Today’s Internet Protocol (IP), the Internet’s network-layer protocol, provides
a best-effort service to all users without any guaranteed bandwidth. However,
for certain applications that have stringent network performance requirements
in terms of bandwidth, it is significantly important to provide Quality of Service (QoS) guarantees in IP networks. The end-to-end available bandwidth of a
network path, i.e., the residual capacity that is left over by other traffic, is determined by its tight link, that is the link that has the minimal available bandwidth.
The tight link may differ from the bottleneck link, i.e., the link with the minimal
capacity.
Passive and active measurements are the two fundamental approaches used
to estimate the available bandwidth in IP networks. Unlike passive measurement tools that are based on the non-intrusive monitoring of traffic, active tools
are based on the concept of self-induced congestion. The dispersion, which
arises when packets traverse a network, carries information that can reveal relevant network characteristics. Using a fluid-flow probe gap model of a tight link
with First-in, First-out (FIFO) multiplexing, accepted probing tools measure the
packet dispersion to estimate the available bandwidth. Difficulties arise, however, if the dispersion is distorted compared to the model, e.g., by non-fluid
traffic, multiple tight links, clustering of packets due to interrupt coalescing
and inaccurate time-stamping in general. It is recognized that modeling these
effects is cumbersome if not intractable.
To alleviate the variability of noise-afflicted packet gaps, the state-of-the-art
bandwidth estimation techniques use post-processing of the measurement results, e.g., averaging over several packet pairs or packet trains, linear regression,
or a Kalman filter. These techniques, however, do not overcome the basic assumptions of the deterministic fluid model. While packet trains and statistical
post-processing help to reduce the variability of available bandwidth estimates,
these cannot resolve systematic deviations such as the underestimation bias
in case of random cross traffic and multiple tight links. The limitations of the
state-of-the-art methods motivate us to explore the use of machine learning in
end-to-end active and passive available bandwidth estimation.
We investigate how to benefit from machine learning while using standard packet train probes for active available bandwidth estimation. To reduce
the amount of required training data, we propose a regression-based scaleinvariant method that is applicable without prior calibration to networks of arbitrary capacity. To reduce the amount of probe traffic further, we implemen
a neural network that acts as a recommender and can effectively select the
probe rates that reduce the estimation error most quickly. We also evaluate our
method with other regression-based supervised machine learning techniques.
Furthermore, we propose two different multi-class classification-based methods for available bandwidth estimation. The first method employs reinforcement learning that learns through the network path’s observations withou
having a training phase. We formulate the available bandwidth estimation as a
single-state Markov Decision Process (MDP) multi-armed bandit problem and
implement the "-greedy algorithm to find the available bandwidth, where " is
a parameter that controls the exploration vs. exploitation trade-off.
We propose another supervised learning-based classification method to obtain reliable available bandwidth estimates with a reduced amount of network
overhead in networks, where available bandwidth changes very frequently. In
such networks, reinforcement learning-based method may take longer to converge as it has no training phase and learns in an online manner. We also evaluate our method with different classification-based supervised machine learning techniques. Furthermore, considering the correlated changes in a network’s
traffic through time, we apply filtering techniques on the estimation results in
order to track the available bandwidth changes.
Active probing techniques provide flexibility in designing the input structure. In contrast, the vast majority of Internet traffic is Transmission Contro
Protocol (TCP) flows that exhibit a rather chaotic traffic pattern. We investigate
how the theory of active probing can be used to extract relevant information
from passive TCP measurements. We extend our method to perform the estimation using only sender-side measurements of TCP data and acknowledgmen
packets. However, non-fluid cross traffic, multiple tight links, and packet loss
in the reverse path may alter the spacing of acknowledgments and hence increase the measurement noise. To obtain reliable available bandwidth estimates
from noise-afflicted acknowledgment gaps we propose a neural network-based
method.
We conduct a comprehensive measurement study in a controlled network
testbed at Leibniz University Hannover. We evaluate our proposed methods
under a variety of notoriously difficult network conditions that have not been
included in the training such as randomly generated networks with multiple
tight links, heavy cross traffic burstiness, delays, and packet loss. Our testing
results reveal that our proposed machine learning-based techniques are able to
identify the available bandwidth with high precision from active and passive
measurements. Furthermore, our reinforcement learning-based method without any training phase shows accurate and fast convergence to available bandwidth estimates.