Editor’s Note: Welcome to our weekly Reality Check column. We’ve gathered a group of visionaries and veterans in the mobile industry to give their insights into the marketplace.
Everyone knows that service providers are dealing with the growth of mobile data traffic. What’s not common knowledge is that mobile data is creating a tremendous upsurge of Diameter signaling traffic in the process.
According to Joe McGarvey, principal analyst at Current Analysis, “Just as SIP has become the protocol of choice for setting up communications at the exterior of IP networks, Diameter is the chosen protocol for all of the chatter that goes on within IP networks, including communications between policy decision points, policy enforcements points, charging engines and subscriber data repositories. It also plays a role in the roaming-based communications between adjacent LTE networks and between LTE networks and 2G/3G networks.”
The upsurge is driving operators to seek new solutions to efficiently route and manage Diameter in their 3G and 4G mobile data networks.
Diameter routing challenges
Without a separate Diameter signaling infrastructure at the network core to facilitate signaling between network elements, endpoints such as online charging systems (OCSs), mobility management entities (MMEs), policy control and charging rules functions (PCRFs) and home subscriber servers (HSSs) would have to establish direct connections to one another. The connections would form an inefficient and difficult to manage mesh-like architecture. While this may suffice initially, as traffic levels grow the lack of a signaling infrastructure would pose a number of challenges, including:
–Scalability: Network endpoints would be burdened with all session-related tasks such as routing, traffic management, redundancy and service implementation – an overwhelming amount of complexity.
–Congestion control: The Diameter protocol lacks standardized methodologies for handling element congestion, leaving service provides at the mercy of each network element’s unique settings and capabilities.
–Topology hiding: Service providers require a network interconnect point to avoid potential security breaches associated with exposing their network topology to other operators. As functions like charging and policy scale, operators are faced with added operational complexity if they have to segment their subscribers, or configure every charging or policy client to be able to access every server.
–Interoperability testing: With no separate signaling or session framework, interoperability tests must be performed at every existing node when a new node or software load is activated. These activities consume a considerable amount of operator time and resources, with costs increasing in proportion to the number of tests that must be performed.
–Subscriber-to-HSS mapping: Without a separate Diameter signaling infrastructure, integration of a multi-vendor HSS environment – either through network design or corporate acquisitions – is complicated and more expensive to manage.
–Policy and charging session binding: Effective delivery of policy control Diameter messages and efficient management of charging-related Diameter traffic requires session stateful routing.
Diameter networks signaling architecture
Centralizing Diameter routing in a standalone network element creates a signaling architecture that reduces the cost and complexity of the core network and enables core networks to grow efficiently.
As is the case with other protocols, network equipment vendors often use their own variants of the Diameter protocol based on how they believe a specific interface should be implemented. Each variant can differ slightly from that of another vendor, although both meet defined specifications. The result is interworking issues when multi-vendor equipment is combined in one network – a common approach for operators building a best-of-breed solution. The issue can also emerge when operators connect their network to other parties, like mobile virtual network operators. A centralized Diameter signaling router establishes a single point for the mediation of different Diameter variants.
Also, a Diameter signaling router can interwork Diameter and non-Diameter messages. This is required when operators want to introduce Diameter-based protocols into a network already supporting legacy protocols. As Jim Eller, principal analyst of wireless infrastructure at ABI Research said to operators in its “Policy Management for Mobile Broadband” report, “If you interconnect to legacy networks using SS7 or other protocols, you should consider a Diameter gateway.”
In addition, a streamlined Diameter signaling architecture:
–Simplifies network expansion by managing routing configuration changes for new endpoints.
–Facilitates network monitoring by providing a centralized vantage point in the signaling network. A performance management system can use a single network element to analyze subscriber, device and overall network activities without a costly distributed probe architecture approach.
–Creates a gateway to other networks – 2G, 3G and 4G – to support inter-carrier roaming and security requirements.
–Reduces provisioning, maintenance and interoperability testing associated with adding new network nodes.
ABI Research summed up the future of the market: “Operators eventually need Diameter and Diameter routers.” Diameter-related tasks will only grow in importance, and operators will discover new uses as their networks evolve. In the coming months, we’ll further explain the benefits of a holistic Diameter network and identify use cases for both 3G and 4G networks.
Jason Emery is Director of Product Management at Tekelec. He has more than 20 years of next-generation signaling experience, and has authored or co-authored more than 10 U.S. patents and invention disclosures.
