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Flexisip

A complete, modular and scalable SIP server, includes a push gateway, to deliver SIP incoming calls or text messages on mobile device platforms where push notifications are required to receive information when the app is not active in the foreground.

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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