public interface SipLimiterFilter
Filter for limiting initial SIP requests.
Each filter instance will be passed an initial SIP request to decide if it
can be considered for limiting or if it should be excluded from limiting.
If any filter instance returns false from isLimitable then SIS will forcibly
use a unit from the limiter and not block the request.
Care should be taken to minimise the overhead of processing the filter
conditions. Filters are not guaranteed to be invoked and must not be
programmed in a way that affects application state. Filter execution
order is not deterministic.