Load Balancing (Active/Active Mode) - ZyXEL Communications ZyWall 35 Support Notes

ZyWALL 35 Support Notes

Load Balancing (Active/Active Mode)

With ZyWALL's load balancing function, users can utilize WAN1 and WAN2 interface at the same time.
Every time new outgoing TCP sessions come to ZyWALL's LAN or DMZ, ZyWALL will decide which
WAN interface to throw the packet out. The connection is then controlled by a session manager inside
ZyWALL to make sure every packet going back and forth of this TCP session will go out through the
same interface as the initial one. Similar mechanism is also applied to UDP/ICMP traffic to make sure the
returned packets always go through the same interface as the first one. Following we introduce three
different methods ZyWALL's WAN1 and WAN2 share Internet loading.
Least Load First: ZyWALL measures outbound loading, inbound loading or outbound + inbound loading
within a preset time frame.
Weighted Round Robin: ZyWALL decides the loading ratio of WAN1 and WAN2. For example if 9:2 is
setup, this means the number of TCP sessions going from WAN1 and WAN2 in average is 9 to 2.
Spill Over: A threshold is preset for primary WAN, once the loading exceeds the threshold within a
measured period of time, the secondary WAN will take over. Once the loading of primary WAN decreases,
then the next session will go through the primary WAN.
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