QoS evaluation of diffserv-aware constraint-based routing schemes for multi-protocol label switching networks

Abstract

Differentiated Services (DiffServ) and Multi-Protocol Label Switching (MPLS) are attracting attention as Quality of Service (QoS) technologies for the large-scale Internet. DiffServ cannot offer end-to-end QoS by itself, because it controls per-hop packet forwarding order with relative priority according to its class. Achieving end-to-end QoS requires traffic engineering support by using MPLS and Constraint-Based Routing (CBR) schemes in addition to DiffServ. CBR schemes compute explicit routes for Label-Switched Paths (LSPs), which specify packet forwarding routes in MPLS networks. In this paper, we assume two DiffServ classes: Expedited Forwarding (EF) class which corresponds to voice traffic requiring small path delay, and Best Effort (BE) class which corresponds to data traffic requiring high throughput. Four DiffServ-aware CBR schemes are constructed, based on a combination of route computation algorithms and LSP-types depending on whether or not DiffServ classes are considered. In addition to the schemes, we propose a DiffServ-aware CBR scheme that uses a different route computation algorithm for each class. By simulating path accommodations for two-class traffic between every node pair, we evaluate QoS achieved by the five DiffServ-aware CBR schemes. The results show that the proposed scheme can offer better QoS for each class.