Bandwidth Measurement Of IP Network

Along with the rapid development of Internet technology andnetwork business, the demands for network resources isincreasing unprecedentedly, so the network also becomes morecomplex. To support different QoS (Quality of Service), moreand more network application programs need to learn the networkperformance parameters such as delay, bandwidth, throughputand so on. The network performance drops significantly becauseof the network load becoming heavy, and network equipmentoverloaded by the increasing network users and applications,which demand us to examine and analysis the network performance,so that the network performance can be improved. Therefore thenetwork performance measurement becomes an important andpopular theme. Efficient network measurement will be alsohelpful in securing the network and assuring the network workssmoothly.As a metric used to describe the capacity of the networktransferring information, Bandwidth reflects end-to-end pathdirectly, including link capacity and available bandwidth,which is the base of managing the network performance andcontrolling the quality of services. There are many kinds ofAlgorithms and tools on bandwidth measurement, but among whichthere still has no appropriate tools for the networkapplication programs such as web services. That is because theprograms can't install programs on the other end. None but thepathchar doesn't need the collaboration of the other end, yetthe pathchar has some disadvantages such as it can only measurelink capacity, and need the network path to be symmetrical,which restrict its application. After an in-depth study on the former models and algorithmson bandwidth measurement, this paper brings forward a newalgorithm—Timestamp-based Packet Tetrad Algorithm (TPTA):the source end sends packet tetrad which has the time stampoptions with ICMP echo. Based on the relationships of thedifference of the packets length, the changes of the timedifference that the packets pass through the link, the linkcapacity and the cross traffic, the link capacity and availablebandwidth can be worked out. The TPTA has been verifiedconcisely in network simulator and practice. TPTA has thesecharacteristics:●It doesn't need the assistance of the destination end,because the source end sends packet tetrad, having thetime stamp options with ICMP echo, to the network.Furthermore, the required time measurement can be gottenaccording to the ICMP.●It doesn't demand that the path is symmetrical, becausewhen the router set the time in the packets header, thetime will not change later, that is to say, the time hasnothing to do with the following links.●It has the capacity of anti-jamming, because it canfiltrate part of the data that fail in queuing, and itdoesn't be interfered by the cross traffic in thefollowing links.●It has a good accuracy. Thanks to the packet tetrad, iteliminates the error caused by increase of the length ofthe packet when the packet pass through data-link layerand physical layer.●It can measure link capacity and available bandwidth ofany link at the same time in a path, also it can get thebottleneck bandwidth and the available bandwidth through hop-by-hop measurement.