Tomado de wikipedia:
The Back-to-Back User Agent (B2BUA) acts as a user agent to both ends of a Session Initiation Protocol (SIP) call. The B2BUA is responsible for handling all SIP signalling between both ends of the call, from call establishment to termination. Each call is tracked from beginning to end, allowing the operators of the B2BUA to offer value-added features to the call.
To SIP clients, the B2BUA acts as a User Agent server on one side and as a User Agent client on the other (back-to-back) side. The basic implementation of a B2BUA is defined in RFC 3261. The B2BUA may provide the following functionalities:
- call management (billing, automatic call disconnection, call transfer, etc.)
- network interworking (perhaps with protocol adaptation)
- hiding of network internals (private addresses, network topology, etc.)
- codec translation between two call legs
Because it maintains call state for all SIP calls it handles, failure of a B2BUA affects all these calls. Often, B2BUAs also terminate and bridge the media streams to have full control over the whole session.
A Signaling gateway, part of a Session Border Controller, or Asterisk PBX are good examples of a B2BUA.
http://www.b2bua.org/
About Sippy B2BUA
The B2BUA is a SIP call controlling component. Unlike a SIP proxy server, which only maintains transaction state, the B2BUA maintains complete call state and participates in all call requests. For this reason it can perform number of functions that are not possible to implement using SIP proxy, such as for example accurate call accounting, pre-paid rating and billing, fail over call routing etc. Unlike PBX-type solutions such as Asterisk for example, the B2BUA doesn’t perform any media relaying or processing, therefore it doesn’t introduce any additional packet loss, delay or jitter into the media path.
Logically, it consts of two independent signalling SIP UA connected by the call control logic.
Features
- 5,000-10,000 simultaneous sessions per server;
- 150-200 calls/second per server;
- Realtime calls control and call data records (CDRs) generation;
- Optional ability to use Sippy RTPproxy for media relaying;
- Optional ability to perform Cisco-compatible RADIUS AAA (Authentication, Authorization and Accounting);
- RFC3261 compliance;
- Seamless compatibility with majority of popular SIP software and hardware on the market today;
- Robustness and Resilience;
- Simple and clean, yet flexible, internal design making implementing new features and services easy;
- B2BUA could be easily combined with other Open Source software, such as SIP Express Router to build complete softswitch solution.
Rendimiento de Asterisk como B2BUA SIP
En VentureVoIP esta este estudio sobre el rendimiento de Asterisk actuando como B2BUA SIP.
El estudio se realizó sobre un server con 2 procesadores Intel Xeon 5140 Dual Core a 2,33 GHz, con 4GB de RAM y Asterisk 1.4.11.
Con esta configuración, Asterisk soporta 1500 llamadas simultáneas sin transcoding y 400 llamadas simultáneas haciendo transcoding de g711 a g729.
El articulo esta: http://www.venturevoip.com/news.php?rssid=1887
Tambien me llamo la atencion esta pagina: http://developer.berlios.de/projects/b2bua/
Asterisk based SIP b2bua realization. It’s patched asterisk and some AGI script. Features: full vovida’s b2bua radius emulation, extended radius attributes, radius failover, LCR, Call failover, Codec based routing and other useful things.
- Development Status: 4 – Beta
- Environment: Console (Text Based)
- Intended Audience: Telecommunications Industry
- License: GNU General Public License (GPL)
- Natural Language: English
- Operating System: POSIX
- Programming Language: C, Perl
