Soft-state protocol

Interesting discussions of soft-state can be found in:
1. S. Raman and S. McCanne, "A Model, Analysis, and Protocol Framework for Soft State-based Communication," Proc. 1999 ACM SIGCOMM (Boston, MA, Aug. 1999)
2. P. Ji, Z. Ge, J. Kurose, and D. Towsley, "A Comparison of Hard-state and Soft-state Signaling Protocols, "Proc. 2003 ACM SIGCOMM (Karlsruhe, Germany, Aug. 2003)
3. J. Lui, V. Misra, and D. Rubenstein, "On the Robustness of Soft State Protocols," Proc. IEEE Int. Conference on Network Protocols (ICNP '04), pp. 50-60.

In a soft-state protocol, the state is removed via a timeout event if it is not explicitly refreshed.