B2BUA
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Back-to-back user agent. A B2BUA is a SIP user agent to both
ends of a SIP call. That is, it both establishes and terminates a
call. In the TISPAN model, the B2BUA provides the application functions
(AF).
In the IMSG, the BSG acts as a B2BUA.
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BGF
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Border gateway function. Resides in the transport layer and
polices and enforces traffic flows based on instructions from the
SPDF.
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BSG
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Border signalling gateway. The BSG controls VoIP media resources
on the router and is responsible for all SIP processing. The border
signalling gateway provides a full B2BUA implementation and an embedded
SPDF.
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Dialog
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A peer-to-peer SIP relationship between two user agents that
persists for some time.
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Gq’
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Interface between the AF (in the IMSG, this is the B2BUA) and
the SPDF that is used to exchange session-based policy setup information
between the SPDF and the AF.
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Ia
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A profile of the interface between an SPDF and the BGF.
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SIP
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Session Initiation Protocol.
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SPDF
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Service policy decision function. The BSG contains an embedded
SPDF that controls the instructions that the BSG sends to the BGF.
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