ZyXEL Communications UAG5100 User Manual page 160

Chapter 11 Trunks
given an equal amount of bandwidth, and then moves to the end of the list; and so on, depending
on the number of queues being used. This works in a looping fashion until a queue is empty.
The Weighted Round Robin (WRR) algorithm is best suited for situations when the bandwidths set
for the two WAN interfaces are different. Similar to the Round Robin (RR) algorithm, the Weighted
Round Robin (WRR) algorithm sets the UAG 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
chances to transmit traffic than an interface with a smaller weight.
For example, in the figure below, the configured available bandwidth of wan1 is 1M and ppp0 is
512K. You can set the UAG to distribute the network traffic between the two interfaces by setting
the weight of wan1 and ppp0 to 2 and 1 respectively. The UAG assigns the traffic of two sessions to
wan1 and one session's traffic to ppp0 in each round of 3 new sessions.
Figure 98 Weighted Round Robin Algorithm Example
Spillover
The spillover load balancing algorithm sends network traffic to the first interface in the trunk
member list until the interface's maximum allowable load is reached, then sends the excess
network traffic of new sessions to the next interface in the trunk member list. This continues as
long as there are more member interfaces and traffic to be sent through them.
Suppose the first trunk member interface uses an unlimited access Internet connection and the
second is billed by usage. Spillover load balancing only uses the second interface when the traffic
load exceeds the threshold on the first interface. This fully utilizes the bandwidth of the first
interface to reduce Internet usage fees and avoid overloading the interface.
In this example figure, the upper threshold of the first interface is set to 800K. The UAG sends
network traffic of new sessions that exceed this limit to the secondary WAN interface.
Figure 99 Spillover Algorithm Example
UAG5100 User's Guide
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