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Configuring the PSTN (FXO) Gateway on the SPA3102
Call Scenarios
ATA Administration Guide 107
6
The number dialed is processed by the dial plan corresponding to the VoIP caller.
If the dial plan choice is 0, no dial plan is needed and the user hears the PSTN dial
tone right after the PIN is entered. If the dial plan choice is not 0, the final number
returned from the dial plan after the complete number is dialed by the caller is
dialed to the PSTN. The caller does not hear the PSTN dial tone (except for a little
leakage before the first digit of the final number is auto-dialed by the ATA device).
If the PSTN Line is busy (off-hook, ringing, or PSTN line not connected) when the
VoIP caller calls, the ATA device replies with 503. If the PIN number is invalid or
entered after the VoIP call leg is connected, the ATA device plays the reorder tone
to the VoIP caller and eventually ends the call when the reorder tone times out.
NOTE If
VoIP Caller ID Pattern
is specified and the VoIP caller ID does not match any of the
given patterns, the ATA device rejects the call with a 403. This rule applies
regardless of the authentication method, even when the source IP address of the
INVITE request is in the
VoIP Access List
.
Using HTTP Digest Authentication
The same scenario can be implemented with HTTP digest authentication when
the calling device supports the configuration of a auth-ID and password to access
the ATA device PSTN gateway. When the VoIP caller calls the PSTN Line, the ATA
device challenges the INVITE request with a 401 response. The calling device
should then provide the correct credentials in a subsequent retry of the INVITE,
computed with the auth-ID and password using MD5.
If the credentials are correct, the target number specified in the user-id field of the
INVITE Request-URI is processed by the dial plan corresponding to the VoIP user
(assuming the dial plan choice is not 0). The final number is then auto-dialed by the
ATA device.
If the credentials are incorrect, the ATA device challenges the INVITE again. If the
auth-ID does not exist in the ATA device configuration, the ATA device replies 403
to the INVITE. If the target number is invalid according to the corresponding dial
plan, the ATA device also replies 403 to the INVITE. Again, if the PSTN Line is busy
at the time of the call, the ATA device replies 503.
NOTE: HTTP Digest Authentication is one way to perform one-stage dialing of a
VoIP-To-PSTN call. The other way is with no authentication require. However, if the
target number is not specified in the Request-URI or the number matches the
account user-id of the PSTN Line, the call reverts to two-stage dialing.