Research On Active Queue Management Mechanism Based On DiffServ In MPLS Networks

With the continuous increase of Internet services and the development of the communication technology of Optical Network, multiple traditional services types (such as curriculums, meetings, phone calls, etc) transport via Internet by means of video, voice, image, etc. As a result, the IP network Quality of Service (QoS) is needed increasing higher. Internet Engineering Task Force (IETF) proposes Multi-Protocol Label Switching (MPLS) technology which makes IP network switches and forwards rapidly, and DiffServ system which makes different QoS type of services is differentiated and provides QoS guarantee. Given the similarity of switching and forwarding mechanism of MPLS and DiffServ, to combine the two technologies and take advantage of the scalability of DiffServ and explicit routing of MPLS is a widely recognized scheme that can solve QoS problem of IP backbone network.Congestion is an inherent property of network, and congestion control is the key of enhancing IP QoS, and that Active Queue Management (AQM) is the core of congestion control. Random Early Detection algorithm is the earliest proposed AQM mechanism and a typical representative of AQM mechanism. IETF recommended RED algorithm to solve the congestion control problem in network. RED can effectively avoid global synchronization of TCP flow. However, RED treats different QoS traffic equally, sensitive to control parameters and leads to sharp decline in QoS performance instability with the service flow increases. In DiffServ system, Multi-level RED (MRED) based on RED takes advantage of classifying mechanism of DiffServ and mark different business with different drop precedence, and set different RED parameters. MRED calculates drop probability independently for different drop precedence, and accordingly differentiates treatment of different service. MRED supports both MPLS and DiffServ, but is sensitive to control parameters and lack of stability. In this paper, I-AMRED that improved from MRED is proposed in order to decrease packet loss ratio and increase throughput in MPLS networks based on DiffServ, and accordingly minish sensitiveness to control parameters and improve stability with the service flow bursts. To verify the effectiveness of I-AMRED algorithm, two experimental schemes are designed and implemented on NS-2network simulation platform. One is multiple senders and multiple service types, and the other is multiple senders and single service type in larger network topology. Experiment results show that Ⅰ-AMRED algorithm increases throughput of networks and largely decreases packet loss ratio of AF PHB traffic, and when data traffic is very large or sharply increases, the performance of throughput and packet loss ratio is improved much better, and has better stability. Sensitiveness to control parameters is also decreased. However, time delay increases to some extent because of more calculations.