Weighted Round Robin; Spillover; Figure 48 Weighted Round Robin Algorithm Example - ZyXEL Communications 35 Series User Manual

ZyWALL 5/35/70 Series User's Guide

7.4.2 Weighted Round Robin

Similar to the Round Robin (RR) algorithm, the Weighted Round Robin (WRR) algorithm sets
the ZyWALL to send traffic through each WAN interface in turn. In addition, the WAN
interfaces are assigned weights. An interface with a larger weight gets more of the traffic than
an interface with a smaller weight.
This algorithm is best suited for situations when the bandwidths set for the two WAN
interfaces are different.
For example, in the figure below, the configured available bandwidth of WAN1 is 1M and
WAN2 is 512K. You can set the ZyWALL to distribute the network traffic between the two
interfaces by setting the weight of WAN1 and WAN2 to 2 and 1 respectively. The ZyWALL
assigns the traffic of two sessions to WAN1 for every session's traffic assigned to WAN2.

Figure 48 Weighted Round Robin Algorithm Example

7.4.3 Spillover

With the spillover load balancing algorithm, the ZyWALL sends network traffic to the primary
interface until the maximum allowable load is reached, then the ZyWALL sends the excess
network traffic of new sessions to the secondary WAN interface. Configure the Route
Priority metrics in the WAN General screen to determine the primary and secondary WANs.
In cases where the primary WAN interface uses an unlimited access Internet connection and
the secondary WAN uses a per-use timed access plan, the ZyWALL will only use the
secondary WAN interface when the traffic load reaches the upper threshold on the primary
WAN interface. This allows you to fully utilize the bandwidth of the primary WAN interface
while avoiding overloading it and reducing Internet connection fees at the same time.
In the following example figure, the upper threshold of the primary WAN interface is set to
800K. The ZyWALL sends network traffic of new sessions that exceeds this limit to the
secondary WAN interface.
133 Chapter 7 WAN Screens