65058359
Group Based Routing in Disconnected Ad Hoc Networks
In this paper, we propose a routing protocol for disconnected ad hoc networks where most nodes tend to move about in groups. To the best of our knowledge, no routing protocol for disconnected ad hoc networks has been designed earlier keeping in mind possible group patterns formed by the movement of nodes. Our protocol works by identifying groups using an efficient distributed group membership protocol, and then routing at the group level, rather than at the node level. The protocol is designed so that existing concepts of routing in disconnected ad hoc networks can be extended to work at the group level. Initial simulations across a broad spectrum of parameters suggest that our protocol performs better in terms of delivery ratio and latency over traditional approaches like AODV [1], and also over disconnected routing approaches like the 2-Hop routing protocol [2].
9811083
Performance enhancement of a contract net protocol based system through instance-based learning
The contract net protocol (CNP) is a widely used coordination mechanism in multiagent systems. It has a lot of communication overhead due to the broadcast of the task announcements. The performance of the CNP degrades drastically when the number of communicating agents and the number of tasks announced increases. Hence, it has problems of scalability. In order to overcome this limitation, an instance-based learning (IBL) mechanism is designed that uses previously stored instances in order to select a target agent. This avoids the expensive bidding process. The scheme is implemented in a simulated distributed hospital system where the CNP is used for resource sharing across hospitals. Experimental results demonstrate that with the incorporation of the IBL, the system performance improves significantly. The system is better scalable with respect to the number of tasks.
46604085
Assertion-based verification turns the corner
The "formal verification method: Getting around the Brick Wall" panel at the 2002Design Automation Conference highlighted the industrial emergence of assertion-based verification and the need to go beyond current methods. Moderator David Dill initiated a discussion on the three brick walls to formal verifcation methods: handling high computational complexity, formulating properties to check, and characterizing the set of legal inputs to the design underverification. The panelists addressed moving to higher abstraction levels and assertion-based.verification as two strategies to solve these problems.
1312822
One Hop Lookups for Peer-to-Peer Overlays
Current peer-to-peer lookup algorithms have been designed with the assumption that routing information at each member node must be kept small, so that the bookkeeping required to respond to system membership changes is also small. In this paper, we show that this assumption is unnecessary, and present a technique that maintains complete routing tables at each node. The technique is able to handle frequent membership changes and scales to large systems having more than a million nodes. The resulting peer-to-peer system is robust and can route lookup queries in just one hop, thus enabling applications that cannot tolerate the delay of multi-hop routing.
100323
Tree based MPLS routing
MPLS (MultiProtocol Label Switching) is a new technology proposed by the IETF [4,10] for network routing, and is being increasingly deployed by the largest Internet service providers. The MPLS technology differs from conventional network protocols in a crucial way: instead of reading the entire packet header at all switching points, the analysis of the packet header is done just once, when the packet header is assigned a stack of labels, and thenceforth, each switching point or router just gets to look at the label at the top of the stack (and the ingress edge), and based only on this information, it has to make a decision about the next-hop node [17,16]. In another departure from conventional routing and in particular from IP source routing, where the entire packet route is explicitly put in the header and popped off along the route, the router can not only pop the top label, it can push other labels on top of the stack.The two parameters of interest in designing MPLS routing protocols are the number of labels used, and the depth of the stack used for routing. Clearly, both cannot be simultaneously minimized, and there is often an interesting trade-off between label size and stack depth: it is obvious that if k labels are used, one must have a stack depth of logk n.In fact, it was not known whether this bound could be achieved even for trees; the best stack depth previously achieved with a constant number of labels was O(log2 n). In this paper, we show that one can indeed get asymptotically optimal upper bounds and route on trees using k labels and a maximum stack depth of O(logk n), and that this trade-off can be achieved using a simpler and more intuitive protocol than the one given in [9]. These tree-routing ideas are then shown to give better routing protocols for planar graphs as well. In particular, we show how to route along near-shortest paths (of length at most (1 + ε) times the shortest-path) with O(log2 n/ε) labels and logarithmic stack depth. We also apply them to graphs with smaller separators, including most large ISP networks.
10822035
An extensible information model for shared scientific data collections
An information model is defined to support sharing of composite-media scientific data. The model consists of data objects and links. Data objects are associated with descriptorswhich contain all the metadata related to the object. A novel aspect of the information model is that both the data and metadata associated with a data object can be in structured or semistructured form. The links in the model are typed, and contain several built-in types such as resolution and derivation link types, to adequately model object relationships in scientific data. The model is extensible in the sense that users are allowed to define new object types and new link types. At the San Diego Supercomputer Center, we are currently investigating issues in providing the necessary infrastructure to implement this model. ©1999 Elsevier Science B.V. All rights reserved.
3072771
A practical approach for microscopy imaging data management (MIDM) in neuroscience
Current data management approaches can easily handle the relatively simple requirements for molecular biology research but not the more varied and sophisticated microscopy imaging data in neuroscience research. We developed a project-oriented experimental imaging data management system through integration of the object-relational Oracle DBMS (database management system) and a distributed file management system, the storage resource broker (SRB). The data model we developed on Oracle9i supports semantic and analytical queries and image content mining. The MIDM provides comprehensive descriptive, structural, spatial and administrative information on microscopy image datasets. The current MIDM is web accessible at http://ncmir.ucsd.edu/CCDB. This paper describes the MIDM architecture and data mode in MIDM.