Attempts to generalize the Internet's point-to-point communication abstraction to provide services like multicast, anycast, and mobility have faced challenging technical problems and deployment barriers. To ease the deployment of such services, this paper proposes an overlay-based Internet Indirection Infrastructure (i3) that offers a rendezvous-based communication abstraction. Instead of explicitly sending a packet to a destination, each packet is associated with an identifier; this identifier is then used by the receiver to obtain delivery of the packet. This level of indirection decouples the act of sending from the act of receiving, and allows i3 to efficiently support a wide variety of fundamental communication services. To demonstrate the feasibility of this approach, we have designed and built a prototype based on the Chord lookup protocol.

The ever increasing demand of new applications has led researchers to propose new network architectures that address limitations of the current Internet. Given the rigidity of the Internet today, overlay networks are used to implement such architectures, in the hope of gaining a large user base. Despite sustained efforts to test and deploy new network architectures (on testbeds such as Planetlab), few of these efforts have attracted a significant number of users. We believe that chances of user acceptance of overlays, and eventually new network architectures, will be substantially improved by enabling users to leverage their functionality without any modifications to their applications and operating systems. In this paper, we present our design, implementation, and experience with OCALA, an overlay convergence architecture that achieves this goal. OCALA interposes an overlay convergence layer below the transport layer, that is composed of an overlay independent sub-layer that interfaces with legacy applications, and an overlay dependent sub-layer that delivers packets to the overlay. Unlike previous efforts, this design enables: (a) simultaneous access to multiple overlays (b) communication between hosts in different overlays (c) communication between overlay hosts and legacy hosts (d) extensibility, allowing researchers to incorporate their overlays into OCALA. We currently support three overlays, i3 [29], RON [1] and HIP [17], on Linux and Windows XP/2000. We (and a few other research groups and end-users) have used OCALA for over a year with many legacy applications ranging from web browsers to remote desktop applications.

Mobile wireless devices have intermittent connectivity, sometimes intentional. This is a problem for conventional Mobile IP, beyond its well-known routing inefficiencies and deployment issues. DHARMA selects a location-optimized instance from a distributed set of home agents to minimize routing overheads; set management and optimization are done using the PlanetLab overlay network. DHARMA’s session support overcomes both transitions between home agent instances and intermittent connectivity. Cross-layer information sharing between the session layer and the overlay network are used to exploit multiple wireless links when available. The DHARMA prototype supports intermittently connected legacy TCP applications in a variety of scenarios and is largely portable across host operating systems. Experiments with DHARMA deployed on more than 200 PlanetLab nodes demonstrate routing performance consistently better than that for best-case Mobile IP. I.

Providing support for legacy applications is a crucial component of many overlay networks, as it allows end-users to instantly benefit from the functionality introduced by these overlays. This paper presents the design and implementation of a proxy-based solution to support legacy applications in the context of the i3 overlay [24]. The proxy design relies on an address virtualization technique which allows the proxy to tunnel the legacy traffic over the overlay transparently. Our solution can preserve IP packet headers on an end-to-end basis, even when end-host IP addresses change, or when endhosts live in different address spaces (e.g., behind NATs). In addition, our solution allows the use of human-readable names to refer to hosts or services, and requires no changes to applications or operating systems. To illustrate how the proxy enables legacy applications to take advantage of the overlay (i.e., i3) functionality, we present four examples: enabling access to machines behind NAT boxes, secure Intranet access, routing legacy traffic through Bro, an intrusion detection system, and anonymous web download. We have implemented the proxy on Linux and Windows XP/2000 platforms, and used it over the i3 service on PlanetLab over a three month period with a variety of legacy applications ranging from web browsers to operating system-specific file sharing.

