Determine Which Monitored Controllers Are Available; Select The Active Controller - Avaya 9608 Administrator's Manual

the administrative/automatic failback parameters and the monitoring intervals might be obtained
via the 46xxsettings file, the PPM, or the deskphone's user interface.
The priority order in which the list is obtained is as follows:
1. Deskphone user interface (set using SIP Craft procedure)
2. PPM
3. Settings file
4. DHCP (Option 242)
Each of these sources might provide a list of controllers (servers). The contents of each one of
these lists is assumed to be in priority order.

2. Determine which monitored controllers are available

Using the Monitored Controllers list, the deskphone performs DNS queries to resolve
hostnames and the signaling protocol (TLS, TCP, UDP in that order when no DNS NAPTR or
SIP URI parameter is located). To determine which of the Monitored Controllers is actually
available to provide service, the phone performs a maintenance activity for each Monitored
Controller. The phone starts the controller search timer and sends a SIP REGISTER (adding
bindings) message to each controller, which may necessitate establishing a TLS or TCP
connection to the controller.
The controller is considered available once a 200 OK response is received in response to the
REGISTER request. Once a controller has been marked as available, the phone unregisters
from the controller. If all the Monitored Controllers are available before the end of the
CONTROLLER_SEARCH_INTERVAL the phone continues with selecting the Active Controller.
If at least one Monitored Controller is available at the end of the
CONTROLLER_SEARCH_INTERVAL, the phone continues determining which controllers are
available.
If a failure response to the REGISTER request is received, the controller is considered
unavailable and depending on the failure code, either retries the query, provides the requested
credentials, abandons the query, or stops monitoring this specific controller entirely.
If no response to the REGISTER request is received within the timeout period, the phone retries
the monitoring attempt using the RECOVERYREGISTERWAIT parameter value as a guideline.

3. Select the active controller

If the value of the SIPREGPROXYPOLICY parameter is "alternate" and a user is logged in, the
phone must attempt and maintain a single active SIP registration with the highest priority
Available Controller; the number of Available Controllers that the phone simultaneously
registers with is the value of the SIMULTANEOUS_REGISTRATIONS parameter. Any additional
controllers are treated as alternate registrations. The phone attempts to register using the
username and password provided during the login process. It also uses the SIPDOMAIN
parameter. The deskphone uses a SIP URI unless SRTP is enabled where a SIPS URI is used.
Controller Determination and Survivability Activity
Issue 1 May 2011 147