Time-efficient algorithms for BGP route configuration

Based on the concept of most popular prefix first, two efficient algorithms for BGP route configuration are proposed. The first algorithm MPPF_SES is designed for solving the single egress selection (SES) problem, and the second algorithm MPPF_MES is for multiple egress selection (MES). MPPF_MES has two variants, one aims at minimizing the total amount of resources consumed for carrying the transit traffic, and the other tries to minimize the egress link capacity required. Compared with the existing algorithms, a comparable performance in terms of network resources consumed can be obtained. In case of SES, our MPPF_SES can carry a given traffic load with much lower egress link capacity requirement. In case of MES, our MPPF_MES tends to provide a more stable performance. Last but not the least, our proposed algorithms have a much lower time complexity than the existing approach.published_or_final_versio

Traffic distribution over equal-cost-multi-paths

To effectively manage the traffic distribution inside a network, traffic splitting is needed for load sharing over a set of equal-cost-multi-paths (ECMPs). In this paper, a new traffic splitting algorithm, called Table-based Hashing with Reassignments (THR), is proposed. Based on the load sharing statistics collected, THR selectively reassigns some active flows from the over-utilized paths to under-utilized paths. The reassignment process takes place in such a way that the packet out-of-order problem is minimized. As compared with the existing traffic splitting algorithms, THR provides close-to-optimal load balancing performance, less than 2% of packets arrived out-of-order, and a very small end-to-end packet delay performance. Although additional traffic monitoring function is needed by THR, we show that the extra complexity incurred is marginal.published_or_final_versio

Time-efficient algorithms for BGP route configuration

Based on the concept of most popular prefix first, two efficient algorithms for BGP route configuration are proposed. The first algorithm MPPF_SES is designed for solving the single egress selection (SES) problem, and the second algorithm MPPF_MES is for multiple egress selection (MES). MPPF_MES has two variants, one aims at minimizing the total amount of resources consumed for carrying the transit traffic, and the other tries to minimize the egress link capacity required. Compared with the existing algorithms, a comparable performance in terms of network resources consumed can be obtained. In case of SES, our MPPF_SES can carry a given traffic load with much lower egress link capacity requirement. In case of MES, our MPPF_MES tends to provide a more stable performance. Last but not the least, our proposed algorithms have a much lower time complexity than the existing approach.published_or_final_versio

BGP ingress-to-egress route configuration in a capacity-constrained AS

The BGP ingress-to-egress route configuration problem is to find a set of paths in an ISP to carry the transit flows, such that the amount of network resources consumed is minimized without violating the bandwidth constraint on all network links. To solve the problem, we first formulate it using Integer Linear Programming (ILP). Due to the high complexity involved in ILP, a heuristic algorithm, called MPPF, is then proposed. MPPF is designed based on the idea that heavily-loaded destination prefixes should be given higher priority to select less expensive edge links and routes. Simulation results show that MPPF requires less network resources and edge link capacity than an alternative heuristic called BTF. © 2005 IEEE.published_or_final_versio

BGP ingress-to-egress route configuration in a capacity-constrained AS

The BGP ingress-to-egress route configuration problem is to find a set of paths in an ISP to carry the transit flows, such that the amount of network resources consumed is minimized without violating the bandwidth constraint on all network links. To solve the problem, we first formulate it using Integer Linear Programming (ILP). Due to the high complexity involved in ILP, a heuristic algorithm, called MPPF, is then proposed. MPPF is designed based on the idea that heavily-loaded destination prefixes should be given higher priority to select less expensive edge links and routes. Simulation results show that MPPF requires less network resources and edge link capacity than an alternative heuristic called BTF. © 2005 IEEE.published_or_final_versio

A quasi-experimental study on a new service option of short-term residential care for older stroke patients

published_or_final_versio

Routing algorithm for provisioning symmetric virtual private networks in the hose model

A virtual private network (VPN) is a private data network where remote sites are connected over a shared provider network. In order to provide secure communications between customer sites, predetermined paths are used to forward data packets. To support quality of service (QoS), bandwidth has to be reserved on these paths. Then, finding appropriate paths in order to optimize the bandwidth used becomes an important problem. In this paper, we study the routing problem of VPNs under the hose model, where VPN endpoints specify the maximum bandwidth they need in sending and receiving data. Some previous works considered the problem under the assumption that all links have infinite capacities. We remove this constraint in our studies and develop enhancement to existing algorithms. Our simulation results show that our algorithm works very well in networks where link capacities are tight. © 2005 IEEE.published_or_final_versio

