Arjuna Sathiaseelan

Enhanced broadband access as a solution to the social and economic problems of the rural digital divide

This article discusses the danger of a growing digital divide between rural and other areas. It presents broadband as increasingly necessary for the delivery of information, health, education, business, social security, public and leisure services. Access to broadband has become vital for rural communities to participate in a progressively digital economy and to overcome problems of physical and social isolation. Yet rural areas are among those most excluded from fast broadband developments. Although this is partly due to technological/economic barriers in reaching more remote locations, even where technology is available, adoption can still be low in rural areas. This article explores the problems of providing broadband in rural Britain, considers various technological approaches and concludes with key development areas for policy and government.

Exploiting the Power of Multiplicity: A Holistic Survey of Network-Layer Multipath

The Internet is inherently a multipath network: For an underlying network with only a single path, connecting various nodes would have been debilitatingly fragile. Unfortunately, traditional Internet technologies have been designed around the restrictive assumption of a single working path between a source and a destination. The lack of native multipath support constrains network performance even as the underlying network is richly connected and has redundant multiple paths. Computer networks can exploit the power of multiplicity, through which a diverse collection of paths is resource pooled as a single resource, to unlock the inherent redundancy of the Internet. This opens up a new vista of opportunities, promising increased throughput (through concurrent usage of multiple paths) and increased reliability and fault tolerance (through the use of multiple paths in backup/redundant arrangements). There are many emerging trends in networking that signify that the Internets future will be multipath, including the use of multipath technology in data center computing; the ready availability of multiple heterogeneous radio interfaces in wireless (such as Wi-Fi and cellular) in wireless devices; ubiquity of mobile devices that are multihomed with heterogeneous access networks; and the development and standardization of multipath transport protocols such as multipath TCP. The aim of this paper is to provide a comprehensive survey of the literature on network-layer multipath solutions. We will present a detailed investigation of two important design issues, namely, the control plane problem of how to compute and select the routes and the data plane problem of how to split the flow on the computed paths. The main contribution of this paper is a systematic articulation of the main design issues in network-layer multipath routing along with a broad-ranging survey of the vast literature on network-layer multipathing. We also highlight open issues and identify directions for future work.

Use of Quickstart for Improving the Performance of TFRC-SP Over Satellite Networks

The TCP-friendly rate control for small packets (TFRC-SP) protocol was designed for applications including streaming audio and voice over IP which send small packets. The long round trip delay of a satellite link could degrade the performance of such applications including streaming audio and VoIP that use TFRC-SP. In this paper, we analyze the performance of TFRC-SP carrying live streaming audio and VoIP over networks that include satellite paths. We also propose using the quickstart algorithm along with TFRC-SP to improve the performance of these applications over a satellite link

SCANDEX: Service Centric Networking for Challenged Decentralised Networks

Do-It-Yourself (DIY) networks are decentralised networks built by an (often) amateur community. As DIY networks do not rely on the need for backhaul Internet connectivity, these networks are mostly a mix of both offline and online networks. Although DIY networks have their own homegrown services, the current Internet-based cloud services are often useful, and access to some services could be beneficial to the community. Considering that most DIY networks have challenged Internet connectivity, migrating current service virtualisation instances could face great challenges. Service Centric Networking (SCN) has been recently proposed as a potential solution to managing services more efficiently using Information Centric Networking (ICN) principles. In this position paper, we present our arguments for the need for a resilient SCN architecture, propose a strawman SCN architecture that combines multiple transmission technologies for providing resilient SCN in challenged DIY networks and, finally, identify key challenges that need to be explored further to realise the full potential of our architecture.

TCP-Friendly Rate Control (TFRC) for bursty media flows

TCP-Friendly Rate Control (TFRC) was originally designed for multimedia streaming applications where continuous data was available at the sender. However, TFRC is not well-suited to the variable rate traffic presented by many modern adaptive media codecs. One way to counter this deficiency would be for the sender to continue to transmit at the media rate during periods of silence, known as padding. This use of padding can ensure acceptable application performance. However, it also degrades network performance, and decreases the usefulness of TFRC congestion control. Recent standardisation has resulted in a new revised TFRC specification. This paper describes candidate methods that were evaluated as a part of this revision and presents the first analysis of the new TFRC specification including a comparison this with the proposed Faster Restart method. It evaluates behaviour both in terms of the application performance benefit and the implications on other network traffic that share an Internet bottleneck and shows that the new methods improve the performance of bursty media. Although Faster Restart allowed TFRC to better support bursty applications, the additional gain was determined to be small when combined with the revised TFRC specification. Finally, revised TFRC is shown to remove the former incentive for padding, substantially improving the performance of other network traffic sharing a congested network.