Overlays have enabled several new and popular distributed applications such as Akamai, Kazaa, and Bittorrent. However, the lack of an overlay-aware network stack has hindered the widespread use of general purpose overlay packet delivery services [16, 29, 26]. In this paper, we describe the design and implementation of Oasis, a system and toolkit that enables legacy operating systems to access overlay-based packet delivery services. Oasis combines a set of ideas – network address translation, name resolution, packet capture, dynamic code execution – to provide greater user choice. We are in the process of making the Oasis toolkit available for public use, specifically, to ease the development of PlanetLab-based packet delivery services. 1.

Reactive or proactive mobile applications require continuous monitoring of their physical and computational environment to make appropriate decisions in time. These applications need to monitor data streams produced by sensors and react to changes. When mobile sensors and applications are connected by low-bandwidth wireless networks, sensor data rates may overwhelm the capacity of network links or of the applications. In traditional networks and distributed systems, flow-control and congestion-control policies either drop data or force the sender to pause. When the data sender is sensing the physical environment, however, a pause is equivalent to dropping data. Arbitrary data drops are not necessarily acceptable to the reactive mobile applications receiving sensor data. Data distribution systems must support applicationspecific policies that selectively drop data objects when network or application buffers overflow. In this paper we present a data-dissemination service, PACK, which allows applications to specify customized data-reduction policies. These policies define how to discard or summarize data flows wherever buffers overflow on the dissemination path, notably at the mobile hosts where applications often reside. The PACK service provides an overlay infrastructure to support mobile data sources and sinks, using application-specific datareduction policies where necessary along the data path. We uniformly apply the data-stream “packing ” abstraction to buffer overflow caused by network congestion, slow receivers, and the temporary disconnections caused by end-host mobility. We demonstrate the effectiveness of our approach with an application example and experimental measurements. 1

The Host Identity Protocol (HIP) is a promising solution for dynamic network interconnection. HIP introduces a namespace based on cryptographically generated Host Identifiers. In this paper, two different API variants for accessing the namespace are described, namely the legacy and the native APIs. Furthermore, we present our implementation experience on applying the APIs to a number of applications, including FTP, telnet, and personal mobility. Well-known problems of callbacks and referrals, i.e., passing the IP address within application messages, are considered for FTP in the context of HIP. We show that the callback problem is solvable using the legacy API. The APIs are important for easy transition to HIP-enabled networks. Our experimentation with well-known network applications indicate that porting applications to use the APIs is realistic.

Ubiquitous-computing environments are heterogeneous and volatile in nature. Systems that support ubicomp applications must be self-managed, to reduce human intervention. In this paper, we present a general service that helps distributed software components to manage their dependencies. Our service proactively monitors the liveness of components and recovers them according to supplied policies. Our service also tracks the state of components, on behalf of their dependents, and may automatically select components for the dependent to use based on evaluations of customized functions. We believe that our approach is flexible and abstracts away many of the complexities encountered in ubicomp environments. In particular, we show how we applied the service to manage dependencies of context-fusion operators and present some experimental results.

We present a unified, extensible data-centric mobility infrastructure based on declarative networks and composable distributed views over network, router, and host state. Declarative networks are a recent innovation for building extensible network architectures using declarative languages. The data-centric approach both improves flexibility over existing solutions, and is extensible to meet the demands of future mobile applications and services. We demonstrate the flexibility of distributed queries used in declarative networks by specifying and implementing mobile services, e.g., overlaybased solutions for host mobility, customizable routing, service discovery and composition, and location-based services. A prototype based on the P2 declarative networking system has been implemented, with which we evaluated two overlaybased mobility schemes (ROAM and DHARMA). 1.

We propose a compact routing architecture to support mobility in a scalable manner. Our routing architecture requires a route table of size of O ( √ n log(n)) in order to provide a path stretch with a provable upper bound of 3. This is the optimal path stretch. Our architecture is built upon the theory of compact routing, which has so far been utilized in static networks only. This is the first attempt to the best of our knowledge to transpose such architecture into a network with mobility support. Our contribution is to adapt the static theory of compact routing to a class of networks with mobile leaf nodes and a static core infrastructure.