Adaptive marking for assured forwarding service

This letter looks at the problem of achieving specific quality of service (QoS) goals of individual flows by flexibly managing resources available to an aggregated source. We present an adaptive marker based on a TCP performance model within a Diffserv network, and show that the aggregated marker can maintain state of individual flows at the edge of the network and utilize this state effectively in adaptively marking packets of individual flows to meet their QoS goals     

Towards overhead mitigation in state-free geographic forwarding protocols for wireless sensor networks

Wireless Networks - Routing has been the most consumptive of all processes engaged in the Wireless Sensor Network communications, thus improving this consumptive process by minimizing the number of...     

Towards a resource management and service deployment framework

Owing to the increase in both heterogeneity and complexity in today's networking systems, the need arises for new network‐based services architectures. They must provide flexibility and efficiency in the definition, deployment and execution of the services and, at the same time, handle the adaptability and evolution of such services. In this paper we present an approach that applies a Web‐service‐based resource management framework. It enables the provision of parallel applications as QoS‐aware applications, whose performance characteristics may be dynamically negotiated between a client application and service providers. Our component model allows context dependencies to be explicitly expressed and dynamically managed with respect to the hosting environment, computational resources and dependencies on other components. In such a model the resource management, in terms of representation, allocation and management of the resources, plays a vital role regarding the efficiency of the entire dynamic service deployment architecture. Copyright © 2007 John Wiley & Sons, Ltd.     

Towards Quality of Experience-based reputation models for future web service provisioning

This paper concerns the applicability of reputations systems for assessing Quality of Experience (QoE) for web services in the Future Internet. Reputation systems provide mechanisms to manage subjective opinions in societies and yield a general scoring of a particular behavior. Thus, they are likely to become an important ingredient of the Future Internet. Parameters under evaluation by a reputation system may vary greatly and, particularly, may be chosen to assess the users?? satisfaction with (composite) web services. Currently, this satisfaction is usually expressed by QoE, which represents subjective users?? opinions. The goal of this paper is to present a novel framework of web services where a reputation system is incorporated for tracking and predicting of users?? satisfaction. This approach is a beneficial tool which enables providers to facilitate service adaptation according to users?? expectations and maintain QoE at a satisfactory level. Presented reputation systems operate in an environment of composite services that integrate client and server-side. This approach is highly suitable for effective QoE differentiating and maximizing user experience for specific customer profiles as even the service and network resources are shared.     

Contention-based forwarding for mobile ad hoc networks

Existing position-based unicast routing algorithms which forward packets in the geographic direction of the destination require that the forwarding node knows the positions of all neighbors in its transmission range. This information on direct neighbors is gained by observing beacon messages each node sends out periodically.

Due to mobility, the information that a node receives about its neighbors becomes outdated, leading either to a significant decrease in the packet delivery rate or to a steep increase in load on the wireless channel as node mobility increases. In this paper, we propose a mechanism to perform position-based unicast forwarding without the help of beacons. In our contention-based forwarding scheme (CBF) the next hop is selected through a distributed contention process based on the actual positions of all current neighbors. For the contention process, CBF makes use of biased timers. To avoid packet duplication, the first node that is selected suppresses the selection of further nodes. We propose three suppression strategies which vary with respect to forwarding efficiency and suppression characteristics. We analyze the behavior of CBF with all three suppression strategies and compare it to an existing greedy position-based routing approach by means of simulation with ns-2. Our results show that CBF significantly reduces the load on the wireless channel required to achieve a specific delivery rate compared to the load a beacon-based greedy forwarding strategy generates.     

Fast incremental updates for pipelined forwarding engines

Pipelined ASIC architectures are increasingly being used in forwarding engines for high-speed IP routers. We explore optimization issues in the design of memory-efficient data structures that support fast incremental updates in such forwarding engines. Our solution aims to balance the memory utilization across the multiple pipeline stages. We also propose a series of optimizations that minimize the disruption to the forwarding process caused by route updates. These optimizations reduce the update overheads by over a factor of two for a variety of different core routing tables and update traces.     

Low-power data forwarding for VLIW embedded architectures

Proposes a low-power approach to the design of embedded very long instruction word (VLIW) processor architectures based on the forwarding (or bypassing) hardware, which provides operands from interstage pipeline registers directly to the inputs of the function units. The power optimization technique exploits the forwarding paths to avoid the power cost of writing/reading short-lived variables to/from the register file (RF). Such optimization is justified by the fact that, in application-specific embedded systems, a significant number of variables are short-lived, that is, their liveness (from first definition to last use) spans only few instructions. Values of short-lived variables can thus be accessed directly through the forwarding registers, avoiding writeback to the RF by the producer instruction and successive read from the RF by the consumer instruction. The decision concerning the enabling of the RF writeback phase is taken at compile time by the compiler static scheduling algorithm. This approach implies a minimal overhead on the complexity of the processor control logic and, thus, no critical path increase. The application of the proposed solution to a VLIW embedded core has shown an average RF power saving of 7.8% with respect to the unoptimized approach on the given set of target benchmarks.     

