A network device implements congestion management of sessions of a network protocol. In one implementation, an incoming request component receives session requests for a negotiation session between the network device and a second network device. A capacity pool stores a value relating to capacity of the network device to continue to efficiently process the session requests. New sessions are initiated when the value stored in the capacity pool is less than an estimate of the capacity of the network device at which the network device maximizes processor usage while minimizing session timeouts.