AudioCodes Mediant 500 E-SBC, User Manual

Page: 890 / 920

User's Manual 890 Document #: LTRT-10437
Mediant 500 E-SBC
Parameter Description
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 this parameter, and then subtracts this random
number from the original expiry time value. For example,
assume that the original expiry time is 120 and this 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 this
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.
Web: SBC Proxy Registration Time
CLI: sbc-prxy-rgstr-time
[SBCProxyRegistrationTime]
Defines the duration (in seconds) for which the user is
registered in the proxy database (after the device forwards the
REGISTER message). When set to 0, the device sends the
Expires header's value as received from the user to the proxy.
The valid range is 0 to 2,000,000 seconds. The default is 0.
Web: SBC Survivability
Registration Time
CLI: sbc-surv-rgstr-time
[SBCSurvivabilityRegistrationTi
me]
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.
[SBCEnableSurvivabilityNotice] 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.