Gautam Barua

Bio: Gautam Barua is an academic researcher from Indian Institute of Technology Guwahati. The author has contributed to research in topics: Consistency (database systems) & Network packet. The author has an hindex of 7, co-authored 34 publications receiving 394 citations. Previous affiliations of Gautam Barua include Indian Institutes of Information Technology & Indian Institute of Technology Patna.

A formal framework for on-line software version change

Abstract: The usual way of installing a new version of a software system is to shut down the running program and then install the new version. This necessitates a sometimes unacceptable delay during which service is denied to the users of the software. An online software replacement system replaces parts of the software while it is in execution, thus eliminating the shutdown. While a number of implementations of online version change systems have been described in the literature, little investigation has been done on its theoretical aspects. We describe a formal framework for studying online software version change. We give a general definition of validity of an online change, show that it is in general undecidable and then develop sufficient conditions for ensuring validity for a procedural language.

Tracing attackers with deterministic edge router marking (DERM)

Abstract: Tracing the attackers in a distributed denial-of-service(DDoS) attack is particularly difficult since attackers spoof the source addresses We present a novel approach to IP Traceback – Deterministic Edge Router Marking (DERM) The proposed scheme is scalable to thousands of attackers, is very simple to implement at the routers, has no bandwidth overhead and needs minimal processing and storage requirements at the victim As each complete mark fits into a single packet, our scheme can also be used for per-packet filtering and as a congestion signature in a pushback protocol The traceback procedure requires a small number of packets and can be performed during the post-mortem analysis of an attack Only limited co-operation is required from Internet Service Providers (ISP) They do not have to reveal the topology of their internal networks.

Performance comparison of two on-demand routing protocols for mobile ad hoc networks

Abstract: AODV and DSR are two of the most important routing protocols for ad hoc networks. In this article, we make a comparison of these routing protocols in context of the services offered by them to the transport layer. We first study the interactions between the Transport and MAC layer and then, based on observations, propose metrics to measure the effectiveness of the two routing protocols. Detailed simulations are then performed to compare the performance of AODV and DSR under varying load, mobility and network size and connectivity. Our work makes clear the need for routing protocols to consider network load as an important factor in addition to path length while computing routes. In addition, we find that a suitable caching mechanism is necessary for scalability of a routing protocol and that its effectiveness increases with increasing connection density and decreasing mobility.

Caching of routes in ad hoc on-demand distance vector routing for mobile ad hoc networks

Abstract: Ad hoc networks are characterized by multihop wireless connectivity, frequently changing network topology and the need for efficient dynamic routing protocols. Recent comparative studies between Ad hoc on demand routing protocols like Ad hoc On demand Distance Vector routing (AODV) and Dynamic Source Routing (DSR) (the two on demand routing protocols for Ad hoc networks) have shown that AODV performs better than DSR for high mobility cases but faces the problem of high routing and MAC load as compared to DSR. This is because DSR resort to aggressive use of caching of routes while AODV does not. In this paper, we have incorporated caching of routes in AODV with the aim to reduce the routing and MAC load of AODV without changing the basic structure of the protocol. A detailed simulation model with MAC and physical layer models is used to study the effect of caching of routes in AODV and to compare its performance with AODV without cache and DSR. We show that caching of routes in AODV can lead to significant reduction in routing and MAC load as well as in delay in delivering the packet as compared to AODV without much compromise in terms of packet delivery fraction.

CRESQ: providing QoS and security in ad hoc networks

Abstract: Ad hoc networks, which have seen a drastic increase in their usage scenarios and convergence of different applications' traffic, are getting ready to support QoS and secure traffic. Existing protocols for ad hoc networks provide little or no support for QoS and security. We present a new routing protocol 'CRESQ' for ad hoc networks, with adequate support for QoS using resource reservation. Ad hoc networks pose certain unique challenges for QoS implementation, in addition to those presented by the wireline and wireless scenarios where resource reservation, high speed of the mobile nodes, and frequent hand-offs from the base-stations are the issues. Additional challenges in ad hoc networks are attributed to mobility of intermediate nodes, absence of routing infrastructure, and low bandwidth and computational capacity of the nodes. The proposed protocol 'CRESQ' takes all these limitations into account and provides a general framework for implementation of QoS. CRESQ, which is a cluster based routing protocol, effectively uses the clustering to minimize the routing overhead and to provide QoS guarantees. CRESQ is a source routing protocol, with an ability for localized route recovery to minimize route and QoS re-establishment delay. Simulations have shown that CRESQ performs considerably better than the existing protocols, in terms of packet drop ratio and routing overhead.

A survey of software refactoring

Abstract: We provide an extensive overview of existing research in the field of software refactoring. This research is compared and discussed based on a number of different criteria: the refactoring activities that are supported, the specific techniques and formalisms that are used for supporting these activities, the types of software artifacts that are being refactored, the important issues that need to be taken into account when building refactoring tool support, and the effect of refactoring on the software process. A running example is used to explain and illustrate the main concepts.

Providing database as a service

Abstract: We explore a novel paradigm for data management in which a third party service provider hosts "database as a service", providing its customers with seamless mechanisms to create, store, and access their databases at the host site. Such a model alleviates the need for organizations to purchase expensive hardware and software, deal with software upgrades, and hire professionals for administrative and maintenance tasks which are taken over by the service provider. We have developed and deployed a database service on the Internet, called NetDB2, which is in constant use. In a sense, a data management model supported by NetDB2 provides an effective mechanism for organizations to purchase data management as a service, thereby freeing them to concentrate on their core businesses. Among the primary challenges introduced by "database as a service" are the additional overhead of remote access to data, an infrastructure to guarantee data privacy, and user interface design for such a service. These issues are investigated. We identify data privacy as a particularly vital problem and propose alternative solutions based on data encryption. The paper is meant as a challenge for the database community to explore a rich set of research issues that arise in developing such a service.

Architecture-based runtime software evolution

Abstract: Continuous availability is a critical requirement for an important class of software systems. For these systems, runtime system evolution can mitigate the costs and risks associated with shutting down and restarting the system for an update. We present an architecture-based approach to runtime software evolution and highlight the role of software connectors in supporting runtime change. An initial implementation of a tool suite for supporting the runtime modification of software architectures, called ArchStudio, is presented.

Dynamic software updating

Abstract: Many important applications must run continuously and without interruption, yet must be changed to fix bugs or upgrade functionality. No prior general-purpose methodology for dynamic updating achieves a practical balance between flexibility, robustness, low overhead, and ease of use.We present a new approach for C-like languages that provides type-safe dynamic updating of native code in an extremely flexible manner (code, data, and types may be updated, at programmer-determined times) and permits the use of automated tools to aid the programmer in the updating process. Our system is based on dynamic patches that both contain the updated code and the code needed to transition from the old version to the new. A novel aspect of our patches is that they consist of verifiable native code (e.g. Proof-Carrying Code [17] or Typed Assembly Language [16]), which is native code accompanied by annotations that allow on-line verification of the code's safety. We discuss how patches are generated mostly automatically, how they are applied using dynamic-linking technology, and how code is compiled to make it updateable.To concretely illustrate our system, we have implemented a dynamically-updateable web server, FlashEd. We discuss our experience building and maintaining FlashEd. Performance experiments show that for FlashEd, the overhead due to updating is typically less than 1%.