User's Manual 264 Document #: LTRT-12809
Mediant 800 MSBR
between the IP-PBX, and two ITSP's and the local PSTN.
The enterprise has an IP-PBX located behind a Firewall/NAT:
• IP-PBX IP address: 10.15.4.211
• Transport protocol: UDP
• Voice coder: G.711
• IP-PBX users: 4-digit length extension number and served by two ITSPs.
• The enterprise also includes remote IP-PBX users that communicate with the IP-
PBX via the device. All dialed calls from the IP-PBX consisting of four digits
starting with digit "4" are routed to the remote IP-PBX users.
Using SIP trunks, the IP-PBX connects (via the device) to two different ITSP's:
• ITSP-A:
♦ Implements Proxy servers with fully qualified domain names (FQDN):
"Proxy1.ITSP-A" and "Proxy2.ITSP-B", using TLS.
♦ Allocates a range of PSTN numbers beginning with +1919, which is
assigned to a range of IP-PBX users.
♦ Voice coder: G.723.
• ITSP-B:
♦ Implements Proxy servers with IP addresses 216.182.224.202 and
216.182.225.202, using TCP.
♦ Allocates a range of PSTN numbers beginning with 0200, which is assigned
to a range of IP-PBX users.
♦ Voice coder: G.723.
Registration and authentication is required by both ITSP's, which is performed by the
device on behalf of the IP-PBX. The SIP REGISTER messages use different URI's
(host name and contact user) in the From, To, and Contact headers per ITSP as well
as username and password authentication.
Outgoing calls from IP-PBX users are routed according to destination:
• If the calls are dialed with the prefix "+81", they are routed to ITSP-A (Region A).
• If the calls are dialed with the prefix "9", they are routed to the local PSTN
network.
• For all other destinations, the calls are routed to ITSP-B.
The device is also connected to the PSTN through a traditional T1 ISDN trunk for local
incoming and outgoing calls. Calls dialed from the enterprise's IP-PBX with prefix '9'
are sent to the local PSTN. In addition, in case of Internet interruption and loss of
connection with the ITSP trunks, all calls are rerouted to the PSTN.
The figure below provides an illustration of this example scenario:
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