For an RSVP-enabled network, a soft state refers to a state in routers and end nodes that can be updated by certain RSVP messages.

RSVP takes a "soft state" approach to managing the reservation state in routers and hosts. RSVP soft state is created and periodically refreshed by Path and Resv messages. The local state of an LSP is deleted if no matching refresh messages arrive before the expiration of a "cleanup timeout" interval. The local state of an LSP may also be deleted by an explicit "teardown" message. At the expiration of each "refresh timeout" period and after a state change, RSVP scans its state to build and forward Path and Resv refresh messages to succeeding hops.

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