Allocation of End-to-End Delay Objectives for Networks Supporting SMDS

Abstract

In this paper, the end-to-end delay objective allocation problem for networks supporting Switched Multi-megabit Data Service (SMDS) is considered. Traditionally, for engineering tractability, end-to-end service objectives are allocated to network elements in such a way that, if the allocated service objective for each network element is satisfied then the end-to-end service objectives are satisfied. Such an objective allocation strategy is referred to as a feasible objective allocation strategy.

For networks supporting SMDS, the delay objectives state that 95% of the packets delivered from the origin Subscriber Network Interface (SNI) to the destination SNI should be within a given time threshold. From network monitoring point of view, this percentile type of delay objectives makes it complicated to compute feasible allocation strategies so that network elements instead of each origin-destination pair should be monitored. From network planning point of view, these end-to-end percentile-type delay objectives usually impose an excessively large number of nonconvex and complicated constraints (delay distributions are convolved, assuming delays are mutually independent).

The emphasis of this paper is three fold: (i) to propose an efficient and generic approach to replacing the set of end-to-end percentile-type delay constraints by a simpler set of network element utilization constraints (small size and convex), (ii) to investigate how this approach could be adopted in conjunction with a number of possible allocation schemes and (iii) to compare the relative effectiveness (in terms of the utilization thresholds determined) using M/M/1 and M/D/1 queueing models. The significance of this work is to provide a general and effective way to calculate engineering thresholds on the network element utilization factors when percentile types of end-to-end delay objectives are considered. This work lays a foundation to help the system planners/administrators monitor, service, expand and plan networks supporting SMDS.