Research On Network Available Bandwidth Measurement

The main function of network measurement is to acquire the relevant information and operation status of network. Network measurement provides critical input information for network operation and management,which play an important role. Recently, Network measurement is widely concerned by the research community. In view of various measurement problems, people put forward a variety of measurement methods. At present, network measurement problems mainly include end-to-end(link) available bandwidth measurement, end-to-end(link) delay measurement, end-to-end(link) loss rate measurement and network traffic information measurement. There are two kinds of end-to-end available bandwidth measurement methods: active measurement and passive measurement. Active measurement methods inject probe traffic into network, and estimate the available bandwidth by analyzing the information of probing packets. Passive measurement refers to installing the traffic monitoring devices on network path. This paper mainly studies the active measurement methods.Gap-based measurement methods assume that the path contains only one link,and inject packet pair into the path. The cross traffic will enlarge the gap between the two packet in the packet pair when the packet pair goes through the path. So we can establish the relationship between sending packet gaps, receiving packet gaps and available bandwidth, which is called single-hop model. In multi-hops environment, gap-based measurement methods thinks that, the relationship between sending packet gaps, receiving packet gaps and available bandwidth on the narrow link can be defined by single-hop model. Gap-based measurement methods see the packet gap measured in the receiver as the packet gap when leaving the narrow link. Obviously, the gap measured in the receiver is not equal to the gap when leaving the narrow link. In this paper, based on this disadvantage, the classical Spruce algorithm has been improved. The new algorithm Improved-Spruce changed the probing packet structure, introduced discarding strategy timely.Rate-based measurement method is based on the principle of self- induced congestion. If the sending rate of probing packets is larger than the available bandwidth,the path is congested, the receiving rate of probing packets will be smaller than the sending rate of probing packets. If the sending rate of probing packets is not larger than the available bandwidth, the path is not congested, the receiving rate of probing packets will be equal to the sending rate of probing packets. These algorithms send several packet trains with different rate, and then try to look for the critical state, in which sending rate of packet train equals to receiving rate of packet train. The probing rate can be regarded as the available bandwidth estimation value. This kind of measurement method injects a large number of probing traffic, which increase the network load. This paper presents a new algorithm ABLSF(algorithm based least square fitting), the algorithm needn’t to send probing traffic whose rate is less than the available bandwidth. ABLSF derived new relationship between sending rate of packet train and receiving rate of packet train.A simple line can identify the available bandwidth quickly.