ZyXEL Communications ZYWALL 35 - Weighted Round Robin; Figure 89 Least Load First Example; Table 34 Least Load First: Example 1; Table 35 Least Load First: Example 2

Chapter 8 WAN Screens
ZyWALL 5/35/70 Series User’s Guide
169
Figure 89 Least Load First Example
If the outbound bandwidth utilization is used as the load balancing index and the measured
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.
8.4.1.2 Example 2
This example uses the same network scenario as in Figure 89 on page 169, but uses both the
outbound and inbound bandwidth utilization in calculating the load balancing index. If the
measured inbound stream throughput for both WAN 1 and WAN 2 is 1600K, the ZyWALL
calculates the average load balancing indices as shown in the table below.
Since WAN 1 has a smaller load balancing index (meaning that it is less utilized than WAN 2),
the ZyWALL will send the next new session traffic through WAN 1.
8.4.2 Weighted Round Robin
Round Robin routes traffic on a rotating basis and is activated only when a WAN interface has
more traffic than the configured available bandwidth. On the ZyWALL with two WAN
interfaces, an amount of traffic is sent through the first interface. The second interface is also
given an equal amount of traffic, and then the same amount of traffic is sent through the first
interface again; and so on. This works in a looping fashion until there is no outgoing traffic.
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.
Table 34 Least Load First: Example 1
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
Table 35 Least Load First: Example 2
INTERFACE
OUTBOUND INBOUND
AVERAGE LOAD
BALANCING INDEX
(OM / OA + IM / IA) / 2
AVAILABLE
(OA)
MEASURED
(OM)
AVAILABLE
(IA)
MEASURED
(IM)
WAN 1 512 K 412 K 8000 K 1600 K ( 0.8 + 0.2) / 2 = 0.5
WAN 2 256 K 198 K 2000 K 1600 K ( 0.77 + 0.8 ) / 2 = 0.79