Diameter Routing: Core vs. Edge

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Diameter Routing: Core vs. Edge

By TMCnet Special Guest
Jason Emery
  |  August 01, 2011

This article originally appeared in the August issue of INTERNET TELEPHONY

ABI Research (News - Alert) predicts mobile data traffic to increase at a compound annual growth rate of 39 percent from 2011 to 2016, from 7,955 petabytes this year to 60,508 petabytes in five more years. To put it in perspective, the 2016 number equals about 845,000 years of HDTV video.

To move and monetize all of this data, behind the scenes operators rely heavily on the Diameter protocol. Diameter controls how content traverses equipment and devices. For example, it carries the messages that give subscribers permission to access websites, applications and services. It delivers charging commands so service providers can correctly bill customers based on usage, time of day and other filters. Diameter is also essential for mobility management, giving subscribers the ability to roam onto partner networks.

Diameter communicates between network equipment such as the policy and charging rules function, policy and charging enforcement function, several gateways, the gateway GPRS support node, subscriber databases, mobility management engine, and other network equipment.

As operators move to all-IP LTE (News - Alert) and IMS networks – and their underlying equipment such as MMEs, PCRFs and LTE home subscriber servers – their dependence on Diameter will exponentially increase. As Joe McGarvey, principal analyst at Current Analysis (News - Alert), writes, “A massive expansion of Diameter chatter, accordingly, will be the natural byproduct of the continuing explosion of mobile broadband networks.”

McGarvey adds, “What’s missing from current networks is the ability to handle this coming onslaught of Diameter signaling activity. The current solutions available for operators involve configuring each Diameter-based component in the network with the ability to communicate with all other components. While this addresses immediate internal issues, such a mesh-based signaling model will not scale and is not applicable to issues outside of the network related to roaming. Diameter signaling routers – as well as gateways and load balancers – relieve Diameter-based components of connectivity requirements and essentially establishes a centralized facility in the network [that] becomes the single point in the network for solving connectivity, interoperability and addressability issues.”

Tekelec (News - Alert) believes many of the problems encountered in initial SS7 network deployments are also problems in new Diameter networks. Implementing a centralized, hierarchical Diameter routing network helps to address those issues, similar to the benefits achieved by creating centralized SS7 networks years ago.

Two different approaches exist for the location of these functionalities: the core network and the network edge. Some specific reasons to locate Diameter routing in the core network include:

·         Frequency of routing changes

Diameter traffic routing is inherently dynamic, based on multiple factors, including the number of concurrent sessions, the state of network equipment and a subscriber’s location. As networks evolve and grow, operators need to update routing tables to maintain network efficiency. With a Diameter routing node at the core of the network, routing updates are made in one place, rather than at every endpoint in the network.

·         Diameter traffic characteristics

Many Diameter endpoints are comprised of several servers, each with its own address. A core Diameter routing node can provide sophisticated load balancing and traffic management algorithms to both increase efficiency and to offer value-added capabilities, such as ensuring that all of the traffic associated with a unique session arrives at the same endpoint server.

·         Number of connections

Networks relying on Diameter have large numbers of core network elements that must maintain unique associations with the others. That places a heavy burden on the endpoints as the number of nodes grows. Edge-based routers are typically designed to support a smaller number of connections – since fewer connections exist between edges than in the core. Diameter signaling routers designed for core routing can scale as needed to support the array of core network equipment using Diameter.

·         Network and traffic management

As with SS7 networks, Diameter networks require dynamic intelligence to minimize the impact caused by the failure or congestion of individual network nodes. Core Diameter routers implement network management functions to deal with faults and re-route traffic in real time when problems occur. Edge Diameter routers lack the concepts of network management and traffic management, deferring to gateways or other connected endpoints to handle failures and congestion.

·         Operational support

Core Diameter routers centralize operations, administration, maintenance and provisioning, and integrate sophisticated debugging and performance measurement facilities – where edge Diameter routers may not.

The question for Diameter routers is not if but when. And when the time arrives, operators will be best suited to consider their long-term Diameter needs.

Future use cases will likely include many of the following: charging and policy traffic load balancing, subscriber address resolution for both IMS and LTE networks, inter-operator roaming, translation of Diameter variants, interworking Diameter and non-Diameter nodes, and providing a centralized point for monitoring Diameter traffic. These tasks – and many others – are best enabled with a Diameter signaling router in the core of the network.

Jason Emery is director of product management at Tekelec (www.tekelec.com).

 


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Edited by Stefania Viscusi

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