Clearwater is IMS in the Cloud. IMS (the IP Multimedia Subsystem) is the standards-based architecture that has been adopted by most large telcos as the basis of their IP-based voice, video and messaging services, replacing legacy circuit-switched systems and previous generation VoIP systems based on softswitching. Clearwater follows IMS architectural principles and supports all of the key standardized interfaces expected of an IMS core network. But unlike traditional implementations of IMS, Clearwater was designed from the ground up for the Cloud. By incorporating design patterns and open source software components that have been proven in many global Web applications, Clearwater achieves an unprecedented combination of massive scalability and exceptional cost-effectiveness. Project Clearwater is sponsored by Metaswitch Networks.
What does Clearwater do?
Clearwater provides SIP-based call control for voice and video communications and for SIP-based messaging applications. You can use Clearwater as a standalone solution for mass-market VoIP services, relying on its built-in set of basic calling features and standalone susbscriber database, or you can deploy Clearwater as an IMS core in conjunction with other elements such as Telephony Application Servers and a Home Subscriber Server.
When deployed as an IMS core, Clearwater does everything that you’d expect an IMS core to do, incorporating Proxy CSCF (Call Session Control Function), Interrogating CSCF and Serving CSCF, together with Breakout Gateway Control Function. Clearwater also includes a WebRTC gateway, and natively supports interworking between WebRTC clients and standard SIP-based clients, using SIP over WebSocket signaling.
What do I need to deploy Clearwater?
The standard Clearwater distribution is designed for fast deployment on Amazon Web Services. You can stand up a large-scale Clearwater deployment on AWS in a couple of hours using the scripts included in the distribution. Once you’re comfortable with how Clearwater works on AWS, you can adapt it for your own private cloud environment – or you could offer production services from a Clearwater deployment on AWS. Clearwater works with most standard SIP clients including desktop softphones such as Jitsi, mobile softphones such as Sipdroid and business phones such as Polycom Soundpoint.
How do I connect Clearwater to other networks?
A completely standalone Clearwater deployment will, of course, support communications only between and among clients connected to Clearwater. Most real-world deployments will require connectivity to other networks. Clearwater supports the standard IMS interfaces for interconnecting with other IMS networks and with SIP-based media gateways (such as the Metaswitch Universal Media Gateway) for interconnecting with the PSTN over circuit-switched trunks. When connecting Clearwater with other service providers over SIP trunks, a Session Border Controller such as the Metaswitch Perimeta SBC is recommended to provide security at the demarcation point.
What kinds of services can I offer with Clearwater?
Clearwater’s built-in TAS enables you to offer voice and video calling services, including basic calling features such as Call Forwarding, Call Barring and Caller ID / Privacy services. To offer more sophisticated services, you will need to connect additional network elements to Clearwater. For example, if you want to offer a multi-way calling feature, then you would need to connect a Media Resource Function element to Clearwater. You can use Clearwater to support Hosted PBX and other such rich telephony services with the aid of an external TAS such as Metaswitch’s MetaSphere Multimedia TAS. And you can use Clearwater as the IMS core to support 3GPP standard services such as Voice over LTE (VoLTE) with a suitable TAS and SCC-AS (Service Centralization and Continuity Application Server).
What does Clearwater cost to run?
Cost modelling of large scale Clearwater systems on Amazon AWS suggest that, for a typical user profile, average running costs for the signaling control plane and subscriber data storage functions of Clearwater should be less than 2 US cents per subscriber per year. Your mileage may vary. In particular, if you choose to deploy Media Relay or Media Resource Functions in the Cloud, then you may need to take additional bandwidth costs into account.
Is Clearwater suitable for Network Functions Virtualization?
Network Functions Virtualization or NFV is, without any doubt, the hottest topic in the telco network space right now. It’s an approach to building telco networks that moves away from proprietary boxes wherever possible to use software components running on industry-standard virtualized IT infrastructures. Over time, many telcos expect to run all their network functions operating at Layer 2 and above in an NFV environment, including IMS. Since Clearwater was designed from the ground up to run in virtualized environments and take full advantage of the flexibility of the Cloud, it is extremely well suited for NFV. Almost all of the ongoing trials of Clearwater with major network operators are closely associated with NFV-related initiatives.