Diagnostic accuracy of mediastinal width measurement on posteroanterior and anteroposterior chest radiographs in the depiction of acute nontraumatic thoracic aortic dissection

We aimed to explore the diagnostic accuracy of various mediastinal measurements in determining acute nontraumatic thoracic aortic dissection with respect to posteroanterior (PA) and anteroposterior (AP) chest radiographs, which had received little attention so far. We retrospectively reviewed 100 patients (50 PA and 50 AP chest radiographs) with confirmed acute thoracic aortic dissection and 120 patients (60 PA and 60 AP chest radiographs) with confirmed normal aorta. Those who had prior history of trauma or aortic disease were excluded. The maximal mediastinal width (MW) and maximal left mediastinal width (LMW) were measured by two independent radiologists and the mediastinal width ratio (MWR) was calculated. Statistical analysis was then performed with independent sample t test. PA projection was significantly more accurate than AP projection, achieving higher sensitivity and specificity. LMW and MW were the most powerful parameters on PA and AP chest radiographs, respectively. The optimal cutoff levels were LMW = 4.95 cm (sensitivity, 90 %; specificity, 90 %) and MW = 7.45 cm (sensitivity, 90 %; specificity, 88.3 %) for PA projection and LMW = 5.45 cm (sensitivity, 76 %; specificity, 65 %) and MW = 8.65 cm (sensitivity, 72 %; specificity, 80 %) for AP projection. MWR was found less useful and less reliable. The use of LMW alone in PA film would allow more accurate prediction of aortic dissection. PA chest radiograph has a higher diagnostic accuracy when compared with AP chest radiograph, with negative PA chest radiograph showing less probability for aortic dissection. Lower threshold for proceeding to computed tomography aortogram is recommended however, especially in the elderly and patients with widened mediastinum on AP chest radiograph. © 2012 The Author(s).published_or_final_versio

Automobile hybrid air conditioning technology

Author name used in this publication: Y. P. B. YeungAuthor name used in this publication: K. W. E. ChengVersion of RecordPublishe

Can short-term residential care for stroke rehabilitation help to reduce the institutionalization of stroke survivors?

Background: Stroke survivors may not be receiving optimal rehabilitation as a result of a shortage of hospital resources, and many of them are institutionalized. A rehabilitation program provided in a short-term residential care setting may help to fill the service gap. Objectives: The primary objectives of this study were, first, to examine whether there were significant differences in terms of rehabilitation outcomes at 1 year after admission to the rehabilitation program (defined as baseline) between those using short-term residential care (intervention group) and those using usual geriatric day hospital care (control group), and, second, to investigate whether lower 1-year institutionalization rates were observed in the intervention group than in the control group. Participants: 155 stroke survivors who completed at least the first follow-up at 4 months after baseline. Intervention: The intervention group was stroke survivors using self-financed short-term residential care for stroke rehabilitation. The control group was stroke survivors using the usual care at a public geriatric day hospital. Measurements: Assessments were conducted by trained research assistants using structured questionnaires at baseline, 4 months, and 1 year after baseline. The primary outcome measures included Modified Barthel Index score, Mini-Mental Status Examination score, and the institutionalization rate. Results: Cognitive status (as measured by Mini-Mental Status Examination score) of patients in both groups could be maintained from 4 months to 1 year, whereas functional status (as measured by Modified Barthel Index score) of the patients could be further improved after 4 months up to 1 year. Meanwhile, insignificant between-group difference in rehabilitation outcomes was observed. The intervention participants had a significantly lower 1-year institutionalization rate (15.8%) than the control group (25.8%). Conclusion: Short-term residential care for stroke rehabilitation promoted improvements in rehabilitation outcomes comparable with, if not better than, the usual care at geriatric day hospital. Furthermore, it had a significantly lower 1-year institutionalization rate. This type of service could be promoted to prevent institutionalization.published_or_final_versio