Submitted by Rafael Santana (rafael.silvasantana@ufpe.br) on 2017-04-26T16:31:53Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO- Igor Nogueira de Oliveira.pdf: 1932477 bytes, checksum: de99161e3dad0c3f6869af876a3e2b5a (MD5) / Made available in DSpace on 2017-04-26T16:31:53Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO- Igor Nogueira de Oliveira.pdf: 1932477 bytes, checksum: de99161e3dad0c3f6869af876a3e2b5a (MD5) Previous issue date: 2016-03-04 / Desde sua padronização, o protocolo Hypertext Transfer Protocol (HTTP) tornou-se o estado da arte em protocolos de transporte da internet, sendo utilizado para transmissão de arquivos hipertexto e hipermídias, como áudio e vídeo de forma cada vez mais interativa. Porém, o HTTP em suas versões 1.0 e 1.1 apresenta pontos que podem ser otimizados, como o fato de atender requisições de forma síncrona, o que normalmente atrasa a renderização de páginas Web podendo vir a afetar a qualidade de experiência dos usuários. Recentemente, o protocolo HTTP foi atualizado para a versão HTTP/2, recebendo diversas modificações, direcionadas principalmente a melhorias no tocante ao uso dos recursos de rede. Dentre estas melhorias, podese citar a adição do recurso push, que permite que o servidor Web responda a uma solicitação com mais de um recurso ao mesmo tempo. Este trabalho apresenta uma análise de desempenho do recurso push no transporte de páginas Web em conexões HTTP/2. Para tanto, foram realizados experimentos em um ambiente simulado, replicando características de rede presentes na internet. Foram adotados o Total Download Time (TDT) e o Page Load Time (PLT) como métricas de análise e a execução do experimento foi realizada através de requisições de páginas web com diferentes quantidades e tamanhos de objetos. Através dos resultados obtidos, foi possível observar que apesar do protocolo HTTP/2 possuir recursos para a melhoria do carregamento de páginas Web o uso inadequado destes recursos pode causar, em determinadas configurações, degradações no carregamento das páginas. / Since its standardization, the Hypertext Transfer Protocol (HTTP) has been considered the state of the art for transmission of hypertext and hypermedia files, such as audio and vídeo in an interactive way. However, 1.0 and 1.1 versions of HTTP present some weaknesses that may be optimized, such as synchronized requests, which typically slow Web pages rendering thus affecting the end user experience. Recently, the protocol was updated to the 2.0 version and received several modifications, focused mainly on improvements in the network usage. Among these improvements one can cite the addition of push, a feature that allows the server to reply to a request with more than one resource simultaneously. This work presents a performance analysis of push feature on the transport of web pages on HTTP/2 connections. Therefore, experiments were conducted on a prototype environment using Total Download Time (TDT) and Page Load Time (PLT) as metrics, and Web page requests with different amounts and sizes of objects. From the results, one can observe that despite presenting features to improve Web page load time, improper use of these HTTP/2 resources may lead, on certain conditions, to the opposite effect.

Swedbank är en av Sveriges största företag inom finanssektorn med drygt fyra miljoner privatkunder och försöker ständigt utveckla sina tjänster så att de är lättåtkomliga och lättanvända för kunderna. För att tillfredsställa sina kunders behov av en snabb och lättåtkomlig bank så vill Swedbank minska på laddningstiderna till sina finanstjänster, särskilt de mobila tjänsterna då det är där uppkopplingarna är som långsammast. Uppdraget var att göra en prestandaanalys av HTTP/2 som är den senaste versionen av HTTP-protokollet. Efter att ha genomfört arbetet ska Swedbank veta vad dem kan anpassa för att göra sina tjänster så optimala som möjligt för framtiden.Resultatet visade att med hjälp av HTTP/2’s nya funktioner, bland annat det binära ramlagret, uppnåddes en prestandaökning på 44% av totala laddningstiden på Swedbank’s hemsida. Testerna genomfördes i en lokal labbmiljö där de olika HTTP versionerna installerades och mätvärden dokumenterades. Detta ansågs som ett bra resultat utan att ha genomfört någon fördjupande konfiguration. / Swedbank is one of Sweden’s biggest banks with estimated four million private customers and they are constantly trying to improve their services so they become more user-friendly and faster. To satisfy their customer’s need of fast and easy services Swedbank wants to lower the loading times on the web services to the user experience is faster and smoother, especially for the users doing their banking on a smartphone. The mission is to do a per-formance analysis of the new HTTP protocol HTTP/2 and take out the most essential parts so Swedbank knows what to take advantage of when installing the new versions on their servers to achieve optimal services.The results showed that after implementing HTTP/2’s new features, Swedbank’s website performance increased with 44% in total loading time. The tests were performed in a local experimental environment where the earlier HTTP versions was installed and the perfor-mance metrics was documented.

