Shirshanka Das

SPAWN: a swarming protocol for vehicular ad-hoc wireless networks

Future vehicular networks are expected to deploy short-range communication technology for inter-vehicle communication. In addition to vehicle-to-vehicle communication, users will be interested in accessing the multimedia-rich Internet from within the vehicular network. This motivates a compelling application of Co-operative Networking in the Vehicular Ad-Hoc network where the Ad Hoc network extends and complements the Internet. The broadcast nature of the wireless medium drives us to explore different design paradigms from the ones used in typical wired settings.A new paradigm in content delivery on the Internet using peer-peer swarming protocols is emerging [1,2]. We propose SPAWN, a simple cooperative strategy for content delivery in future vehicular networks. We study the issues involved in using such a strategy from the standpoint of Vehicular Ad-Hoc networks. Several enhancements to a popular swarming protocol (BitTorrent) are discussed including a gossip mechanism that leverages the inherent broadcast nature of the wireless medium, and a piece-selection strategy that uses proximity to exchange pieces quicker. Preliminary results show that SPAWN increases the perceived performance of the network, resulting in faster downloads for popular files.

A cross-layer framework for wireless LAN QoS support

The IEEE 802.11x based wireless LAN technologies are leading the indoor Internet distribution in education, business and home environments. They are usually deployed as wireless extension of a broadband access to the network (i.e. DSL, cable modem, etc). These technologies are based on CSMA/CA media access with a positive MAC layer acknowledgement and a retransmission mechanism that aids noisy channel propagation condition and eventual undetected collisions. While TCP traffic benefits from a layer 2 retransmission policy the multimedia traffic experiences large delays and jitter resulting in a poor user experience. We satisfy the emerging user need of a MAC layer Quality of Service (QoS) support by taking advantage from layers 4-7 information. We believe the concepts and the architectural design presented are suitable to enhance QoS support in wireless technologies.

QoS-aware multiple spanning tree mechanism over a bridged LAN environment

Todays emerging traffic is far removed from the traffic trends seen during the early days of Ethernet technology. As a result, the current IEEE 802.1 standards and its extensions to the spanning tree protocol fall short of providing satisfactory quality of service for traffic which has a significant amount of QoS-sensitive multimedia and VoIP traffic. In the current and near-future scenario of campus-wide networks with significantly large layer-2 clusters and numerous virtual LANs (VLANs), we show significant shortcomings of the basic spanning tree and the multiple spanning tree protocols with regard to QoS. We propose a novel, simple, and yet highly effective enhancement to the multiple spanning tree protocol to achieve a high degree of QoS by keeping in perspective the different characteristics of the various traffic types in the Diffserv framework. We discuss the problems of the current standards and present in detail our proposed extension to overcome them. Our simulation results show good improvements in throughput and significant benefits in delay for all classes of traffic to conclusively prove our claims.

The Case for Servers in a Peer-to-Peer World

The increasing ease of self-expression and web-publishing has resulted in an explosion in the amount of content being generated in the current Internet. Besides traditional sources such as news portals, regular users are documenting their lives and thoughts and other people are subscribing, downloading and viewing this content. A lot of content therefore is being generated at the edge and consumed by the edge. Traditional client-server architectures are known to be in-effective in handling large correlated bursts of user demands. However, with RSS becoming more popular, such flash crowd scenarios will be more and more commonplace due to automated polling and downloads. Peer to peer protocols such as BitTorrent provide an attractive solution for such scenarios. BitTorrent networks are scalable, and the expected download time is independent of the arrival rate of peers (content consumers). However, the base performance of a BitTorrent network may not be fast enough from a user or content publishers perspective. Besides, BitTorrent gives poor results towards the end of a flash crowd when most of the large burst of arrivals have downloaded and left, and there are not too many peers online. We motivate the need for a content delivery network with well connected servers to participate in BitTorrent delivery streams. The servers are dynamically added and function as cushions to handle increase in demand as well as bolster a delivery stream when there is a paucity of users.

