ZyXEL UAG4100 User Guide - Page 196
Load Balancing Algorithms, Least Load First, Weighted Round Robin
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Chapter 11 Trunks • If that interface's connection goes down, the UAG can still send its traffic through another interface. • You can define multiple trunks for the same physical interfaces. Load Balancing Algorithms The following sections describe the load balancing algorithms the UAG can use to decide which interface the traffic (from the LAN) should use for a session2. The available bandwidth you configure on the UAG refers to the actual bandwidth provided by the ISP and the measured bandwidth refers to the bandwidth an interface is currently using. Least Load First The least load first algorithm uses the current (or recent) outbound bandwidth utilization of each trunk member interface as the load balancing index(es) when making decisions about to which interface a new session is to be distributed. The outbound bandwidth utilization is defined as the measured outbound throughput over the available outbound bandwidth. Here the UAG has two WAN interfaces connected to the Internet. The configured available outbound bandwidths for wan1 and ppp0 are 512K and 256K respectively. Figure 127 Least Load First Example The outbound bandwidth utilization is used as the load balancing index. In this example, the measured (current) outbound throughput of wan1 is 412K and ppp0 is 198K. The UAG calculates the load balancing index as shown in the table below. Since ppp0 has a smaller load balancing index (meaning that it is less utilized than wan1), the UAG will send the subsequent new session traffic through ppp0. Table 84 Least Load First Example INTERFACE OUTBOUND AVAILABLE (A) wan1 512 K ppp0 256 K MEASURED (M) 412 K 198 K LOAD BALANCING INDEX (M/A) 0.8 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 2. In the load balancing section, a session may refer to normal connection-oriented, UDP or SNMP2 traffic. UAG Series User's Guide 196