ZyXEL Communications UAG4100 User Manual page 153

• 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 session
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 91 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 68 Least Load First Example
OUTBOUND
INTERFACE
AVAILABLE (A)
wan1 512 K
ppp0 256 K
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.
Chapter 11 Trunks
MEASURED (M)
412 K
198 K
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2
. The available bandwidth you
LOAD BALANCING INDEX
(M/A)
0.8
0.77