MPLS fast reroute (MPLS-FRR) mechanisms deviate the traffic in case of network failures at the router closest to the outage location to achieve an extremely fast reaction time. We review the one-to-one backup and the ...
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MPLS fast reroute (MPLS-FRR) mechanisms deviate the traffic in case of network failures at the router closest to the outage location to achieve an extremely fast reaction time. We review the one-to-one backup and the facility backup that are options for MPLS-FRR to deviate the traffic via a detour or a bypass around the failed elements, respectively. Basically, the backup paths can take the shortest path that avoids the outage location from the point of local repair to the tail-end router or to the merge point with the primary path. We suggest two simple modifications that lead to a new path layout which can be implemented by one-to-one and by facility backup. We evaluate the backup capacity requirements, the length of the backup paths, and the number of backup paths per primary path in a parametric study regarding the network characteristics. Our proposals save a considerable amount of backup capacity compared to the standard mechanisms. They are suitable for application in practice since they are simple and conform to the standards.
This paper studies load balancing for multipath Internet routing. We focus on hash-based load balancing algorithms that work on the flow level to avoid packet reordering which is detrimental for the throughput of tran...
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This paper studies load balancing for multipath Internet routing. We focus on hash-based load balancing algorithms that work on the flow level to avoid packet reordering which is detrimental for the throughput of transport layer protocols like TCP. We propose a classification of hash-based load balancing algorithms, review existing ones and suggest new ones. Dynamic algorithms can actively react to load imbalances which causes route changes for some flows and thereby again packet reordering. Therefore, we investigate the load balancing accuracy and flow reassignment rate of load balancing algorithms. Our exhaustive simulation experiments show that these performance measures depend significantly on the traffic properties and on the algorithms themselves. As a consequence, our results should be taken into account for the application of load balancing in practice.
Autonomous vehicles seem to be a promising approach to both reducing traffic congestion and improving road safety. However, for such vehicles to coexist safely, they need to coordinate their behaviour to ensure that t...
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Autonomous vehicles seem to be a promising approach to both reducing traffic congestion and improving road safety. However, for such vehicles to coexist safely, they need to coordinate their behaviour to ensure that they do not collide with each other. This coordination is typically based on (wireless) communication between vehicles and needs to satisfy stringent real-time constraints. However, realtime message delivery cannot be guaranteed in dynamic wireless networks which means that existing coordination models that rely on continuous connectivity cannot be employed. In this paper, we present a novel coordination model for autonomous vehicles that does not require continuous real-time connectivity between participants in order to ensure that system safety constraints are not violated. This coordination model builds on a real-time communication model for wireless networks that provides feedback to entities about the state of communication. The coordination model uses this feedback to ensure that vehicles always satisfy safety constraints, by adapting their behaviour when communication is degraded. We show that this model can be used to coordinate vehicles crossing an unsignalised junction
MPLS fast reroute (MPLS-FRR) mechanisms deviate the traffic in case of network failures at the router which is closest to the outage location to achieve an extremely fast reaction time. We review the facility backup t...
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MPLS fast reroute (MPLS-FRR) mechanisms deviate the traffic in case of network failures at the router which is closest to the outage location to achieve an extremely fast reaction time. We review the facility backup that is an option for MPLS-FRR that deviates the traffic via a bypass around the failed elements. Basically, the backup path can take the shortest path that avoids the outage location from the point of local repair to the merge point with the primary path. We suggest two new simple modifications that lead to a new path layout which can be implemented by the facility backup. We evaluate the backup capacity requirements, the length of the backup paths, and the number of backup paths in a parametric study regarding the network characteristics. Our proposals save a considerable amount of backup capacity compared to the standard mechanisms. They are suitable for application in practice since they are simple and conform to the standards
This paper reviews the Internet-inspired security work on delay tolerant networking, in particular, as it might apply to space missions, and identifies some challenges arising, for both the Internet security community...
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This paper reviews the Internet-inspired security work on delay tolerant networking, in particular, as it might apply to space missions, and identifies some challenges arising, for both the Internet security community and for space missions. These challenges include the development of key management schemes suited for space missions as well as a characterization of the actual security requirements applying. A specific goal of this paper is therefore to elicit feedback from space mission IT specialists in order to guide the development of security mechanisms for delay tolerant networking
In this paper we propose to approximate the waiting time distribution function (DF) of the waiting customers in a M/G/1-infin queuing system by a gamma-distribution whose parameters alpha and beta are set by means of ...
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In this paper we propose to approximate the waiting time distribution function (DF) of the waiting customers in a M/G/1-infin queuing system by a gamma-distribution whose parameters alpha and beta are set by means of the first and second moment of the waiting time that are obtained from the Takacs recursion formula. Discrete-time analysis (DTA) is another approximation approach for the same objective. We show first for analytically feasible special cases that DTA is very accurate and then we use it to validate the accuracy of the new gamma-approximation for wide parameter ranges regarding the service time distribution. We show that the gamma-approximation respects well even the third moment of the service time distribution. As the new approach is very simple and fast, it may be used by engineers with only little background in queuing theory to calculate quantiles for real-time control loops in technical systems
ITS architectures encourage integration of individual intelligent transportation systems into comprehensive platforms and enable sharing of information across a wide variety of systems and services. This paper present...
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ITS architectures encourage integration of individual intelligent transportation systems into comprehensive platforms and enable sharing of information across a wide variety of systems and services. This paper presents a spatial programming model that has been designed as part of the iTransIT ITS framework to provide a standardized way to build value-added transportation user services and ultimately to deliver contextual transportation information to users. The spatial programming model is based on a topographical approach to modeling space that enables services to use potentially overlapping spatial context to correlate independently defined distributed information. This programming model has been evaluated by building a context-aware service for multi-modal urban journey planning
The Java messaging service (JMS) is a middlewareoriented messaging technology working according to the publish/ subscribe principle. If subscribers install filter rules on the JMS server, JMS can be used as a message ...
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The Java messaging service (JMS) is a middlewareoriented messaging technology working according to the publish/ subscribe principle. If subscribers install filter rules on the JMS server, JMS can be used as a message routing platform, but it is not clear whether its message throughput is sufficiently high to support large-scale systems. In this paper we investigate the capacity of the Websphere Message Queue JMS server. In contrast to other studies, we focus on the message throughput in the presence of filters and show that filtering reduces the performance significantly. We also present a model that describes the service time for a single message depending on the number of installed filters and validate it by measurements. This model helps to calculate the system throughput for specific application scenarios.
The Java messaging service (JMS) is a means to organize communication among distributed applications according to the publish/subscribe principle. If the subscribers install filter rules on the JMS server, JMS can be ...
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The Java messaging service (JMS) is a means to organize communication among distributed applications according to the publish/subscribe principle. If the subscribers install filter rules on the JMS server, JMS can be used as a message routing platform, but it is not clear whether its message throughput is sufficiently high to support large-scale systems. We perform measurements for the FioranoMQ JMS server and derive a simple model for its message processing time that takes message filters and the message replication grade into account. Then, we analyze the JMS server capacity and the message waiting time for various application scenarios. We show that the message waiting time is not an issue as long as the server throughput is sufficiently high. Finally, we assess the capacity of two different distributed JMS architectures whose objective is to increase the capacity of the JMS beyond the limit of a single server.
Pervasive computing is a developing area. Due to significant technological developments, assistive devices that were impossible to make or that were not even considered for manufacture are now available. The creation ...
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