Mobile nodes in some challenging network scenarios suffer from intermittent connectivity and frequent partitions e.g. battlefield and disaster recovery scenarios. Disruption Tolerant Network (DTN) technologies are designed to enable nodes in such environments to communicate with one another. Several DTN routing schemes have been proposed. In order for the DTN technology to be useful, enhancements need to be made to legacy applications e.g. emails, web browsers, instant messaging etc to enable

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... ch applications to work over DTNs. In this paper, we present a DTN Jabber proxy which we have developed to allow mobile devices to run Jabber applications over DTN. Our proxy can identify group chat messages which enable our prototype to perform last mile multicast and hence minimize the wireless bandwidth usage. I. INTRODUCTION With the advancement in technology, many users carry wireless computing devices e.g. PDAs, cell-phones etc. Such devices can form mobile ad hoc networks and communicate with one another via the help of intermediate nodes. Such ad hoc networks are very useful in several scenarios e.g. battlefield operations, vehicular ad hoc networks and disaster response scenarios. Many ad hoc routing schemes have been designed for ad hoc networks but such routing schemes are not useful in some challenging network scenarios where the nodes have intermittent connectivity and suffer frequent partitioning. Recently, disruption tolerant network technologies [1],[2] have been proposed to allow nodes in such an extreme networking environment to communicate with one another. Several DTN routing schemes e.g. [3],[4] have been proposed. Although routing is an important design issue for such sparsely connected networks, it is important to ensure that popular legacy applications e.g. emails, web browser, instant messaging can operate over challenged networks that run DTN. Several projects have studied email over DTN e.g. in the context of military networks [5], nomadic community networks [6] and heterogeneous environments [7]. The first two approaches are proxy-based approaches but such approaches do not exploit the opportunistic communication opportunities available between mobile nodes. In [7], DTN gateways are deployed to store mail messages destined to a server/client on the Internet and intermediate DTN nodes can store mail messages destined to recipients which are mobile DTN nodes for forwarding in the future. Apart from email, the instant text messaging application is another popular application that many mobile users often use. There are multiple open-source text messaging applications e.g. Chat, Jabber. In this paper, we describe a Jabber proxy that we develop to allow mobile devices to run Jabber application over DTN. Our Jabber proxy provides several functions: (a) redirects the Jabber traffic through the DTN stack, (b) ensures that the internal timeout timers inherent to TCP do not expire, (c) parses connect/disconnect messages to allow mobile nodes to join and leave at will, and (d) parses group chat messages such that last mile multicast transmission can be used to reduce wireless bandwidth usage.