Along with the increasing diversity of educational markup languages there is a strong need for flexible integration of such content into learning platforms. Therefore, we have identified four basic mechanisms: plain l...
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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 ...
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ISBN:
(纸本)9783800729456
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. In this paper, we investigate the capacity of the high performance JMS server implementation by Fiorano. 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 forecast the system throughput for specific application scenarios.
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 and compare the one-to-one bac...
In this paper we present a novel framework supporting distributed network management using a self-organizing peer-to-peer over-lay network. The overlay consists of several distributed Network Agents which can perform ...
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Restoration or protection switching mechanisms protect traffic in packet-switched networks against local outages by deviating it around the failure location. This assures connectivity, but sufficient backup capacity i...
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Restoration or protection switching mechanisms protect traffic in packet-switched networks against local outages by deviating it around the failure location. This assures connectivity, but sufficient backup capacity is also needed to maintain quality of service (QoS) for the duration of the outage. To that end, sufficient capacity must be provided on the links so that the network can survive a set of protected failure scenarios without congestion due to redirected traffic. The self- protecting multipath (SPM) is a protection switching mechanism for which the required backup capacity can be minimized by linear optimization methods. However, unprotected multi-failures may lead to congestion in such "resilient networks" since backup capacity may be missing. In this paper, we quantify and compare the impact of unprotected double failures on the QoS for the optimized SPM, single shortest path routing (SSP), and equal- cost multipath (ECMP) routing.
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.
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
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
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