Lately signaling has gained attention as a culprit of network outages and congestion. Signaling storms have arisen from localized events and small subscriber bases, giving signaling overall a bad name.
Operators, however, should welcome an increase in Diameter signaling, the messages responsible for authorization, authentication and access (AAA), policy, charging, quality of service (QoS) and mobility management.
Much of signaling’s bad rep is owed to radio access network (RAN) signaling. These messages only establish an internet connection so that the data itself can reach the device. Revenues for connections themselves are very small, yet the volume of these signaling messages required to establish and then release the connection is significant. For example, when a subscriber connects to the internet and downloads an email, 50 or more signaling messages traverse back and forth between the RAN and the gateway GPRS support node (GGSN).
But when a subscriber connects to Facebook and stays logged into the account all day, the number of messages mushrooms. The reason is that the service provider does not maintain the internet connection all day. Instead, the connection ends after the initial data is sent and received. The device then re-establishes the data connection seconds later, polls the Facebook server for updates, and releases the connection – requiring another round of RAN signaling messages. And so on and so forth – up to billions of messages per day, with little incremental associated revenue.
Diameter signaling traffic, on the other hand, directly correlates to operators’ increased data revenues. The communications among policy servers, charging systems and subscriber databases that Diameter signaling enables are pre-requisites for operators to offer personalized mobile data services. These include tiered tariffs, shared data plans, loyalty programs, “toll-free” or sponsored usage, QoS for specific applications, and enhanced over-the-top (OTT) applications. The result is a bottom-line boost that unlimited services would never provide.
This “good” signaling increases as service providers begin monetizing their data networks. For example, when a subscriber wishes to purchase a higher service tier, the GGSN/packet gateway (PGW) will send a Diameter message to the policy server (PCRF) to identify restrictions to be applied based on the subscriber plan. The PCRF will then send a Diameter message to the subscriber database to retrieve the subscriber’s profile (data quota, preferences, usage etc.) and send this data back to the policy server. The PCRF, in turn, sends this information to the GGSN/PGW for enforcement. That's around five Diameter messages to support one interaction on a tiered service plan. And this is a simple example.
Diameter is also the protocol that connects the policy server with the deep-packet-inspection (DPI) equipment and the other policy enforcement control points, and communicates policy rules to the enforcement points throughout the network. It also provides the connection between the policy server and billing and charging systems.
As a tier one service provider told me, “100% of our revenue-generating LTE services depend on Diameter signaling.” In other words, data revenues will strongly correlate to increases in Diameter signaling. The key is to welcome Diameter traffic by both managing and monetizing it at the network core. This will not only avoid signaling storms, but also create an architecture that will scale with subscriber, application and data growth.
Doug Suriano is chief technology officer at Tekelec