Modeling and Control of Rare Segments in BitTorrent with Epidemic Dynamics

Despite its existing incentives for leecher cooperation, BitTorrent file sharing fundamentally relies on the presence of seeder peers. Seeder peers essentially operate outside the BitTorrent incentives, with two caveats: slow downlinks lead to increased numbers of "temporary" seeders (who left their console, but will terminate their seeder role when they return), and the copyright liability boon that file segmentation offers for permanent seeders. Using a simple epidemic model for a two-segment BitTorrent swarm, we focus on the BitTorrent rule to disseminate the (locally) rarest segments first. With our model, we show that the rarest-segment first rule minimizes transition time to seeder (complete file acquisition) and equalizes the segment populations in steady-state. We discuss how alternative dissemination rules may {\em beneficially increase} file acquisition times causing leechers to remain in the system longer (particularly as temporary seeders). The result is that leechers are further enticed to cooperate. This eliminates the threat of extinction of rare segments which is prevented by the needed presence of permanent seeders. Our model allows us to study the corresponding trade-offs between performance improvement, load on permanent seeders, and content availability, which we leave for future work. Finally, interpreting the two-segment model as one involving a rare segment and a "lumped" segment representing the rest, we study a model that jointly considers control of rare segments and different uplinks causing "choking," where high-uplink peers will not engage in certain transactions with low-uplink peers.Comment: 18 pages, 6 figures, A shorter version of this paper that did not include the N-segment lumped model was presented in May 2011 at IEEE ICC, Kyot

DIY networking as a facilitator for interdisciplinary research on the hybrid city

DIY networking is a technology with special characteristics compared to the public Internet, which holds a unique potential for empowering citizens to shape their hybrid urban space toward conviviality and collective awareness. It can also play the role of a “boundary object” for facilitating interdisciplinary interactions and participatory processes between different actors: researchers, engineers, practitioners, artists, designers, local authorities, and activists. This position paper presents a social learning framework, the DIY networking paradigm, that we aim to put in the centre of the hybrid space design process. We first introduce our individual views on the role of design as discussed in the fields of engineering, urban planning, urban interaction design, design research, and community informatics. We then introduce a simple methodology for combining these diverse perspectives into a meaningful interdisciplinary collaboration, through a series of related events with different structure and framing. We conclude with a short summary of a selection of these events, which serves also as an introduction to the CONTACT workshop on facilitating information sharing between strangers, in the context of the Hybrid City III conference

CSMA Local Area Networking under Dynamic Altruism

In this paper, we consider medium access control of local area networks (LANs) under limited-information conditions as befits a distributed system. Rather than assuming "by rule" conformance to a protocol designed to regulate packet-flow rates (e.g., CSMA windowing), we begin with a non-cooperative game framework and build a dynamic altruism term into the net utility. The effects of altruism are analyzed at Nash equilibrium for both the ALOHA and CSMA frameworks in the quasistationary (fictitious play) regime. We consider either power or throughput based costs of networking, and the cases of identical or heterogeneous (independent) users/players. In a numerical study we consider diverse players, and we see that the effects of altruism for similar players can be beneficial in the presence of significant congestion, but excessive altruism may lead to underuse of the channel when demand is low

D3.13 MAZI as an experiment in interdisciplinarity: the outcome of a self-reflection exercise (version 3)

[Executive summary] This is the final version (#3) of the MAZI deliverables that propose self-reflections as a way of dealing with collective work in interdisciplinary action and research projects. Its goal is to provide a meta-perspective of the self-reflection outcome documented in detail in previous deliverables. More specifically, this document overviews the process as carried out in MAZI, and based on this experience It develops three categories of action toward shaping common spaces for inter- and transdisciplinary research. These are namely a) communities of practice around DIY networking technology (Section 2); b) transdisciplinary co-design of the MAZI toolkit across-localities (Section 3); and c) learning, appropriation of knowledge, sustainability and knowledge transfer (Section 4). It concludes with a few important lessons learned for the design of future projects, namely the positive impact of assigning overlapping leading roles to partners in interdisciplinary research, and the need for carefully designed intimate spaces for self reflection

Faving Reciprocity in Content Sharing Communities A comparative analysis of Flickr and Twitter

