Chapter 8 Trunk

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.

Table 63 Least Load First Example

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

 

 

 

 

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

 

179

ZyWALL 110/310/1100 Series User’s Guide