No abstract

There is a growing interest in the use of variants of the Transmission Control Protocol (TCP) in high-speed networks. ns-2 has implementations of many of these high-speed TCP variants, as does Linux. ns-2, through an extension, permits the incorporation of Linux TCP code within ns-2 simulations. As these TCP variants become more widely used, users are concerned about how these different variants of TCP might interact in a real network environment -how fair are these protocol variants to each other (in their use of the available capacity) when sharing the same network. Typically, the answer to this question might be sought through simulation and/or by use of an experimental testbed. So, we compare with TCP NewReno the fairness of the congestion control algorithms for 5 high-speed TCP variants -BIC, Cubic, Scalable, High-Speed and Hamilton -on both ns-2 and on an experimental testbed running Linux. In both cases, we use the same TCP code from Linux. We observe some differences between the behaviour of these TCP variants when comparing the testbed results to the results from ns-2, but also note that there is generally good agreement.

We present experimental results evaluating fairness of several proposals to change the TCP congestion control algorithm, in support of operation on high bandwidth-delayproduct (BDP) network paths. We examine and compare the fairness of New Reno TCP, BIC, Cubic, Hamilton-TCP, Highspeed-TCP and Scalable-TCP. We focus on four different views of fairness: TCP-friendliness, RTT-fairness, intraand inter-protocol fairness.

Abstract-Many new transport protocols are being defined, including, for example, variants of the Transmission Control Protocol (TCP), to better match the requirements of new applications. A key issue in the evaluation of protocol flows, in terms of their performance, is how fair they are to other flows. Specifically, it is important to understand how a mix of existing and/or new protocols will interact with each other when using the same network resources. Such observations help to inform protocol design, and allow an assessment of potential impacts on users. We present a simple, yet effective, methodology for examining a specific case of inter-flow fairness based solely on measurements of flow performance. As well as using an existing fairness metric, we propose a new metric which provides a richer information summary for the evaluation of fairness.

Although often at odds, journalists and politicians share many of the same problems on social media. Both are obliged to maintain a public profile and to remain cheerful and polite, no matter how gross the provocation. Both struggle with the competing demands of professionalism and likeabilityoften a zero-sum game. Both seek trust and respect on platforms notorious for dishonesty and no-holds-barred disdain. Both may also be seen as authority figures, part of the establishment, and thus fair game for cutting down to size. Pugnacious criticism of politicians has always been a part of the system. When Lord Bew chaired a government report on intimidation of MPs, partly in response to the increase of abuse on social media, he said at its launch: "Politics is a rough old game, and it should be a rough game." MPs' postbags have always contained abuse; but social media has allowed a level of personal hostility that has disturbed politicians and commentators. It has also removed traditional filters that protected politicians. Secretaries used to bin the most vicious letters from the "green-ink brigade" a colour the unhinged seem to favour-but now every insult comes on phones. While the hatred and threats aimed at politicians, particularly on Twitter, had been an issue for some time, the death of MP Jo Cox in 2016 threw it into sharp focus. She had been subject to abuse on Twitter in relation to her Remainer stance. Although her killer had not sent threats himself, he researched right-wing groups online and repeatedly shouted "Britain First" as he stabbed her.