Dealing with node mobility in ad hoc wireless network

A Mobile “Ad hoc” wireless NETwork (MANET) is a network established for a special, often extemporaneous service customized to applications. The ad hoc network is typically set up for a limited period of time, in an environment that may change from application to application. As a difference from the Internet where the TCP/IP protocol suite supports a vast range of applications, in the MANET the protocols are tuned to a specific customer and application (eg, send a video stream across the battlefield; find out if there is a fire in the forest; establish a videoconference among several teams engaged in a rescue effort, etc). The customers move and the environment may change dynamically and unpredictably. For the MANET to retain its efficiency, the ad hoc protocols at various layers may need to self-tune to adjust to environment, traffic and mission changes. From these properties emerges the vision of the MANET as an extremely flexible, malleable and yet robust and formidable network architecture. Indeed, an architecture that can be deployed to monitor the habits of birds in their natural habitat, and which, in other circumstances, can be organized to interconnect rescue crews after a Tsunami disaster, or yet can be structured to launch deadly attacks onto unsuspecting enemies.

A hierarchical multipath approach to QoS routing: performance and cost evaluation

Efforts to provide connection oriented service over the inherently best-effort Internet started almost right after its birth. Today, there exist a multitude of solutions that have been proposed but have never been implemented due to their impracticability. We propose a practical solution for fast, low cost, scalable, and yet accurate QoS routing. We propose to use hierarchical approaches to make the scheme practical and cost-effective. At the same time, we increase network utilization and decrease inaccuracy of stale information by the use of multiple paths. An extensive simulation of the various permutations of schemes over a large set of topologies and traffic conditions validate the proposed schemes and prove conclusively that hierarchical schemes with multiple path capabilities not only result in significantly lower overhead, but also give high levels of QoS performance. This paper presents the architecture of our schemes, the multiple path computation algorithm, and the simulation results validating our claims.

Efficient building method of multiple spanning tree for QoS and load balancing

Current traffic patterns are far removed from the traffic trends seen during the early days of Ethernet technology. Therefore, the current IEEE 802.1 standard and its extensions to the spanning tree protocol fall short of providing-satisfactory quality of service for traffic which has a significant amount of QoS-sensitive traffic. In addition, they do not provide a mechanism for stabilizing the traffic load among a whole bridged network where usually the root switch has to handle all the traffic from its child switches. In the current and near-future scenario of switching networks with significantly large layer-2 clusters and numerous VLANs, we show significant shortcomings of the basic spanning tree and the multiple spanning tree protocols with regard to QoS and load balancing. We propose to incorporate a bridge ID scheme of a regional root identifier which is used in multiple spanning tree instance (MSTI) to provide an efficient MSTI building method for QoS and load balancing. Through this scheme, the traffic source of a point-to-multipoint (P2MP) application can set itself as the root of MSTI satisfying the QoS constraint while roots of several regular MSTIs are built in a distributed way. We discuss the problem of building MSTI for P2MP applications and regular MSTIs and present in detail our proposed scheme. Our experiments for two cases show good improvement of QoS in terms of delay and load balancing of the whole bridge network.

A Practical QoS Network Management System Considering Load Balancing of Resources

This paper presents a load balancing scheme for Multipath QoS Routing in QMulator which was created by UCLA and utilized for QoS network. With this multipath routing, QMulator has showed that it was ready to address the varied characteristics of traffic and can assure a high degree of adherence to the quality of service demand as well as the load balancing in the sense of scattering packets. But it did not consider the whole network resources, such as link utilization or load balancing. The objective of this paper is to verifty the original benefits gotten from the multipath scheme and to use specific paths among several paths which are marked as lowest path utilization, the average of each link utilization in the path. The extensive experiments in QMulator showed that the proposed path utilization scheme gave the less variance values in each link where random traffics and flows were delivered and worked as load balacing metric in QMulator.