You need a robust signaling solution in 5G too!
I live and breathe signaling. To me signaling is the heart and soul of any network. Without signaling, a network is like a human body without brain. We have experienced the needs of efficient signaling solutions in 4G networks in the form of Diameter Signaling Controller (DA/DEA/DRA). The same is expected to continue with 5G and there’s no reasons why signaling requirements will be different for 5G. The need to have a robust signaling solution is extremely important to ensure communication between various network functions in any unexpected circumstances.
5G has become reality in 2019, and the technology adoption around the globe has been much faster than expected. While in the last couple of years most operators primarily focused on deploying 3GPP NSA (Non-stand alone, also called 5G EPC) in 2019 we see that most Tier1 operators are now seriously considering and planning the SA (Stand Alone) option.
The reason I mention NSA and SA options is to differentiate between respective network architectures from signaling perspective. While the NSA option continues to use Diameter protocol in the core network as in 4G, the SA option introduces a new Services Based Architecture (SBA) that uses HTTP/2 protocol for communication between various network functions.
Before I discuss what to expect for 5G, lets me first summarize what I believe are the major challenges for communication service providers.
The 5G challenges for CSP’s
Cloud native based new SBA architecture is fantastic and brings some unprecedented benefits. But does this solve all the signaling related issues that service providers have today? Probably not! Signaling related concerns for 5G are similar to the concerns in today’s 4G networks. Let me summarize them here:
Handling overload and signaling peaks
Every time I talk to customers, the first question they ask is how overload, failover and signaling peaks will be handled in 5G networks. How do they maximize network throughput under overload situations?
These are very valid concerns because CSP’s have already experienced these issues in their existing EPC networks (4G). This won’t be different for 5G, as overload situations can happen any time, in any network. It can be argued that, being cloud native, 5G Core network functions may scale faster than virtual machine based network functions to cater to the sudden increase in signaling traffic, but it remains to be seen whether scale out is faster than signaling peaks. Nonetheless, this is an acknowledged challenge for several CSP’s.
Network security concerns are another big challenge. There have been several incidents where service providers have reported that their network was attacked, and critical information was stolen, destroyed or services were made unavailable. The biggest challenge here is securing roaming interfaces which are primary sources for attacks and are outside control of CSP’s. Similar to 4G, this is applicable to 5G networks too.
Despite the fact that standards have strongly emphasized security in 5GC architecture such as mandatory use of TLS (Transport Layer Security), we cannot overlook the use of internet-based HTTP protocol in the core network. The HTTP protocol is widely used online and has been used for decades. Hackers know the ins and outs of this protocol and are able to organize advanced attacks. Most telecom networks are closed networks, built on trust and are probably not sufficient to handle advanced attacks that originate outside their networks.
Networks are becoming increasingly complex. With the introduction of 5G, there will be three signaling networks to manage in parallel: SS7, Diameter and HTTP. This results in additional costs to build and manage the overall network, which is a big challenge for CSP’s - firstly because ARPU constantly decreases, and secondly OPEX/CAPEX increases. CSPs therefore need a unified signaling solution that can help reduce their expenses to bring down operational efficiencies and stay competitive.
We now know the challenges, what’s the solution?
The different challenges described above are addressed in different 3GPP releases. 3GPP release 15 focuses on the support of session binding and 5G roaming. In the 3GPP Rel. 16 the additional need for signaling robustness concept is taken care of by the Service Communication Proxy:
- Binding support function (Rel-15)
- Security Edge Protection Proxy (Rel-15)
- Service communication Proxy (Rel-16)
Binding Support Function (BSF)
BSF is quite similar to what we call Diameter Routing Agent (DRA) in 4G. This function is mainly responsible for binding various sessions that originate on different interfaces in the network but share common criteria, for example sessions belonging to the same subscriber. As we see in 4G, DRA becomes mandatory as soon as you have two servers (PCRFs/OCCs/AAAs) in the network. Similarly, you need a BSF as soon as you have two or more PCFs and a binding use case - either Voice over NR or an AF/NEF interaction. It’s here we see that BSF also enables scalable policy solution. Without BSF, you can´t scale your policy/charging (PCF/CHF) network.
