Shashank Khanvilkar

Virtual private networks: an overview with performance evaluation

Virtual private networks have gained immense popularity among commercial and defense organizations because of their capability to provide secure connectivity at lower costs. Several commercial and open source VPN products are now available that can be configured to provide VPN services with varying characteristics. This article studies some of the most popular open-source Linux-based VPN solutions (OSLVs) and compares them with respect to network performance (measured in terms of overhead, bandwidth utilization, and latency/jitter), features and functionalities (e.g., algorithm plugins and routing), and operational concerns (defined by security and scalability). Our experiments suggest that there is no single OSLV solution that excels in all considered aspects, and a combination of different VPN products and/or trade-off among desired characteristics may be required to deliver optimal performance. Our experiments also suggest that on an average, OSLVs using UDP-based tunnels have 50 percent lower overhead, 80 percent higher bandwidth utilization, and 40-60 percent lower latency/jitter than those using TCP.

Dynamic adaptive QoS provisioning over GPRS wireless mobile links

The General Packet Radio Service (GPRS) offers performance guaranteed packet data services to mobile users. A dynamic adaptive guaranteed quality-of-service (QoS) provisioning scheme is proposed over GPRS wireless mobile links via the guaranteed QoS media access control (GQ-MAC) protocol and the accompanying adaptive prioritized-handoff call admission control (AP-CAC) protocol to maintain QoS guarantees under the effect of mobile handoffs. The GQ-MAC protocol supports bounded access delay and packet-loss probability for respective delay and loss sensitive traffic, and dynamic adaptive resource allocation for bursty traffic. The AP-CAC protocol provides dynamic adaptive prioritized admission by differentiating handoff requests of different traffic classes with higher admission priorities over new calls via the dynamic multiple guard channels scheme, which adapts the channel capacity limits reserved for the multiple handoff request classes in each radio cell based on the current estimates of their arrival rates derived from the current number of ongoing calls in neighboring radio cells and the mobility pattern.

Tool integration for flexible simulation of distributed algorithms

Over the last two decades, considerable research has been done in distributed operating systems, which can be attributed to faster processors and better communication technologies. A distributed operating system requires distributed algorithms to provide basic operating system functionality like mutual exclusion, deadlock detection, etc. A number of such algorithms have been proposed in the literature. Traditionally, these distributed algorithms have been presented in a theoretical way, with limited attempts to simulate actual working models. This paper discusses our experience in simulating distributed algorithms with the aid of some existing tools, including OPNET and Xplot. We discuss our efforts to define a basic model‐based framework for rapid simulation and visualization, and illustrate how we used this framework to evaluate some classic algorithms. We have also shown how the performance of different algorithms can be compared based on some collected statistics. To keep the focus of this paper on the approach itself, and our experience with tool integration, we only discuss some relatively simple models. Yet, the approach can be applied to more complex algorithm specifications. Copyright

Experimental evaluations of open-source Linux-based VPN solutions

Virtual private networks (VPNs) provide a low-cost alternative to leased lines and as such, are becoming increasingly popular among commercial and defense organizations for providing vital inter-office connectivity. Several commercial and open-source VPN products are now available that mainly differ in their capabilities to provide safe and secure services. In this paper, we study fifteen popular open-source Linux-based VPN solutions (OSLVs) and compare them with respect to network performances (bandwidth, delay and latency/jitter), supported features & functionalities (algorithm plug-ins and routing) and operational concerns (security and scalability). Experiments suggest that there is no single OSLV that excels in all the considered aspects and a combination of different solutions and/or tradeoff among desired characteristics may be required to deliver an optimal performance. Also network performance results suggest that OSLVs using UDP tunnels introduce 50% lower overhead, utilize 80% higher bandwidth and have 40-60% lower latency/jitter than those based on TCP

6 – Multimedia Systems: Content-Based Indexing and Retrieval

This chapter focuses on two major issues pertaining to multimedia systems: (1) storage and encoding standards for image and video data and (2) content-based indexing and retrieval of multimedia data. First, the chapter briefly outlines theoretical foundations of image and video compression and then explores some widely used compression and encoding standards for multimedia. Content-based indexing and retrieval of multimedia is an emerging research area that has received wide attention from the research community over the past decade. It also explains fundamental issues related to the representation of multimedia data and discusses salient indexing and retrieval approaches. This chapter surveys the domain of content-based indexing and retrieval for image and video data in depth. Issues, such as low-level feature-based modeling, dimensionality reduction, and relevance feedback, are discussed.

