Minimizing Backbone Ethernet Traffic for Enabling Interzonal Messages in Software-Defined Vehicles

While in recent years backbone bandwidth has experienced substantial growth, little has changed in the access network. “Last mile” still remains the bottleneck between a high capacity LAN or home network and the backbone. Passive optical network (PON) is a technology viewed by many as an attractive solution to this problem. In this study, we discuss and evaluate design issues for PON access networks. Specifically, to drive the cost of an access network down, it is very important to have an efficient, scalable solution. We believe that a PON based on polling, with data encapsulated in Ethernet frames, possesses the best qualities, such as dynamic bandwidth distribution, use of a single downstream and a single upstream wavelength, ability to provision a fractional wavelength capacity to each user, and ease of adding a new user. To support dynamic bandwidth distribution, we propose an interleaved polling algorithm. We then suggest a scheme for in-band signaling that allows using a single wavelength for both downstream data and control message transmission. To obtain realistic simulation results, we generated synthetic traffic that exhibits the properties of self-similarity and long-range dependence. We then analyzed the network performance and its effect on various types of traffic, e.g., best-effort data traffic, VBR video traffic and CBR streams.

In this paper we present a Table less Position based Routing (TPR) scheme for low power data centric wireless sensor networks. TPR is localized, uses greedy forwarding approach, and does not rely on neighborhood information. These characteristics reduce the communication overhead (no neighborhood information exchange), make the protocol highly scalable (no routing tables are maintained and beacons are not exchanged when a node leaves or enters the networks), and it performs better in mobile environments (as the next hop is non-deterministic and is computed at real time). It also deals with dead end problems by a recovery strategy in a distributed and localized way. TPR is implemented in the OMNET++ based discrete event simulation environment PAWiS (simulation framework for low power wireless sensor networks). The results show that TPR provides guaranteed delivery, extended network life time, and a mechanism to route on the basis of end to end delay and/or energy consumption.

We present a link capacity estimation model and a hybrid routing scheme for wireless mesh networks which aims at improving throughput. The multi-source interference between links and frame capture behaviors of nodes are analyzed. Our model provides estimated values which can indicate the relative quality of wireless links. And we present a routing metric which combines multiple factors based on the estimated values. The proposed routing scheme which is independent of special routing protocols adopts different strategies for the traffic of accessing the Internet and the end-to-end traffic. Besides, we introduce a new gateway-assisted routing technique to further improve the performance. Simulation results show that the estimation model provides accurate estimated values enough for route selection, and the routing scheme improves end-to-end throughput by 185% compared with legacy AODV[14] protocol.

In this paper, we present a smart energy routing scheme for wireless sensor networks in order to improve the overall energy efficiency and the reliability in the network. Preliminary experiments have been conducted in the experiment environment and show a promising result. In the future, we will continue to improve the scheme and conduct more and longer experiments to precisely measure the benefits of our scheme.

In this paper, we present a methodology employing statistical analysis and stochastic geometry to study geometric routing schemes in wireless ad hoc networks. In particular, we analyze the network-layer performance of one such scheme, the random [ 1/ 2]disk routing scheme, which is a localized geometric routing scheme in which each node chooses the next relay randomly among the nodes within its transmission range and in the general direction of the destination. The techniques developed in this paper enable us to establish the asymptotic connectivity and the convergence results for the mean and variance of the routing path lengths generated by geometric routing schemes in random wireless networks. In particular, we approximate the progress of the routing path toward the destination by a Markov process and determine the sufficient conditions that ensure the asymptotic connectivity for both dense and large-scale ad hoc networks deploying the random [ 1/ 2]disk routing scheme. Furthermore, using this Markov characterization, we show that the expected length (hop count) of the path generated by the random [ 1/ 2]disk routing scheme normalized by the length of the path generated by the ideal direct-line routing, converges to 3π/4 asymptotically. Moreover, we show that the variance-to-mean ratio of the routing path length converges to 9π <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /64-1 asymptotically. Through simulation, we show that the aforementioned asymptotic statistics are in fact quite accurate even for finite granularity and size of the network.

Deployment of Gigabit Ethernets in metropolitan areas creates new opportunities to save costs by converging data and telephone services. The primary question of our study is whether emerging metropolitan networks can meet the QoS requirements necessary to connect GSM and UMTS base stations. These requirements on delay, jitter, and loss are significantly more stringent than the ones for VoIP and have to be met at the presence of bursty cross traffic. Therefore, we have probed ETH's campus network which spans the metropolitan area of Zurich with traffic comparable to encapsulated E1 traffic from base stations and have measured perceived QoS. Our findings show that the campus network generally meets the QoS requirements. However, the perceived QoS degrades with increasing network utilization.To further investigate the impact of the configuration of Ethernet switches on perceived QoS, we have conducted a simulation study. The results show that the perceived QoS is better when switch buffers are limited to small sizes of 1 MB compared to setups where the number of frames in the buffer is limited. From these results we infer that metropolitan Gigabit Ethernets are well suited for connecting GSM and UMTS base stations.

