Asterisk – Open Source PBX

Asterisk는 PBX 기본 및 그 이상의 기능을 Linux 혹은 MacOSX 상에서 구현한 Software이다. 많은 VoIP 프로토콜을 지원하고 있으며 업계 표준 규격을 모두 따르고 있다.

The Asterisk core module

• PBX switch – 많은 유저와 자동 기능들 사이에서의 교환기 역할을 해주는 Core 모듈
• Application Launcher – 음성사서함, 자동음악연주, 디렉토리 목록등 유저 부가 서비스 모듈
• Codec Translator – 통신표준에 맞는 다양한 사운드 포맷/코덱 지원
• Scheduler and I/O manager – 분산처리및 low-level에서의 scheduling

상용 제품에 버금가는 기능으로 호처리기능, CTI기능, 확장성, 코덱, 프로토콜, CTI호환, PRI호환에 대해서는 아래와 같다.

Call Features

• ADSI On-Screen Menu System
• Alarm Receiver
• Append Message
• Authentication
• Automated Attendant
• Blacklists
• Blind Transfer
• Call Detail Records
• Call Forward on Busy
• Call Forward on No Answer
• Call Forward Variable
• Call Monitoring
• Call Parking
• Call Queuing
• Call Recording
• Call Retrieval
• Call Routing (DID & ANI)
• Call Snooping
• Call Transfer
• Call Waiting
• Caller ID
• Caller ID Blocking
• Caller ID on Call Waiting
• Calling Cards
• Conference Bridging
• Database Store / Retrieve
• Database Integration
• Dial by Name
• Direct Inward System Access
• Distinctive Ring
• Distributed Universal Number Discovery (DUNDi™)
• Do Not Disturb
• E911
• ENUM
• Fax Transmit and Receive (3rd Party OSS Package)
• Flexible Extension Logic
• Interactive Directory Listing
• Interactive Voice Response (IVR)
• Local and Remote Call Agents
• Macros
• Music On Hold
• Music On Transfer
  • Flexible Mp3-based System
  • Random or Linear Play
  • Volume Control
• Predictive Dialer
• Privacy
• Open Settlement Protocol (OSP)
• Overhead Paging
• Protocol Conversion
• Remote Call Pickup
• Remote Office Support
• Roaming Extensions
• Route by Caller ID
• SMS Messaging
• Spell / Say
• Streaming Media Access
• Supervised Transfer
• Talk Detection
• Text-to-Speech (via Festival)
• Three-way Calling
• Time and Date
• Transcoding
• Trunking
• VoIP Gateways
• Voicemail
  • Visual Indicator for Message Waiting
  • Stutter Dialtone for Message Waiting
  • Voicemail to email
  • Voicemail Groups
  • Web Voicemail Interface
• Zapateller

Computer-Telephony Integration

• AGI (Asterisk Gateway Interface)
• Graphical Call Manager
• Outbound Call Spooling
• Predictive Dialer
• TCP/IP Management Interface

Scalability

• TDMoE (Time Division Multiplex over Ethernet)
  • Allows direct connection of Asterisk PBX
  • Zero latency
  • Uses commodity Ethernet hardware
• Voice-over IP
  • Allows for integration of physically separate installations
  • Uses commonly deployed data connections
  • Allows a unified dialplan across multiple offices

Codecs

• ADPCM
• G.711 (A-Law & μ-Law)
• G.723.1 (pass through)
• G.726
• G.729 (through purchase of commercial license through Digium)
• GSM
• iLBC
• Linear
• LPC-10
• Speex

Protocols

• IAX™ (Inter-Asterisk Exchange)
• H.323
• SIP (Session Initiation Protocol)
• MGCP (Media Gateway Control Protocol
• SCCP (Cisco® Skinny®)

Traditional Telephony Interoperability

• E&M
• E&M Wink
• Feature Group D
• FXS
• FXO
• GR-303
• Loopstart
• Groundstart
• Kewlstart
• MF and DTMF support
• Robbed-bit Signaling (RBS) Types
• MFC-R2 (Not supported by Digium. However, a patch is available at Voip-info.org)

PRI Protocols

• 4ESS
• BRI (ISDN4Linux)
• DMS100
• EuroISDN
• Lucent 5E
• National ISDN2
• NFAS

VoIP기능 및 특히 H.323, SIP, MGCP, SCCP 프로토콜 스택이 다 포함되어 있고, ADPCM, G.711, G.723.1, G.726, G.729, GSM, iLBC, Linear, LPC-10, Speex Codec을 다 지원한다. Open Source이니 해당 부분의 처리 로직도 확인할수 있다.

Asterisk : http://www.asterisk.org/