Pushing the Frontier: Exploring the African Web Ecosystem

It is well known that Africas mobile and fixed Internet infrastructure is progressing at a rapid pace. A flurry of recent research has quantified this, highlighting the expansion of its underlying connectivity network. However, improving the infrastructure is not useful without appropriately provisioned services to utilise it. This paper measures the availability of web content infrastructure in Africa. Whereas others have explored web infrastructure in developed regions, we shed light on practices in developing regions. To achieve this, we apply a comprehensive measurement methodology to collect data from a variety of sources. We focus on a large content delivery network to reveal that Africas content infrastructure is, indeed, expanding. However, we find much web content is still served from the US and Europe. We discover that many of the problems faced are actually caused by significant inter-AS delays in Africa, which contribute to local ISPs not sharing their cache capacity. We discover that a related problem is the poor DNS configuration used by some ISPs, which confounds the attempts of providers to optimise their delivery. We then explore a number of other websites to show that large web infrastructure deployments are a rarity in Africa and that even regional websites host their services abroad. We conclude by making suggestions for improvements.

Performance of VoIP using DCCP over a DVB-RCS Satellite Network

The datagram congestion control protocol (DCCP) is a new IETF-defined transport protocol for Internet multimedia. The DCCP congestion control identifier 4 (CCID4) was specifically designed to support the stream of small packets generated by applications such as voice over IP (VoIP). This uses equation based congestion control. The long round trip delay when the path includes a satellite link could therefore degrade the performance of VoIP. In this paper, we analyze using simulation the performance of VoIP using CCID4 over a DVB-RCS network. We also analyze the different variants of CCID4 that have been proposed. The paper concludes that the current algorithm of CCID4 suffers for paths with appreciable delay when used to support voice calls with a bursty nature. The results show that these effects are only partially mitigated by the currently proposed variants of CCID4.

Virtual Public Networks

Universal access to Internet is crucial. Several initiatives have recently emerged to enable wider access to the Internet. Public Access WiFi Service (PAWS) enables free Internet access to all and is based on Lowest Cost Denominator Networking (LCDNet) -- a set of network techniques that enable users to share their home broadband network with the public. LCDNet takes advantage of the available unused capacity in home broadband networks and allows Less-than-Best Effort (LBE) access to these resources. LCDNet can enable third-party stakeholders, such as local governments, to setup, configure and operate home networks for public Internet access in cooperation with Internet Service Providers. Software-defined networking (SDN) creates new opportunities for the remote configuration and management of such networks at large scale. In this paper, we present Virtual Public Networks (VPuN), home networks created, deployed and managed through an evolutionary SDN control abstraction. This offers more flexibility to users and network operators, allowing them to share and control the network, while providing opportunities for new stakeholders to emerge as virtual network operators.

Software-defined wireless mesh networks for internet access sharing

Universal access to Internet is crucial, and as such, there have been several initiatives to enable wider access to the Internet. Public Access WiFi Service (PAWS) is one such initiative that takes advantage of the available unused capacity in home broadband connections and allows Less-than-Best Effort (LBE) access to these resources, as exemplified by Lowest Cost Denominator Networking (LCDNet). PAWS has been recently deployed in a deprived community in Nottingham, and, as any crowd-shared network, it faces limited coverage, since there is a single point of Internet access per guest whose availability depends on user sharing policies.To mitigate this problem and extend the coverage, we use a crowd-shared wireless mesh network (WMN), at which the home routers are interconnected as a mesh. Such a WMN provides multiple points of Internet access and can enable resource pooling across all available paths to the Internet backhaul. In order to coordinate traffic redirections through the WMN, we implement and deploy a software-defined WMN (SDWMN) control plane in one of the CONFINE community networks. We further investigate the potential benefits of a crowd-shared WMN for public Internet access by performing a comparative study between a WMN and PAWS. Our experimental results show that a crowd-shared WMN can provide much higher utilization of the shared bandwidth and can accommodate a substantially larger volume of guest traffic.

Reorder notifying TCP (RN-TCP) with explicit packet drop notification (EPDN)

Numerous studies have shown that packet reordering is common, especially in networks where there is high degree of parallelism and different link speeds. Reordering of packets decrease the TCP performance of a network, mainly because it leads to overestimation of the congestion in the network. In this paper, we analyse the performance of networks when reordering of packets occur. We propose a proactive solution that could significantly improve the performance of the network when reordering of packets occurs. We report results of our simulation experiments, which support this claim. Our solution is based on enabling the senders to distinguish between dropped packets and reordered packets. Copyright