Analysis of exhaustive limited service for token ring networks

Token ring operation is well-understood in the cases of exhaustive, gated, gated limited, and ordinary cyclic service. There is no current data, however, on queueing models for the exhaustive limited service type. This service type differs from the others in that there is a preset maximum (omega) on the number of packets which may be transmitted per token reception, and packets which arrive after token reception may still be transmitted if the preset packet limit has not been reached. Exhaustive limited service is important since it closely approximates a timed token service discipline (the approximation becomes exact if packet lengths are constant). A method for deriving the z-transforms of the distributions of the number of packets present at both token departure and token arrival for a system using exhaustive limited service is presented. This allows for the derivation of a formula for mean queueing delay and queue lengths. The method is theoretically applicable to any omega. Fortunately, as the value of omega becomes large (typically values on the order of omega = 8 are considered large), the exhaustive limited service discipline closely approximates an exhaustive service discipline

Queueing models for token and slotted ring networks

Currently the end-to-end delay characteristics of very high speed local area networks are not well understood. The transmission speed of computer networks is increasing, and local area networks especially are finding increasing use in real time systems. Ring networks operation is generally well understood for both token rings and slotted rings. There is, however, a severe lack of queueing models for high layer operation. There are several factors which contribute to the processing delay of a packet, as opposed to the transmission delay, e.g., packet priority, its length, the user load, the processor load, the use of priority preemption, the use of preemption at packet reception, the number of processors, the number of protocol processing layers, the speed of each processor, and queue length limitations. Currently existing medium access queueing models are extended by adding modeling techniques which will handle exhaustive limited service both with and without priority traffic, and modeling capabilities are extended into the upper layers of the OSI model. Some of the model are parameterized solution methods, since it is shown that certain models do not exist as parameterized solutions, but rather as solution methods

Documentation for the token ring network simulation system

A manual is presented which describes the language features of the Token Ring Network Simulation System. The simulation system is a powerful simulation tool for token ring networks which allows the specification of various Medium Access Control (MAC) layer protocols as well as the specification of various features of upper layer ISO protocols. In addition to these features, it also allows the user to specify message and station classes virtually to any degree of detail desired. The choice of a language instead of an interactive system to specify network parameters was dictated by both flexibility and time considerations. The language was developed specifically for the simulation system, and is very simple. It is also user friendly in that language elements which do not apply to the case at hand are ignored rather than treated as errors

Initial experience and outcome of a new hemodialysis access device for catheter-dependent patients

ObjectiveThe effects of a new long-term subcutaneous vascular access device were studied in access-challenged patients who were poor candidates for fistulas or grafts due to venous obstruction. Bacteremia rates, patency, and function of the Hemodialysis Reliable Outflow (HeRO) Vascular Access Device (Hemosphere Inc, Minneapolis, Minn) were evaluated.MethodsThe HeRO device consists of a 6-mm expanded polytetrafluoroethylene graft attached to a 5-mm nitinol-reinforced silicone outflow component designed to bypass venous stenoses and enter the internal jugular vein directly, providing continuous arterial blood flow into the right atrium. The HeRO device was studied in a multicenter clinical trial to test the hypothesis that access-challenged patients would experience a statistically significant reduction in bacteremia rates compared with a tunneled dialysis catheter (TDC) literature control of 2.3/1000 days. HeRO-related bacteremia rates, adequacy of dialysis, patency, and adverse events were analyzed.ResultsThe HeRO device was implanted in 36 access-challenged patients who were followed for a mean 8.6 months (9931 HeRO days). The HeRO-related bacteremia rate was 0.70/1000 days. All HeRO-related bacteremias occurred during the bridging period when a TDC was still implanted before HeRO graft incorporation. HeRO adequacy of dialysis (mean Kt/V) was 1.7. HeRO primary patency was 38.9%, and secondary patency was 72.2%.ConclusionsIn access-challenged patients, a statistically significant reduction in HeRO-related bacteremia was noted compared with TDC literature. The device had similar function and patency compared with conventional arteriovenous graft literature

The State of Accreditation Readiness in Georgia: A Case Study

Background: Georgia’s public health districts first began exploring the idea of national public health accreditation in 2008 when Cobb & Douglas Public Health included accreditation in their strategic plan. In May 2015, Cobb & Douglas Public Health was the first Georgia public health district to achieve national accreditation status. This article discusses the current state of accreditation readiness in Georgia and explores strengths and barriers to accreditation. Methods: This study utilized a case study approach in order to examine PHAB accreditation efforts in Georgia within a real life context. Data came from three sources: nine Accreditation Readiness Assessments, a PHAB Pre-Application Technical Assistance Survey, and state-wide Accreditation Readiness Survey. Results: The Accreditation Readiness Assessments resulted in several lessons learned about common strengths and barriers to accreditation. Strengths included a dedicated staff and supportive Boards of Health. Barriers included accreditation fees and a lack of personnel time. The PHAB Pre-application TA Survey revealed that the majority of those surveyed would recommend TA to other agencies pursuing PHAB accreditation (91%). The Accreditation Readiness Survey revealed that 14 of 18 GA public health districts are either PHAB accredited (1 district), actively pursuing PHAB accreditation (2 districts), or planning to apply (11 districts). This includes 116 of the 159 Georgia counties (73%). Conclusions: The results of this case study show that 72% of Georgia’s public health districts are engaged in accreditationrelated activities. This includes activities such as accreditation readiness assessment, community health assessment, QI council and plan development, strategic planning, and policy review

The State of Accreditation Readiness in Georgia: A Case Study

Background: Georgia’s public health districts first began exploring the idea of national public health accreditation in 2008 when Cobb & Douglas Public Health included accreditation in their strategic plan. In May 2015, Cobb & Douglas Public Health was the first Georgia public health district to achieve national accreditation status. This article discusses the current state of accreditation readiness in Georgia and explores strengths and barriers to accreditation. Methods: This study utilized a case study approach in order to examine PHAB accreditation efforts in Georgia within a reallife context. Data came from three sources: nine Accreditation Readiness Assessments, a PHAB Pre-Application Technical Assistance Survey, and state-wide Accreditation Readiness Survey. Results: The Accreditation Readiness Assessments resulted in several lessons learned about common strengths and barriers to accreditation. Strengths included a dedicated staff and supportive Boards of Health. Barriers included accreditation fees and a lack of personnel time. The PHAB Pre-application TA Survey revealed that the majority of those surveyed would recommend TA to other agencies pursuing PHAB accreditation (91%). The Accreditation Readiness Survey revealed that 14 of 18 GA public health districts are either PHAB accredited (1 district), actively pursuing PHAB accreditation (2 districts), or planning to apply (11 districts). This includes 116 of the 159 Georgia counties (73%). Conclusions: The results of this case study show that 72% of Georgia’s public health districts are engaged in accreditationrelated activities. This includes activities such as accreditation readiness assessment, community health assessment, QI council and plan development, strategic planning, and policy review