Chapter 3: Configuring The Spa9000 For Itsp Interoperability; About Lvs And Sip - Linksys SPA9000 Administration Manual

Configuring the SPA9000 for ITSP Interoperability
3
Configuring the SPA9000 for ITSP
Interoperability
This chapter provides configuration details for the purpose of helping you to ensure that your
infrastructure properly supports the LVS.
• "About LVS and SIP, " on page 39
• "Network Address Translation (NAT) and Voice over IP (VoIP), " on page 40
• "Firewalls and SIP, " on page 43
• "Configuring SIP Timer Values, " on page 44

About LVS and SIP

The LVS is implemented using open standards, such as Session Initiation Protocol (SIP), to help
ensure interoperation with all ITSPs that support SIP. This section provides information about
the SIP requests and the settings that you may need to adjust on your network or your SPA9000
to help ensure interoperability.
The VoIP telephone service is coordinated by SIP requests and responses, whether the calls are
internal or external. Figure 3-1
stations in the LVS. The SPA9000 acts as a SIP proxy and establishes a session. After the session
is established, Real Time Protocol (RTP) traffic flows directly between the two client stations.
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
are 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.
Linksys Voice System Administration Guide
illustrates the SIP requests and responses between client
Figure 3-1 SIP Requests and Responses for Internal Calls
SIP Proxy
SIP Proxy
Figure 3-2, UserA and UserB are client stations that
About LVS and SIP
SIP Proxy
39