Chapter 8 WAN Screens

Figure 104 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.

Table 31 Least Load First: Example 1

INTERFACE

OUTBOUND

 

LOAD BALANCING INDEX

AVAILABLE (A)

MEASURED (M)

(M/A)

 

 

 

WAN 1

512 K

412 K

0.8

 

 

 

 

WAN 2

256 K

198 K

0.77

 

 

 

 

8.4.1.2 Example 2

This example uses the same network scenario as in Figure 104 on page 167, 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.

Table 32 Least Load First: Example 2

 

OUTBOUND

 

INBOUND

 

AVERAGE LOAD

INTERFACE

 

 

 

 

AVAILABLE

MEASURED

AVAILABLE

MEASURED

BALANCING INDEX

 

(OM / OA + IM / IA) / 2

 

(OA)

(OM)

(IA)

(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

 

 

 

 

 

 

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.

 

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ZyWALL 2WG User’s Guide