NEC Univerge sv8500 Manual page 2406

<Health Check (changeover to SR-MGC operation)>
When no response is sent back
twice (determined by ASYDL,
SYS1, Index 852, b0-b3) after
Telephony Server sends Health
Check request packet, it is
assumed as connection failure
between Telephony Server and
SR-MGC.
<Health Check sequence (during the SR-MGC is in stand-by mode)>
Telephony Server sends a Health Check request
packet to SR-MGC at intervals of 30 seconds
(default 30 seconds, determined by ASYDL,
SYS1, Index 850)
Telephony Server waits 5 seconds to
receive Health Check response packet from
SR-MGC
(default 5 seconds, determined by ASYDL,
SYS1, Index 851)
Telephony
Server
Health Check request packet
Health Check request packet
Telephony
Server
Health Check request packet
Health Check response packet
Health Check request packet
Health Check response packet
VOL.2-2153
SR-MGC
SR-MGC waits Health Check request
packet from Telephony Server for 60 seconds
(default 60 seconds, determined by the value of
ASYDL, SYS1 Index 850 × Index 852, b0-b3).
If the request has not been received, the SR-MGC
accepts registration of IP terminals in the remote office.
SR-MGC
SR-MGC sends back Health Check
response packet to Telephony Server
as soon as receiving Telephony
Server's request.
SR-MGC