The IPv4 traffic characteristics are deeply related to the 1500 byte limit, a consequence of the payload capacity of the Ethernet frame. This paper describes how this limit may impact future IPv6 traffic and tests some aspects of traffic behavior for new values. To assess this, real IPv4 traffic was transformed to IPv6 traffic, with several simple assumptions. It is showed that in some circumstances, the change from IPv4 to IPv6 causes an overhead in terms of number of transmitted bytes that is irrelevant when compared to the overhead of the number of transmitted packets. Conclusions point to the possible existence of increased routing and switching effort resulting from the shift to the IPv6 protocol. The paper also suggests that a wider limit could decrease significantly the number of generated packets.

&lt;p&gt;TCP was conceived to ensure reliable node-to-node communication in moderate-bandwidth, moderate-latency, WANs. As it is now a mature Internet standard, it is the default connection-oriented protocol in networks built from commodity components, including Internet data centers. Data centers, however, rely on high-bandwidth, low-latency networks for communication. Moreover, their communication patterns, especially those generated by distributed applications such as MapReduce, often take the form of synchronous multi-node to node bursts. Under the right conditions, the network switch buffer overflow losses induced by these bursts confuse TCP's feedback mechanisms to the point that TCP throughput collapses. This collapse, termed TCP Incast, results in gross underutilization of link capacities, significantly degrading application performance.&lt;/p&gt; &lt;p&gt;Conventional approaches to mitigating Incast have focused on single-path solutions, for instance, adjusting TCP's receive windows and timers, modifying the protocol itself, or adopting explicit congestion notifications. This thesis explores complementary multi-path approaches to avoiding Incast's onset. The principal idea is to use the regularity and high connectivity of typical data center networks, such as the increasingly popular fat-tree topology, to better distribute multi-node to node bursts across the available paths, thereby avoiding the switch buffer overflows that induce TCP Incast.&lt;/p&gt; &lt;p&gt;The thesis's main contributions are: (1) development of new oblivious, multi-path, routing schemes for fat-tree networks, (2) derivation of relations between the schemes and Incast's onset, and (3) investigation of a novel "front-back" approach to minimizing the packet reordering introduced by multipath routing. Formal analyses are focused on relating schemes' worst-case loading of certain network resources - expressed as oblivious performance ratios (OPRs) - to Incast's onset. Potential benefits are assessed through ns-3 simulations on fat-trees under a variety of communication patterns. Results indicate that over a variety of experimental conditions, the proposed schemes reduce the incidence of TCP Incast compared to standard routing schemes.&lt;/p&gt;

In ATM local area networks, several kinds of traffic, such as data, video and voice, are likely to coexist. Some of this traffic has stringent delay and jitter requirements, which can only be guaranteed to be met through bandwidth reservation. In contrast, other kinds of traffic, like data traffic, are not delay sensitive, but should be loss-free and are highly bursty and unpredictable. If some of the link capacity is reserved for connections having delay constraints, the non-reserved part is available for other connnections. In addition, as the reserved traffic may not be fully utilising the bandwidth it required (especially if peak rate allocation is performed), the unused-reserved bandwidth could also be made available for other connections. We therefore define a service called (or elastic) service, where sources can transmit on a best effort basis, consuming as much bandwidth as they can from both the non-reserved and the unused-reserved bandwidth. Such a service, offered in addition to the service with bandwidth reservation, is particularly suited to easily handle bursty data traffic because it does not have to evaluate traffic descriptors. As no bandwidth is allocated, however, a control mechanism is required to prevent losses due to the contention for resources. Every cell lost inside the network would in fact trigger the retransmission of a whole frame, which would result in a very poor throughput. For this reason, we choose to support the best-effort service inside the network with a loss-free congestion control scheme. The scheme should protect the network against misbehaving sources and be simple to implement. In addition, the best-effort service must not affect the reserved traffic, and it should be fair according to a definition of fairness we base on the max-min algorithm. Having reviewed various families of control mechanisms that have been proposed in the literature, and pointed out their limitations, we conclude that a hop-by-hop scheme is more likely to provide the tight control required for highly unpredictable traffic. The various requirements led us to define and study a backpressure mechanism. It uses thresholds to stop traffic coming to an intermediate buffer before losses occur, and to restart it when the congestion is over. Through extensive simulations and analysis, we show that the mechanism successfully prevents losses in the network and may lead to a better utilization of network resources. However, the mechanism proves to be unfair due to its inability to identify and control the sources contributing most to the congestion. We then specify a more sophisticated backpressure scheme able to control the best-effort traffic both selectively, that is on a per-connection basis, and globally, on a per-link basis. The scheme dynamically adapts its thresholds to the number of connections present in the intermediate buffers. In addition, it makes use of a particular queueing policy in the switch buffers, called fair queueing. We validate these choices through simulations and analysis, and show that even under extreme load, our loss-free, best-effort service remains efficient and fair, while generating a very low amount of overhead traffic. In order to implement the scheme in ATM local area networks, a UNI protocol is defined in order to be included in both the terminal and switch adapters. The protocol was submitted by the author to the ITU and included in Recommendations I.150 and I.361. We then show that our mechanism, besides being efficient and conforming to the standard, can also be implemented by making use of a currently available ATM component, the segmentation & reassembly product SARA chipset. Finally, we consider the transport of best-effort traffic over wide area networks as well as public networks and suggest the use of backpressure, associated with dynamic bandwidth allocation schemes.

