The UK is expecting to roll out the first 5G networks in 2020, with the city of Glasgow recently announcing its hopes to become the UK’s testbed for the technology. Many anticipate a boost for businesses and services as a result of 5G, and everywhere you look, pressure is intensifying on service providers to scale and secure their networks.

Changes to the European Union’s roaming regulations and raised awareness of security risks are fueling dramatic increases in GPRS Tunneling Protocol (GTP) traffic.

GTP is not a historical relic yet. It is still shaping the evolutionary direction and eventual functionality of 5G. Harness it correctly and consumer expectations for quality of service will be met. Drop the ball and you’ll soon be in trouble. Roaming behavior is changing, and as a result, GRX/IPX carriers need to be prepared to adapt roaming traffic accordingly to meet demand.

Looking at Ericsson’s data on mobile data and traffic, data growth follows a steady pattern between 2012 to 2016. However, that begins to change in 2017 – largely driven by consumers using their phones in the home more regularly, opting for 4G or WiFi. Last year’s sharp rise in mobile data growth will only continue with the introduction of 5G. The increased reliability and speed provided by 4G makes it a more popular choice while using mobile devices. Especially with more devices sharing and being connected to the home WiFi – smart TVs, voice assistants, and the plethora of other smart appliances making their way into the home.

Easy as GTP

5G – Kārlis Dambrāns

As ever, service providers are locked in a race to satisfy increasingly data-hungry consumers while maintaining network performance. More than ever before, this is creating a need to correlate GTP control and data traffic on a per-subscriber level.

Essentially, GTP is a network protocol that enables packet networks to signal and carry data between devices and applications. Originally GTP was used for GPRS (so-called 2.5G) networks. Today, accelerating GTP tunnels and offloading GTP data traffic is critical to the performance of 3G and 4G networks, as well as Internet of Things (IoT) and M2M traffic management and load balancing in the core network.

GTP is also used between other nodes, including Voice-over-WiFi-related evolved Packet Data Gateway (ePDG) scenarios. In addition, it is the basis for the emerging Packet Forwarding Control Plane (PFCP), a 5G-focused protocol. ePDG controls the border between the mobile core and the public internet.

Indeed, the rise in data usage has left many considering whether voice will continue to play a role for service provider’s business models, but the reality is that voice continues to contribute to almost half of the revenues generated by mobile operators worldwide. To deliver the experience consumers demand for voice services, 5G coverage will need to be ubiquitous.

The 3GPP Release 14 Specification on Control Plane User Plane (CUPS) allows service providers to scale the control plane and user plane independently. Flexibility in network deployment and operation is enabled because providers can deploy additional user plane resources to meet unpredictable growth, without the need to do the same for the control place. Thus, the functionality of the existing nodes is not affected when extra deployments are sent to one but not the other.

A Service Based Architecture will be introduced with 5G to accommodate the changing environment and faster growth of data. These protocols will be API-based; the clearly defined methods of communication set out between APIs (Application Programming Interface) makes for easier development because code generators, security mechanisms and programming tools and libraries are make readily available.

It’s important to note that User Plane Traffic (UPT) will remain largely untouched and GTP will maintain the same role as it has with 4G. However, the control plane will see a number of changes. The various interfaces of the new 5G Core Network are demonstrated in the diagram below. Most will remain HTTP/2 based, but the indicated green interfaces (N3 and N9) in the below diagram will change to respectively sit between the (R)AN and the User Plane Function (UPF), as well as between one UPF to the other.

Security challenges

Recently, the GSMA has raised awareness of security vulnerabilities as the native GTP protocol lacks strong, built-in security mechanisms. Various protocols have been investigated by the GSMA Fraud Security group and the resulting FS.20 document (entitled GTP Security) currently acts as guideline for GSMA members. An example demonstrated by Karsten Nohl and Luca Melette at Chaos Communication Camp 2015 revealed the ease with which GTP can be hacked – warning the industry of the fraud and privacy risks for the information exchanged between different mobile networks, completely hidden from users.

The most common GTP security issues include confidential data disclosures, denial of service, network overloads and a range of fraud activities. Prevention depends on circumstance but, as a minimum, solutions that provide full traffic visibility and an all-encompassing Distributed Denial of Service (DDoS) protection should be in place.

Smart routing

Another key challenge is to effectively route and distinguish between GTP traffic. A subscriber’s traffic will differ wildly from that destined for mobile virtual network operators (MVNO) or a network slice dedicated to IoT. Charting a course for GTP traffic is usually based on the content of GTP messages (GTP Information Elements) and also – but not limited to – other aspects like source and destination. A smart GTP routing function can select the right Packet Gateway (PGW) or network slice that best suits a specific service.

Fortunately, existing technology is capable of harnessing advanced routing, proxy and security functionalities while being able to access GTP Information Elements. There are over 100 types of these, which include APN, IP Address, MS-ISDN, RAT Type, PDN Type (v4/v6), user location info, aggregate max bit rate and quality of service. If, say, a terminal wants web access, it can select the Internet APN, which is conveyed via GTP. It then allows the network to select the right, or best available, PGW to route the traffic towards the Internet. It is also possible to support various GTP Proxy cases such as routing MVNO and a service provider’s own traffic to different destinations using the same APN.

GTP is going nowhere and it is vital that service providers grasp how to optimize’s its capabilities in both the present and the imminent era of 5G. It is a cutthroat industry out there. Customers don’t hang around for long if services fall short and their traffic is delayed.

Peter Nas is senior solution architect at F5 Networks