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Chapter 8 Trunk
ZyWALL 110/310/1100 Series User’s Guide
179
Figure 101 Least Load First Example
The outbound bandwidth utilization is used as the load balancing index. In this example, the
measured (current) outbound throughput of WAN 1 is 412K and WAN 2 is 198K. The ZyWALL
calculates the load balancing index as shown in the table below.
Since WAN 2 has a smaller load balancing index (meaning that it is less utilized than WAN 1), the
ZyWALL will send the subsequent new session traffic through WAN 2.
Weighted Round Robin
Round Robin scheduling services queues on a rotating basis and is activated only when an interface
has more traffic than it can handle. A queue is given an amount of bandwidth irrespective of the
incoming traffic on that interface. This queue then moves to the back of the list. The next queue is
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 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
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 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 and one session's traffic to wan2 in each round of 3 new sessions.
Figure 102 Weighted Round Robin Algorithm Example
Table 63 Least Load First Example
INTERFACE
OUTBOUND
LOAD BALANCING INDEX
(M/A)
AVAILABLE (A) MEASURED (M)
WAN 1 512 K 412 K 0.8
WAN 2 256 K 198 K 0.77