Warding off WAN Gridlock: Page 4 of 21

The box has a pass-through failover relay, which means it turns into a wire when the power is off. While downloading a file, we unplugged the PacketShaper and the transfer continued, though obviously with no QoS control. The products from Allot and Sitara also offer this capability.

Initially, you'll probably install the PacketShaper in monitor-only mode. This is so you can gather a list of protocols being used and determine what is causing problems. Protocols are assigned "classes," and policies can be set on any class. Protocols that use a lot of bandwidth or appear often will show up in the "traffic" class listing. Less frequently seen protocols end up in the "default" class. You can create subclasses as well, based on host name, address, subnet or ports; Citrix and HTTP traffic can be subdivided even further. Each class can be assigned a chunk of dedicated bandwidth, and you can set maximum and minimum rates per connection.

We set a policy to give HTTP a minimum of 20 Kbps and a burst of 50 Kbps per connection on a series of small HTTP transfers, and got an average of 21 Kbps. If there isn't enough bandwidth to fit the guarantees, you can choose to refuse the traffic, squeeze it into whatever is available no matter how small, or in the case of Web traffic, redirect to an alternate URL.

Priority Controls

In addition to assigning minimum and maximum bandwidth for a class, you can control traffic by giving it a priority from 0 to 7; traffic with a higher priority gets more bandwidth. You can assign bursty traffic a higher or lower priority as well. When priorities are equal, the bandwidth is weighted based on number transactions. We gave Web and FTP traffic the same priority and ran five Web and 10 FTP users. This resulted in Web traffic getting 15 Mbps instead of its standard 22 Mbps.