Measuring and simulating an 802.3 CSMA/CD LAN

A single 802.3 CatTier Sense Multiple Access/Collision Detection (CSMA/CD) segment is measured resulting in throughput, response times and workstation parameters for several network nodes. During the measurements, the network can'ied an artificial workload with the characteristics of a real-life workload. A simulation of the laboratory test is developed using the artificial workload parameters and the 802.3 CSMA/CD standard of the Consultative Committee for International Telephony and Telegraphy (CCITT). The measurements show that it is possible to determine the workstation parameters with a great accuracy using simple throughput measurements on an otherwise empty network. It is then possible to isolate exact ethernet parameters during throughput measurements on a network with a known workload. The behaviour measured is reproduced in a simple simulation. The results of the simulation conform to the measured values. Some conclusions are that a 802.3 CSMA/CD segment can be measured and simulated with accurate results. The simulation environment is used to model a real-life ethernet network in circumstances that can not be measured in a real-life situation. Parameters that can be used to fine-tune the simulation are the interframe gap time, and the workstation distance on a network

Measuring and Modeling Computer Networks

Electrical Engineering, Mathematics and Computer Scienc

Measuring and simulating an 802.3 CSMA/CD LAN

A single 802.3 CatTier Sense Multiple Access/Collision Detection (CSMA/CD) segment is measured resulting in throughput, response times and workstation parameters for several network nodes. During the measurements, the network can'ied an artificial workload with the characteristics of a real-life workload. A simulation of the laboratory test is developed using the artificial workload parameters and the 802.3 CSMA/CD standard of the Consultative Committee for International Telephony and Telegraphy (CCITT). The measurements show that it is possible to determine the workstation parameters with a great accuracy using simple throughput measurements on an otherwise empty network. It is then possible to isolate exact ethernet parameters during throughput measurements on a network with a known workload. The behaviour measured is reproduced in a simple simulation. The results of the simulation conform to the measured values. Some conclusions are that a 802.3 CSMA/CD segment can be measured and simulated with accurate results. The simulation environment is used to model a real-life ethernet network in circumstances that can not be measured in a real-life situation. Parameters that can be used to fine-tune the simulation are the interframe gap time, and the workstation distance on a network

Propensity score-matched analysis of oncological outcome between stent as bridge to surgery and emergency resection in patients with malignant left-sided colonic obstruction

Background: Although self-expandable metal stent (SEMS) placement as bridge to surgery (BTS) in patients with left-sided obstructing colonic cancer has shown promising short-term results, it is used infrequently owing to uncertainty about its oncological safety. This population study compared long-term oncological outcomes between emergency resection and SEMS placement as BTS.Methods: Through a national collaborative research project, long-term outcome data were collected for all patients who underwent resection for left-sided obstructing colonic cancer between 2009 and 2016 in 75 Dutch hospitals. Patients were identified from the Dutch Colorectal Audit database. SEMS as BTS was compared with emergency resection in the curative setting after 1: 2 propensity score matching.Results: Some 222 patients who had a stent placed were matched to 444 who underwent emergency resection. The overall SEMS-related perforation rate was 7.7 per cent (17 of 222). Three-year locoregional recurrence rates after SEMS insertion and emergency resection were 11-4 and 13.6 per cent (P= 0-457), disease-free survival rates were 58-8 and 52.6 per cent (P= 0-175), and overall survival rates were 74-0 and 68-3 per cent (P= 0.231), respectively. SEMS placement resulted in significantly fewer permanent stomas (23.9 versus 45.3 per cent; P < 0-001), especially in elderly patients (29.0 versus 57.9 per cent; P < 0-001). For patients in the SEMS group with or without perforation, 3-year locoregional recurrence rates were 18 and 11.0 per cent (P= 0.432), disease-free survival rates were 49 and 59.6 per cent (P= 0-717), and overall survival rates 61 and 75.1 per cent (P= 0.529), respectively.Conclusion: Overall, SEMS as BTS seems an oncologically safe alternative to emergency resection with fewer permanent stomas. Nevertheless, the risk of SEMS-related perforation, as well as permanent stoma, might influence shared decision-making for individual patients.Research into fetal development and medicin