Over The Top

Description

Over The Top (OTT) denotes service providers that deliver content, applications, and communications services directly to end-users via the public internet, using the internet access provided by telecommunications network operators. In the 3GPP context, OTT services are distinct from operator-managed IMS (IP Multimedia Subsystem) services like VoLTE. They run on top of the operator's IP transport layer (the 'dumb pipe') without the operator's involvement in service control, billing, or quality assurance for the application layer. Examples include Skype, WhatsApp, Netflix, and YouTube.

From an architectural perspective, the mobile network provides the underlying IP Connectivity Access Network (IP-CAN) – such as LTE or 5G NR data bearers – which offers best-effort internet access. The OTT service provider operates its own application servers in data centers or cloud platforms. The User Equipment (UE) runs a client application that establishes an encrypted connection (e.g., via TLS/HTTPS, WebRTC) directly to these OTT servers. The 3GPP core network (EPC or 5GC) is unaware of the specific OTT application; it merely routes IP packets between the UE and the internet. This contrasts with operator-managed services, where the core network elements (like P-CSCF in IMS) are deeply involved in session control and policy enforcement.

OTT services work by leveraging the standardized IP connectivity of mobile networks. The UE attaches to the network, establishes a Packet Data Network (PDN) connection or a Protocol Data Unit (PDU) Session with an Access Point Name (APN) for internet access, and receives an IP address. The OTT application on the device then uses this IP connectivity to communicate with its remote servers. Key differentiators are the lack of integration with 3GPP charging systems (using app-store or credit card billing instead) and typically no guaranteed Quality of Service (QoS) from the operator, though some operators offer sponsored data or QoS differentiation packages. 3GPP studies OTT impacts to understand traffic patterns, develop policy controls, and explore potential collaborations or new business models like edge computing partnerships.

Purpose & Motivation

The OTT phenomenon emerged due to the widespread adoption of IP-based mobile broadband (starting with HSPA and LTE), which provided sufficient bandwidth and always-on connectivity for rich internet applications. It solved the problem of service innovation being bottlenecked by slow operator development and deployment cycles. Entrepreneurs and tech companies could rapidly develop and globally deploy applications (like voice, video, messaging) directly to consumers without needing to negotiate with hundreds of operators worldwide or integrate into complex telecom signaling systems.

OTT services addressed limitations of traditional telecom services, which were often siloed, expensive (e.g., international SMS), and lacked rich features. They leveraged the internet's open, end-to-end principle and cloud scalability. For 3GPP, the rise of OTT created both challenges and opportunities. Challenges included declining revenues from legacy services (voice, SMS) and increased, unpredictable data traffic straining networks. Opportunities included increased data subscription demand and potential new roles for operators, such as providing enhanced connectivity (e.g., network slicing), edge hosting for OTT applications, or exposing network APIs (via NEF in 5G) for improved service quality.

3GPP began formally studying OTT in Release 12 to understand its technical and business impacts, leading to work on policy enhancements, traffic detection, and architectural evolutions like Service Capability Exposure that allow secure, standardized interaction between the network and OTT providers. This acknowledges that while OTT bypasses traditional service layers, collaboration can create value for both sides in the 5G era.

Key Features

• Services delivered independently over operator-provided internet access
• No integration with 3GPP service control or charging systems (e.g., IMS)
• Typically uses end-to-end encryption between the UE app and OTT servers
• Relies on best-effort IP transport unless enhanced by operator agreements
• Enables rapid, global service deployment without per-operator integration
• Drives high, variable data traffic on mobile networks

Evolution Across Releases

Defining Specifications