Active networking offers a change in the usual network paradigm: from passive carrier of bits to a more general computation engine. The implementation of such a change is likely to enable radical new applications that cannot be foreseen today. Large-scale deployment, however, involves significant challenges in interoperability and security. Less clear, perhaps, are the "immediate" benefits of such a paradigm shift, and how they might be used to justify migration towards active networking. In this paper, we focus on the benefits of active networking with respect to a problem that is unlikely to disappear in the near future: network congestion. In particular, we consider application-specific processing of user data within the network at congested nodes. Given an architecture in which applications can specify intra-network processing, the bandwidth allocated to each application's packets can be reduced in a manner that is tailored to the application, rather than being applied generically....

This paper describes a new methodology for protocol design, using incremental construction of the protocol from elements called “protocol boosters ” on an as-needed basis. Protocol boosters allow: (1) dynamic protocol customization to heterogeneous environments, and (2) rapid protocol evolution. Unlike alternative adaptation approaches, such as link layer, conversion, and termination protocols, protocol boosters are both robust (end-to-end protocol messages are not modified) and maximize efficiency (does not replicate the functionality of the end-to-end protocol). We give examples of error and congestion control boosters and give initial results from booster implementations. 1

In high speed networks, packet processing is relatively expensive while bandwidth is cheap. Thus it pays to add information to packet headers to make packet processing easier. While this is an old idea, we describe several specific new mechanisms based on this principle. We describe a new technique, source hashing, which can provide O(1) lookup costs at the Data Link, Routing, and Transport layers. Source hashing is especially powerful when combined with the old idea of a flow ID; the flow identifier allows packet processing information to be cached, and source hashing allows efficient cache lookups. Unlike Virtual Circuit Identifiers (VCIs), source hashing does not require a round trip delay for set up. In an experiment with the BSD Packet Filter implementation, we found that adding a flow ID and a source hash improved packet processing costs by a factor of 7. We also found a 45% improvement when we conducted a similar experiment with IP packet forwarding. We also describe two other ...

We reconsider several issues related to fragmentation and reassembly in IP. We first reconsider reassembly. We describe a simple expected case optimization that improves reassembly performance to 38 instructions per fragment if the fragments arrive in FIFO order (the same assumption made in header prediction) which has been implemented in the NetBSD kernel. Next, we introduce the new idea of Graceful Intermediate Reassembly (GIR), which is a generalization of the existing IP mechanisms of destination and hop-by-hop reassembly. In GIR, we coalesce the fragments at an intermediate router in order to use the largest sized packets on its outgoing interface. We show that GIR always outperforms hop-by-hop reassembly and can be implemented economically in routers with small processing and memory costs. We then reconsider fragmentation. We show that avoiding fragmentation has costs of its own in terms of increased packet processing and/or round-trip delays. We describe measurements in which TC...

The most recent advancements in computer hardware and communications make the mobile computing paradigm tangible and feasible. One of the major factors affecting mobile computing is communication protocols efficiency. This paper proposes and discusses an Adaptive Queuing Protocol which targets advanced mobile database applications. The protocol has two main objectives. Firstly, to compensate for the relatively slow speed of some existing mobile communication links. Secondly, to reduce the cost of communications by reducing link usage. In achieving these aims, our goal has been to reduce the total data volume that the link must carry, and at the same time ensure adequate response time for all classes of transactions. Results of computer simulation are presented and discussed. 1. Introduction Recent advances in miniaturisation and cellular technology make the computing paradigm ubiquitous and are extending the scope of database applications. While distributed databases have been studied...

This paper is focused on an efficient protocol implementation based on flexible user protocol interface (UPI) configurable for different service options and protocol processing architectures. The XTPL implementation discussed in this paper is developed based on the BERKOM eXpress Transfer Protocol (XTP) Lite version for HP 9000 / 7x Series using HP-UX 9.0 operating system. This implementation supports the dynamical configuration of user protocol interfaces intended to provide different objectives: - optimization of the user data copy operations (use of the "single copy archtecture") - selectable QoS options for application layer framing, reliability and checksumming. Performance analyses are included to show the flexible use of user protocol interfaces, in particular the reliable single and dual copy interface, dependent on the application traffic of the connections. Keywords: User Protocol Interface, Application Programming Interface (API), Application Layer Framing, Single Copy....

The performance enhancement of communication protocols is an essential step toward the building of high performance communication subsystems. Integrated Layer Processing (ILP) has been proposed as an engineering principle for the optimization of communication protocol implementations. However, the applicability of this principle to complete operational communication subsystems has not been yet addressed. This is in part due to the lack of high performance implementation of presentation and transport functions. In this paper, we show to what extent "ILP based " optimizations improve the performance of some data manipulation functions (e.g. presentation encoding or checksumming) independently. We present how some of these implementation optimization techniques were applied to the ASN.1 encodings rules. We also analyze the impact of such optimization techniques according to the support hardware. A prototype implementation of the XTP protocol is also described. ILP based optimization applied to the checksum calculation algorithm show that an important performance enhancement can be achieved. These results should facilitate the support of ILP within an operational communication subsystem.

Many emerging real-time applications generate layered data streams, which can be used effectively to adapt multicast real-time transmissions to heterogeneous bandwidth environments. However, these applications have not changed with regard to being sensitive to transient congestion and cannot wait a full round-trip time for sender-initiated adaptation. In this paper we propose the Selective Truncating Internetwork Protocol (STRIP) supporting layered data transfer, and capable of handling congestion at a finer level of granularity by truncating packets, i.e., stripping off less important data. STRIP interoperates with the traditional IP infrastructure and can be introduced in a step-by-step fashion, starting with routers where the bene ts are obvious, such as routers connected to bandwidth constrained links with a surplus of processing capacity. We describe the design and architecture of STRIP and compare it with solutions for differentiated forwarding on a per-packet basis. STRIP provides a simple mechanism that can meet the demands for real-time flows effectively by supporting low delay forwarding, avoiding data-unit reordering, and supporting various drop priorities at the same time.

. We describe some of the issues in the design of a new packet switched network protocol. Adaptation to various network technologies along the dimensions of speed, error model, robustness, etc., is a goal for this new protocol. We look at the adaption in size of the packet header to the speed and robustness of the underlying network to allow efficient communication on low-speed wireless networks, for example. We also explore issues in resource reservation and multicast for real-time multimedia, the notion of a network "flow", a hybrid of datagrams and virtual circuits, and suggest common solutions for both mobile and multicast routing. The authors are engaged in the design of a network protocol, NP++, whose goal is flexibility over a wide dynamic range of speeds and varying kinds of hardware switching elements. 1 Introduction The last quarter century has produced mainly two sorts of packet-switched networks: virtual circuit and datagram. Virtual circuit networks emulate circuit switch...

Simulation is a scientific method which is largely dominated by computers and has allowed the testing and assessment of many models before actual implementation. This paper proposes an approach to construction of a simulation that models the behaviour of an adaptive queuing protocol (AQP). AQP was developed for database applications on mobile computers in distributed multidatabase environment but also can be used in many other areas including distributed operating systems. By constructing the simulation model it is possible to both prove that it can be implemented, and at the same time study its expected behaviour in mobile computing environment. The results of the simulation are analysed and discussed. 1 Introduction An ongoing project dealing with mobile computing issues at the Department of Computer Technology, Monash University has resulted in a number of proposals and models targeting various aspects and research areas of distributed computing systems with mobile hosts. This pape...