This article presents MST, a communication-efficient message library for fast graph traversal on exascale clusters. The key idea is to follow the multi-level network topology to perform topology-aware message aggregation, where small messages are gathered and scattered at each level of domain. To facilitate message aggregation, we equip MST with flexible buffer management including active buffer switching and dynamic buffer expansion. We implement MST on the newest-generation Tianhe supercomputer and evaluated its performance using various traversal-centric algorithms on both synthetic trillion-scale graphs and real-world big graphs. The results show that MST-based graph traversal is orders of magnitude faster than that based on Active Messages Library (AML). For the Graph500-BFS benchmark, MST-based Tianhe (with 77.2 K nodes) outperforms the Fugaku supercomputer (with 148.5 K nodes) by 18.53%, while Fugaku is ranked No. 1 in the latest Graph500-BFS ranking (June 2023). MST also greatly improves graph processing performance on other commercial large-scale computing systems at the National Supercomputing Center in Changsha (NSCC) and WuzhenLight.

Existing routing schemes in opportunistic networks can be classified two categories: multi-copy based schemes and single-copy based schemes. Multi-copy based schemes can increase the robustness of networks and reduce average delay. However, they consume a large amount of network resources and induce large overhead. Single-copy based schemes can save network resources, but it is difficult to guarantee the transmission delay and packet delivery ratio for these schemes. Hence, how to design an efficient routing scheme which can make a tradeoff between multi-copy schemes and single-copy schemes in opportunistic networks with limited resources is a challenging issue. Inspired by this issue, in this paper, we propose a novel routing scheme based on game theory in opportunistic networks under limited resources, named GTR. In GTR, we map the message transmission to a multi-player bargaining model. By constructing proper utility function, GTR can save the network resources, and achieve better performance in dense opportunistic networks. Our extensive simulation results also demonstrate this point, and GTR performs better compared to some classical routing schemes in terms of packet delivery ratio, average delay, overhead ratio and average hops.

In this paper, we present a deterministic key pre-distribution scheme for wireless sensor network using combinatorial designs adapting a group- and cluster-based approach. Clusters are formed by taking a collection of nodes, and those clusters are further taken collectively to form groups. Three types of communications enable us to achieve connectivity of desired level. Our scheme provides better resilience (both in case of node and links) as compared to some other schemes, while keeping the number of secret keys to be stored at each node significantly less.

Continuous network connectivity has always been a significant issue in the area of networks. Delay Tolerant Networks(DTNs) provides an architecture that casts upon the problems of discontinuity in the network and tries to solve it. Such dropping of connectivity is found in tremendous terrestrial atmosphere and planetary systems. Instead of traditional communication system of delivering data from source to destination through continuous connectivity, DTNs uses the intermediate nodes to relay messages from source to destination. Sometimes these nodes act selfishly and can deny to relay packets for saving their resources like energy, buffer etc and that is why they may not agree to forward data packets which leads to lack of cooperation and hence hampers transferability in the network. To combat this selfish behavior various incentives or rewards have been proposed to these nodes such they assist with each other and make the network communication smoother. Packet replication control based prophet routing strategy for DTNs (PRCP) uses replication control based incentive mechanism in prophet routing algorithm which has shown better values of parameters compared to existing ones.

This paper investigates routing strategies for mobile and heterogeneous multi-hop wireless networks. We leverage the knowledge about users mobility to improve the efficiency of route discovery and of the following data forwarding phase. In particular, we exploit group mobility behaviors, which allow us to apply a distributed on-line algorithm for the recognition of aggregated mobility patterns. Hence, we adopt a novel routing strategy that uses the aggregate structure formed within this algorithm to simplify the exchange of signaling and data messages. Finally, we demonstrate and quantify the benefits obtained with the proposed technique by means of a simulator for heterogeneous wireless networks.

Effective local dynamic routing strategy for air route networks