PDF of this tutorialBy leveraging the current state-of-the-art in telephony signaling, digital message-based systems bring together an optimal balance of efficiency, scalability, and robustness, along with the extensibility needed for advanced services.
Improved Efficiency
Message-based information can be sent and acknowledged across a common channel for many different connections. The use of common channel signaling (CCS) allows for significantly more efficient use of system bandwidth as compared to the channel associated signaling (CAS) used in bit-based schemes where dedicated signaling bandwidth is required for every connection. In addition, CCS messages need not be associated with any specific connection, thus making it possible to efficiently implement system-enhancing mechanisms, such as automated status reporting, software updates, etc. during off-peak periods. The bottom-line results from message-based signaling include faster call setup, better utilization of network resources, and much greater scalability.
Robust Quality
The inherent two-way communications methods used in message-based signaling provide for assured transmission and automatic retransmission of any message that is not received. This not only provides a higher level of quality for each individual connection, it also gives network management systems access to a rich stream of ongoing statistical information, such as frequency of retransmissions, which can be used for making proactive routing and configuration adjustments to anticipate and avoid catastrophic failures.
Advanced Services
Because any number of explicit messages can be created as required, a message-based system can be extended to specifically encompass any new circumstance, as compared to bit-based systems that often resort to using the same bit code to mean different things in different situations. This inherent extensibility, along with two-way communication, has enabled message-based systems like SS7 to implement advanced revenue-enhancing services such as caller I.D., one-number services, number portability, etc.
In addition, because both end points of a message-based connection can participate in a two-way negotiation, the network design can be extended to include built-in mechanisms for automatically managing forward and backward compatibility issues between multiple system revision levels. In addition, the two-way negotiation capability gives a message-based system significantly greater flexibility for interfacing with a wider range of customer premises equipment (CPE). Standardization of messages ensures interoperability, even among equipment from different manufacturers.
Figure 2. Signaling
