Preemption-aware routing for QoS-enabled networks

This paper presents a new preemption-aware quality of service (QoS) routing algorithm for instantaneous request (IR) call connections in a QoS-enabled network where resources are shared between instantaneous request (IR) and book-ahead (BA) call connections. Book-ahead reservation which confirms the availability of resources in advance is a highly attractive technique for time sensitive applications that require high amount of bandwidth with guaranteed QoS. One of the major concerns in the implementation of BA reservation is the preemption of on-going instantaneous requests (IR) call connections. Preemption disrupts service continuity which is seen as detrimental from users´ perceived QoS definition found in recent studies. Existing QoS routing algorithms focus on resource conservation or load balancing as the key objective to attain in addition to guaranteed QoS. No work known to these authors has yet focused on the preemption problem of on-going IR call connections at routing stage. We present a mathematical formulation to compute the preemption probability of an IR call connection at routing stage based on the current IR and future BA load information. We propose a routing strategy by formulating a link cost function comprising of calculated preemption probability of incoming IR call connection and hop count. Simulation results confirm that QoS routing based on the proposed link cost function significantly outperforms both shortest path and widest path routing algorithms in terms of preemption and call blocking rate.