arXiv subjects

Wolfram Lautenschlaeger

Publications and source records attributed to Wolfram Lautenschlaeger.

4 recordsLinked to original sources

arXiv2021

A Scalable Factory Backbone for Multiple Independent Time-Sensitive Networks

Convergence of time-sensitive machine control networks as part of the operational technology (OT) with the ubiquitous information technology (IT) networks is an essential requirement for the ongoing digitalization of production. In this paper, we review the fundamental differences between both technologies, the challenges to be solved, existing and upcoming solutions like TSN and their limitations. Furthermore, we introduce an Ethernet extension for a backbone network at factory scale and line rates of 10 - 100Gbit/s. The backbone is intended to carry massive amounts of IT traffic together with the traffic of multiple independent OT networks at the precision of leading-edge field bus technologies in the sub-microsecond range. The backbone remains transparent and does not require changes to the attached OT sub-networks. We prove our claims by prototype measurements, interoperability tests and field trials.

cs.NI↗

arXiv2016

The Weak Convergence of TCP Bandwidth Sharing

TCP is the dominating transmission protocol in the Internet since decades. It proved its flexibility to adapt to unknown and changing network conditions. A distinguished TCP feature is the comparably fair resource sharing. Unfortunately, this abstract fairness is frequently misinterpreted as convergence towards equal sharing rates. In this paper we show in theory as well as in experiment that TCP rate convergence does not exist. Instead, the individual TCP flow rate is persistently fluctuating over a range close to one order of magnitude. The fluctuations are not short term but correlated over long intervals, so that the carried data volume converges rather slowly. The weak convergence does not negate fairness in general. Nevertheless, a particular transmission operation could deviate considerably.

cs.NI↗

arXiv2016

Global Synchronization Protection for Bandwidth Sharing TCP Flows in High-Speed Links

In a congested network link, synchronization effects between bandwidth-sharing TCP flows cause wide queue length oscillations, which may translate into poor link utilization if insufficiently buffered. We introduce global synchronization protection (GSP), a simple extension to the ordinary operation of a tail-drop queue that safely suppresses the flow synchronization. Our minimalistic solution is well suited for scaling with leading-edge link rates: it adds only few extra operations in the fast path and does not require accelerated memory access compared to the line rate. GSP makes it easier to provide advanced control of TCP congestion in high-speed links and in low-power packet processing hardware. Using experiments with a Linux prototype of GSP, we show that, despite its exclusive focus on removing global synchronization, the new scheme performs as well as far more complex active queue management (AQM) schemes like CoDel and PIE.

cs.NI↗

arXiv2014

A Deterministic TCP Bandwidth Sharing Model

Traditionally TCP bandwidth sharing has been investigated mainly by stochastic approaches due to its seemingly chaotic nature. Even though of great generality, the theories deal mainly with expectation values, which is prone to misinterpretation with respect to the Quality-of-Experience (QoE). We disassemble TCP operating conditions into dominating scenarios and show that bandwidth sharing alone follows mostly deterministic rules. From the analysis we derive significant root causes of well-known TCP aspects like unequal sharing, burstiness of losses, global synchronization, and on buffer sizing. We base our model on a detailed analysis of bandwidth sharing experiments with subsequent mathematical reproduction.

cs.NI↗