Traffic locality characteristics in a parallel forwarding system

Due to the widening gap between the performance of microprocessors and that of memory, using caches in a system to take advantage of locality in its workload has become a standard approach to improve overall system performance. At the same time, many performance problems finally reduce to cache performance issues. Locality in system workload is the fact that makes caching possible. In this paper, we first use the reuse distance model to characterize temporal locality in Internet traffic. We develop a model that closely matches the empirical data. We then extend the work to investigate temporal locality in the workload of multi‐processor forwarding systems by comparing locality under different packet scheduling schemes. Our simulations show that for systems with hash‐based schedulers, caching can be an effective way to improve forwarding performance. Based on flow‐level traffic characteristics, we further discuss the relationship between load‐balancing and hash‐scheduling, which yields insights into system design. Copyright © 2003 John Wiley & Sons, Ltd.     

Design and evaluation of a pipelined forwarding engine

Recent advances in broadband technology have caused forwarding engines to handle pack- ets with over 10 gigabit per second. In this paper, we present a high-speed forwarding pipeline which can finish all of the routing and forwarding tasks in the way of pipelining. We also establish the analysis model of the pipeline with which one can evaluate some key performance parameters of the forwarding engine such as forwarding rate and forwarding delay. We find that the pipeline is of good scalability and can forward unicast packets up to the speed of 40Gbit/s.     

Intelligent beaconless geographical forwarding for urban vehicular environments

A Vehicular Ad hoc Network is a type of wireless ad hoc network that facilitates ubiquitous connectivity between vehicles in the absence of fixed infrastructure. Source based geographical routing has been proven to perform well in unstable vehicular networks. However, these routing protocols leverage beacon messages to update the positional information of all direct neighbour nodes. As a result, high channel congestion or problems with outdated neighbour lists may occur. To this end, we propose a street-aware, Intelligent Beaconless (IB) geographical forwarding protocol based on modified 802.11 Request To Send (RTS)/ Clear To Send frames, for urban vehicular networks. That is, at the intersection, each candidate junction node leverage digital road maps as well as distance to destination, power signal strength of the RTS frame and direction routing metrics to determine if it should elect itself as a next relay node. For packet forwarding between Intersections, on the other hand, the candidate node considers the relative direction to the packet carrier node and power signal strength of the RTS frame as routing metrics to elect itself based on intelligently combined metrics. After designing the IB protocol, we implemented it and compared it with standard protocols. The simulation results show that the proposed protocol can improve average delay and successful packet delivery ratio in realistic wireless channel conditions and urban vehicular scenarios.     

Per-domain packet scale rate guarantee for expedited forwarding

The expedited forwarding per-hop behavior (EF PHB) was recently replaced by a new definition, called packet scale rate guarantee (PSRG), under the Differentiated Services (DiffServ) framework. This replacement raises two challenges. One is the implementation of a PSRG server. Another is the provision of per-domain PSRG. Specifically, for the former, an open issue is whether hierarchical schedulers can provide PSRG; for the latter, it is not clear whether and how per-domain PSRG can be provided in the presence of flow aggregation. Since, in DiffServ networks, flow aggregation is a natural phenomenon and hierarchical scheduling is high-likely desired, these two challenges become even more critical. To address the first challenge, we introduce a new concept called latency-rate worst-case service guarantee (LR-WSG). We prove that, if a server provides LR-WSG, it also provides PSRG. We show that many well-known schedulers support LR-WSG, which include not only one-level schedulers but also their hierarchical versions. To address the second challenge, we first prove that PSRG can be extended from per-node to per-domain if no flow aggregation is performed. The proof is notable in that it depends solely on the concept of PSRG itself. We then investigate the provision of per-domain PSRG in presence of flow aggregation. We propose to use packet scale fair aggregator (PSFA) to aggregate flows. We show that, with PSFA, per-domain PSRG can be provided in spite of flow aggregation. We finally provide a brief discuss on the viability of using PSFA in DiffServ networks and define an expedited forwarding per-domain behavior (EF PDB).     

