As communications service providers (CSPs) continue to build and deploy 4G LTE networks, they are finding that they need to understand some critical concepts as they move from circuit switched 2G and 3G networks to all IP packet switched networks. Of these, IP security rides high on that list of technologies to master. The Internet has become an open environment susceptible to malicious activity. If your assets are not secured, you are guaranteed to be attacked and compromised by one or more unscrupulous organisations.
They may do it for financial gain, selling the stolen data to parties, as a paid service, for your competitors to disrupt your business, or even just for personal enjoyment because they found that they could compromise your infrastructure. We may not use resources such as the M61 Vulcan shown in the picture, it is important to develop and implement the proper security tools to protect the latest wireless networks.
Growth in the Data Plane
While many CSPs already have solutions in place to protect parts of the packet data network (PDN) infrastructure, they often do not understand how the implementation of a 4G LTE network architecture changes the security requirements. The S/Gi interface, or the part of the network connecting the mobile subscribers to the Internet will have a significant increase in data volumes as more LTE enabled mobile devices are used. In addition, with the increased speeds available, we expect to see 4G wireless technologies competing with fixed-line data services such as DSL and cable. This will change the type of content seen and the mobile CSP will need to develop enhanced policies to manage and secure these services.
Another concern is that LTE expects the mobile devices to be IPv6 enabled, while much of the PDN is still expected to be using IPv4 technologies for some time. This requires the ability to translate IPv6 addresses to IPv4 addresses using a carrier-grade NAT (CGNAT) technology, while maintaining a proper security infrastructure. This includes the ability to protect the pool of IPv4 addresses being used in the CGNAT solution and all of the devices’ communications being translated.
Packets in the Control Plane
More significantly, the control plane of the LTE network will change from a circuit-switched network to an IP-based architecture. Diameter, SIP and DNS are the primary protocols that will be used to manage the control plane as the CSPs start implementing voice over LTE (VoLTE). Securing and managing this infrastructure will be critical to the services delivered to the subscribers and protecting their privacy. The Home Subscriber Service (HSS) and Policy Charging and Rules Function (PCRF) depend on Diameter, an open standardised protocol used on IP networks, while the Call Session and Control Function (CSCF) systems and Application Servers (AS) within the IP Multimedia Subsystem (IMS) utilise another public standardised communication technology called Session Initiation Protocol (SIP).
Figure 1. The complexity of the IMS network architecture
It is important to note that third-party applications developed by independent people in addition to the subscribers and their LTE device will have direct access to the IMS network components through the SIP protocol. This means that potential malicious or poor programming will have the ability to directly affect and access the control plane of the LTE network and be able to disrupt it or obtain unauthorised access to private information such as subscriber profiles, unless proper security measures are put in place.
The CSPs need to understand the implications of migrating to an IP network infrastructure and how the packet-based network must be managed significantly differently from the legacy circuit-switched environment. Proper planning and testing is required to successfully build a robust and secure 4G LTE network. It is important to leverage the existing work done on IP networks over the past 20 years, utilise the knowledge of your colleagues and vendors. Apply the proper availability and security practices learned from these resources to design the next generation wireless networks.