Cao Le Thanh Man

ImTCP: TCP with an inline measurement mechanism for available bandwidth

We introduce a novel mechanism for actively measuring available bandwidth along a network path. Instead of adding probe traffic to the network, the new mechanism exploits data packets transmitted in a TCP connection (inline measurement). We first introduce a new bandwidth measurement algorithm that can perform measurement estimates quickly and continuously and is suitable for inline measurement because of the smaller number of probe packets required and the negligible effect on other network traffic. We then show how the algorithm is applied in RenoTCP through a modification to the TCP sender only. We call the modified version of RenoTCP that incorporates the proposed mechanism ImTCP (Inline measurement TCP). The ImTCP sender adjusts the transmission intervals of data packets, then estimates available bandwidth of the network path between sender and receiver utilizing the arrival intervals of ACK packets. Simulations show that the new measurement mechanism does not degrade TCP data transmission performance, has no effect on surrounding traffic and yields acceptable measurement results in intervals as short as some RTTs (round-trip times). We also give examples in which measurement results help improving TCP performance.

ICIM: An Inline Network Measurement Mechanism for Highspeed Networks

In high-speed networks, such as 1-Gbps or higher networks, bandwidth measurement algorithms that utilize packet transmission/arrival intervals, such as packet trains and packet pairs, have a number of problems. First, network measurement for large bandwidth requires short packet transmission intervals, which causes a heavy load on the CPU. Second, network interface cards for high-speed networks usually employ Interrupt Coalescence (IC), which rearranges the arrival intervals of packets and causes bursty transmission of packets. In the present study, we introduce ICIM (Interrupt Coalescence-aware inline measurement), a new bandwidth measurement approach that overcomes these two problems. ICIM utilizes the data packets of an active TCP connection for the measurement. In order to determine the available bandwidth, rather than adjusting the packet transmission intervals, the TCP sender instead adjusts the number of packets involved in a burst and checks whether the inter-intervals of the bursts of corresponding ACK packets are increased or not. Simulation results show that ICIM can measure the bandwidth as high as some Gbps while requiring a number of data packets that is only 1/100 of that of the existing stream-based algorithm.

A merged inline measurement method for capacity and available bandwidth

We have proposed a new TCP version, called ImTCP (Inline measurement TCP), in [1]. The ImTCP sender adjusts the transmission intervals of data packets, and then utilizes the arrival intervals of ACK packets for the available bandwidth estimation. This type of active measurement in a TCP connection (inline measurement) is preferred because it delivers measurement results that are as accurate as active measurement, even though no extra probe traffic is injected into the network. In the present research, we combine a new capacity measurement function with the currently used measurement method to enable simultaneous measurement of both capacity and available bandwidth in ImTCP. The capacity measurement algorithm is essentially based on the packet pair technique, but also consider the estimated available bandwidth values for data filtering or data calculation, so that this algorithm promises better measurement results than current packet-pair-based measurement algorithms.

A New Available Bandwidth Measurement Technique for Service Overlay Networks

We introduce a new measurement algorithm for the available bandwidth in a network path between two endhosts. This algorithm is an adaptation from existing active measurement methods for the purpose of being applied in inline network measurement. Inline network measurement method measures the available bandwidth by using packets which an active TCP connection transmits, instead of using probe packets, as in the existing methods. The measurement is performed by inferring network characteristics information from transmitting and receiving intervals of TCP data and ACKnowledgement packets. Inline network measurement is useful in service overlay networks, in which up-to-date information on the available bandwidth in the underlying IP network should be known as early as possible. In this paper, we first introduce the measurement algorithm and then discuss the problems with applying the proposed measurement algorithm to an active TCP connection. We evaluate the proposed measurement algorithm using simulation experiments and show that it can provide an estimation of available bandwidth every 2-4 RTTs. Moreover, the accuracy of measurement results can be maintained considerably well while the number of packets in a measurement is reduced by approximately 90% in comparison with existing methods.

Inferring Available Bandwidth of Overlay Network Paths Based on Inline Network Measurement

We introduce ImSystem, a distributed system that infers real-time information concerning the available bandwidth of all of the paths in the overlay networks, using a technique called inline network measurement. The key concept in ImSystem is that, when the overlay hosts transmit overlay traffic, they deploy the traffic to perform inline network measurements and exchange results with each other. ImSystem performs supplemental active measurements only when overlay traffic is insufficient for inline measurements, and therefore injects very little probe traffic onto the network. In addition, we enhance the system to ImSystem Plus, in which conflicts of the supplemental active measurements are greatly reduced, providing that the IP network topology is known. The simulation results show that the proposed systems have the same accuracy as that when all paths are measured by active measurements, while using only a small amount of probe traffic.

A Simultaneous Inline Measurement Mechanism for Capacity and Available Bandwidth of End-to-End Network Path

We previously proposed a new version of TCP, called Inline measurement TCP (ImTCP), in [2], [3]. The ImTCP sender adjusts the transmission intervals of data packets and then utilizes the arrival intervals of ACK packets for available bandwidth estimation. This type of active measurement is preferred because the obtained results are as accurate as those of other conventional types of active measurement, even though no extra probe traffic is injected onto the network. In the present research, we develop a new capacity measurement function and combine it with ImTCP in order to enable simultaneous measurement of both capacity and available bandwidth in ImTCP. The capacity measurement algorithm is a new packet-pair-based measurement technique that utilizes the estimated available bandwidth values for capacity calculation. This new algorithm promises faster measurement than current packet-pair-based measurement algorithms for various situations and works well for high-load networks, in which current algorithms do not work properly. Moreover, the new algorithm provides a confidence interval for the measurement result.

Inline bandwidth measurement techniques for gigabit networks

We introduce an inline measurement method that can overcome difficulties in measurement task in high-speed network environment, such as short packet transmission intervals and Interrupt Coalescence function deployed in the high-speed Network Interface Cards. The method adjusts the number of packets involved in a packet burst of an active TCP connection, and utilises the inter-intervals of the bursts of the corresponding ACK packets for bandwidth measurement. Experiment results show that the proposed inline measurement method can measure the bandwidth in the network paths at least 1-Gbps or higher.

An inline measurement method for capacity of end-to-end network path

We previously proposed a new version of TCP, called inline measurement TCP (ImTCP), in Cao Le Thanh Man et al. (2004). The ImTCP sender adjusts the transmission intervals of data packets and then utilizes the arrival intervals of ACK packets for available bandwidth estimation. This type of active measurement is preferred because the obtained results are as accurate as those of other conventional types of active measurement, even though no extra probe traffic is injected onto the network. In the present research, we combine a new capacity measurement function with ImTCP in order to enable simultaneous measurement of both capacity and available bandwidth in ImTCP. The capacity measurement algorithm is a new packet-pair-based measurement technique that utilizes the estimated available bandwidth values for capacity calculation. This new algorithm promises faster measurement than current packet-pair-based measurement algorithms for various situations and works well for high-load networks, in which current algorithms do not work properly. Moreover, the new algorithm provides a confidence interval for the measurement result.