Flexisip

Product Overview

Flexisip is a complete, modular, and scalable SIP server that offers an easy-to-install solution for deploying your own SIP service. This out-of-the-box solution provides all the features required to run a SIP VoIP service, with a focus on interconnecting with Apple's and Google's push notification systems. Flexisip can be deployed in various scenarios, including cloud, embedded, and as a push gateway, making it an ideal choice for organizations looking to integrate SIP services into their existing infrastructure.

Main Features

Flexisip offers the following main features:

PROXY

• Transport protocols: SIP/UDP, SIP/TCP, and SIP/TLS
• Digest and TLS client certificate authentication
• Routing based on a registrar database or static route file, with forking
• Interconnected with push notifications systems for reliably notifying mobile apps of incoming calls or messages (including support for RFC8599 for the transmission of push notification information through REGISTER requests)
• "Store and forward" logic for SIP MESSAGE (IM) to deliver text messages when the recipient connects to the network
• NAT-aware with a built-in media relay module and ICE/STUN support for high-level event logging for activity monitoring
• Real-time statistics available through a command-line interface
• High availability and cluster mode for large deployments
• ExternalAuthentication, a proxy module that performs SIP request authentication based on the inputs of an external HTTP service

PRESENCE

• Manages SIP SUBSCRIBE and PUBLISH from client applications to:
  • Identify users of the service within the address book
  • Provide users with real-time presence status
• Offers a "Server known resource lists" feature that allows directly provisioning a Liblinphone-based client with a server-defined contact list, together with associated presence information

CONFERENCE (for group messaging and group calling)

• Entirely SIP-based solution
• Efficient management of groups and participants
• Multi-device support
• Notifications of group events (users joining or leaving, new admins, etc.)
• Can be integrated into an existing third-party server for more details, see our wiki

Implemented Standards

Flexisip supports the following standards:

• SIP, RFC 3261
• An Extension to the Session Initiation Protocol (SIP), RFC 3581 (use of rport parameter)
• A Session Initiation Protocol (SIP) Event Package for Registrations, RFC 3680
• Extension Header Field for Registering Non-Adjacent Contacts, RFC3327
• Managing Client-Initiated Connections in the Session Initiation Protocol (+sip.instance parameter), RFC 5626
• Connection reuse in the Session Initiation Protocol (alias parameter), RFC 5923
• GRUUs; RFC 5627
• Push Notification with the Session Initiation Protocol (SIP), RFC 8599