AudioCodes Mediant 800B User Manual page 1147

User's Manual
Parameter
SBC Survivability Registration Time
sbc-surv-rgstr-time
[SBCSurvivabilityRegistrationTime]
[SBCEnableSurvivabilityNotice]
Version 7.0
61. Configuration Parameters Reference
the proxy or registrar server. Upon a successful registration
or subscription, the server sends a SIP 200 OK response.
If the expiry time was unchanged by the server, the device
applies this feature and changes the expiry time in the SIP
200 OK response before forwarding it to the user;
otherwise, the device does not change the expiry time.
This feature is useful in scenarios where multiple users
may refresh their registration or subscription
simultaneously, thereby causing the device to handle many
such sessions at a given time. This may result in an
overload of the device (reaching maximum session
capacity), thereby preventing the establishment of new
calls or preventing the handling of some user registration
or subscription requests. When this feature is enabled, the
device assigns a random expiry time to each user
registration or subscription and thus, ensuring future user
registration and subscription requests are more distributed
over time (i.e., do not all occur simultaneously).
The device takes any random number between 0 and the
value configured by the parameter, and then subtracts this
random number from the original expiry time value. For
example, assume that the original expiry time is 120 and
the parameter is set to 10. If the device randomly chooses
the number 5 (i.e., between 0 and 10), the resultant expiry
time will be 115 (120 minus 5).
The valid value is 0 to 20. The default is 10. If set to 0, the
device does not change the expiry time.
Notes:

The lowest expiry time that the device sends in the 200
OK, regardless of the resultant calculation, is 10
seconds. For example, if the original expiry time is 12
seconds and the parameter is set to 5, theoretically, the
new expiry time can be less than 10 (e.g., 12 – 4 = 8).
However, the expiry time will be set to 10.

The expiry time received from the user can be changed
by the device before forwarding it to the proxy. This is
configured by the SBCUserRegistrationTime parameter.
Defines the duration of the periodic registrations between
the user and the device, when the device is in survivability
state (i.e., when REGISTER requests cannot be forwarded
to the proxy and are terminated by the device). When set
to 0, the device uses the value set by the
SBCUserRegistrationTime parameter for the device's
response.
The valid range is 0 to 2,000,000 seconds. The default is 0.
Enables the device to notify Aastra IP phones that the
device is currently operating in Survivability mode. When
this occurs, the Aastra IP phones display the message,
"Stand Alone Mode" on their LCD screens. Survivability
mode occurs when connectivity with the WAN fails and as
a result, the device enables communication between IP
phone users within the LAN enterprise.
1147
Description
Mediant 800B Gateway and E- SBC