A back-to-back user agent (B2BUA) is a logical network element in Session Initiation Protocol (SIP) applications.[1] SIP is a signaling protocol for managing multimedia Voice over Internet Protocol (VoIP) telephone calls. A back-to-back user agent operates between both end points of a communications session and divides the communication channel into two call legs, and mediates all SIP signaling between the endpoints of the session, from establishment to termination. As all control messages for each call flow through the B2BUA, a service provider may implement value-added features available during the call.
In the originating call leg, the B2BUA acts as a user agent server (UAS) and processes the request as a user agent client (UAC) to the destination end, handling the signaling between end points back-to-back. A B2BUA maintains complete state for the calls it handles. Each side of a B2BUA operates as a standard SIP user agent network element as specified in RFC 3261.
In addition to call management, a B2BUA may provide billing services, internetworking for protocol conversions, and hiding of network-internal topology and information.
B2BUAs are often implemented in media gateways to bridge the media streams, in addition to the signaling path, for full control over the session.
^RFC 3261, SIP: Session Initiation Protocol, IETF, The Internet Society (2002)
April 10, 2024
back, back, user, agent, back, back, user, agent, b2bua, logical, network, element, session, initiation, protocol, applications, signaling, protocol, managing, multimedia, voice, over, internet, protocol, voip, telephone, calls, back, back, user, agent, operat. A back to back user agent B2BUA is a logical network element in Session Initiation Protocol SIP applications 1 SIP is a signaling protocol for managing multimedia Voice over Internet Protocol VoIP telephone calls A back to back user agent operates between both end points of a communications session and divides the communication channel into two call legs and mediates all SIP signaling between the endpoints of the session from establishment to termination As all control messages for each call flow through the B2BUA a service provider may implement value added features available during the call In the originating call leg the B2BUA acts as a user agent server UAS and processes the request as a user agent client UAC to the destination end handling the signaling between end points back to back A B2BUA maintains complete state for the calls it handles Each side of a B2BUA operates as a standard SIP user agent network element as specified in RFC 3261 In addition to call management a B2BUA may provide billing services internetworking for protocol conversions and hiding of network internal topology and information B2BUAs are often implemented in media gateways to bridge the media streams in addition to the signaling path for full control over the session A signaling gateway part of a session border controller is an example of a B2BUA Call flow diagram editB2BUA Alice Server Bob INVITE F1 gt 100 Trying F2 lt INVITE F3 gt 100 Trying F4 lt 180 Ringing F5 180 Ringing F6 lt lt 200 OK F7 200 OK F8 lt lt ACK F9 ACK F10 gt gt RTP Media RTP Media lt gt lt gt BYE F11 gt BYE F12 200 OK F13 gt lt 200 OK F14 lt See also editReal time Transport ProtocolReferences edit RFC 3261 SIP Session Initiation Protocol IETF The Internet Society 2002 Retrieved from https en wikipedia org w index php title Back to back user agent amp oldid 1166068690, wikipedia, wiki, book, books, library,
