Abstract We propose to research the interaction between users and web servers in Internet , and we call that ¡§Session - Based model¡§ . Then we add some policies to the session-based model , we define that is ¡§Session - Based Management¡§ . For the explosive growth of Internet service¡]eg.,e-commerce¡K¡^, we consider about what users want and tracing users¡¦ behaviors , those are what we want to research and analysis . We using ¡§cookie¡§ , what is the technique to use on the Client-Server model of Internet . This make server directly and easily know some information about users . So server supply quality of service to user what they have identified . Then we trace technologies of cookie which are used in some popular web sites¡]eg., eBay , ubid , kimo , openfind¡^, and analyze the impact of users about those technologies . For example , we classify the Internet service to ¡V shopping cart¡Bsearch engine¡K Finally , we construct our e-commerce web site to parsing every packets through our site , getting the information what we want from those packets , and then we define our some policies into our Session-Based model . The infrastructure of our implementation environment is in Server Cluster Architecture , which is the most popular one this time . More and more ISPs¡]Internet Service Provider¡^or ICPs¡]Internet Content Provider¡^construct their web sites in this kind of structure . In our cluster system , our distributor will analyze all kinds of packets from all heterogeneous servers . Using our technique will make distributor to learn how to know the user information and identify the users , so distributor will know how to supply users¡¦ session-based priority¡Bdifferentiated service and so on . We actually implement our mechanisms in our server cluster system .

South Africa has the largest number of people living with HIV and the largest HIV treatment program in the world, supplying antiretroviral therapy (ART) to 66% of the 7.6 million people living with HIV in the country in 2019. To reach the remaining 34%, the already overburdened health system needs to find ways of attracting and retaining groups at higher risk of attrition and optimizing convenience for providers and patients. We identified three examples of “differentiated service delivery”, an approach that adapts HIV services to patient and health system needs: (1) male clinics, attended and staffed exclusively by men, (2) youth clinics, exclusively for youth aged 12–25, offering flexible hours and youth-targeted services and (3) a pharmacy-led fast-track ART refill program where stable ART patients can pick up medication without seeing a clinician. We explore attrition (defined as death or loss to follow-up at end of follow-up time) in these services using data from a large, established HIV cohort in Khayelitsha, a high HIV-prevalence, low-income area in South Africa. The first study examines whether males attending two male clinics (Male Clinic 1 and Male Clinic 2) show lower attrition compared to those attending general primary healthcare clinics. Using exposure propensity scores, we matched male clinic patients 1:1 to males at other clinics and used Cox proportional hazards regression to estimate the association between attrition and attending a male clinic. In the unmatched cohort, patients from male clinics (n=784) were younger than males from general clinics (n=2726), median age: 31.2 vs 35.5 years. Those initiating at male clinics had higher median CD4 counts at ART initiation (Male Clinic 1: 329 [210–431], Male Clinic 2: 364 [IQR: 260–536] vs. general clinics 258 [IQR: 145–398] cells/mm3). The matched analysis included 1563 person-years among 1568 patients. Patients initiating ART at male clinics had lower attrition (HR: 0.83; 95% CI: 0.69–1.00). When matching and modelling was conducted for Male Clinic 1 and 2 separately, only the more established Male Clinic 1 showed a protective effect (HR 0.83; 95% CI: 0.65–1.07). The second study investigates whether attrition from care among youth (aged 12–25) on ART is lower among youth attending two youth clinics (Youth Clinic A and Youth Clinic B) compared to those attending general primary healthcare clinics. We also conducted a sub-analysis of patients attending adherence clubs (a model of ART delivery led by a lay facilitator, including a peer support group). We hypothesized that the effect of peer support in adherence clubs might be enhanced by the age-specific clubs at the youth clinics. It may also be further enhanced by additional elements of the adherence club model offered only in Youth Clinic A, including integration of family planning. Youth at the youth clinics were more likely than those at general clinics to have initiated ART before August 2011, particularly those at Youth Clinic B (23% compared to 11% at general clinics). The distribution of age, sex, and CD4 count at ART initiation was similar across youth and general clinics. We observed a protective effect of youth clinics