The Internet protocols were designed to emphasize simple routing elements and intelligent hosts. However, there are applications that benefit from allowing hosts to customize or program routers, a concept known as active networking. Since routers are shared, this raises challenges with delivering sufficient flexibility while preserving or improving performance, security, and safety. PLAN (Packet Language for Active Networks) is a language designed for the SwitchWare active network architecture. This architecture comprises active packets containing PLAN programs that invoke service routines over an active OS. PLAN is based on the polymorphic lambda calculus and provides a restricted set of primitives and datatypes that enables reasoning about its impact on network resources based on features of the language design. This paper focuses on the PLAN language with the aim of consolidating a variety of studies that were carried out in the years after its introduction in 1998. These studies include the requirements for PLAN, its design, programming in PLAN, the specification and theory of PLAN, and its use in networking applications.

Currently the Internet has only one level of name resolution, DNS, which converts user-level domain names into IP addresses. In this paper we borrow liberally from the literature to argue that there should be three levels of name resolution: from user-level descriptors to service identifiers; from service identifiers to endpoint identifiers; and from endpoint identifiers to IP addresses. These additional levels of naming and resolution (1) allow services and data to be first class Internet objects and (2) facilitate mobility and provide an elegant way to integrate middleboxes into the Internet architecture. We further argue that flat names are a natural choice for the service and endpoint identifiers. Hence, this architecture requires scalable resolution of flat names, a capability that distributed hash tables (DHTs) can provide.

We propose using application specific virtual machines (ASVMs) to reprogram deployed wireless sensor networks. ASVMs provide

We present SNAP (Safe and Nimble Active Packets), a new scheme for programmable (or active) packets centered around a new lowlevel packet language. Unlike previous active packet approaches, SNAP is practical: namely, adding significant flexibility over IP without compromising safety and security or efficiency. In this paper we show how to compile from the well-known active packet language PLAN [7] to SNAP, showing that SNAP retains PLAN's flexibility; give proof sketches of its novel approach to resource control; and present experimental data showing SNAP attains performance very close to that of a software IP router. Keywords---Active networks, active packets, capsules, resource control. I.

Network monitoring is a vital part of modern network infrastructure management. Existing techniques either present a restricted view of network behavior and state, or do not efficiently scale to higher network speeds and heavier monitoring workloads. Considering these shortcomings we present a novel architecture for programmable packet-level network monitoring. Our approach allows users to customize the monitoring function at the lowest possible level of abstraction to suit a wide range of monitoring needs: we use operating system mechanisms that result in a programming environment providing a high degree of flexibility, retaining fine-grained control over security, and minimizing the associated performance overheads. We present the implementation of this architecture as well as a set of experimental applications.

Ad hoc networks, where mobile nodes communicate via multihop wireless links, facilitate network connectivity without the aid of any pre-existing networking infrastructure. The intrinsic attributes of ad hoc networks, such as dynamic network topology, limited battery supply, constrained wireless bandwidth and quality, and large number of heterogeneous nodes, make network management significantly more challenging than stationary and wireline networks. In particular, the conventional client/serverbased manager-agent management paradigm falls short of addressing these issues. In this paper, we describe the Guerrilla Management Architecture to facilitate adaptive and autonomous management of ad hoc networks and demonstrate its capability via simulation. Apart from its functionalities, the management capability itself is scalable to accommodate the sheer number and heterogeneity of nodes, autonomous and survivable to adapt to network dynamics, and economical to minimize management overhead.

PLAN (Packet Language for Active Networks) [4] is a highly flexible and usable active packet language, whereas SNAP (Safe and Nimble Active Packets) [11] offers significant resource usage safety and achieves much higher performance compared to PLAN, but at the cost of flexibility and usability. Ideally, we would like to combine the good properties of PLAN with those of SNAP. We have achieved this end by developing a compiler that translates PLAN into SNAP. The compiler allows us to achieve the flexibility and usability of PLAN, but with the safety and efficiency of SNAP. In this paper, we describe both languages, highlighting the features that require special compilation techniques. We then present the details of our compiler and experimental results to evaluate our compiler with respect to code size.

EZCab is a proof-of-concept ubiquitous computing application that allows people to book nearby cabs using their cell phones or PDAs equipped with short-range wireless network interfaces. EZCab discovers and books free cabs using mobile ad hoc networks of vehicles. We have implemented an EZCab prototype on top of Smart Messages, a middleware architecture based on execution migration, which we had developed to provide a common execution environment for outdoor ubiquitous computing applications. The experimental and simulation results have demonstrated the feasibility of EZCab.

Abstract—Ad hoc networks can be used not only as data carriers for mobile devices but also as providers of a new class of services specific to ubiquitous computing environments. Building services in ad hoc networks, however, is challenging due to the rapidly changing operating contexts, which often lead to situations where a node hosting a certain service becomes unsuitable for hosting the service execution any longer. We propose a novel model of service provisioning in ad hoc networks based on the concept of contextaware migratory services. Unlike a regular service that executes always on the same node, a migratory service can migrate to different nodes in the network in order to accomplish its task. The migration is triggered by changes of the operating context, and it occurs transparently to the client application. We designed and implemented a framework for developing migratory services. We built TJam, a proof-of-concept migratory service that predicts traffic jams in a given region of a highway by using only car-to-car short-range wireless communication. The experimental results obtained over an ad hoc network of personal digital assistants (PDAs) show the effectiveness of our approach in the presence of frequent disconnections. We also present simulation results that demonstrate the benefits of migratory services in large-scale networks compared to a statically centralized approach. Index Terms—Mobile computing, mobile applications, ubiquitous computing, distributed programming, distributed systems. 1

Byte-code representations in active networks provide architectural neutrality and code compactness; however, the resulting execution speed is typically poor due to interpretation overhead. This paper shows that the performance of capsule-based active networks can benefit from compiling active network programs into native network processor instructions at traversed routers (just-in-time compilation). A key aspect of the paper is to demonstrate that just-in-time compilers for active networks can be fast and small enough for applicability in the datapath of network processors. The approach has been implemented based on the SNAP active network framework for the PowerNP network processor.