In a class of methods for measurement of available path capacity and other capacity-related metrics in a network, trains of probe packets are transmitted from a sender to a receiver across a network path, and the sequences of time stamps at sending and reception are analyzed. In large-scale implementations there may potentially be interference between the probe-packet trains corresponding to several concurrent measurement sessions, due to congestion in the network and common measurement end points. This paper outlines principles for large-scale deployments of network capacity measurement methods using standardized network functionality. Further, the paper provides an in-depth study of dimensioning and scalability challenges related to the measurement end-points of such systems. The main result is a framework for dimensioning of large-scale network capacity measurement systems based on TWAMP. The framework is based on a method for explicit calculation of queuelength and waiting-time distributions, where results from M/G/1 queuing theory are combined with Monte Carlo integration.

The first study that investigates the characteristics of received probe packets and the reliability of bandwidth estimates when actively measuring the available bandwidth over radio interfaces in mobile communication networks is presented. Knowledge of available bandwidth is very useful in various contexts, e.g. in network management and adaptive streaming applications. Bandwidth measuring tools have so far primarily been designed for and evaluated in wired networks. However, such tools should also be examined in wireless networks since the use of, e.g., mobile broadband is rapidly increasing. The properties of wired and wireless links differ substantially, which affect the performance of the tools. We have made active-probing experiments over a high-speed downlink shared channel, which is used for High-Speed Downlink Packet Access (HSDPA) in the mobile communication technology UMTS, and over a forward traffic channel in CDMA2000 1xEV-DO. Both experiments were performed over commercial networks. They show that one cannot always expect uniform per-packet processing over the radio channel in mobile networks, which is expected by many probing tools. This reduces the reliability of the available-bandwidth estimates, however we suggest how this can be handled. Finally, the mobile-network measurements are compared to experiments performed in an IEEE 802.11 wireless LAN, where the radio channel does not create the same packet-processing behaviour. We also discuss the possibility of using the probe traffic for the purpose of identifying the communication technology at the bottleneck of the network path, assumed this is a wireless broadband link, by mapping specifications of standardised communication technologies to observed probe-traffic characteristics. Copyright © 2011 John Wiley & Sons, Ltd.

Network tomography enables operators to monitor and take action based on path measurements between nodes, often located at the network edge. State-of-the-art network tomography solutions use tools to measure performance parameters such as jitter, loss and round-trip time between multiple nodes.

This paper presents a novel probing scheme which can be used for estimating the available bandwidth of subpaths, without the requirement of control over both endpoints of a network path. Instead of a probe-packet receiver, this scheme uses the ICMP capability of routers. An estimate of the available bandwidth from the endpoint to a router is obtained in much the same way as for state-of-the-art end-to-end probing methods. Taking into account ICMP packet generation limitations and delay, the estimate should be interpreted as a lower bound of the actual available bandwidth.By combining estimates for several routers along a path, it is possible to obtain lower bound estimates also for subpaths between routers. These bounds may be further sharpened if combined with an estimate from an end-to-end measurement. From the obtained subpath bounds, it may be possible to identify a portion of the end-to-end path containing the bottleneck link. It is also possible to infer lower bounds for the individual router hops.In order to demonstrate the feasibility of this ICMP-based scheme, the paper reports on a measurement study conducted over the Internet.

This paper presents a filter-based method BART (Bandwidth Available in Real-Time) for real-time estimation of end-to-end available bandwidth in packet-switched communication networks. BART relies on self-induced congestion, and repeatedly samples the available bandwidth of the network path with sequences of probe-packet pairs. The method is light-weight with respect to computation and memory requirements, and performs well when only a small amount of probe traffic is injected. BART uses Kalman filtering, which enables real-time estimation. It maintains a current estimate, which is incrementally improved with each new measurement of the inter-packet time separation in a sequence of probe-packet pairs. It is possible to tune BART according to specific needs. The estimation performance can be significantly enhanced by employing a change-detection technique. An implementation of BART has been evaluated in a physical test network with carefully controlled cross traffic. In addition, experiments have been performed over the Internet as well as over a mobile broadband connection.

The knowledge of the present available bandwidth on a network path is essential in numerous contexts, such as network management and streaming applications. A network path nowadays often contains at least one wireless link. This is obviously true for mobile users having a wireless connection to the Internet through a laptop or mobile terminal. The existing tools for measuring end-to-end available bandwidth are developed and optimized for paths with only guided media links. Since the characteristics for wired links and radio links differ in many aspects, such as fluctuations in capacity and stability, the network tools need to be evaluated also for network paths containing wireless links. In this investigation we have performed experiments over a high-speed downlink UMTS channel. This makes the present paper unique in the sense that it evaluates and analyzes the applicability of available-bandwidth measurement tools over a radio interface in a wide-area mobile communication network. For the experiments, a commercial mobile network has been used. The measurements show that it is feasible to achieve reliable estimates under certain circumstances. However, some cases pose challenges which motivate further studies.