Transport Protocol Throughput Fairness

Interest continues to grow in alternative transport protocols to the Transmission Control Protocol (TCP). These alternatives include protocols designed to give greater efficiency in high-speed, high-delay environments (so-called high-speed TCP variants), and protocols that provide congestion control without reliability. For the former category, along with the deployed base of ‘vanilla’ TCP – TCP NewReno – the TCP variants BIC and CUBIC are widely used within Linux: for the latter category, the Datagram Congestion Control Protocol (DCCP) is currently on the IETF Standards Track. It is clear that future traffic patterns will consist of a mix of flows from these protocols (and others). So, it is important for users and network operators to be aware of the impact that these protocols may have on users. We show the measurement of fairness in throughput performance of DCCP Congestion Control ID 2 (CCID2) relative to TCP NewReno, and variants Binary Increase Congestion control (BIC), CUBIC and Compound, all in “out-of-the box” configurations. We use a testbed and endto- end measurements to assess overall throughput, and also to assess fairness – how well these protocols might respond to each other when operating over the same end-to-end network path. We find that, in our testbed, DCCP CCID2 shows good fairness with NewReno, while BIC, CUBIC and Compound show unfairness above round-trip times of 25ms

An Experimental Investigation of TCP Performance in High Bandwidth-Delay Product Paths.

The performance of the Internet is determined not only by the network and hardware technologies that underlie it, but also by the software protocols that govern its use. In particular, the TCP transport protocol is responsible for carrying the great majority of traffic in the current internet, including web traffic, email, file transfers, music and video downloads. TCP provides two main functions. First, it provides functionality to detect and retransmit packets lost during a transfer thereby providing a reliable transport service to higher layer applications. Second, it enforces congestion control. That is, it seeks to match the rate at which packets are injected into the network to the available network capacity. A particular aim here is to avoid so-called congestion collapse, prevalent in the late 1980s prior to the inclusion of congestion control functionality in TCP. Over the last decade or so, the link speeds within networks have increased by several orders of magnitude. While the TCP congestion control algorithm has proved remarkably successful, it is now recognised that its performance is poor on paths with high bandwidth-delay product, e.g. see [13, 8, 14, 26, 12] and references therein. With the increasing prevalence of high speed links, this issue is becoming of widespread concern. This is reflected, for example, in the fact that the Linux operating system now employs an experimental algorithm called BIC-TCP[26] while Microsoft are actively studying new algorithms such as Compound-TCP[25]. While a number of proposals have been made to modify the TCP congestion control algorithm, all of these are still experimental and pending evaluation as they change the congestion control in new and significant ways and their effects on the network are not well understood. In fact, the basic properties of networks employing these algorithms may be very different to networks of standard TCP flows. The aim of this thesis is to address, in part, this basic observation

On the Experimental Evaluation of Vehicular Networks: Issues, Requirements and Methodology Applied to a Real Use Case

One of the most challenging fields in vehicular communications has been the experimental assessment of protocols and novel technologies. Researchers usually tend to simulate vehicular scenarios and/or partially validate new contributions in the area by using constrained testbeds and carrying out minor tests. In this line, the present work reviews the issues that pioneers in the area of vehicular communications and, in general, in telematics, have to deal with if they want to perform a good evaluation campaign by real testing. The key needs for a good experimental evaluation is the use of proper software tools for gathering testing data, post-processing and generating relevant figures of merit and, finally, properly showing the most important results. For this reason, a key contribution of this paper is the presentation of an evaluation environment called AnaVANET, which covers the previous needs. By using this tool and presenting a reference case of study, a generic testing methodology is described and applied. This way, the usage of the IPv6 protocol over a vehicle-to-vehicle routing protocol, and supporting IETF-based network mobility, is tested at the same time the main features of the AnaVANET system are presented. This work contributes in laying the foundations for a proper experimental evaluation of vehicular networks and will be useful for many researchers in the area.Comment: in EAI Endorsed Transactions on Industrial Networks and Intelligent Systems, 201

An Experimental Investigation of TCP Performance in High Bandwidth-Delay Product Paths.

The performance of the Internet is determined not only by the network and hardware technologies that underlie it, but also by the software protocols that govern its use. In particular, the TCP transport protocol is responsible for carrying the great majority of traffic in the current internet, including web traffic, email, file transfers, music and video downloads. TCP provides two main functions. First, it provides functionality to detect and retransmit packets lost during a transfer thereby providing a reliable transport service to higher layer applications. Second, it enforces congestion control. That is, it seeks to match the rate at which packets are injected into the network to the available network capacity. A particular aim here is to avoid so-called congestion collapse, prevalent in the late 1980s prior to the inclusion of congestion control functionality in TCP. Over the last decade or so, the link speeds within networks have increased by several orders of magnitude. While the TCP congestion control algorithm has proved remarkably successful, it is now recognised that its performance is poor on paths with high bandwidth-delay product, e.g. see [13, 8, 14, 26, 12] and references therein. With the increasing prevalence of high speed links, this issue is becoming of widespread concern. This is reflected, for example, in the fact that the Linux operating system now employs an experimental algorithm called BIC-TCP[26] while Microsoft are actively studying new algorithms such as Compound-TCP[25]. While a number of proposals have been made to modify the TCP congestion control algorithm, all of these are still experimental and pending evaluation as they change the congestion control in new and significant ways and their effects on the network are not well understood. In fact, the basic properties of networks employing these algorithms may be very different to networks of standard TCP flows. The aim of this thesis is to address, in part, this basic observation

SatERN: a PEP-less solution for satellite communications

In networks with very large delay like satellite IPbased networks, standard TCP is unable to correctly grab the available resources. To overcome this problem, Performance Enhancing Proxies (PEPs), which break the end-to-end connection and simulate a receiver close enough to the sender, can be placed before the links with large delay. Although splitting PEPs does not modify the transport protocol at the end nodes, they prevent the use of security protocols such as IPsec. In this paper, we propose solutions to replace the use of PEPs named SatERN. This proposal, based on Explicit Rate Notification (ERN) protocols over IP, does not split connections and is compliant with IP-in-IP tunneling solutions. Finally, we show that the SatERN solution achieves high satellite link utilization and fairness of the satellite traffic