A comparison of hard-state and soft-state signaling protocols

ABSTRACT

One of the key infrastructure components in all telecommunication networks, ranging from the telephone network, to VC-oriented data networks, to the Internet, is its signaling system. Two broad approaches towards signaling can be identified: so-called hard-state and soft-state approaches. Despite the fundamental importance of signaling, our understanding of these approaches - their pros and cons and the circumstances in which they might best be employed - is mostly anecdotal (and occasionally religious). In this paper, we compare and contrast a variety of signaling approaches ranging from a "pure" soft state, to soft-state approaches augmented with explicit state removal and/or reliable signaling, to a "pure" hard state approach. We develop an analytic model that allows us to quantify state inconsistency in single- and multiple-hop signaling scenarios, and the "cost" (both in terms of signaling overhead, and application-specific costs resulting from state inconsistency) associated with a given signaling approach and its parameters (e.g., state refresh and removal timers). Among the class of soft-state approaches, we find that a soft-state approach coupled with explicit removal substantially improves the degree of state consistency while introducing little additional signaling message overhead. The addition of reliable explicit setup/update/removal allows the soft-state approach to achieve comparable (and sometimes better) consistency than that of the hard-state approach.

REFERENCES

• 1: L. Berger and D. Gan and G. Swallow and P. Pan and F. Tommasi and S. Molendini, RSVP Refresh Overhead Reduction Extensions, RFC 2961, April, 2001.
• 2: B. Cain and S. Deering and B. Fenner and A. Thyagarajan, Internet Group Management Protocol, Version 3, RFC 3376, Oct., 2002.
• 3: D. Clark, The design philosophy of the DARPA internet protocols, Symposium proceedings on Communications architectures and protocols, p.106-114, August 16-18, 1988, Stanford, California, United States
• 4: S. Deering, Host Extensions for IP Multicasting, RFC 1112, August, 1989.
• 5: Stephen Deering , Deborah L. Estrin , Dino Farinacci , Van Jacobson , Ching-Gung Liu , Liming Wei, The PIM architecture for wide-area multicast routing, IEEE/ACM Transactions on Networking (TON), v.4 n.2, p.153-162, April 1996 [doi>10.1109/90.490743]
• 6: D. Estrin and D. Farinacci and A. Helmy and D. Thaler and S. Deering and M. Handley and V. Jacobson and C. Liu and P. Sharma and L. Wei, Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification, RFC2362, http://www.faqs.org/rfcs/rfc2362.html, June, 1998.
• 7: W. Fenner, Internet Group Management Protocol, Version 2, RFC 2236, Nov., 1997.
• 8: Sally Floyd , Van Jacobson , Ching-Gung Liu , Steven McCanne , Lixia Zhang, A reliable multicast framework for light-weight sessions and application level framing, IEEE/ACM Transactions on Networking (TON), v.5 n.6, p.784-803, Dec. 1997 [doi>10.1109/90.650139]
• 9: M. Handley and H. Schulzrinne and E. Schooler and J. Rosenberg, SIP: Session Initiation Protocol, RFC 2543, Mar., 1999.
• 10: Ping Ji and Zihui Ge and Jim Kurose and Don Towsley, A Comparison of Soft-state Versus Hard-state Signaling, University of Massachusetts at Amherst, 2003.
• 11: Kazaa file sharing network, Kazaa file sharing network, http://www.cazaa.com/, 2002.
• 12: Ping Pan and Henning Schulzrinne, Staged Refresh Timers for RSVP, 2nd Global Internet Conference, 1997, Phoenix, AZ.
• 13: Partridge, C. and Pink, S., An Implementation of the Revised Internet Stream Protocol (ST-2), Journal of Internetworking: Research and Experience, 3, 1, March, 1992.
• 14: Q2931, Q2931, ITU-T Recommendation.
• 15: Suchitra Raman , Steven McCanne, A model, analysis, and protocol framework for soft state-based communication, Proceedings of the conference on Applications, technologies, architectures, and protocols for computer communication, p.15-25, August 30-September 03, 1999, Cambridge, Massachusetts, United States
• 16: Puneet Sharma , Deborah Estrin , Sally Floyd , Van Jacobson, Scalable Timers for Soft State Protocols, Proceedings of the INFOCOM '97. Sixteenth Annual Joint Conference of the IEEE Computer and Communications Societies. Driving the Information Revolution, p.222, April 09-11, 1997
• 17: Topolcic, C., Experimental Internet Stream Protocol: Version 2 (ST-II), Internet RFC 1190, October, 1990.
• 18: M. Dorsch , Z. Ge , M. Keaton , J. Shapiro, SANDS: Specialized Active Networking for Distributed Simulation, Proceedings of the 2002 DARPA Active Networks Conference and Exposition, p.365, May 29-30, 2002
• 19: Zhang, L. and Deering, S. and Estrin, D. and Shenker, S. and Zappala, D., RSVP: A New Resource ReSerVation Protocol, IEEE Network, September, 1993.
• 20: Stephen Deering , Deborah L. Estrin , Dino Farinacci , Van Jacobson , Ching-Gung Liu , Liming Wei, The PIM architecture for wide-area multicast routing, IEEE/ACM Transactions on Networking (TON), v.4 n.2, p.153-162, April 1996 [doi>10.1109/90.490743]

INDEX TERMS

Primary Classification:
  C. Computer Systems Organization
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.2 Network Protocols

General Terms:
Design, Performance

Keywords:
hard-state, signaling, soft-state