International audienceIn the Web 2.0 era, users share and discover interesting content via a network of relationships created in various social networking or content sharing sites. They can become for example contacts, followers or friends and express their appreciation of specific content uploaded by their peers by faving, retweeting or liking them depending on whether they are in Flickr, Twitter or Facebook respectively. Then they can discover additional content of interest through the lists of favorites of their contacts and so on. This faving (or favoring) functionality becomes thus a central part of content sharing communities for two purposes: (a) it helps the propagation of content amongst users and (b) it stimulates users' participation and activity. In this paper, we make a first step to understand users' faving behavior in content sharing communities in terms of reciprocity using publicly available datasets from Flickr and Twitter. Do users favor content only when they really appreciate it or they often feel the need to reciprocate when their content is appreciated by one of their contacts or even by a stranger? Do people take advantage of this process to gain popularity? What is the impact of the design, the social software, of a specific community and the type of content shared? These are some of the questions that our first results help to answer

From an idea to a scalable working model: merging economic benefits with social values in Sardex

The remarkable growth of Sardex as a local currency throughout the island of Sardinia over the past 4 years motivated an in-depth look at its starting assumptions, its design and operational principles, and its socio- economic context. The paper looks at Sardex as a social innovation start-up, as a medium of exchange and unit of account, as an online and offline mutual credit system, and as a closed economic community or ‘circuit’. The analysis relies on interviews of circuit members conducted in the Summer of 2014 and benefits from the reflexive point of view of one of its founders. The main findings are that trust was and continues to be fundamentally important for the creation and operation of the local Sardex currency and of the circuit, and that Sardex mediates both economic and social value(s). These properties make it an ideal space for experimentation in socio-economic innovation that can be characterized as a ‘laboratory of institutional learning.

From an idea of a scalable working model: merging economic benefits with social values in Sardex

The remarkable growth of Sardex as a local currency throughout the island of Sardinia over the past 5 years motivated an in-depth look at its starting assumptions, design and operational principles, and socioeconomic context. The paper looks at Sardex as a social innovation start-up, a medium of exchange and unit of account, an online and offline mutual credit system, and a closed economic community or ‘circuit’. The analysis relies on semi-structured in-depth interviews of circuit members and benefits from the reflexive point of view of one of its founders. The main findings are that trust was and continues to be fundamentally important for the creation and operation of the mutual credit system, and that Sardex encompasses and mediates both economic and social value(s). Compared to other mutual credit systems, in addition to its unique design features Sardex is distinguished by its federated model of expansion and its strong commitment to keeping a balance between the economic and social aspects. In Sardex, money’s fungibility is defined by market utility and social values at the same time

Central urban space as a hybrid common infrastructure

In this paper we document and reflect on an ongoing co-design process of a new urban space, by the name L200, located in a very central and precious location in Zurich. L200 has the characteristics of an urban node at the confluence of many networks, a hub like railway stations provide these days but at a different spatial scale, acting as a much needed infrastructure for various commoning activities, among others. L200 is designed as a hybrid space, hosting a DIY digital platform, which is being co-created as a commons itself through a long-term participatory process and provides a building block for an alternative, bottom-up, vision to the “smart city”. In terms of participatory design, we experiment with, and advocate for, a structured laissez-faire methodology that frames both the physical and digital space as interconnected common infrastructures that the members of the association are free to use “as if it was their own” for limited periods of time. This participation through action approach allows for needs, ideas, and interventions to manifest naturally without any pressure or expectations. This means that the corresponding research for producing tools, methodologies, and designs need to advance in a slower than usual pace, and integrate many perspectives that use different languages and have different priorities. This slow design process allows for various forms of peer learning to occur. The paper lays out the overall L200 project in its full complexity through the dual role assumed by the authors, as researchers and activists, highlighting specific decisions, actions, and methodologies that contribute to the on-going research on infrastructuring the commons

Alternative internet(s) – what are they and do they have a future?

This is the first post in a series on alternative internet(s), following a workshop on the topic at the LSE in September, organised by Mélanie Dulong de Rosnay, Francesca Musiani, Alison Powell and Panayotis Antoniadis. The authors introduce the key topics that will be covered in the series here