A practical method for the efficient resolution of congestion in an on-path reduced-state signalling environment

Abstract

Currently, the standardisation of on-path signalling protocols is going on within the Next Steps in Signalling (NSIS) Working Group of the IETF. NSIS is responsible for the definition of a general IP signalling protocol. The first use case of the proposed protocol is flow-level resource management. One of the considered reservation methods, reduced-state mode, is based on the Resource Management in DiffServ (RMD) framework. Since it relies only on per-class state information in interior routers, it has a number of benefits including scalability, low complexity, and low memory consumption. However, the price of simplicity is decreased efficiency in case of exceptional situations. The most demanding task for RMD is the handling of congestion that may occur after a failure resulting in re-routing of flows onto a new path. Resolving a suddenly evolved overload without per-flow states is a highly non-trivial task. We present a low complexity mechanism which easily handles the undesirable situation, and we give guidelines to set the parameters of our scheme based on worst-case calculations. © IFIP International Federation for Information Processing 2005.