CHAPTER60 Configuration Parameters Reference
Mediant 4000 SBC | User's Manual
Parameter Description
configure voip > sbc settings >
sbc-rand-expire
[SBCRandomizeExpires]
Enables the device to change the expiry
time in the Expires header of SIP 200 OK
responses for user registration or
subscription requests.
The feature is useful in scenarios where
multiple users may refresh their registration
or subscription simultaneously, 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), preventing the establishment of
new calls or preventing the handling of
some user registration or subscription
requests. However, when this feature is
enabled, the device assigns a random
expiry time to each user registration or
subscription, ensuring future user
registration and subscription requests are
more distributed over time (i.e., do not all
occur simultaneously).
The valid value is 0 (disabled) to 20 (any
value from 1 to 20 is considered enabled).
The default is enabled (10). If disabled (i.e.,
0), the device does not change the expiry
time. If enabled, the device assigns a
random expiry time as follows:
■ If the received expiry time is less than
610 sec, the device reduces the time by
up to 10 sec. For example, if the
received expiry time is 110 sec, the
device reduces it to anywhere between
100 (i.e., 110 – 10) and 110 sec.
■ If the received expiry time is greater
than 610 sec, the device reduces the
time to anywhere between 600 sec and
the received expiry time. For example, if
the received expiry time is 700 sec, the
device reduces it to anywhere between
600 and 700 sec.
■ Minimum expiry time:
✔ The minimum expiry time that the
device can reduce REGISTER
messages to is 30 sec and
SUBSCRIBE messages to 120
sec. For example, if the received
expiry time in a REGISTER
message is 35 sec, the device
reduces the time to any value
between 30 and 35 sec (and not by
10 seconds -- between 25 and 35).
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