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M2M Cellular Gateway
transfer mission instantly by only changing routing path to failover interface. The dialing‐up time
of failover connection is saved since it has been connected beforehand. For some mission‐critical
applications, this gateway supports "Seamless Failover"
interface failover process.
So, the initial status of two WAN connections for Seamless Failover is shown in following diagram.
Next, Failover and Failback processes are shown in following diagram. Their steps are:
S 1: When system discovers the primary WAN connection is failed.
S 2: System starts the failover process.
S 3: System changes the data routing path to the failover WAN interface for further data
transmitting. It is faster than the one in the normal mode of failover since routing change is
simpler than dialing up a new WAN connection.
S 4: System keeps trying to recover the failed primary WAN connection. Once it is recovered,
system starts the failback process.
S 5: When failback process starts, system will leave alive the current WAN connection via Failover
WAN interface, but no more data transmitting.
S 6: System changes the data routing path back to the primary WAN interface as same state as at
the beginning of system normal operation.
Index skipping is used to reserve slots for new function insertion, when required.
ISP
DSLAM
Connected and
Data Transferring
Cellular Network
7
to shorten switch time during WAN
Gateway
WAN‐1: ADSL
WAN‐2: 3G/4G
Connected but just
Keep Alive
Initial Status
60
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