Avaya 1000 Installation And Commissioning Manual page 57

Survivability
When the main office Signaling Server fails and an Alternate Signaling Server is available, the MG
1000B IP Phones reset and reregisters with the main office Call Server through the Alternate
Signaling Server, and continue to receive call processing services from the main office Call Server.
If no Alternate Signaling Server is available, the MG 1000B IP Phones reset and register with the
call server. IP Phones that were registered with the call server before the main office Signaling
Server failure was detected are then redirected back to the main office and register with the Voice
Gateway Media Card. These telephones stay in Normal Mode. IP Phones that registered with the
call server after the main office Signaling Server failure was detected stay registered at the Branch
Office.
If the Main Office has VTRK applications on the failed Signaling Server, the NCS de-registers the
Main Office from its database. Therefore, redirection from local mode cannot be completed. If the
alternative Signaling Server has no TPS services configured (for example, it is purely an NRS,
Personal Directory (PD) Server, or pure VTRK), once again, redirection cannot be completed. The
correct scenario occurs when the NCS has a static endpoint for the Main Office Node IP so there is
no VTRK dependency. All TPSs configured at the Main Office have the same H.323 ID. The Branch
Office maintains a connection to the NCS, or alternative NCS. In this particular case, IP Phones are
redirected to the Main Office even when a primary Signaling Server fails.
When an MG 1000B IP Phone powers up, it registers first with the MG 1000B TPS, and second with
the MG 1000B Call Server. It is then redirected to the main office by the call server. The MG 1000B
TPS queries the Primary NCS for the main office node IP address to redirect the IP Phone. The
NCS provides the IP based on BUID value. If there are several routes for a particular BUID route,
the smaller route cost factor is chosen. If the Primary NCS is down or unreachable, the MG 1000B
TPS queries the Alternate NCS. If the MG 1000B TPS receives a positive response, the MG 1000B
IP Phone is redirected to the main office. If the Alternate NCS is also down or unreachable,the MG
1000B TPS queries the Failsafe NRS. If a successful response is received from the Failsafe NRS,
the IP Phone registers with the main office. Otherwise, if neither an Alternate NRS nor a Failsafe
NRS is available, the MG 1000B IP Phone remains in Local Mode at the Branch Office, the MG
1000B telephones remain in Local Mode, displaying a Server Unreachable (1) message and
receives all call processing services from the CP PM in the MG 1000B Core.
MG 1000B IP Phones in Normal Mode remain registered with the main office when the Primary NRS
fails and no Alternate or Failsafe NRS is available. They can call any main office telephone or IP
Phones in Normal Mode in other branch offices. However, they cannot call any MG 1000B digital
telephones, analog (500/2500-type) telephones, or any external number through the MG 1000B
trunks in the normal way, because the Virtual Trunks are not available. (MG 1000B digital or analog
(500/2500-type) telephones are accessible if alternate routing is available through the PSTN.) The
user has the option of staying in Normal Mode, or going to Local Mode manually by resetting the
telephone or using Test Local Mode. In Local Mode, the IP Phones can make local calls to other IP
Phones, digital telephones, and analog (500/2500-type) telephones at the Branch Office. They can
also be used to make outgoing PSTN calls as usual.
You must plan for, and obtain, the Primary and optional Alternate NRS addresses for installing the
Branch Office feature software. Determine the NRS role, that is, the Alternate or Failsafe
configuration, for the MG 1000B Signaling Server.
Avaya recommends that the NRS in the MG 1000B be configured as a Failsafe NRS. If the MG
1000B IP Phones go into Local Mode, they can use the MG 1000B NRS services.
For Avaya CallPilot Mini and Avaya CallPilot 201i applications, a Message Waiting Indication (MWI)
does not survive a Mode change (Normal to Local or Local to Normal). The message itself is
preserved, but the lamp indicator may not be lit after the Mode change.
June 2014 Branch Office Installation and Commissioning
57
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