Linux for Enterprise: Bandwidth Management

Access to unrestricted bandwidth allows employees to start heavy downloads for music and movies, all of which eat huge chunks of bandwidth. Even if these are managed, simple Internet applications such as instant messengers can themselves be bandwidth hogs. To analyze and alleviate this, PCQlinux 2004 has an option for you, which can be used to distribute bandwidth among the users. 

To implement bandwidth management with Pcqlinux 2004, start by choosing to install a Gateway Server. Next, select both the Web server and Management options in the Package Selection screen. This will automatically install Squid proxy server as well as Webmin on PCQLinux 2004. 

After installation, open a Web browser and point to http:// 127.0.0.1:10000. This opens a Webmin interface, and prompts you for the administrative username and password. Log in using the root account and password. 

Within Webmin, select Servers>Squid Proxy. This is where you set up bandwidth control, which consists of two steps. One is to create an ACL (Access Control List) and the other to create a delay pool.

You can add delay pools for your incoming bandwidth to distribute it among users according to their needs

Creating ACL

Bandwidth management in Squid can be done based on specific client MAC addresses, IP addresses and even for specific applications. The best option is to use a mix of all three criteria. In the Squid configuration menu, go to the Access control option. You will get some default ACLs that are already made. Create access controls using any one of the options given which suits your need the closest and click the create button. For instance, you can select either by client IP or port numbers so that bandwidth can also be set for individual applications.

After that you get an interface for entering the ACL name, the IP range and the net mask. If you want to allocate bandwidth to a single IP, then you can give the same IP in the IP range options. You can similarly create ACLs for other IP ranges also. You can even give your own message in the ‘failure’ text box. The client will get a failure message if the clients falls in the rule set for ACL. Once the ACLs have been created, you have to add the newly created ACL in proxy restrictions on the main ACL interface. The action to be set is Allow and the ACL needs to be selected from ‘Match
ACL’ category.

Creating delay pools 

Delay pools provide a means to restrict bandwidth usage of clients. With delay pools, clients can be restricted at the individual level or in groups. For creating delay pools, go to the main Squid configuration interface and select the Delay pool option. The delay pool number is automatically generated by Webmin, and can be from the three classes. Select class 2 ‘Aggregate and Individual’ and then specify the minimum and maximum bandwidth that needs to be allocated for the individual and the total bandwidth to all the users as governed by the ACL rules. Once the details have been entered, you need to attach the ACL that was created. After saving you can now restart squid simply by clicking on the Start Squid link from the webpage. All clients should point their proxy settings to this computer at port no 3128, which is the default port at which Squid functions.

Sanjay Majumder