Filters are used to try to reduce load and improve bandwidth management. RSVP uses soft sate to maintain information about reservation. Soft sate is information that is periodically refreshed by interested parties. In RSVP, senders and receivers refresh the state at routers. Senders are required to periodically retransmit path messages to allow new receivers to learn of the flow, to remind routers that the flow exists, and to adapt to routing changes.
Receivers periodically retransmit their reservation messages to remind routers of their reservation.