In addition, BSF also enables session correlation between Diameter and HTTP/2. We know that IMS will continue to be the voice engine for 5G too, as it has no plans to introduce SBA in near future i.e. it will still use diameter protocol. For example, a 5G subscriber who wants to make voice calls, will initiate the voice session on diameter but it must be connected to the same PCF which was previously selected while creating an N7 session over HTTP/2 in 5GC. BSF will correlate between diameter and HTTP/2 sessions and bind them to select the same PCF instance.
Security Edge Protection Proxy (SEPP)
As I mentioned earlier, CSP´s concerns about security continue to grow for 5G. In addition to roaming threats, 5G poses even greater threats to CSPs networks due to the growing IoT space. SEPP in 5G will be playing quite a similar role as DEA does in 4G. It sits on the edge of the network protecting the CSP´s network from threats originating from roaming partners and IPX providers.
Similar to DEA in 4G, it performs centralized roaming partner management, topology hiding, and throttling traffic over an agreed limit with roaming partners to name a few.
What is different with SEPP is that it also supports security procedures, certificate exchange and application layer security. In summary, you’ll need SEPP as soon as you need to connect your network to roaming partner networks.
Service Communication Proxy
Service Communication Proxy (SCP) is one of the most important pieces of the the 5G core netword. This network function is quite similar to Diameter Agent in 4G (complemented with some NRF functionalities) , which sits in the middle of the network and performs crucial functions. Such crucial functions are network topology simplification by signaling aggregation and routing, load balancing/load distribution, overload handling, message parameters harmonization to ease multi-vendor integration, message prioritization to increase network throughput under overload situations and signaling peak protection to mention a few.
The fact that signaling flows pass through SCP makes it even more significant. Since it has the complete network view (obtained from NRF) which can be used to take several actions, such as failover as and when needed. It enables end-to-end signaling tracing and central monitoring, which makes network-wide troubleshooting much easier.
Even though SCP is not mandatory in 3GPP architecture (Rel16 option C), it is one of the most important function (complemented by NRF) to bring robustness in the 5G core network. We’ve seen with 4G regarding how DSC adds value to the overall network. There are practically no service providers in the world without a DSC. Similarly, all 5GC networks are expected to have SCP.
How to achieve operational efficiency?
We now know that from a functionality perspective, we have quite similar signaling requirements in 5GC as we do in 4G EPC/IMS/VoLTE/Charging. Despite new SBA architecture, most use cases like roaming, session binding and central signaling node remain applicable for 5G. This is also one of the reasons why signaling solutions for 5G are extremely important.
But wait - We mentioned an important challenge of operational efficiency earlier in this blog post. Even though we have all the required signaling functions available in 5G, we can’t overlook the fact that these will add up to the number of nodes/VNFs in the network. This also means they need to be integrated and managed along with diameter functions, which results in additional operational costs to the service provider.
What is a dual-mode core and how does it support 5G signaling?
Dual-mode 5G Core is our offering to build 5G core networks, combining in the same software platform all EPC and 5GC network functions for a smooth migration into 5G, while bringing more operational efficiency to the network. It introduces a single piece of software which takes care of all the signaling needs of the CSP. It’s vital to implement a dual mode signaling solution in the network to increase operational efficiency and reduce complexity in the network. If you have separate 4G and 5G functions, you’ll need to maintain separate lifecycles (including installation, SW upgrades and patches). This is time consuming and costly. A dual-mode core solution enables to reduce the time to market for new services, and to manage TCO with efficiency during the migration to 5G.
Read more in the dual-mode 5G Core solution brief
Signaling requirements, challenges and use cases in 5G are quite similar to that of 4G networks. Service providers need to seriously consider introducing these signaling functions (SCP, BSF and SEPP) to 5GC right from the beginning, along with other main network functions defined in 3GPP SBA architecture. This will help CSP’s to build a strong foundation of future-proof robust 5G core networks.
Want to know more?
Read the latest white paper "Indirect communication for service-based architecture in 5G core"
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