Filters

The syntax for creating a filter is shown below:

tc filter [ add | del | change | get ] dev STRING
       [ prio PRIO ] [ protocol PROTO ]
       [ root | classid CLASSID ] [ handle FILTERID ]
       [ [ FILTER_TYPE ] [ help | OPTIONS ] ]

       tc filter show [ dev STRING ] [ root | parent CLASSID ]
Where:
FILTER_TYPE := { rsvp | u32 | fw | route | etc. }
FILTERID := ... format depends on classifier

The interpretation of the fields:

• prio represents the priority that is assigned to the filter.
• protocol is used by the filter to identify packets belonging only to that protocol. As already mentioned, no two filters can have the same priority and protocol field.
• root indicates that the filter is at the root of the link sharing hierarchy.
• classid represents the handle of the class to which the filter is applied.
• handle represents the handle by which the filter is identified uniquely. The format of the filter is different for different classifiers.

Having discussed the general syntax for creating, deleting and changing queuing discipline, classes and filters, let us now take a look at the various queuing disciplines that currently supported in linux.