A dataset for buffering delays due to the interaction between the Nagle algorithm and the delayed acknowledgement algorithm in cyber-physical systems communication

Abstract

In this article, we provide the research community with a dataset for the buffering delays that data packets experience at the TCP sending side in the realm of Cyber-Physical Systems (CPSs) and IoT. We focus on the buffering that occurs at the sender side due to the the adverse interaction between the Nagle algorithm and the delayed acknowledgement algorithm, which both were originally introduced into TCP to prevent sending out many small-sized packets over the network. These two algorithms are turned on (enabled) by default in most operating systems. The dataset is collected using four real-life operating systems: Windows, Linux, FreeBSD, and QNX (a real-time operating system). In each scenario, there are three separate different (virtual) machines running various operating systems. One machine, or an end-host, acts a data source, another acts as a data sink, and a third acts a network emulator that introduces artificial propagation delays between the source and the destination. To measure buffering delay at the sender side, we record for each sent packet the two time instants: when the packet is first generated at the application layer, and when it is actually sent on the physical network. In each case, 10 different independent experiment replications/runs are executed. Here, we provide the full distribution of all delay samples represented by the cumulative distribution function (CDF), which is expressed mathematically by $F_X\left(x\right)=P(X\le x),$ where $x$ is the delay measured in milliseconds, and $P$ is the probability operator. The data exhibited here gives an impression of the amount and scale of the delay occurring at sender-side in TCP. More importantly, the data can be used to investigate the degree these delays affect the performance of cyber-physical systems and IoT or other real-time applications employing TCP.

Keywords: IoT communication; Protocol parameter tuning; Real-life operating systems; Real-time communication; Sender-side delay; TCP buffering.

Fig. 1

The CDF values of the sender-side buffering delays for the four different operating systems when the Nagle algorithm is enabled and when the round-trip propagation delay between the sender and the receiver is 30 ms.

Fig. 2

The CDF values of the sender-side buffering delays for the Windows operating systems when the Nagle algorithm is enabled and for different round-trip propagation delay between the sender and the receiver.

Fig. 3

The CDF values of the sender-side buffering delays for the QNX operating systems when the Nagle algorithm is both enabled and disabled, and when the round-trip propagation delay between the sender and the receiver is 10 ms.

Fig. 4

Experimental Setup: VM1, VM2, and VM3 are virtual machines running on the physical machine and are connected via a software router inside the hypervisor.

Fig. 5

The Layering Model of Network Protocols with example protocols in each layer.