against attrition: HR 0.81 (95% CI: 0.70–0.93) for Youth Clinic A and 0.85 (0.74–0.98) for Youth Clinic B, compared to youth at general clinics. Youth Clinic A club patients had lower attrition after joining an adherence club compared to general clinic patients in adherence clubs (crude HR: 0.56, 95% CI: 0.32–0.96; adjusted HR: 0.48, 95% CI: 0.28–0.85), while Youth Clinic B showed a smaller difference (crude HR: 0.83, 95% CI: 0.48–1.45; adjusted HR: 1.07, 95% CI: 0.60–1.90). The third study assesses attrition among patients in a pharmacy-led fast-track ART refill program compared to matched stable, otherwise healthy, patients who were eligible for the fast-track program at the same point in time and at the same facility but did not join. Matched pairs were followed from the date of the fast-track patient’s first fast-track ART pick-up, and attrition was compared using Cox proportional hazards regression. Fast-track patients and matched controls had similar characteristics at ART initiation and at fast-track enrolment. Fast-track patients were less likely to have previously experienced tuberculosis (23% vs 28%), diabetes (1% vs 7%) and hypertension (12% vs 27%), compared to those not in fast-track. Fast-track enrolment was highly protective against attrition (HR: 0.40; 95% CI: 0.31–0.51). We hypothesized that some of the association could be explained by confounding, arising from clinicians differentially referring patients to fast-track, possibly based on social, health, or mental health characteristics not reflected in the data. In a bias analysis using a plausible range of effects of such unmeasured confounding, the hazard ratio accounting for random and systematic error was 0.60 (95% interval: 0.42–0.89). All three studies show some protective effects of these differentiated models of service delivery against attrition. While stand-alone youth and male clinics are not feasible in all settings, and fast-track models may not be suited to all patients, these results suggest that multiple approaches tailored to specific populations’ needs can contribute to improving retention.

Asymmetric digital subscriber line (ADSL) is a broadband access technology capable of delivering large bandwidth over existing copper telephone line infrastructure. This research aims at characterizing and analyzing TCP/IP performance in presence of a new protocol stack (TCP/IP over PPP and ATM) being promoted for one of the ADSL network architectures. Using extensive simulations, we verify the adverse effects of asymmetric links on the performance of TCP and additional throughput degradation caused by the overhead at the AAL5- ATM layers. This study involves unidirectional as well as bi-directional data transfer using different traffic mixes including bursty and non-bursty types of traffic. Bi-directional data transfer over asymmetric links results in ACK compression wherein TCP acknowledgements (ACKs) get bunched together behind larger data packets, further exacerbating the effect of asymmetry on TCP performance. By implementing the simulation model for PPP encapsulation over AAL5, we characterize its effect in terms of throughput degradation and excessive delay. We quantify the improvement in the throughput obtained by delaying the TCP ACKs and by TCP/IP header compression. These techniques being effective for unidirectional traffic over asymmetric links, however, do not prove as effective when ATM enters the scenario or in presence of bi-directional data transfer. Further, we implemented a simulation model of the Smart ACK Dropper (SAD), a technique to regulate the flow of TCP ACKs. Considerable improvement in performance especially in the presence of unidirectional data transfer is achieved using the SAD technique. Although the improvement is to a lesser extent in the presence of bi-directional data traffic, SAD helps the network in quickly recovering from the impact of ACK compression. We also propose and implement certain customized queuing/scheduling and policing mechanisms to enable differentiated servicing of TCP ACKs and data packets, and mitigate the effect of ACK compression. While providing considerable TCP performance improvement in presence of SAD, custom queuing also allows fair sharing of bandwidth between TCP flows, unlike priority queuing, which starves the low priority flow. The committed access rate (CAR)policing scheme provides considerable performance improvement when used with SAD, and is especially useful when TCP ACKs compete with bursty data traffic over the slower upstream. / Master of Science

