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proxy represents its own domain. As the name suggests, the proxy model assumes that
you are talking to a SIP proxy or session border controller, while the gateway model
assumes you are talking to a SIP user agent. However, the two models are quite similar.
As a general rule, use the gateway trunk first, and if you have an issue, try changing the
trunk type.
PSTN
Figure 4-5. Example of Outbound Proxy Trunk
Inbounds Calls
How the System Identifies a Trunk
When a new call comes into the system, the system must determine whether the call
is an internal extension or an outside call that is configured to a trunk. To do this, it
From
first looks at the
then from a registration trunk, it looks for a
Appendix B for information on the SIP INVITE). The
system when the trunk is registered (Figure 4-6). Although it is not a predefined SIP
parameter, the
line
the call is routed to.
Figure 4-6. Line Parameter in REGISTER Request of SIP Trace
SIP Gateway Trunk
SBC
field to see if it matches an extension. If it's not an extension,
parameter is used by many SIP implementations to identify where
Chapter 4: Trunks
line
parameter in the SIP INVITE (see
line
parameter is set by the
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