ZyXEL ZyWALL USG 20 User Guide - Page 290
Load Balancing Algorithms, Least Load First, Weighted Round Robin
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Chapter 12 Trunks 12.1.2 What You Need to Know • Add WAN interfaces to trunks to have multiple connections share the traffic load. • If one WAN interface's connection goes down, the ZyWALL sends traffic through another member of the trunk. • For example, you connect one WAN interface to one ISP and connect a second WAN interface to a second ISP. The ZyWALL balances the WAN traffic load between the connections. If one interface's connection goes down, the ZyWALL can automatically send its traffic through another interface. You can also use trunks with policy routing to send specific traffic types through the best WAN interface for that type of traffic. • If that interface's connection goes down, the ZyWALL 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 ZyWALL can use to decide which interface the traffic (from the LAN) should use for a session2. The available bandwidth you configure on the ZyWALL 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. Weighted Round Robin 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 (see Section 12.4 on page 295), the Weighted Round Robin (WRR) algorithm sets the ZyWALL to send traffic through each interface in turn. In addition, the interfaces are assigned weights. An interface with a larger weight gets more of the traffic than an interface with a smaller weight. 290 2. In the load balancing section, a session may refer to normal connection-oriented, UDP or SNMP2 traffic. ZyWALL USG 20/20W User's Guide