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Scheduling for Proportional Differentiated Services on the InternetSelvaraj, Manimaran 13 December 2002 (has links)
Proportional Differentiated Services can be provisioned in terms of bandwidth, delay, or packet loss. Several studies contributed schedulers and packet droppers that achieved proportional bandwidth, delay, or loss differentiation. However, all these schemes differentiated in terms of only one of the three metrics. A simple, unified, scalable, and robust scheme to simultaneously control all three metrics was felt important. By controlling just delay and packet loss, proportional differentiation can be achieved in terms of all three metrics. A robust adaptive scheduler for proportional delay differentiation services is presented. Proportional services are further policed by a class based packet dropper. The combination of the adaptive scheduler and the packet dropper treats different traffic classes proportionally in terms of all three metrics. Simulation experiments show that regardless of the network traffic characteristics, our scheme can effectively differentiate services in terms of bandwidth, delay, and loss simultaneously.
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Adaptive Flow Control Scheme for Differentiated ServicesHsieh, Jin-Shing 13 July 2000 (has links)
Differentiated Services architecture permits the allocation of different levels of service to different users. And the Assured Forwarding Per-Hop-Behavior Group defined different drop precedence in the DS routers to provide soft guarantees. However, it has been observed that the drop precedence cannot achieve the desired target rates because of the strong interaction of the transport protocol with packet drops in the Internet.
An Internet Service Provider (ISP) does not know what kind of traffic will be sent into the network, so the Internet Service Provider should be able to adapt different types of clients and provides certain quality of services (QOS).
We propose a new flow control scheme to enhance the edge routers in a Differentiated Services network with the adaptive drop precedence according to actual flow rates to improve the fairness among the different types of traffics through the Differentiated Services network.
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Incorporating a Rate Control Mechanism into Differentiated Services NetworksHsu, Yi-Shiou 18 July 2000 (has links)
Differentiated services (Diffserv) is a scalable architecture and
is proposed to provide QoS guarantee services in the current
best effort network environment.
In this thesis, we will introduce the Diffserv model and the Diffserv
router components in detail. Related works proposed by researchers
to improve the performance of the Diffserv networks are categorized
and discussed. Common challenges in the Diffserv networks are
pointed out. Then a weighted fair share algorithm is proposed to solve
these challenges.
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Adaptive Traffic Conditioner in the Differentiated Services NetworkLiu, Hsu-jung 19 November 2003 (has links)
Many congestion control mechanisms have been proposed to solve the problems of a high loss rate and inefficient utilization of network resources in the present Internet. This problem is caused by competition between traffic flows while the network is congested. Differentiated Services (DiffServ) architecture permits the allocation of various levels of traffic resource requirements needed for Quality of Service (QoS). Random Early Detection (RED) is an efficient mechanism to pre-drop packets before actual congestion occurs, and it is capable of introducing a random early packet dropping scheme, and based on the queue length in reaching a certain degree of fairness for resource utilization. However, it still suffers from a lack of robustness among light traffic load, or in heavy traffic load using fixed RED parameters. In this dissertation, we modified the RED scheme and proposed a novel adaptive RED model, which we named the OURED model, to enhance the robustness of resource utilization so that it could be utilized in the DiffServ edge router. The OURED model introduces two additional packet dropping traces, one is Over Random Early Detection (ORED), which is used to speed up the dropping of packets when the actual rate is higher than the target rate, and the other one is the Under Random Early Detection (URED), used to slow down the packet dropping rate in the reverse situation. The simulation results show that OURED is not only more robust than MRED in resource utilization, but that it also can be implement efficiently in the DiffServ edge router.
Another model proposed in this dissertation is the Age-Based packet discarding Traffic Conditioner. For the reason that the file sizes of on going flows are fairly disparate on the current network, we propose an ¡§Age-Based¡¨ packet discard scheme in the Traffic Conditioner of a gateway, to improve the performance of file transmission. The on going flows will be grouped to three classes of priority according to their ¡§age¡¨ as network congestion occurs and the simulation results show that the proposed model can work efficiently in most of the congestion conditions.
