Project Name: Priority Control of TCP Communication using IXA
Explicit Congestion Notification Mechanism Based on Class Based Queueing
Recently, the Internet has been widely spread, and then more variety network services are provided. In general, such network services are categorized by their requirement of the network quality. For example, real time sound and/or movie services are delay sensitive services, while the file transfer services require reliable transfer rather than shorter delay. However, the de facto standard network layer protocol IP (Internet Protocol) of the Internet does not care of their difference. If it can control the network based on the categories, the total effectiveness of the network throughput should be increased.
In order to solve the problem, many functions, such as ECN (Explicit Congestion Notification) and DiffServ (Differentiated Services) are proposed to be implemented for routers. In DiffServ, a priority is assigned to quality required from each service, and a router provides a priority control with respect to the assigned priority. CBQ (Class Based Queueing) is the one of typical methods to realize DiffServ.
In CBQ, a router prepares a queue for each priority class, and assigns fixed available bandwidth to the class. When the router receives a packet, it stores the packet in the queue corresponding to the priority of the packet. Then, CBQ provides a priority control where the router selects a packet to be transferred from its queues by the length of each queue and the upper bound of the available bandwidth of each class. Moreover, a higher priority class can temporally borrow a part of bandwidth from a lower priority class, if the lower priority class can afford to give the part of its assigned bandwidth.
DiffServ has realized the priority control for IP. Since the control is reflected from only the status of each router, it does not consider of the status of each end-to-end connection. From this fact, our research hypothesis is that introducing ECN to CBQ on DiffServ results in more effective total throughput. Since a router with the ECN mechanism can notify its congestion status to each end node, the sender can begin its flow control before the router observes heavy congestion. However, CBQ fixes available bandwidth of each class, even when heavy congestion occurs. By introducing ECN to CBQ, when the router is notified the observation of light congestion by ECN, the proposal method restricts bandwidth of a lower priority class, and provides an extra bandwidth to a higher priority class.
In the university program, the above proposal method is implemented on the IXP1200 systems. The experimentations for evaluation described in the above proposal method are executed under the basic network model. In this model, each source terminal sends data with different quality to a receiver. In this situation, their throughput, average transfer speed, and average delay time are also evaluated.
Abstract: CBQ is a popular mechanism to process specific services by priority such as real-time communication. Authors propose improve version CBQ. It can change upper limit of bandwidth dynamically according to as each priority queue length. In this paper, we discuss this improve version CBQ how to implement on Network Processor IXP1200. In accordance with this discussion, we implement this mechanism on Network Processor IXP1200 and evaluate improve version.
To ask about our project, please contact to:
Professor Yoshihiko Ebihara or Associate Professor Shigetomo Kimura
Institute of Information Sciences and Electronics, University of
Tsukuba
1-1-1 Ten'noudai, Tsukuba, Ibaraki, 305-8573
JAPAN