Trunks
See the Trunks section for related information on these screens.
Trunks Overview
You can group multiple interfaces together into trunks to have multiple connections share the traffic load to increase overall network throughput and enhance network reliability. If one interface's connection goes down, the ZyWALL sends traffic through another member of the trunk. For example, you can use two interfaces for WAN connections. You can connect one interface to one ISP (or network) and connect the another to a second ISP (or network). The ZyWALL can balance the load between multiple connections (see Load Balancing Introduction ). If one interface's connection goes down, the ZyWALL can automatically send its traffic through another interface.
You can use policy routing to specify through which interface to send specific traffic types. You can use trunks in combination with policy routing. You can also define multiple trunks for the same physical interfaces. This allows you to send specific traffic types through the interface that works best for that type of traffic, and if that interface's connection goes down, the ZyWALL can still send its traffic through another interface.
Trunk Scenario Examples
Suppose one of the ZyWALL's interfaces is connected to an ISP that is also your Voice over IP (VoIP) service provider. You may want to set that interface as active and set another interface (connected to another ISP) to passive. This way VoIP traffic goes through the interface connected to the VoIP service provider whenever the interface's connection is up.
Another example would be if you use multiple ISPs that provide different levels of service to different places. Suppose ISP A has better connections to Europe while ISP B has better connections to Australia. You could use policy routing and trunks to send traffic for your European branch offices primarily through ISP A and traffic for your Australian branch offices primarily through ISP B.
Load Balancing Introduction
On the ZyWALL, load balancing is the process of dividing traffic loads between multiple interfaces. This allows you to improve quality of service and maximize bandwidth utilization.
Maybe you have two connections with different bandwidths. For jitter-sensitive traffic (like video for example), you could set up a trunk group that uses spillover or weighted round robin load balancing to make sure that most of the jitter-sensitive traffic goes through the higher-bandwidth interface.
For some traffic connections, you might want to use least load first load balancing in order to even out the distribution of the traffic load.
Load Balancing Algorithms
The following sections describe the load balancing algorithms that the ZyWALL can use to decide which interface the traffic (from the LAN) should use for a session1. 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
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.
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.
This algorithm is best suited for situations when the bandwidths set for the two WAN interfaces are different.
Spillover
With the spillover load balancing algorithm, the ZyWALL sends network traffic to the first interface in the trunk member list until the interface's maximum allowable load is reached, then the ZyWALL sends the excess network traffic of new sessions to the next interface in the trunk member list. This continues as long as there are more member interfaces and traffic to be sent through them.
In cases where the first interface in the trunk member list uses an unlimited access Internet connection and the secondary WAN uses a per-use timed access plan, the ZyWALL will only use the next interface in the trunk member list when the traffic load exceeds the threshold on the first interface. This allows you to fully utilize the bandwidth of the first interface to reduce Internet usage fees and avoid overloading the interface.
Trunk Summary
Configuring a Trunk
Click Network > Interface > Trunk and then the Add (or Edit) icon to open the Trunk Edit screen.
1In the load balancing section, a session may refer to normal connection-oriented, UDP and SNMP2 traffic.