RapidIO traffic management and flow arbitration protocol

The RapidIO data-streaming logical layer provides a segmentation and reassembly service to higher layers. Since a RapidIO receiver can potentially receive 64-kbyte PDUs from 64-kbyte senders, the memory requirements for successfully reassembling fragments is huge (~4 Gbytes). As RapidIO-based hardware chips have limited memory, efficient arbitration algorithms/protocols are needed that can fairly share memory among competing traffic streams, under constraints imposed by the standard. In this article we show that absence of proper arbitration can lead to deadlocks and system underutilization. We then develop a Flow Arbitration Protocol (now a part of RapidIO 2.0) as an extension to existing specification. A defining characteristic of this protocol is that memory resources can be reserved for single- and multi-PDU transfers.

7 – Multimedia Networks and Communication

This chapter discusses two popular protocol architectures, and SIP that are specifically designed to support distributed multimedia applications. The term multimedia refers to diverse classes of media employed to represent information. Multimedia traffic refers to the transmission of data representing diverse media over communication networks. It discusses general classification of media types from a networking/communication point of view and introduces some common media types like text, audio, images, and video. Further, this chapter discusses the inadequacy of the current best-effort Internet model to satisfy the multimedia traffic requirements. It describes three enhanced architectures: integrated services, differentiated services, and multi-protocol label switching. Next, this chapter presents some standard approaches for meeting the functional requirements posed by multimedia traffic and two protocol architectures that are introduced for the Internet protocol stack to satisfy these requirements. Current efforts to support multimedia traffic over the cellular/wireless networks are described.

QoS provisioning over GPRS wireless mobile links

The general packet radio service (GPRS) offers performance guaranteed packet data services to mobile users. This paper presents a guaranteed quality-of-service (QoS) provisioning scheme over GPRS wireless mobile links by proposing a guaranteed QoS media access control (GQ-MAC) protocol and an accompanying prioritized handoff call admission control (PH-CAC) protocol to maintain QoS guarantees under the effect of mobile handoffs. The GQ-MAC protocol supports bounded channel access delay for delay-sensitive traffic, bounded packet loss probability for loss-sensitive traffic, and dynamic adaptive resource allocation for bursty traffic. The PH-CAC protocol provides prioritized admission by differentiating handoff requests with different higher admission priorities over new calls via a multiple guard channel scheme.

NIS07-1: Efficient transmission of MP3 streams over VPNs

Multimedia applications communicating over a VPN, can leverage the security properties of a VPN with its performance drawbacks by securing only a part of its data. Selecting appropriate packets for security, however, is still an open research problem and novel methods need to be developed that can guarantee the privacy of a conversation even when a relatively large percentage of data is sent in the open. In this paper, we discuss one approach for securing MP3 audio. Here, we capitalize on the fundamental structure of data as defined in the MP3 standard and identify key fields that are necessary for decoding. We conjecture that the privacy of an MP3 stream can be guaranteed, if only these fields are secured. Since these fields are 17 to 32 bytes per MP3 frame, they constitute only 4% to 7.6% of a typical stream sampled/encoded at 44.1 Khz/128 Kbps. We prove this conjecture and demonstrate the performance gains of this approach when streaming over VPNs.

Towards a scalable and flexible architecture for virtual private networks

Virtual Private Networks (VPNs) are commonly used to provide secure connectivity over public networks. VPNs use tunnels to provide encryption, compression, and authentication functions, which are identically applied to every packet passing through them. However, this behavior may be overly rigid in many situations where the applications require different functions to be applied to different parts of their streams. Current VPNs are unable to offer such differential treatment, posing a heavy computational burden on edge routers, reducing their flexibility and degrading network performance. Additionally, the administrative cost of maintaining these tunnels is as high as O(N2) for an N node VPN. In this paper, we propose and evaluate a flexible VPN architecture (called Flexi-Tunes) where within a single VPN tunnel, different VPN functions are applied to different packet streams. Flexi-Tunes also replaces the traditional point-to-point tunnels with packet switched tunnels that improve scalability by reducing administrative costs to O(N). Simulation of this enhanced model demonstrates 170% improvement in bandwidth and 40 times improvement in end-to-end delay.