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Dynamic Traffic Adjustment for End-to-End Proportional Differentiated Services on MPLS NetworksHsieh, Chin-Chung 27 August 2004 (has links)
In this thesis, we propose a dynamic traffic adjustment scheme for end-to-end proportional differentiated services (EEPDS) on MPLS networks. When the Egress LSR (Label Switch Router) first observes that the proportional ratio of multiple flows could not be maintained, it will locate the performance bottlenecks by sending control messages to all the traversed LSR. In the proposed scheme, the identified bottleneck routers may have to drop the packets of traffic flows that do not require any QoS assurance (for example, the best-effort flows). Moreover, if dropping packets of the best-effort flows could not meet the goals of maintaining proportional ratios, the Ingress LSR would have to shape the traffic rates of sending flows proportionally based on the throughput values observed by the Egress LSR. Once a bottleneck router regains its sufficient bandwidth released by other traffic flows, it will send out control packets to notify the Ingress LSR to recover the original sending rates. Eventually, the proposed EEPDS mechanism can meet the goals of maintaining the proportional ratios by dynamically tuning the traffic flows.
For the purpose of demonstration, we implement the EEPDS scheme by using MNS simulator. According to the experimental results, the EEPDS scheme has shown that it can meet the proportional ratios of multiple traffic flows even under severe network congestions, where multiple performance bottlenecks may occur. Finally, we observe that the processing overhead of the proposed EEPDS scheme is very small, since it is triggered only when the Egress LSR detects the situation of unsatisfied proportional ratios.
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Implementace QoS v přístupové síti / QoS Implementation in Access NetworkAdámek, David January 2008 (has links)
This diploma thesis deals with computer networks which play a key role in present society. More and more demands are placed on these networks (especially on quality of services and throughput) because of fast-growing developement of services such as voice and video real-time transmissions. All the packets in typical Ethernet networks are equal. Therefore it is sometimes impossible for the application to maintain required throughput speed of a network. For this case it is useful to take some mechanisms into the consideration. These mechanisms (sometimes called QoS) are able to distinguish different types of transmissions and traffic, analyze them and then prioritize them according to some pre-defined set of rules. The most famous mechanisms are Integrated Services and Differentiated Services. The implementation of Differentiated Services is the goal of this thesis.
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Service Quality Perspective and Customer Satisfaction: : Xingya Technical Communication CompanyChi, Yuan, Quan, Yaqi January 2016 (has links)
Aim: The purpose of this study is to investigate the evaluation and conceptualization of service quality and its interactive impacts for customer satisfaction. This study provides some positive and constructive proposal to make up the service gap ,and provides preliminary results supported by SERVQUAL model to measure the mutual interactions between service quality and customer satisfaction. Service quality and customer satisfaction have been studied by the help of quality dimensions and some suggestions are offered for improving service quality. Methods: The primary data have been collected through interviews and questionnaires. The secondary data has been collected through literature review. Case study approach is used to identify the current relationship between service quality and consumer satisfaction. Result and Conclusions: We used five service quality dimensions to measure service quality and customer satisfaction. After survey is conducted, it has been clear that there are two dimensions (Empathy and Responsiveness) made a significant service gap between our target company and the key customer groups. The gap is the Differentiated service and the Service promptness. We also give our suggestions to make up the gap. Providing differentiated services. Scheduling to the workload rather than to workers’ traditional schedules Empowering as many staffs as possible to deal with the problems and providing initial training on how to solve most common problems Customer segmentation, providing the characteristic services to customers. Providing characteristic services to customers Contributions of the thesis / Value: We believe that this thesis will help Xingya Technical Communication Company (XTCC) to become more aware of service quality and constantly updated the service to overcome the customer complaints. And after the study, we find that the service quality dimensions (Empathy and Responsiveness) are the controversial issues. We think this study can provide some useful information for this research area. Implications: This survey contributes to the topic both at practical and theoretical levels. We also put forward our suggestions for the target service provider in order to help them improve service quality in the future.
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Quality-consciousness in Large-scale Content Distribution in the InternetGupta, Minaxi 23 July 2004 (has links)
Content distribution is the primary
function of the Internet today.
Technologies like multicast and
peer-to-peer networks hold the potential
to serve content to large populations in
a scalable manner. While multicast
provides an efficient transport
mechanism for one-to-many and
many-to-many delivery of data in an
Internet environment, the peer-to-peer
networks allow scalable content location
and retrieval among large groups of
users in the Internet.
Incorporating quality-consciousness in
these technologies is necessary to
enhance the overall experience of
clients. This dissertation focuses on
the architectures and mechanisms to
enhance multicast and peer-to-peer
content distribution through
quality-consciousness. In particular,
the following aspects of
quality-consciousness are addressed: 1)
client latency, 2) service
differentiation, and 3) content quality.
