Originally published in TMCNet: Next Generation Communications on June 6, 2017 

As communications service providers (CSPs) build next generation networks, they’re challenged with managing many architectural design changes in the new network core as they integrate old and new signaling elements seamlessly. The two major signaling players that are leading the space are SS7 (Signaling System No. 7) and Diameter. We’ll take a look at both and all their potential facets and drawbacks.

SS7

SS7 has been around since 1975 and is a set of telephony signaling protocols used to set up and tear down most of the world’s PSTN telephone calls. It also performs number translation, local number portability, prepaid billing, Short Message Service (SMS), and other mass market services. Being a high-speed and high-performance packet-based communications protocol, SS7 can communicate significant amounts of information when setting up a call, during the call, and at the end of the call, which permits for rich call-related services.

In the past few years, SS7 has shown a resurgence of investments due to operators modernizing some of their older signaling infrastructure. But that ended in 2016 when the market started to decline again. We’re currently into the ‘long tail’ decline of the SS7 market.

Today, the acceleration of the deployment of Long-Term Evolution (LTE)/Evolved Packet Core (EPC), Voice over LTE (VoLTE) and IP Multimedia Subsystem (IMS) networks continues. All of these are defined using Session Initiation Protocol (SIP) and Diameter-based signaling as opposed to the legacy SS7 signaling associated with 2G/3G mobile networks.

The number of LTE subscribers continues to rapidly increase and mobile service providers must focus on new LTE/Evolved Packet Core (EPC) revenue-generating services. However, many mobile service providers also still have legacy SS7 networking equipment. Migrating to LTE/EPC and Diameter-based signaling networks will be key in order to offer new services to their customers while still addressing their legacy infrastructure.

Diameter Signaling

Diameter Signaling is a newer signaling protocol that enables communication among Internet protocol network elements. It can be thought of as the language that servers and software use to communicate within the core of the LTE network. As mentioned before, it’s been showing strong growth, as opposed to SS7. This is due growth in LTE traffic and in the number of network nodes within the core network that speak to each other using diameter signaling.

In 2016 the DSC market grew 33 percent year over year to $750M. We forecast that in 2017 the total Diameter Signaling Controller (DSC) market (product and services) will grow by an additional 53 percent to reach $1.1B as LTE and VoLTE deployments—and subscriptions—continue to grow. At the end of 2016, LTE subscriptions stood at 1.7B or 23 percent of the worldwide total, and because of that the DSC market grew by 33 percent to $750M. Therefore, we believe that the DSC market could have a very long and large growth potential. We forecast that in 2021, LTE subscriptions will amount to 4.2B, which is still just 48 percent of the worldwide total. The DSC market should reach $2.1B and will continue to be a vital one for the coming decade.

Virtualization

Spurred by increasing competition from over-the-top service providers like Apple, Facebook, Google and Skype, mobile operators have an urgent need to transition and adapt their networks. They must be able to quickly develop, deploy and monetize competing services as well as open their networks to new services that may originate from outside of the operator.

This need for ‘service agility’ for network operators is being enabled by the increasing maturity of Network Function Virtualization (NFV) technology whereby certain network nodes, including DSCs, will increasingly be virtualized. In other words, over time mobile network cores will look like more like the datacenters you would find at the OTT service providers, as opposed to more traditional central offices with many racks of purpose-built equipment. Currently, many DSCs are software products that run on third-party server hardware. Increasingly, virtualization features are being added to DSCs. For example, in many cases DSC capacity can be distributed and load-balanced across multiple servers.  In 2016, we saw about 10percent of the market was virtual and estimate that in 2021 that number will go up to 70percent.

However, operators are being very cautious about making any changes to their networks. They see the upgrade as not being worth the investment resulting in a slower uptake than we’re seeing from LTE, but signaling is well suited to be virtualized.

Security

One issue that affects both protocols is security, in many aspects of the carrier networks.

Vulnerabilities in SS7 were being publicly discussed as far back as 2008 with telecom engineers warning of possible risks for mobile operators and its associated risks to subscribers. At the heart of an operator’s network, SS7 contains highly important data such as a subscriber’s identity, status and location, providing the operator with the ability to manage communications and bill their subscribers for the services they use. Loopholes in the SS7 protocol can be exploited to allow criminals to listen in on conversations, monitor messages, determine a subscriber’s location, manipulate network and subscriber data, and generally disrupt services.

Recent research indicates that SS7 has been widely misused for gaining access to the core network. Several attacks have been carried out exploiting SS7 by malicious attackers and other unauthorized entities such as intelligence agencies. Some operators have moved to LTE and Diameter Signaling for enhanced security. While LTE and Diameter Signaling offer higher quality and resilient over the air security, they still require special security capabilities and features to secure the core network against attacks.

Mobile operators and the industry at large are increasingly beginning to take these issues very seriously. Under the lead of an international association, the GSMA, a group of leading mobile operators and telecom vendors have united to develop preventive measures and standardize the firewall to protect both SS7 and Diameter Signaling security and the consistency of signaling networks world-wide. In an approach designed to ensure the privacy of mobile communication, the majority of fraudulent scenarios have been researched and recommendations on increased network security have been issued. But all threats have still yet to be resolved.

5G

Many of the normative aspects of emerging 5G standards are still in development but early indications are that diameter will remain the signaling protocol for 5G networks.  Given that there will certainly be new functional entities within 5G networks that will need to communication both with each other and legacy nodes, diameter signaling controller will remain a vital function to facilitate and enable these communications, be responsible for security between nodes, and control for surges or ‘storms’ in signaling traffic.