Backbone networks are responsible for long-haul data transport serving many clients with a large volume of data. Since long-haul data transport service must rely on a robust high capacity network the current technology broadly adopted by the industry is Wavelength Division Multiplexing (WDM). WDM networks enable one single ber to operate with multiple high capacity channels, drastically increasing the ber capacity. In WDM networks each channel is associated with an individual wavelength. Therefore a whole wavelength capacity is assigned to a connection, causing waste of bandwidth in case the connection bandwidth requirement is less than the channel total capacity. In the last half decade, Elastic Optical Networks (EON) have been proposed and developed based on the fexible use of the optical spectrum known as the exigrid. EONs are adaptable to clients requirements and may enhance optical networks performance. For these reasons, research community and data transport providers have been demonstrating increasingly high interest in EONs which are likely to replace WDM as the universally adopted technology in backbone networks in the near future. EONs have two characteristics that may limit its ecient resources use. The spectrum fragmentation, inherent to the dynamic EON operation, decrease the network capacity to assign resources to connection requests increasing network blocking probability. The spectrum fragmentation also intensifides the denial of service to higher rate request inducing service unfairness. Due to the fact EONs were just recently developed and proposed, the aforementioned issues were not yet extensively studied and solutions are still being proposed. Furthermore, EONs do not yet provide specific features as differentiated service mechanisms. Differentiated service strategies are important in backbone networks to guarantee client\'s diverse requirements in case of a network failure or the natural congestion and resources contention that may occur at some periods of time in a network. Impelled by the foregoing facts, this thesis objective is three-fold. By means of developing and proposing a mechanism for routing and resources assignment in EONs, we intend to provide differentiated service while decreasing fragmentation level and increasing service fairness. The mechanism proposed and explained in this thesis was tested in a EON simulation environment and performance results indicated that it promotes beneficial performance enhancements when compared to benchmark algorithms. / Redes backbone s~ao responsáveis pelo transporte de dados à longa distância que atendem a uma grande quantidade de clientes com um grande volume de dados. Como redes backbone devem basear-se em uma rede robusta e de alta capacidade, a tecnologia atual amplamente adotada pela indústria é Wavelength Division Multiplexing (WDM). Redes WDM permitem que uma única fibra opere com múltiplos canais de alta largura de banda, aumentando drasticamente a capacidade da fibra. Em redes WDMcada canal está associado a um comprimento de onda particular. Por conseguinte, toda capacidade do comprimento de onda é atribuída a uma única conexão, fazendo com que parte da largura de banda seja desperdiçada no caso em que a requisição de largura de banda da conexão seja menor do que a capacidade total do canal. A partir da metade da última década, as Redes Ópticas Elásticas (Elastic Optical Networks - EON) têm sido propostas e desenvolvidas com base no uso flexível do espectro óptico conhecido como flexigrid. EONs s~ao adaptáveis às requisições por banda dos clientes e podem, portanto, melhorar o desempenho das redes ópticas. Por estas razões, EONs têm recebido cada vez mais interesse dos meios de pesquisa e provedores de serviço e provavelmente substituirão WDM como a tecnologia universalmente adotada pela indústria em redes backbone. EONs têm duas características que podem limitar a utilização eficiente de recursos. A fragmentação do espectro, inerente à operação dinâmica das EONs, pode diminuir a capacidade da rede em distribuir recursos ao atender às solicitações por conexões aumentando a probabilidade de bloqueio na rede. A fragmentação do espectro também intensifica a negação de serviço a solicitações por taxa de transmissão mais elevada, gerando injustiça no serviço prestado. Como EONs foram desenvolvidas recentemente, respostas às questões acima mencionadas ainda estão sob estudo e soluções continuam sendo propostas na literatura. Além disso, EONs ainda não fornecem funções específicas como um mecanismo que proveja diferenciação de serviço. Estratégias de diferenciação de serviço são importantes em redes backbone para garantir os diversos requisitos dos clientes em caso de uma falha na rede ou do congestionamento e disputa por recursos que podem ocorrer em alguns períodos em uma rede. Impulsionada pelos fatos anteriormente mencionados, esta tese possui três objetivos. Através do desenvolvimento e proposta de um mecanismo de roteamento e atribuição de recursos para EONs, temos a intenção de disponibilizar diferenciação de serviço, diminuir o nível de fragmentação de espectro e aumentar a justiça na distribuição de serviços. O mecanismo proposto nesta tese foi testado em simulações de EONs. Resultados indicaram que o mecanismo proposto promove benefícios através do aprimoramento da performance de uma rede EON quando comparado com algoritmos de referência.

