Browsing by Author "Banerjee, Suman"
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Item Analysis of the NICE Application Layer Multicast Protocol(2002-08-01) Banerjee, Suman; Bhattacharjee, BobbyApplication layer multicast protocols organize a set of hosts into an overlay tree for data delivery. Each host on the overlay peers with a subset of other hosts. Since application layer multicast relies only on an underlying unicast architecture, multiple copies of the same packet can be carried by a single physical link or node on the overlay. The stress at a link or node is defined as the number of identical copies of a packet carried by that link or node. Stretch is another important metric in application layer multicast, which measures the relative increase in delay incurred by the overlay path between pairs of members with respect to the direct unicast path. In this paper we study the NICE application layer multicast protocol to quantify and study the tradeoff between these two important metrics --- stress and stretch in scalably building application layer multicast paths. Also UMIACS-TR-2002-60Item The Case for a Multi-hop Wireless Local Area Network(2003-12-18) Lee, Seungjoon; Banerjee, Suman; Bhattacharjee, BobbyWe propose a multi-hop wireless LAN architecture and demonstrate its benefits to wireless clients. For this architecture, we define implementation paths that allow interoperation with existing wireless LANs and therefore lead to an incremental deployment of this system. We quantify the performance benefits of the proposed schemes through measurements in realistic wireless LAN environments. We also examine the performance of such multi-hop wireless LANs through detailed simulation studies. Our results show that such multi-hop extensions can significantly improve the wireless access experience (in terms of data throughput, latency, etc.) for clients who enable such mechanisms. More interestingly, when multi-hop extensions are enabled by some of the clients, it also positively impacts the performance at other clients that are completely unaware of such extensions. UMIACS-TR-2003-73Item A Clustering Scheme for Hierarchical Routing in Wireless Networks(2000-03-01) Banerjee, Suman; Khuller, SamirIn this paper we present a clustering scheme to create hierarchies for wireless networks. A cluster is defined as a subset of vertices, whose induced graph is connected. In addition, a cluster is required to obey certain constraints that are useful for hierarchical routing. While all these constraints cannot be met simultaneously for general graphs, we show how for wireless network topologies, such a clustering can be obtained. We also present simulation results from a distributed implementation of this scheme to demonstrate its convergence and stability properties.Item Efficient Data Processing using Cross Layer Hints(2002-12-19) Banerjee, Suman; Agrawala, Ashok; Kramer, Michael J.Conventional network stacks define a layered architecture, where each layer implements a set of services and exports a well-defined interface to be used by its immediate upper layer. A key design choice of the layered architecture has been to provide isolation between the functional modules of distinct layers. While such an architecture provides an useful abstraction for system development, the strict isolation of this layered architecture limits the flexibility of tailoring the behavior of the lower layers of the stack to the needs of the application. In this paper we define a new architecture, called X-Tags, which allows flexible interaction between layers for cooperative data processing without impacting the isolation property. In this architecture, applications use special tags to provide semantic hints for data processing to lower layers. We motivate the usefulness of this architecture by describing ts applicability to some emerging applications. UMIACS-TR-2002-59Item Efficient Geographic Routing in Multihop Wireless Networks(2006-01-13T21:40:55Z) Lee, Seungjoon; Bhattacharjee, Bobby; Banerjee, SumanWe propose a new link metric called normalized advance (NADV) for geographic routing in multihop wireless networks. NADV selects neighbors with the optimal trade-off between proximity and link cost. Coupled with the local next hop decision in geographic routing, NADV provides an adaptive and efficient cost-aware routing strategy. Depending on the objective or message priority, applications can use the NADV framework to minimize various types of link cost. In this paper we present efficient methods for link cost estimation and perform detailed simulations in diverse scenarios. Our results show that NADV outperforms current schemes in many aspects: for example, in high noise environments with frequent packet losses, the use of NADV leads to 83% higher delivery ratio. When compared to centralized routing, geographic routing using NADV finds paths whose cost is close to the optimum.Item Measuring Traffic on the Wireless Medium: Experience and Pitfalls(2003-01-21) Yeo, Jihwang; Banerjee, Suman; Agrawala, AshokA number of measurement studies have examined traffic characteristics in wireless networks. Most of these measurements have been conducted from the wired portion of the network. In this paper we argue that such measurements are not sufficient to expose either the characteristics of the wireless medium or how such characteristics impact traffic patterns. While it is easier to make consistent measurements in the wired part of a network, such measurements can not observe the significant vagaries present in the wireless medium itself. As a consequence constructing an efficient and accurate measurement system from a wireless vantage point is important but usually quite difficult. In our work we have explored the various issues in implementing such a system to monitor traffic in an 802.11 based wireless network. We identify different challenges in making such measurements and provide detailed experimental evidence in their supports. Our work shows that the wireless measurement allows us to infer much richer information about the medium characteristics than is possible with a measurements made on the wired part of the network. We apply our measurement technique to study the end-to-end wireless network delay. We show that wireless monitoring can effectively identify the causes of end-to-end delays. (UMIACS-TR-2002-101)Item Minimum Energy Paths for Reliable Communication in Multi-hop Wireless Networks(2002-01-31) Banerjee, Suman; Misra, ArchanCurrent algorithms for minimum-energy routing in wireless networks typically select minimum-cost multi-hop paths. In scenarios where the transmission power is fixed, each link has the same cost and the minimum-hop path is selected. In situations where the transmission power can be varied with the distance of the link, the link cost is higher for longer hops; the energy-aware routing algorithms select a path with a large number of small-distance hops. In this paper, we argue that such a formulation based solely on the energy spent in a single transmission is misleading --- the proper metric should include the total energy (including that expended for any retransmissions necessary) spent in reliably delivering the packet to its final destination. We first study how link error rates affect this retransmission-aware metric, and how it leads to an efficient choice between a path with a large number of short-distance hops and another with a smaller number of large-distance hops. Such studies motivate the definition of a link cost that is a function of both the energy required for a single transmission attempt across the link and the link error rate. This cost function captures the cumulative energy expended in reliable data transfer, for both reliable and unreliable link layers. Finally, through detailed simulations, we show that our schemes can lead to upto 30-70% energy savings over best known current schemes, under realistic environments.Item A Protocol for Scalable Application Layer Multicast(2001-09-05) Banerjee, Suman; Bhattacharjee, Bobby; Parthasarathy, SrinivasanWe describe a new application-layer multicast protocol that is specifically designed to scale to large groups. Our scheme is based upon a hierarchical clustering of the application-layer multicast peers and can be used to produce a number of different data delivery trees with specific properties. On average, group members using our protocol maintain only a constant amount of state about other group members, and incur a constant amount of control overhead. We present extensive simulations of both our protocol and the Narada protocol over Internet-like topologies. Our results show that for groups of size 32 or more, we reduce control overhead by orders of magnitude, and link stress by 25%, while retaining similar end-to-end latencies and failure recovery properties.Item Rover Technology: Enabling Scalable Location-Aware Computing(2002-01-31) Banerjee, Suman; Agarwal, Sulabh; Kamel, Kevin; Kochut, Andrzej; Kommareddy, Christopher; Nadeem, Tamer; Thakkar, Pankaj; Trinh, Bao; Youssef, Adel; Youssef, Moustafa; Larsen, Ron; Shankar, A. Udaya; Agrawala, AshokLocation-aware computing involves the automatic tailoring of information and services based on the current location of the user. We have designed and implemented Rover, a system that enables location-based services, as well as the traditional time-aware, user-aware and device-aware services. To achieve system scalability to very large client sets, Rover servers are implemented in an "action-based" concurrent software architecture that enables fine-grained application-specific scheduling of tasks. We have demonstrated feasability through implementations for both outdoor and indoor environments on multiple platforms. (Also UMIACS-TR 2001-89)Item Scalable Application Layer Multicast(2002-08-01) Banerjee, Suman; Bhattacharjee, Bobby; Kommareddy, ChristopherWe describe a new scalable application-layer multicast protocol, specifically designed for low-bandwidth data streaming applications with large receiver sets. Our scheme is based upon a hierarchical clustering of the application-layer multicast peers and can support a number of different data delivery trees with desirable properties. We present extensive simulations of both our protocol and the Narada application-layer multicast protocol over Internet-like topologies. Our results show that for groups of size 32 or more, our protocol has lower link stress (by about 25%), improved or similar end-to-end latencies and similar failure recovery properties. More importantly, it is able to achieve these results by using orders of magnitude lower control traffic. Finally, we present results from our wide-area testbed in which we experimented with 32-100 member groups distributed over 8 different sites. In our experiments, average group members established and maintained low-latency paths and incurred a maximum packet loss rate of less than 1% as members randomly joined and left the multicast group. The average control overhead during our experiments was less than 1 Kbps for groups of size 100. Also UMIACS-TR-2002-53Item Scalable Resilient Media Streaming(2003-06-04) Banerjee, Suman; Braud, Ryan; Lee, Seungjoon; Bhattacharjee, Bobby; Srinivasan, AravindWe present a low-overhead media streaming system, called SRMS (Scalable Resilient Media Streaming) that can be used to scalably deliver streaming data to a large group of receivers. SRMS uses overlay multicast for data distribution to a large group of users. SRMS leverages a probabilistic loss recovery technique to provide high data delivery guarantees even under large network losses and overlay node failures. Through detailed analysis in this paper, we show that this loss recovery technique (and consequently SRMS) has efficient scaling properties --- the overheads at each overlay node asymptotically decrease to zero with increasing group sizes. We also present a detailed description of the SRMS architecture. The clients in the SRMS system are able to interoperate with existing media streaming servers that use RTP for data transport. One of the interesting features of SRMS is that it can simultaneously support clients with disparate access bandwidths. It enables the necessary bandwidth adaptations using standard Real-time Transport Protocol (RTP) mechanisms, e.g. RTP translators. We have implemented and evaluated the SRMS system in detail on an emulated network as well as on a wide-area testbed with up to 128 clients. Our results show that clients using SRMS achieve high (> 97%) data delivery ratios with low overheads (< 5%) even for very high failure rates (upto five per minute). (UMIACS-TR-2003-51)Item Scalable Secure Group Communication over IP Multicast(2001-05-16) Banerjee, Suman; Bhattacharjee, BobbyWe introduce and analyze a scalable re-keying scheme for implementing secure group communications IP multicast. We show that our scheme incurs constant processing, message, and storage overhead for a re-key operation when a single member joins or leaves the group, and logarithmic overhead for bulk simultaneous changes to the group membership. These bounds hold even when group dynamics are not known a-priori. Our re-keying algorithm requires a particular clustering of the members of the secure multicast group. We describe a protocol to achieve such clustering and show that it is feasible to efficiently cluster members over realistic Internet-like topologies. We evaluate the overhead of our own re-keying scheme and also of previously published schemes via simulation over an Internet topology map containing over 280,000 routers. Through analysis and detailed simulations, we show that this re-keying scheme performs better than previous schemes for a single change to group membership. Further, for bulk changes, our algorithm outperforms all previously known schemes by several orders of magnitude in terms of actual bandwidth usage, processing costs and storage requirements.