39,647 research outputs found
Modeling SpaceWire networks with network calculus
The SpaceWire network standard is promoted by the ESA and is scheduled to be used as the sole on-board network for future satellites. This network uses a wormhole routing mechanism that can lead to packet blocking in routers and consequently to variable end-to-end delays. As the network will be shared by real-time and non real-time traffic, network designers require a tool to check that temporal constraints are verified for all the critical messages. Network Calculus can be used for evaluating worst-case end-to-end delays. However, we first have to model SpaceWire components through the definition of service curves. In this paper, we propose a new Network Calculus element that we call the Wormhole Section. This element allows us to better model a wormhole network than the usual multiplexer and demultiplexer elements used in the context of usual Store-and-Forward networks. Then, we show how to combine Wormhole Section elements to compute the end-to-end service curve offered to a flow and illustrate its use on a industrial case study
Flow Allocation for Maximum Throughput and Bounded Delay on Multiple Disjoint Paths for Random Access Wireless Multihop Networks
In this paper, we consider random access, wireless, multi-hop networks, with
multi-packet reception capabilities, where multiple flows are forwarded to the
gateways through node disjoint paths. We explore the issue of allocating flow
on multiple paths, exhibiting both intra- and inter-path interference, in order
to maximize average aggregate flow throughput (AAT) and also provide bounded
packet delay. A distributed flow allocation scheme is proposed where allocation
of flow on paths is formulated as an optimization problem. Through an
illustrative topology it is shown that the corresponding problem is non-convex.
Furthermore, a simple, but accurate model is employed for the average aggregate
throughput achieved by all flows, that captures both intra- and inter-path
interference through the SINR model. The proposed scheme is evaluated through
Ns2 simulations of several random wireless scenarios. Simulation results reveal
that, the model employed, accurately captures the AAT observed in the simulated
scenarios, even when the assumption of saturated queues is removed. Simulation
results also show that the proposed scheme achieves significantly higher AAT,
for the vast majority of the wireless scenarios explored, than the following
flow allocation schemes: one that assigns flows on paths on a round-robin
fashion, one that optimally utilizes the best path only, and another one that
assigns the maximum possible flow on each path. Finally, a variant of the
proposed scheme is explored, where interference for each link is approximated
by considering its dominant interfering nodes only.Comment: IEEE Transactions on Vehicular Technolog
Towards Provably Invisible Network Flow Fingerprints
Network traffic analysis reveals important information even when messages are
encrypted. We consider active traffic analysis via flow fingerprinting by
invisibly embedding information into packet timings of flows. In particular,
assume Alice wishes to embed fingerprints into flows of a set of network input
links, whose packet timings are modeled by Poisson processes, without being
detected by a watchful adversary Willie. Bob, who receives the set of
fingerprinted flows after they pass through the network modeled as a collection
of independent and parallel queues, wishes to extract Alice's embedded
fingerprints to infer the connection between input and output links of the
network. We consider two scenarios: 1) Alice embeds fingerprints in all of the
flows; 2) Alice embeds fingerprints in each flow independently with probability
. Assuming that the flow rates are equal, we calculate the maximum number of
flows in which Alice can invisibly embed fingerprints while having those
fingerprints successfully decoded by Bob. Then, we extend the construction and
analysis to the case where flow rates are distinct, and discuss the extension
of the network model
Throughput Optimal Flow Allocation on Multiple Paths for Random Access Wireless Multi-hop Networks
In this paper we consider random access wireless multi-hop mesh networks with
multi-packet reception capabilities where multiple flows are forwarded to the
gateways through node disjoint paths. We address the issue of aggregate
throughput-optimal flow rate allocation with bounded delay guarantees. We
propose a distributed flow rate allocation scheme that formulates flow rate
allocation as an optimization problem and derive the conditions for
non-convexity for an illustrative topology. We also employ a simple model for
the average aggregate throughput achieved by all flows that captures both
intra- and inter-path interference. The proposed scheme is evaluated through
NS-2 simulations. Our preliminary results are derived from a grid topology and
show that the proposed flow allocation scheme slightly underestimates the
average aggregate throughput observed in two simulated scenarios with two and
three flows respectively. Moreover it achieves significantly higher average
aggregate throughput than single path utilization in two different traffic
scenarios examined.Comment: Accepted for publication at the 9th IEEE BROADBAND WIRELESS ACCESS
WORKSHOP (BWA2013), IEEE Globecom 2013 Workshop
Reducing Congestion Effects by Multipath Routing in Wireless Networks
We propose a solution to improve fairness and increasethroughput in wireless networks with location information.Our approach consists of a multipath routing protocol, BiasedGeographical Routing (BGR), and two congestion controlalgorithms, In-Network Packet Scatter (IPS) and End-to-EndPacket Scatter (EPS), which leverage BGR to avoid the congestedareas of the network. BGR achieves good performancewhile incurring a communication overhead of just 1 byte perdata packet, and has a computational complexity similar togreedy geographic routing. IPS alleviates transient congestion bysplitting traffic immediately before the congested areas. In contrast,EPS alleviates long term congestion by splitting the flow atthe source, and performing rate control. EPS selects the pathsdynamically, and uses a less aggressive congestion controlmechanism on non-greedy paths to improve energy efficiency.Simulation and experimental results show that our solutionachieves its objectives. Extensive ns-2 simulations show that oursolution improves both fairness and throughput as compared tosingle path greedy routing. Our solution reduces the variance ofthroughput across all flows by 35%, reduction which is mainlyachieved by increasing throughput of long-range flows witharound 70%. Furthermore, overall network throughput increasesby approximately 10%. Experimental results on a 50-node testbed are consistent with our simulation results, suggestingthat BGR is effective in practice
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