Kamailio top-notch SIP Server ( Former OpenSIR )

Combining its SIP core capabilities and extensible APIs, building VoIP and Unified Communication Platforms using Kamailio (K) is straightforward.

Some of the features that Kamailio offers:

• Robust and Performant SIP (RFC3261) Server flavours
  • Registrar server
  • Location server
  • Proxy server
  • SIP Application server
  • Redirect server
• Flexibility
  • small footprint – suitable for embedded devices – the binary file is small size, functionality can be stripped/added via modules
  • plug&play module interface – ability to add new extensions, without touching the core, therefore assuring a great stability of core components
  • modular architecture – core, internal libraries and module interface to extend the server’s functionality
  • impressive extension repository – overall 150 modules are included in the Kamailio source tree
• SIP Routing Capabilities
  • stateless and transactional stateful SIP Proxy processing
  • serial and parallel forking
  • NAT traversal support for SIP and RTP traffic
  • load balancing with many distribution algorithms and failover support
  • flexible least cost routing
  • routing failover
  • replication for High Availability (HA)
    
• Transport Layers
  • support for communication via UDP, TCP, TLS and SCTP
  • IPv4 and IPv6
  • transport layer gatewaying (IPv4 to IPv6, UDP to TLS, a.s.o.)
  • SCTP multi-homing and multi-streaming
    
• Asynchronous Processing
  • asynchronous TCP handling
  • asynchronous SIP message processing
  • asynchronous inter-process message queues communication system
• Secure Communication
  • Digest SIP User authentication
  • Authorization via ACL or group membership
  • IP and Network authentication
  • TLS support for SIP signaling
  • transparent handling of SRTP for secure audio
  • TLS domain name extension support
  • authentication and authorization against database (MySQL, PostgreSQL, UnixODBC, BerkeleyDB, Oracle, text files), RADIUS and DIAMETER
• IP and DNS
  
  • support for SRV and NAPTR DNS lookups
  • SRV DNS failover
  • ENUM support
  • internal DNS caching system – avoid DNS blocking
  • IP level Blacklists
  • multi-homed and multi-domain support
  • topology hiding – hide IP addresses in SIP headers to protect your network architecture
• Accounting
  • event based accounting
  • configurable accounting data details
  • multi-leg call accounting
  • storage to database, Radius or Diameter
    
• Configuration File
  • scripting language for configurations file. With a syntax similar to scripting languages, the configuration offers a powerful and flexible way to deploy custom SIP services.
  • pseudo-variables to access and manage parts of the SIP messages and attributes specific to users and server
  • transformations to modify existing pseudo-variables, accessing only the wanted parts of the information
  • over 1000 parameters, variables and functions exported to config file
  • runtime update framework – to avoid restarting the SIP server when needing to change the config parameters
• External Interaction via
  • text-based management interface via FIFO file, udp, xmlrpc and unix sockets
  • RPC control interface – via XMLRPC, UDP or TCP
• Rich Communication Services
  
  • SIP SIMPLE Presence Server (rich presence)
  • Presence User Agent
  • XCAP support
  • Presence DialogInfo support – SLA/BLA
  • Instant Messaging
    
• Monitoring and Troubleshooting
  • SNMP – interface to Simple Network Management Protocol
  • config file step-by-step debugger
  • remote control via XMLRPC
  • internal statistics exported via RPC and SNMP
  • flexible debug and error message logging system – log custom messages including any header or pseudo-variable and parts of SIP message structure.
• Extensibility APIs
  • Perl Programming Interface – embed your extensions written in Perl
  • Java SIP Servlet Application Interface – write Java SIP Servlets to extent your VoIP services and integrate with web services
  • Lua Programming Interface
  • Python Programming Interface
• Multiple Database Backends
  • (MySQL, PostgreSQL, UnixODBC, BerkeleyDB, Oracle, text files) and other database types which have unixodbc drivers
  • connections pool
  • different backends can be used at same time (e.g., accounting to Oracle and authorization against MySQL)
• Interconnectivity
  • straightforward interconnection with PSTN gateways
  • gateway to sms or xmpp and other IM services
  • interoperability with SIP enabled devices and applications such as SIP phones (Snom, Cisco, etc.), Media Servers (Asterisk, FreeSwitch, etc.)
    
• Miscellaneous
  • CPL – Call Processing Language (RFC3880)
  • Internal generic caching system
  • Memcached connector
  • CLI – kamctl and sercmd
  • Web Management Interface: Siremis
• Extensive documentation for both administrators and developers

Scalability:

• Kamailio can run on embedded systems, with limited resources – the performances can be up to hundreds of call setups per second
• used as load balancer in stateless mode, Kamailio can handle over 5000 call setups per second
• on systems with 4GB memory, Kamailio can serve a population over 300,000 online subscribers
• System can easily scale by adding more Kamailio servers
• Kamailio can be used in geographic distributed VoIP platforms
• Kamailio least-cost-routing scales up to millions of routing rules
• straightforward failover and redundancy