Pipeline Publishing, Volume 7, Issue 10
This Month's Issue:
Unlocking Next Gen Networks
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The road to LTE is paved with Diameter
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By Ron de Lange

We all know mobile data traffic is skyrocketing, fueled by the rampant use of smartphones, tablets, and compelling applications such as mobile video and social networking. And there is no slowdown in sight.

Operators know that their 3G networks are not equipped to manage this high level of traffic growth. They’re looking to all-Internet protocol (IP) networks such as long term evolution (LTE) and IP multimedia subsystem (IMS) to provide the bandwidth required to support data-hungry devices and applications and to cost effectively address the growing gap between traffic and revenue growth.

According to the Global mobile Supplier Association’s (GSA) recent report, 180 operators in 70 countries are currently investing in LTE, with at least 64 LTE networks anticipated to be in commercial service by the end of 2012. As LTE networks are deployed over the next few years, operators will be faced with a number of challenges as their networks become more complex, including scalability and cost management. Diameter can help address those challenges.

3G networks are not equipped to manage this high level of traffic growth.



extensive use of Diameter protocol interfaces for LTE and IMS networks, but the organization has not defined a separate Diameter signaling infrastructure.

Without a separate Diameter signaling infrastructure at the network core to facilitate signaling between network elements, endpoints such as mobility management entities (MMEs) and home subscriber servers (HSSs) must utilize direct signaling connections to each other, forming a mesh-like network architecture. Network endpoints must handle all session-related tasks such


Why Diameter Signaling?

The majority of operators around the globe still connect their networks through the exchange of well-defined SS7 messages. As networks evolve, SS7 signaling is being replaced by Diameter and SIP-based equivalents. While LTE defines Diameter-based rather than SS7 interfaces, the majority of SS7 functionalities still have to be performed in LTE networks.

The Diameter protocol, using stream control transmission protocol (SCTP) for transport, is used widely in the all-IP, service-oriented IMS and LTE architectures. Within the IMS control and service planes, Diameter plays a central role in policy, charging, authentication, and mobility management.

Diameter Routing Challenges

The Third Generation Partnership Project (3GPP) has specified the


as routing, traffic management, redundancy, and service implementation. Initially, implementing an IMS or LTE network without a signaling core may be sufficient, but as traffic levels grow, the lack of a capable signaling infrastructure poses a number of significant challenges, including:

  • Scalability: Each endpoint must maintain a separate SCTP association with each of its Diameter peers as well as the status of each, placing a heavy burden on the endpoints as the number of nodes grows.
  • Congestion control: Diameter lacks the well-defined congestion control mechanisms found in other protocols such as SS7. For example, if an HSS has multiple Diameter front ends, the lack of sufficient congestion control increases the risk of a cascading HSS failure.


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