by November 5, 2002 0 comments

“Bandwidth-management system? Hmmm, why? After all, I have a 512 Mbps leased-line connection,” a typical manager at a big corporation may ask. But his employees may be ftp’ing MP3s all through the day or listening to audio streams! This typical manager may one fine day see his company website opening at 2.53 Kbps and all hell will break loose! So it makes sense to preempt this by using bandwidth-management systems.

Bandwidth-management system can be hardware or software based. But the software ones have performance issues because they use system hardware to work instead of having their own dedicated hardware

We will talk about implementing a hardware-based bandwidth management system, PacketShaper 1500 from Tulip IT Services. Such a hardware box would be put between the Internet and your local LAN.

Setting it up
We set up the device in the following configuration.

To configure and manage the PacketShaper, you have the option of a serial console connection, a browser-based user interface and a telnet option. The serial port would need to be used in case the network configuration of the device is not known. 

Once connected in the network topology that you want, software configuration starts by giving it a static IP on your network–, in this case. The site router and gateway IP are also specified. The first time configuration is done through the guided setup from the serial console. After the initial configuration you can use the friendlier browser-based to set up rest of the things, like DNS and inbound and outbound rate settings.

It is recommended to run the PacketShaper on your network for some time with bandwidth-management control options switched ‘off’. This allows you to monitor and analyze the type of data traffic. Typically, HTTP traffic would be the highest, but streaming audio/video can also take up your bandwidth. Blocking such traffic is a good idea. See the ‘Top 10’ tab on the management interface to determine such traffic. This will determine your policies.

There are four generic categories (called ‘Partitions’) for which bandwidth management can be set up. These are MissionCritical, Average, LowPriority and Prohibited. Customized categories can be added if needed. Services (called ‘Classes’) can be added to these depending upon their criticality (go to the ‘Manage’ tab for this). For example, traffic like audio streams or instant messengers can go in LowPriority or Prohibited categories. Policies are associated with both Partitions and Classes. There are five types of policies: Rate, Priority, Never admit, Ignore and Discard. Further. With the Rate policy you also need to specify the Guaranteed rate and the Burstable limit and priority. 

You can prevent too much load on the device by preventing it to scan through all data packets even if they are not needed. A good idea is to configure it to overlook such data packets (IPX for instance). If for some reason the PacketShaper fails, the inbound and outbound ports are directly bridged, effectively bypassing the device.

So, cross your fingers, check and double-check your settings and hope to find your IT manager happy.

Ankit Khare

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