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Summary form only given. New emergent distributed multimedia applications require end-to-end quality of service (QoS) guarantees and have stringent constraints on delay, jitter, cost, etc. Taking into account such needs in IP networks stands of utmost necessity. MPLS and traffic engineering provide indeed an adequate mean to establish constrained routes which satisfy application requirements especially in terms of bandwidth and delay. These routes are computed by running a QoS algorithm on the traffic engineering database maintained by an extended IGP routing protocol. In this paper, we first study and analyze three known QoS algorithms, namely SPF-TE, WSPF and DORA. This study is done through very detailed simulations using ONS, a simulator of the OSPF protocol, recently developed and integrated into the well known NS simulator. We show that while all these algorithms outperform clearly SPF, the algorithm usually used within OSPF, DORA algorithm stands slightly better than the two others. Then, we propose three different potential improvements of DORA and propose a new QoS algorithm termed WDORA that incorporates one these improvements. We show that WDORA outperforms DORA for different performance metrics.