Backbone networks are responsible for long-haul data transport serving many clients with a large volume of data. Since long-haul data transport service must rely on a robust high capacity network the current technology broadly adopted by the industry is Wavelength Division Multiplexing (WDM). WDM networks enable one single ber to operate with multiple high capacity channels, drastically increasing the ber capacity. In WDM networks each channel is associated with an individual wavelength. Therefore a whole wavelength capacity is assigned to a connection, causing waste of bandwidth in case the connection bandwidth requirement is less than the channel total capacity. In the last half decade, Elastic Optical Networks (EON) have been proposed and developed based on the fexible use of the optical spectrum known as the exigrid. EONs are adaptable to clients requirements and may enhance optical networks performance. For these reasons, research community and data transport providers have been demonstrating increasingly high interest in EONs which are likely to replace WDM as the universally adopted technology in backbone networks in the near future. EONs have two characteristics that may limit its ecient resources use. The spectrum fragmentation, inherent to the dynamic EON operation, decrease the network capacity to assign resources to connection requests increasing network blocking probability. The spectrum fragmentation also intensifides the denial of service to higher rate request inducing service unfairness. Due to the fact EONs were just recently developed and proposed, the aforementioned issues were not yet extensively studied and solutions are still being proposed. Furthermore, EONs do not yet provide specific features as differentiated service mechanisms. Differentiated service strategies are important in backbone networks to guarantee client\'s diverse requirements in case of a network failure or the natural congestion and resources contention that may occur at some periods of time in a network. Impelled by the foregoing facts, this thesis objective is three-fold. By means of developing and proposing a mechanism for routing and resources assignment in EONs, we intend to provide differentiated service while decreasing fragmentation level and increasing service fairness. The mechanism proposed and explained in this thesis was tested in a EON simulation environment and performance results indicated that it promotes beneficial performance enhancements when compared to benchmark algorithms. / Redes backbone s~ao responsáveis pelo transporte de dados à longa distância que atendem a uma grande quantidade de clientes com um grande volume de dados. Como redes backbone devem basear-se em uma rede robusta e de alta capacidade, a tecnologia atual amplamente adotada pela indústria é Wavelength Division Multiplexing (WDM). Redes WDM permitem que uma única fibra opere com múltiplos canais de alta largura de banda, aumentando drasticamente a capacidade da fibra. Em redes WDMcada canal está associado a um comprimento de onda particular. Por conseguinte, toda capacidade do comprimento de onda é atribuída a uma única conexão, fazendo com que parte da largura de banda seja desperdiçada no caso em que a requisição de largura de banda da conexão seja menor do que a capacidade total do canal. A partir da metade da última década, as Redes Ópticas Elásticas (Elastic Optical Networks - EON) têm sido propostas e desenvolvidas com base no uso flexível do espectro óptico conhecido como flexigrid. EONs s~ao adaptáveis às requisições por banda dos clientes e podem, portanto, melhorar o desempenho das redes ópticas. Por estas razões, EONs têm recebido cada vez mais interesse dos meios de pesquisa e provedores de serviço e provavelmente substituirão WDM como a tecnologia universalmente adotada pela indústria em redes backbone. EONs têm duas características que podem limitar a utilização eficiente de recursos. A fragmentação do espectro, inerente à operação dinâmica das EONs, pode diminuir a capacidade da rede em distribuir recursos ao atender às solicitações por conexões aumentando a probabilidade de bloqueio na rede. A fragmentação do espectro também intensifica a negação de serviço a solicitações por taxa de transmissão mais elevada, gerando injustiça no serviço prestado. Como EONs foram desenvolvidas recentemente, respostas às questões acima mencionadas ainda estão sob estudo e soluções continuam sendo propostas na literatura. Além disso, EONs ainda não fornecem funções específicas como um mecanismo que proveja diferenciação de serviço. Estratégias de diferenciação de serviço são importantes em redes backbone para garantir os diversos requisitos dos clientes em caso de uma falha na rede ou do congestionamento e disputa por recursos que podem ocorrer em alguns períodos em uma rede. Impulsionada pelos fatos anteriormente mencionados, esta tese possui três objetivos. Através do desenvolvimento e proposta de um mecanismo de roteamento e atribuição de recursos para EONs, temos a intenção de disponibilizar diferenciação de serviço, diminuir o nível de fragmentação de espectro e aumentar a justiça na distribuição de serviços. O mecanismo proposto nesta tese foi testado em simulações de EONs. Resultados indicaram que o mecanismo proposto promove benefícios através do aprimoramento da performance de uma rede EON quando comparado com algoritmos de referência.

