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Shorewall Rate Limiting or QoS

Using tc directly to manage rate limiting can be tricky and a little bit complex to understand. I have found that shorewall provides an easy to use and understand interface to achieve the same purpose. The concept is based on devices, rules and classes as represented by the three files in shorewall – tcdevices, tcrules and tcclasses.

The devices basically refer to the interfaces rate limiting should happen; the rules are the different types of traffic that you wish to implement rules for. ie : all inbound http traffic should be given a certain class; And the classes define how the rating is done for that class.

In my example, I have a 10Mb/s connection to the internet that I need to share between office use, external servers such as DNS and HTTP and some other thing such as VPN access. In my /etc/shorewall/tcdevices I have specified my internet facing interface:

#INTERFACE      IN-BANDWITH     OUT-BANDWIDTH
eth2            10mbit          10mbit

I then define some rules such as :

1       0.0.0.0/0       0.0.0.0/0       tcp     20,21,22
1       0.0.0.0/0       0.0.0.0/0       tcp     -       20,21,22
2       0.0.0.0/0       0.0.0.0/0       tcp     53
2       0.0.0.0/0       0.0.0.0/0       udp     53

The above ‘tags’ the packets that match the follow rules. So as an example, all ssh traffic is tagged as 1. In my full example I have rules that make up 4 tagged ‘classes’. In the tcclasses file I have the following:

#INTERFACE      MARK    RATE    CEIL    PRIORITY        OPTIONS
eth2            1       10*full/100     full    1       
eth2            2       44*full/100     full    2
eth2            3       14*full/100     full    3
eth2            4       28*full/100     full    4
eth2            5       4*full/100      10*full/100    5

What I basically have now is the identification of the type of traffic I want to shape (done by the rules) and over which interface I want to apply the shaping (done by the devices). The classes then determines the amount of bandwidth assigned for each rule.

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