Data analysis shows that the existing
multicast scheduling algorithms behave
unfairly when the access conditions for
the popular files changes. They favor
the popular files while penalizing the
files whose access conditions have not
changed. To maintain the client latency
for all files under dynamic access
conditions we develop a novel multicast
scheduling algorithm that requires no
change in server provisioning.
Service differentiation is a desirable
functionality for both multicast and
peer-to-peer networks. For multicast,
we design a scalable and low overhead
service differentiation architecture.
For peer-to-peer networks, we focus on a
protocol to provide different levels of
service to peers based on their
contributions in the system.
The ability to associate reliable
reputations with peers in a peer-to-peer
network is a useful feature of these
networks. Reliable reputations can help
establish trust in these networks and
hence improve content quality. They can
also be used as a substrate for a
service differentiation scheme for these
networks. This dissertation develops
two methods of tracking peer reputations
with varying degrees of reliability and
overheads.
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A Dynamic Throughput Improvement Scheme with Priority Queues in Differentiated Services NetworksTseng, Fan-Geng 26 July 2000 (has links)
Differentiated-Service networks is designed for solving scalability problems through traffic aggregation. However, it can't guarantee end-to-end QoS of individual flow. In this thesis, we propose a Self-Adaptive Control Scheme for Differentiated-Service networks that can improve the throughput of individual flows dynamically. In this scheme, egress routers monitor the average throughput of individual flow, and send the Self-Adaptive Control Messages to ingress routers if need. The ingress router re-allocate network resources to improve throughput of high-priority flows depending on the Control Messages.
We use NS-2 simulator to prove that our scheme that can improve throughput of high-priority flows dynamically, and suggest that a better time interval of Self-Adaptive control can be determined based on the queue sizes, packets arrival rate and departure rate. Finally, we use Random Early Detection (RED) queue instead of Drop-Tail queue to reduce unfairness of individual flows when there are congestion and insufficient network resources.
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Analysis of RED packet loss performance in a simulated IP WANEngelbrecht, Nico 26 June 2013 (has links)
The Internet supports a diverse number of applications, which have different requirements for a number of services. Next generation networks provide high speed connectivity between hosts, which leaves the service provider to configure network devices appropriately, in order to maximize network performance. Service provider settings are based on best recommendation parameters, which give an opportunity to optimize these settings even further. This dissertation focuses on a packet discarding algorithm, known as random early detection (RED), to determine parameters which will maximize utilization of a resource. The two dominant traffic protocols used across an IP backbone are UDP and TCP. UDP traffic flows transmit packets regardless of network conditions, dropping packets without changing its transmission rates. However, TCP traffic flows concern itself with the network condition, reducing its packet transmission rate based on packet loss. Packet loss indicates that a network is congested. The sliding window concept, also known as the TCP congestion window, adjusts to the amount of acknowledgements the source node receives from the destination node. This paradigm provides a means to transmit data across the available bandwidth across a network. A well known and widely implemented simulation environment, the network simulator 2 (NS2), was used to analyze the RED mechanism. The network simulator 2 (NS2) software gained its popularity as being a complex networking simulation tool. Network protocol traffic (UDP and TCP) characteristics comply with theory, which verifies that the traffic generated by this simulator is valid. It is shown that the autocorrelation function differs between these two traffic types, verifying that the generated traffic does conform to theoretical and practical results. UDP traffic has a short-range dependency while TCP traffic has a long-range dependency. Simulation results show the effects of the RED algorithm on network traffic and equipment performance. It is shown that random packet discarding improves source transmission rate stabilization, as well as node utilization. If the packet dropping probability is set high, the TCP source transmission rates will be low, but a low packet drop probability provides high transmission rates to a few sources and low transmission rates to the majority of other sources. Therefore, an ideal packet drop probability was obtained to complement TCP source transmission rates and node utilization. Statistical distributions were fitted to sampled data from the simulations, which also show improvements to the network with random packet discarding. The results obtained contribute to congestion control across wide area networks. Even though a number of queuing management implementation exists, RED is the most widely used implementation used by service providers. / Dissertation (MEng)--University of Pretoria, 2013. / Electrical, Electronic and Computer Engineering / unrestricted
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