Specifications

Chapter 3: Configuring the Barracuda Link Balancer 25
If you want to employ default link balancing policy, where the link with the greatest available
capacity is used, set the usage group for each link to
Primary.
To assign each link a usage group, edit the link on the
Basic > Links page.
Specifying WAN Link for Outbound Traffic
You can override the link balancing algorithm by creating rules that determine which WAN link
certain kinds of outbound traffic will use. See Specifying the Link Used by Outgoing Traffic on page
26.
Creating Bandwidth or Quality of Service (QoS) Rules
You can create bandwidth rules that specify the priority that the Barracuda Link Balancer gives to
outbound traffic. Bandwidth rules are executed after it has been determined which WAN link the
traffic will use. These rules apply to all traffic, including VPN traffic, regardless of whether the
Barracuda Link Balancer firewall is enabled or not.
Each rule describes a set of traffic based on one or more parameters: source IP address or range,
destination IP address or range, application or applications, time, day of the week, and WAN link. If
the conditions are met, the rule assigns a bandwidth priority and a contention priority.
The bandwidth and contention priority classes are compliant with the DiffServ specification. DiffServ
bits are inserted if the traffic matches the Quality of Service rules on this page. Then, bandwidth and
contention priorities are applied based on those bits, even if they were set by another device. Traffic
that does not have any DiffServ bits set is assigned the Default class.
If the amount of traffic on the network is more than what can be sent, traffic from high priority
applications is allocated a greater share of the bandwidth. The contention priority subdivides traffic
that has the same bandwidth priority level.
Some examples of QoS rules:
• Give higher priority to traffic originating from a set of IP addresses.
• Assign lower priority to FTP traffic so that uploading and downloading of files does not impact
other applications.
• Increase the priority of SIP traffic so that calls are not dropped.
• Give VPN traffic a high priority. You can do this by creating a rule where the source IP address
is the local VPN endpoint and the destination IP address is the remote VPN endpoint.
Configure QoS rules using the
Policy > Bandwidth Mgmt page.
Configure the priority classes for the QoS rules on the
Policy > Configuration page. There are 8
classes per WAN link, each consisting of a minimum and maximum value. Traffic with a given class
is guaranteed to get at least the minimum bandwidth and will get up to the maximum if it is available.
Outbound Traffic Routing
By default, all outgoing traffic is link balanced and NAT'd. Also, the source IP address of outgoing
traffic is the WAN link that is used by the traffic. You can create outbound routing rules to modify
these defaults.
This section covers the following topics: