Browsing by Author "Varadarajan, Srivatsan"
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Item Coverage based Proxy Placement for Content Distribution over the Internet(2002-11-05) Varadarajan, Srivatsan; Harinath, Raja; Srivastava, Jaideep; Zhang, Zhi-LiIn an effort to differentiate service quality, service providers have resorted to employing Content Distribution Networks (CDNs) over the Internet. CDNs deploy geographically distributed proxy servers which manage content on behalf of the service provider's servers forbetter performance and enhanced availability. In this paper we explore the proxy placement problem for content distribution over the Internet. Its goal is to strategically place a number of proxies in the network to optimize certain criteria which improve performance of proxies. We motivate and illustrate the various necessary factors and constraints that need to be taken into account for a good placement of proxies over the Internet whichreflect real world scenario more accurately and which we claim hitherto has not been completely addressed. We introduce a novel concept of host coverage characterizing every Autonomous Systems (AS) and use this stable, coarse grained measure as a long-term estimate of the load being serviced by the proxy system. We validate its applicability through an Internet study. We then pose anoptimal formulation of the proxy placement problem taking into consideration all the relevant factors. We propose a couple of proxy placement algorithms that solve the above problem and analyze their behavior. Finally we present the performance of those algorithms against the optimal solution and other schemes proposed in literature. We also study the stability of the proposed algorithms through avariety of experiments. Keyword: Proxy Placement, Coverage, Internet, ContentDistribution Network (CDN)Item Error Spreading: A Perception-Driven Approach Orthogonal to Error Handling in Continuous Media Streaming(1999-07-21) Varadarajan, Srivatsan; Ngo, Hung Q.; Srivastava, JaideepWith the growing popularity of the Internet, there is increasing interest in using it for audio and video transmission. Periodic network overloads, leading to bursty packet losses, have always been a key problem for network researchers. In a long-haul, heterogeneous network like the Internet, handling such an error becomes especially difficult. Perceptual studies of audio and video viewing have shown that bursty losses have the most annoying effect on people, and hence are critical issues to be addressed for applications such as Internet phone, video conferencing, distance learning, etc. Classical error handling techniques have focused on applications like FTP, and are geared towards ensuring that the transmission is correct, with no attention to timeliness. For isochronous traffic like audio and video, timeliness is a key criterion, and given the high degree of content redundancy, some loss of content is quite acceptable. In this paper we introduce the concept of error spreading, which is a transformation technique that takes the input sequence of packets (from an audio or video stream) and scrambles its packets before transmission. The packets are unscrambled at the receiving end. The transformation is designed to ensure that bursty losses in the transformed domain get spread all over the sequence in the original domain. Our error spreading idea deals with either cases where the stream has or does not have inter-frame dependencies. Perceptual studies have shown that users are much more tolerant of a uniformly distributed loss of low magnitude. We next describe a continuous media transmission protocol based on this idea. We also show that our protocol can be used complementary to other error handling protocols. Lastly, we validate its performance through a series of experiments and simulations. Keywords: Multimedia, network bursty error, permutation scheme.Item On Achieving Lower Consecutive Losses for Continuous Media Streams(1999-02-21) Srivastava, Jaideep; Varadarajan, Srivatsan; Ngo, Hung Q.With the growing popularity of the Internet, there is increasing interest in using it for audio and video transmission. Periodic network overloads, leading to bursty packet losses, have always been a key problem for network researchers. In a long-haul, heterogeneous network like the Internet, handling such an error becomes especially difficult. Perceptual studies of audio and video viewing have shown that bursty losses have the most annoying effect on people, and hence are critical issues to be addressed for applications such as Internet phone, video conferencing, distance learning, etc. Classical error handling techniques have focused on applications like FTP, and are geared towards ensuring that the transmission is correct, with no attention to timeliness. For isochronous traffic like audio and video, timeliness is a key criterion, and given the high degree of content redundancy, some loss of content is quite acceptable. In this paper we introduce the concept of error spreading, which is a transformation technique that takes the input sequence of packets (from an audio or video stream) and scrambles its packet before transmission. The packets are unscrambled at the receiving end. The transformation is designed to ensure that bursty losses in the transformed domain get spread all over the sequence in the original domain. Perceptual studies have shown that users are much more tolerant of a uniformly distributed loss of low magnitude. We next describe a continuous media transmission protocol based on this idea, and validate its performance through an experiment performed on the Internet.Item Performance Evaluation of Media Losses in the Continuous Media Toolkit(1997) Wijesekera, Duminda; Parikh, Shwetal; Varadarajan, Srivatsan; Srivastava, Jaideep; Nerode, AnilRapid growth of multimedia systems, and accordingly research in this area requires fast prototyping environments. The Berkeley Continuous Media Toolkit (GMT} is a popular environment that satisfies this need. Form a human user's perspective, in order for multimedia demonstrations to be comprehensible, the number of audio or video frames dropped and the timing delays in the ones that are displayed, need to be kept to a minimum. Therefore, it is important to know the frame dropping characteristics of CMT. In a series of experiments we rnonir.ored tlHi variation of thPse parameters with respect processor and network loads. It was obsprvrd that loads affen ap,gregau· frame drops at lower rates and consecutive frame drops at higher rates. Because at a higher rates a liarge number of consecutive frames are dropped, the ones that are played appear in a more timely manner. As a solution to observed problems, we present some QoS based approaches to control drop and delay parameters.Item Performance Evaluation of Synchronization Losses in the Continuous Media Toolkit(1997) Wijesekera, Duminda; Parikh, Shwetal; Varadarajan, Srivatsan; Srivastava, Jaideep; Nerode, Anil; Foresti, MarkThis paper presents a performance analysis of synchronization services provided by the Berkeley Continuous Media Toolkit (CMT). The quality of audio-video synchronization is measured against processor and network loads for both remote and local clients. The metrics of analysis are the perceptible and tolerable human perceptual limits reported by Steinmetz, and another metric designed to measure synchronization of lossy media streams. It is shown that according to Steinmetz' metric CMT provides imperceptible audio-video mis-synchronization for about 10 seconds, and tolerable synchronization for about 13 seconds from the start of the clips for local clients under low processor loads. It is also shown that under high loads, synchronization is achieved at the cost of losing media frames.Item Providing Cost-Effective Multimedia Services in a Concurrent Engineering Environment(1997) Wijesekera, Duminda; Parikh, Shwetal; Varadarajan, Srivatsan; Srivastava, Jaideep; Nerode, AnilHandling of multimedia information in a concurrent engineering environment requires that it be delivm·ed in a cost effective manner, yet having high consumc~r satisfaction. Since most such products run on general purpose computers connected by off the shelf networks, multimedia streams are likely to encounter frame losses, delays and mis-synchronizations, resulting in poor quality. This paper presents metrics to measure such qualitative degradations and reports the results of a user study to validate them. Furthermore, this paper includes the results of a performance analysis of the Continuous Media Toolkit (GMT) for constructing multimedia demonstrations, to measure its ability to satisfy parameters obtained in the user survey. In addition, we describe some enhancements that are being made to CMT to ensure user needs are met.