Asterisk (PBX)
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| Asterisk (PBX) | |
|---|---|
| Name | Asterisk |
| Developer | Digium |
| Released | 1999 |
| Operating system | Linux, FreeBSD, macOS |
| License | GNU General Public License |
Asterisk (PBX) is an open-source private branch exchange software platform that implements telephone switching and telephony features for voice over IP and traditional telephony. Initially created for small-business telephony, it has been adopted by enterprises, carriers, and embedded systems and is used alongside projects and organizations in the telecommunications ecosystem such as SIP, VoIP, PSTN, FreeSWITCH, and OpenSIPS. The project has ties to companies and communities including Digium, Sangoma Technologies, Asterisk Project, AsteriskCon, and various standards bodies such as the IETF and the 3GPP.
History
Asterisk was started in 1999 by Mark Spencer at Digium as a flexible alternative to proprietary systems used by companies like Nortel Networks and Avaya. Over time its roadmap intersected with milestones and entities such as asterisk@lists.digium.com mailing lists, events like LinuxWorld and FOSDEM, and standards work at the IETF including sessions on Session Initiation Protocol and codecs such as G.711. The project evolved through major versions and governance changes influenced by organizations including Sangoma Technologies and participation from contributors affiliated with Cisco Systems, Red Hat, Canonical (company), and academic groups. Asterisk’s growth paralleled adoption by service providers represented at conferences such as ITU Telecom World and Mobile World Congress.
Architecture and components
Asterisk’s architecture centers on a modular core implemented in C and runs primarily on Unix-like systems such as Linux, FreeBSD, and distributions maintained by Debian, Ubuntu (operating system), and CentOS. Key components include channel drivers for interfaces like SIP, IAX, and PSTN gateways produced by suppliers such as Digium (company), media processing modules that interoperate with codecs like G.729 and Opus (audio format), and application modules that implement dialplan logic used by deployments at organizations such as NGN, CLEC, and enterprise sites of IBM and HP. Integration points include backends and databases such as MySQL, PostgreSQL, LDAP, and billing platforms similar to those from Amdocs and Oracle Corporation.
Features and capabilities
Asterisk offers call control, conferencing, voicemail, interactive voice response (IVR), call recording, and media bridging used in deployments by carriers like Level 3 Communications and hosted providers like Skype-era integrations. Feature sets include support for protocols and standards such as SIP, IAX2, RTP, RTCP, and codecs including G.729, G.711, and Opus (audio format), enabling interoperability with equipment from Polycom, Yealink, Grandstream, and Cisco Systems. Asterisk also supports features leveraged in contact centers and enterprises—automatic call distribution (ACD), skills-based routing, and integration with CRM systems like Salesforce, SugarCRM, and Microsoft Dynamics.
Configuration and administration
Configuration is typically file-based using dialplan syntax and configuration files managed on systems from vendors like Dell, Hewlett-Packard, and virtualized on platforms such as VMware ESXi and KVM; administrators often use management tools developed by projects and companies such as FreePBX, Issabel, Elastix, and AsteriskNOW. Administrative tasks include provisioning endpoints from manufacturers like Yealink and Polycom, integrating with directory services such as Microsoft Active Directory, and automating deployment with orchestration tools from Ansible, Puppet (software), and Chef (software). Monitoring and logging integrate with observability stacks including Prometheus, Grafana, and logging systems from Splunk.
Security and compliance
Security practices for Asterisk deployments align with guidance from organizations such as CERT Coordination Center, OWASP, and regulatory frameworks including HIPAA and GDPR when handling call data records and media. Hardening includes TLS and SRTP for signaling and media negotiated under workstreams at the IETF, use of authentication tied to identity providers like Okta and Auth0, and perimeter controls interoperating with firewalls from pfSense and vendors such as Cisco Systems and Fortinet. Threat mitigation often references advisories from CVE entries and coordination with projects like OpenSSL and libreswan for cryptographic primitives.
Deployment and integrations
Asterisk is deployed in cloud and on-premises environments offered by providers like Amazon Web Services, Google Cloud Platform, and Microsoft Azure and is embedded in telephony appliances from manufacturers such as Sangoma Technologies and Grandstream. Integrations span SIP trunks from carriers like Twilio and Bandwidth (company), CRM connectors to Salesforce and Zendesk, and middleware such as Kamailio and OpenSIPS for large-scale routing. Enterprises integrate Asterisk with unified communications suites from Microsoft, contact center platforms influenced by Genesys, and telephony analytics solutions from NICE Systems and Verint Systems.
Community and licensing
The Asterisk community includes contributors affiliated with organizations such as Digium, Sangoma Technologies, Digium User Group, and conferences like Asterisk Community Conference and AsteriskCon. Licensing primarily follows the GNU General Public License for core components, with commercial modules and appliances available under proprietary terms from vendors such as Sangoma Technologies and third-party vendors, and ecosystem projects maintained by communities around FreePBX and Elastix. Development coordination occurs through code repositories and continuous integration systems used by projects like GitHub, GitLab, and community forums hosted by vendor and independent sites.