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Rethinking SDM in the era of NFV


Transition to an NFV architecture brings opportunities to rethink the role of SDM within customer network environments.

Data Addressability become the key to capitalize on the benefits of virtualization. This does, however, challange the  concepts and features of subscriber data management (SDM) used in core networks.


Persistency is key

When using NFV, many virtual network functions (VNFs) can be scaled within the network. Orchestration and service chaining provides necessary coherence between VNFs to maintain smooth service delivery.

However, when instances of the VNFs are scaled, the generated customer and application data is saved. For example, IMS applications require access to customer features, such as call forwarding preferences, call routing rules, and some transaction history.  When an IMS function scales up and defers execution to a new instance, the attached data moves along with it. When an instance scales down, the same data moves into a new instance. Multiplied by hundreds of VNFs, managing the lifecycle of the customer data becomes a critical aspect of NFV operations.

So beyond the need for application and data separation—which is driven by business imperatives—VNFs also need data federation.

Using consolidated customer data from a single, logical repository lets applications retrieve information necessary to execute network functions as they scale up or down. If instances are terminated, the data is saved, or if instances are moved between operating environments, data consistency is ensured.

Subscriber data management has evolved, becoming a “network brain” for authentication and authorization at a core network level. The development of 3GPP releases 9, 10, and 11 focus on core network data, authentication, and authorization processes, attached to the network. NFV drives the need for data federation, making SDM the point of federation and consolidation for subscriber data, across CSP operations components. 

Maintain availability

Keeping billable services up and available is the lifeblood for carriers’ bottom line. Availability means that carriers find ways to maintain full mobile services through network failures, traffic surges, and natural disasters. And it’s more than recovering from failed network components or server complexes. It’s measured by the up time and seamless experience of the subscriber.

Industry news articles demonstrate the damage done to company reputations when devastating outages occur, including strong customer dissatisfaction or defection, negative press, and significant out-of-pocket recovery expenses.

In real-time mobile telecommunications environments, CSPs can’t risk their mobile solutions to high-availability designs because downtime costs are too large and business impacts are too great. Those designs are well suited for commercial applications where certain levels of downtime can be rationalized.

Synchronize customer data

Through NFV, network elements are implemented on top of virtual servers. These virtual servers are abstracted from their physical environment, which means their functionality is independent from the hardware plane. Traditionally, subscriber data management (SDM) network functions were implemented as centralized nodes—attached to and servicing their network. They were implemented as appliances located in multiple, geographically dispersed datacenters, with some sites delivering SDM functionality—HLR, HSS, AAA, and UDR—to the whole nationwide network. 

NFV enables new ways to implement SDM nodes, which potentially leads to new topologies for deployment. For example, functional instances of core network elements can be deployed at the edge of the network, which is closer to their attach points and to mobile radio networks. CSPs considering this configuration expect to give their customers with better quality services with less signaling traffic traveling into the core. And, using this approach enables faster service delivery.

Distributed architectures—often referred to as “cloudified”—have more database-related traffic traveling between the distributed instances, with less traffic in the core network. SDM application instances deployed in the edge keeps a physical copy of the data records it updates. These local updates of customer data must be synchronized across instances in order to keep a single, logical-updated copy for individual subscriber data. 

In these new topologies, data repository synchronization protocols are put under significantly more pressure than in traditional implementation topologies. The number of nodes to be synchronized can increase by hundreds, and they can be spread out physically for thousands of miles. But this isn’t the only challenge, since the underlying infrastructure can also be implemented with virtual routers and floating IP addresses. This adds further overlay to the intra-datacenter IP traffic. Thus, it results in lower quality bandwidth for the transmission network.

Unbundle data for open design

SDM architecture shall be designed for separation between the application plane and the data plane.    The result is data provisioning that’s split from the application. Different application front ends operate separately, but use one logical database on the backend. This unique repository is extended to accommodate all supported application front ends, including HLR, EIR, HSS, AAA, and more.

Splitting application data and customer data is the foundation of NFV. And, within SDM environments, it lets you scale solution transaction capacity and data records at different paces. An example is machine to machine (M2M) scenarios where some devices registered within the SDM generate very little traffic—a few syncs per month. There can be millions of connected, stationary devices, such as vending machines that generate low traffic volumes.

In contrast, connected cars generate network traffic similar to how a person produces network traffic with their mobile phones. For example, both move around, sometimes traveling long distances, and they transmit large volumes of data. In this scenario, traffic volume per subscriber requires a high-processing front end with a small database in the backend. In a third example, smart meters, which generate low-traffic volume but need more capacity in its databases.


As CSPs shift to subscriber-centric models that are less network dependent, SDM is gradually taking the role as the “brain of service.”  As such, it’s more critical than ever to provide top-level availability, openness, flexibility, and scalability.


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About the Author


Oded manages Go-To-Market enablement and Solution Marketing for HPE’s Communication Services Business (CSB), His focus is solutions of Subscriber Awareness that allow CSPs to evolve to Customer Centric service delivery, Oded is responsible for bringing together Products, Business, Operations, Sales and Marketing into a coherent Go-To-Market Strategy, across all regions, counties and market segments.

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