22Chapter 2 SRG50 overview
Figure 1 Normal mode
Branch office | Main office |
SRG
IP phones
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| IP phones |
WLAN | Software | VoIP connection over WAN |
handsets | phones | Normal mode |
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IP telephones connected at the SRG are registered with the main office call server and are under main office control. They operate as branch user sets and have access to all telephony services and features that the call server offers to IP telephones connected directly to the main office.
When a branch user set initiates a local PSTN call, the main office sets up the call using the VoIP trunks, which establishes a local media path. Emergency Services Access calls are similarly routed to the SRG PSTN. The telephone is redirected to local mode and the SRG initiates a local PSTN call to 911. For main office callers, the SRG acts as a
When call forwarding has been configured, incoming PSTN calls to the branch user set are forwarded over VoIP trunks (either H.323 or SIP) to the main office, which terminates the call at the branch user. Similarly, calls from analog telephones connected to the SRG to the branch user set are forwarded to the main office over VoIP trunks, which then terminates the call at the branch user. Calls from the branch user set to the analog telephones at the SRG are routed over the VoIP trunks to terminate at the analog telephone. In all these call scenarios, only signaling messages go through the VoIP trunk. The media path is set up directly between the branch user set and the voice gateway at the SRG. This means that these calls do not use any WAN bandwidth between the main office and the branch office after calls are established.
When a branch user IP telephone calls a main office IP telephone and vice versa, the call is a simple
