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Ordered communication in ad hoc networks
Edited by D.A. Agarwal, D.A. Tran, and M.D. Yarvis
1. Introduction
Although the number of IEEE 802.11-based wireless LANs has grown exponentially in recent years, most production-grade 802.11-based networks operate in the infrastructure mode. In this mode, each wireless station communicates with the rest of the world, including other nearby wireless stations, through an access point. While adequate in many cases, this mode does not work well in situations where an access point infrastructure is not available or connecting to the internet is not of major concern. Consider a group of users, each with a laptop equipped with an 802.11 network interface card (NIC), gather at a conference room to have a face-to-face meeting. During the meeting, they need to exchange files among themselves, and have access to other collaborative applications. If the wireless LAN infrastructure is absent or overloaded, these users are better off forming an ad hoc network among themselves than relying on a supporting infrastructure.
However, with existing operating system interfaces and utilities, it is non-trivial to set up a secure ad hoc network among a set of wireless stations even with expert network administrators present. Even when such a network can be set up, sharing files is cumbersome, because a file owner has to explicitly export the files to be shared, e.g. through Windows file sharing, so that others can manually connect to his machine and copy the file. Finally, there is no easy way for these users to securely share applications over an ad hoc wireless network for collaborative work. All these barriers prevent wireless LAN from realizing its potential as the network medium of instant infrastructure for collaborative work. Similar problems exist in other application domains, such as the first responder networks for emergency or crisis handling. The goal of the WShare project is to develop an instant collaboration infrastructure that can transparently and efficiently establish a secure collaboration workspace, including network connectivity, file exchange, and application sharing, on wireless ad hoc networks with only minimal user intervention.
For enabling users to exchange files, WShare provides a shared file repository abstraction. Users can deposit files into or remove files from this shared file space, and the set of files currently in the shared...