The security of a radio system hinges on its ability to effectively authenticate a user. This work proposes a two-factor authentication scheme using a token and a biometric. The users' access rights are determined during authentication and the users are served only those channels of data that they are privileged to receive. The strengths and the weaknesses of the implementation in reconfigurable hardware are identified. The capabilities of the scheme are put into perspective by comparing it to a high-end authentication system and by evaluating the use of standardized APIs and low-end authentication devices. Modifications to the system are suggested to improve the level of security the scheme provides. Finally, a baseline study is carried out to measure the data processing performance of a radio developed in reconfigurable hardware, which uses the proposed authentication scheme. / Master of Science

We developed a price-based resource allocation scheme for Differentiated Service (DiffServ) data networks. The DiffServ framework was proposed to provide multiple QoS classes over IP networks. Since the provider supports multiple service classes, we need a differentiated pricing scheme, as supposed to the flat-rate scheme employed by the Internet service providers of today. Charging efficiently is a big issue. The utility of a client correlates to the amount of bandwidth allocated. One difficulty we face is that determining the appropriate amount of bandwidth to provision and allocate is problematic due to different time scales, multiple QoS classes and the unpredictable nature of users. To approach this problem, we designed a pricing strategy for Admission Control and bandwidth assignment. Despite the variety of existing pricing strategies, the common theme is that the appropriate pricing policy rewards users for behaving in ways to improve the overall utilization and performance of the network. Among existing schemes, we chose auction because it is scalable, and efficiently and fairly shares resources. Our pricing model takes the system's availability and each customer's requirements as inputs and outputs the set of clients who are admitted into the network and their allocated resource. Each client proposes a desired bandwidth and a price that they are willing to pay for it. The service provider collects this information and produces parameters for each class of service they provide. This information is used to decide which customers to admit. We proposed an optimal solution to the problem of maximizing the provider's revenue for the special case where there is only one bottleneck link in the network. Then for the generalized network, we resort to a simple but effective heuristic method. We validate both the optimal solution and the heuristic algorithm with simulations driven by a real traffic scenario. Finally, we allow customers to bid on the duration for which the service is needed. Then we study the performance of those heuristic algorithms in this new setting and propose possible improvements.

Examensarbetet är en studie i felsökning och optimering av IP-telefonisystem i ett befintligt nät. Här beskrivs hur ett IP-telefoninät bör byggas och konfigureras för optimal prestanda utifrån Ciscos rekommendationer. Det aktuella nätet är IT-Partners nät som drivs av Nortel när det gäller IP-telefonidelen. I dagsläget har de vissa återkommande problem när det gäller IP-telefonin t.ex. att samtalet bryts då och då. Det är nämnt vad problemet kan vara och vilka lösningar som skulle passa nätet. I allmänt brister kunskaperna i IP-telefoni vilket medför att problem kan uppstå med att få ett IP-telefonisystem att fungera som det ska. Vidare berättas varför ett IP-telefonisystem inte optimeras redan från första stadiet.

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