Cisco Small Business Pro SPA9000 Administration Manual page 50

Configuring Your System for ITSP Interoperability
About the SPA9000 Voice System and SIP
SPA9000 Voice System Administration Guide
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Figure 1 SIP Requests and Responses for Internal Calls
SIP UA
2
4
RTP
3
1
SIP UA
Likewise, SIP requests and responses are exchanged to support outbound and
inbound calls that are handled through the ITSP service. In
SIP Proxy for Internet Calls,"
registered to the SPA9000. When UserA calls UserC, the SPA9000 directs the
request to the SIP proxy at the ITSP, which is then responsible for routing the
request to UserC. After the session is established, RTP is anchored by the
SPA9000.
Figure 2 SPA9000 as a SIP Proxy for Internet Calls
UserB
UserA
SPA9000
SIP Proxy with
media proxy enabled
manuals search engine
SIP Proxy
SIP Proxy
UserA and UserB are client stations that are
IP Router (firewall)
Hub/switch
Broadband modem
Internet (WAN)
Interface
3
SIP Proxy
Figure 2, "SPA9000 as a
UserC
Internet
ISP
ITSP
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