Technologies and building blocks for fast packet forwarding

We provide a review of the state of the art and the future of packet processing and switching. The industry's response to the need for wire-speed packet processing devices whose function can be rapidly adapted to continuously changing standards and customer requirements is the concept of special programmable network processors. We discuss the prerequisites of processing tens to hundreds of millions of packets per second and indicate ways to achieve scalability through parallel packet processing. Tomorrow's switch fabrics, which will provide node-internal connectivity between the input and output ports of a router or switch, will have to sustain terabit-per-second throughput. After reviewing fundamental switching concepts, we discuss architectural and design issues that must be addressed to allow the evolution of packet switch fabrics to terabit-per-second throughput performance     

Multiple-packet forwarding protocols for frequency-hop packet radio networks

Reliable data distribution within multiple-hop spread-spectrum packet radio networks requires high performance from the network protocols. The high variability in quality among the links and the unique characteristics of frequency-hop spread-spectrum signaling impose special requirements for network protocols that are to be employed in frequency-hop packet radio networks. These features can be exploited in the forwarding protocols by allowing multiple packets to be included in each forwarding attempt. The use of multiple-packet transmissions exploits the capture property of frequency-hop signaling, and it reduces the overhead required for acknowledgments. A potential trade-off arises because the use of multiple-packet transmissions increases the throughput, but in some situations it can also increase the delay. Two new transmission protocols that employ multiple-packet transmissions are described, and their performance is evaluated.     

Towards an event-aware approach for ubiquitous computing based on automatic service composition and selection

Service composition in ubiquitous and pervasive environments is becoming an active research domain which has received widespread attention in recent years. It aims to offer seamless access to a variety of high level and complex functionalities by combining existing services. Several frameworks have been designed to support service composition in ubiquitous and pervasive environments. Although some ubiquitous requirements and challenges are relatively well addressed by the proposed frameworks, others are still at a preliminary stage and should be well explored such as, automatic service composition with little human intervention, context and quality of service management, and service selection under uncertainty and changes. For this end, we propose in this paper a layered design approach for flexible and failure tolerant service composition using two main phases: off-line phase and on-line phase. In the off-line phase, a global graph that links all the available abstract services is generated automatically using rule-based technique. The defined rules aim at optimizing both the number of services and parameters that appear in the global graph. In the on-line phase, a subgraph is extracted spontaneously from the global graph according to the occurred and detected event in the environment at real time. Thereafter, the extracted subgraph is performed using service selection strategies. A prototype implementation including real services for event detection in smart home shows clearly the feasibility of the proposed approach in real environment. Also, the set of performed evaluation tests reveals the interest and the performance of the proposed algorithms.     

Towards efficient distributed service discovery in low-power and lossy networks

Low-power and Lossy Networks (LLNs) have been recognised as a promising technology to achieve ubiquity in the internet of things era. To realise this, service oriented architectures and the emerging IPv6 over low-power wireless personal area network (6LoWPAN) standard are identified as key paradigms. One of the main elements to succeed any service oriented approach is a proficient service discovery protocol. In this paper, we propose EADP: an efficient protocol to announce and discover services in 6LoWPAN networks. EADP adopts a fully distributed approach using an adaptive push–pull model to ensure fast discovery times, low energy consumption and low generated overhead with timely reaction to network dynamics. EADP achieves this by using context-awareness information, delivered by a trickle algorithm. EADP was implemented and evaluated in Contiki using the Cooja simulator. Simulation results show EADP’s capability to realise fast discovery times with low cost in terms of energy and overhead. These achievements make EADP very suitable for pervasive LLN applications.     

A social overlay-based forwarding scheme for mobile social networks

Wireless Networks - In mobile social networks, forwarding is a challenging problem since there may be no end-to-end paths. Existing schemes using overlays are not applicable to pure mobile social...     

A trust-based framework for data forwarding in opportunistic networks

In general, the encounter probability is leveraged to evaluate whether a node is a qualified next-hop forwarder in Opportunistic Networks (OppNets); however, it does not truly present the node’s competency of delivering data in a hostile wireless environment, because a malicious node can arbitrarily bloat that probability to intercept data from others. In this paper, we design a trust-based framework to more accurately evaluate an encounter’s delivery competency, which can be flexibly integrated with a large family of existing data forwarding protocols designed for OppNets. As a case study, we integrate our proposed framework with PROPHET, and demonstrate its effectiveness against “black hole” attacks through experimental study.     

Resource reservation with pointer forwarding schemes for the mobileRSVP

We propose a pointer forwarding scheme for the mobile resource reservation protocol (MRSVP) to reduce the resource reservation cost on the wireless Internet. We show that the pointer forwarding scheme could significantly degrade the reservation cost when a mobile host performs locality movement