multiple levels of con-
trol protocols, starting at the lowest layers with protocol handshakes and session control, and ultimately
culminating in authentication and authorization followed by flow controls during the service session
and tear-downs following service completion. With the advent of IP, this signaling traffic is moving to
IP-based transport and is now running over the same transport infrastructure as service payloads. The
control protocols are very similar, even identical, but the protocol stack has changed and the point of
measurement has also changed.
Sensor networks for signaling data commonly consist of dedicated probe instrumentation, which is
passively connected to the access points into the signaling network. Since this is dedicated instrumenta-
tion, these sensory networks provide real-time information on customers/subscribers and the services
they are invoking, as well as session details regarding service setup, tear-down, and summary results.
Instrumentation points are normally in the access layers of the network, where switches connected
to the out-of-band SS7 network, although with the convergence onto IP-based signaling these instru-
mentation points now often include in-band backhaul and core network links. See Figure 3.9.6 for an
example of signaling-based sensory deployment.
Signaling sensor networks are less well suited for providing detailed characterization of service qual-
ity during the actual delivery process, intrasession or intratransaction. Since they do not have a view
into the actual service payload, signaling sensor networks are also unable to support session playbacks
for reconstructive analysis. Lastly, since they focus exclusively on control data, they do not recognize
nor track congestion or errors within the transport network.