92 research outputs found
Versatile Markovian models for networks with asymmetric TCP sources
In this paper we use Stochastic Petri Nets (SPNs) to study the interaction of multiple TCP sources that share one or two buffers, thereby considerably extending earlier work. We first consider two sources sharing a buffer and investigate the consequences of two popular assumptions for the loss process in terms of fairness and link utilization. The results obtained by our model are in agreement with existing analytic models or are closer to results obtained by ns-2 simulations. We then study a network consisting of three sources and two buffers and provide evidence that link sharing is approximately minimum-potential-delay-fair in case of equal round-trip times. \u
Analytical Model of TCP Relentless Congestion Control
We introduce a model of the Relentless Congestion Control proposed by Matt
Mathis. Relentless Congestion Control (RCC) is a modification of the AIMD
(Additive Increase Multiplicative Decrease) congestion control which consists
in decreasing the TCP congestion window by the number of lost segments instead
of halving it. Despite some on-going discussions at the ICCRG IRTF-group, this
congestion control has, to the best of our knowledge, never been modeled. In
this paper, we provide an analytical model of this novel congestion control and
propose an implementation of RCC for the commonly-used network simulator ns-2.
We also improve RCC with the addition of a loss retransmission detection scheme
(based on SACK+) to prevent RTO caused by a loss of a retransmission and called
this new version RCC+. The proposed models describe both the original RCC
algorithm and RCC+ improvement and would allow to better assess the impact of
this new congestion control scheme over the network traffic.Comment: Extended version of the one presented at 6th International Workshop
on Verification and Evaluation of Computer and Communication Systems (Vecos
2012
TCP smart framing: a segmentation algorithm to reduce TCP latency
TCP Smart Framing, or TCP-SF for short, enables the Fast Retransmit/Recovery algorithms even when the congestion window is small. Without modifying the TCP congestion control based on the additive-increase/multiplicative-decrease paradigm, TCP-SF adopts a novel segmentation algorithm: while Classic TCP always tries to send full-sized segments, a TCP-SF source adopts a more flexible segmentation algorithm to try and always have a number of in-flight segments larger than 3 so as to enable Fast Recovery. We motivate this choice by real traffic measurements, which indicate that today's traffic is populated by short-lived flows, whose only means to recover from a packet loss is by triggering a Retransmission Timeout. The key idea of TCP-SF can be implemented on top of any TCP flavor, from Tahoe to SACK, and requires modifications to the server TCP stack only, and can be easily coupled with recent TCP enhancements. The performance of the proposed TCP modification were studied by means of simulations, live measurements and an analytical model. In addition, the analytical model we have devised has a general scope, making it a valid tool for TCP performance evaluation in the small window region. Improvements are remarkable under several buffer management schemes, and maximized by byte-oriented schemes
A Performance Analysis Model of TCP over Multiple Heterogeneous Paths for 5G Mobile Services
Driven by the primary requirement of emerging 5G mobile services, the demand
for concurrent multipath transfer (CMT) is still prominent. Yet, multipath
transport protocols are not widely adopted and TCP-based CMT schemes will still
be in dominant position in 5G. However, the performance of TCP flow transferred
over multiple heterogeneous paths is prone to the link quality asymmetry, the
extent of which was revealed to be significant by our field investigation. In
this paper, we present a performance analysis model for TCP over multiple
heterogeneous paths in 5G scenarios, where both bandwidth and delay asymmetry
are taken into consideration. The evaluation adopting parameters from field
investigation shows that the proposed model can achieve high accuracy in
practical environments. Some interesting inferences can be drawn from the
proposed model, such as the dominant factor that affect the performance of TCP
over heterogeneous networks, and the criteria of determining the appropriate
number of links to be used under different circumstances of path heterogeneity.
Thus, the proposed model can provide a guidance to the design of TCP-based CMT
solutions for 5G mobile services
Achieving Ultra-Low Latency in 5G Millimeter Wave Cellular Networks
The IMT 2020 requirements of 20 Gbps peak data rate and 1 millisecond latency
present significant engineering challenges for the design of 5G cellular
systems. Use of the millimeter wave (mmWave) bands above 10 GHz --- where vast
quantities of spectrum are available --- is a promising 5G candidate that may
be able to rise to the occasion.
However, while the mmWave bands can support massive peak data rates,
delivering these data rates on end-to-end service while maintaining reliability
and ultra-low latency performance will require rethinking all layers of the
protocol stack. This papers surveys some of the challenges and possible
solutions for delivering end-to-end, reliable, ultra-low latency services in
mmWave cellular systems in terms of the Medium Access Control (MAC) layer,
congestion control and core network architecture
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