4G and 5G signaling controllers: helping network nodes understand each other

July 26, 2022

4G and 5G signaling controllers: helping network nodes understand each other

Telecommunications is a world of standards. The signaling standards enable the network nodes to speak the same language, allowing them to communicate with each other to perform call control functions. Thanks to the standards, network nodes from different vendors can understand each other – isn’t that cool? Let’s talk about 4G and 5G signaling

The standards organizations like 3GPP or IETF are doing a great job, but we know that there is theory and there is reality. The reality is that the standards cannot cover all the interoperability scenarios, especially as some nodes do not work as expected – this may happen with nodes of the same vendor, not to mention with nodes of different vendors.

In the core of the 4G signaling network we have the Diameter Agent (DA), as the signaling transfer point handling the communication between Diameter clients and Diameter servers. The DA can perform message forwarding between clients and server as well as more complex functions, such as for example the Diameter Routing agent (DRA) or the Diameter Edge agent (DEA).

It’s of utmost importance for the communication service providers (CSPs) that the DAs can be integrated with all types of network nodes, so they can handle the end-to-end (E2E) communication between end-nodes in a multi-vendor network topology. This task can be divided into two areas:

  1. The first area is related to the Diameter requirement of establishing a permanent connection between the Diameter peers, which is a process called peering. The DA must meet the peer connectivity requirements so a Diameter connection can be established.
  2. The second area is related to traffic handling and E2E interoperability. When the clients and servers start talking between them, not always the communication is successful. A communication failure may be caused by a protocol misalignment, for example when a message element is not supported in some end node, or by some network situation, for example when an end node is not available. The DA must provide message manipulation and routing capabilities to handle the end-to-end communication requirements.

Talking about a live network, a challenging scenario for the DA integration is a swapping project, where an existing DA is replaced with another vendor DA. This type of project is extremely important for avoiding any impact on live traffic. The new DA must replicate the existing setup in the existing DA, allowing to migrate the live traffic in a smooth way without any impact in the service. The DSC capabilities for message processing and configuration provide customers the chance to have an optimal migration approach according to their network topology and legacy DA functionalities.

Ericsson’s signaling controllers have been deployed in more than 145 customer networks, integrated with all types of network nodes belonging to different Diameter interfaces and different vendors such as Ericsson, Nokia and Huawei. In many of these deployments there were the complex requirements of peering, message manipulation and routing.

Figure 1: Diameter Signaling Controller References

Figure 1: Diameter Signaling Controller References

The DSC adaptation to the network requirements has been proven in the customer delivery projects for peering and end-to-end traffic handling. Once the DSC is on live operation in the customer network, there have been several situations where the DSC has solved interoperability issues just by configuration. Without the DSC these issues would have required SW corrections in the end-nodes with the consequent cost of time and resources. Other key DSC characteristics in live operation are robustness and stability.

The DSC has demonstrated a high level of flexibility by combining peering parameters to meet the peer requirements. There have even been some specific cases when we developed functionality to support a specific requirement from another vendor’s node, as for example the Multiple FQDN feature.

The DSC has also demonstrated a high level of flexibility in the handling of the Diameter traffic. Firstly, with message processing capabilities that allow it to perform complex message manipulations as per the end-nodes requirements. Secondly, with routing capabilities that allow to handle complex routing scenarios.

Signaling controller: continuing the 4G success story with 5G

Now that networks are evolving to 5G, HTTP/2 is going to replace Diameter as the main 3GPP signaling protocol. The feature-rich and fast-developing 5G service-based architecture (SBA) becomes even more demanding regarding inhomogeneous protocol versions and numerous ‘protocol flavors’ of vendors. The Signaling Controller (SC) is the ideal man in the middle to close existing communication gaps, controlled at a central place in the core network.

The SC continues the success story of the DSC. Developed by the same team, it follows the same ways of working, having inherited DSC’s well-known, rock-solid signaling node design. This design enables network level load balancing, prioritization and fault-fencing and fault-fencing, to reliably protect producers from signaling peaks and overload while significantly simplifying the overall network topology and complexity.

The SC allows monitoring 5G SBA traffic through tapping towards north-bound probing and monitoring solutions such as Netscout® plus many more vendors relevant on the market. The SC helps to unify the probing interface on a network level by becoming independent from the non-aligned capabilities and probing protocols of different vendors’ consumers and producers.

Figure 2: Signaling Controller Microservices Architecture

Figure 2: Signaling Controller Microservices Architecture

Compared to the DSC, a main architectural change to the SC is that it’s been designed as cloud native application right from the start. SC can be deployed on any Kubernetes based datacenter, which is the future of multi-CNF and multi-vendor telecom platforms. Installation times shrink from days and hours to minutes and seconds – lifecycle management and ease of use have been pushed to the next level.

Our SC is a Dual Mode 5G Core (DMC) product supporting both 4G and 5G signaling. We are right now entering the integration phase for customers in the US and Europe for our cnDEA & cnDA. With the DMC we are supporting our customers to reduce complexity by providing e.g., the same O&M interface, Lifecycle Management (LCM) & Orchestration. Also, this offers great flexibility to decide how and when to migrate 4G signaling traffic from a physical or virtualized environment towards our future proof cloud native platform.

Figure 3: 5G Signaling Controller References

Figure 3: 5G Signaling Controller References

The SC entered the market in 2020, and today there’s 27 SC nodes serving live traffic in four 5G networks worldwide. This demonstrates SC’s capabilities as the ‘Swiss army knife’ for 5G signaling and roaming. The 5G journey has just started, but the SC has already demonstrated that it can successfully tackle the new challenges, – it’s definitely a product worth talking about!