Les techniques adaptatives de transmission vidéo s’appuient sur un contenu qui est encodé à différents niveaux de qualité et divisé en segments temporels. Avant de télécharger un segment, le client exécute un algorithme d’adaptation pour décider le meilleur niveau de qualité à considérer. Selon les services, ce niveau de qualité doit correspondre aux ressources réseaux disponibles, mais aussi à d’autres éléments comme le mouvement de tête d’un utilisateur regardant une vidéo immersive (à 360°) afin de maximiser la qualité de la portion de la vidéo qui est regardée. L’efficacité de l’algorithme d’adaptation a un impact direct sur la qualité de l’expérience finale. En cas de mauvaise sélection de segment, un client HTTP/1 doit attendre le téléchargement du prochain segment afin de choisir une qualité appropriée. Dans cette thèse, nous proposons d’utiliser le protocole HTTP/2 pour remédier à ce problème. Tout d’abord, nous nous focalisons sur le service de vidéo en direct. Nous concevons une stratégie de rejet d’images vidéo quand la bande passante est très variable afin d’éviter les arrêts fréquents de la lecture vidéo et l’accumulation des retards. Le client doit demander chaque image vidéo dans un flux HTTP/2 dédié pour contrôler la livraison des images par appel aux fonctionnalités HTTP/2 au niveau des flux concernées. Ensuite, nous optimisons la livraison des vidéos immersives en bénéficiant de l’amélioration de la prédiction des mouvements de têtes de l’utilisateur grâce aux fonctionnalités d’initialisation et de priorité de HTTP/2. Les résultats montrent que HTTP/2 permet d’optimiser l’utilisation des ressources réseaux et de s’adapter aux latences exigées par chaque service. / Adaptive video streaming techniques enable the delivery of content that is encoded at various levels of quality and split into temporal segments. Before downloading a segment, the client runs an adaptation algorithm to determine the level of quality that best matches the network resources. For immersive video streaming this adaptation mechanism should also consider the head movement of a user watching the 360° video to maximize the quality of the viewed portion. However, this adaptation may suffer from errors, which impact the end user’s quality of experience. In this case, an HTTP/1 client must wait for the download of the next segment to choose a suitable quality. In this thesis, we propose to use the HTTP/2 protocol instead to address this problem. First, we focus live streaming video. We design a strategy to discard video frames when the band width is very variable in order so as to avoid the rebuffering events and the accumulation of delays. The customer requests each video frame in an HTTP/2 stream which allows to control the delivery of frames by leveraging the HTTP/2 features at the level of the dedicated stream. Besides, we use the priority and reset stream features of HTTP/2 to optimize the delivery of immersive videos. We propose a strategy to benefit from the improvement of the user’s head movements prediction overtime. The results show that HTTP/2 allows to optimize the use of network resources and to adapt to the latencies required by each service.

The purpose of this thesis is to investigate and test the usage of HTTP/2 in dynamic adaptive video streaming as well as to take a look into how it can be used to benefit prefetching algorithms used with branched video. With a series of experiments the performance gains of using HTTP/2 rather than the older standard HTTP/1.1 has been investigated. The results has shown no significant change to player quality and buffer occupancy when using HTTP/2, though our tests has shown in a slight decrease in overall playback quality when using HTTP/2. When using a linear prefetch of two fragments an average quality improvement of 4.59% has been shown, however, the result is inconclusive due to variations in average quality between different values for how many fragments to prefetch. Average buffer occupancy has shown promise with a maximum increase of 12.58%, when using linear prefetch with three fragments. The values for buffer occupancy gains are conclusive. Two implementations for non-linear prefetching has been made. The first one uses HTTP/2 server push to deliver fragments for prefetching and the second one uses client-side invoked HTTP requests to pull fragments from the server. Using HTTP/2 server push has shown in a decrease of 2.5% in average total load time while using client-side pulling has shown in a decrease of 34% in average total load time.

Severe weather impacts life and in this dire condition, people rely on communication, to organize relief and stay in touch with their loved ones. In such situations, cellular network infrastructure\footnote{We refer to cellular network infrastructure as infrastructure for the entirety of this document} might be affected due to power outage, link failures, etc. This urges us to look at Ad-hoc mode of communication, to offload major traffic partially or fully from the infrastructure, depending on the status of it. We look into threefold approach, ranging from the case where the infrastructure is completely unavailable, to where it has been replaced by make shift low capacity mobile cellular base station. First, we look into communication without infrastructure and timely, dissemination of weather alerts specific to geographical areas. We look into the specific case of floods as they affect significant number of people. Due to the nature of the problem we can utilize the properties of Information Centric Networking (ICN) in this context, namely: i) Flexibility and high failure resistance: Any node in the network that has the information can satisfy the query ii) Robust: Only sensor and car need to communicate iii) Fine grained geo-location specific information dissemination. We analyze how message forwarding using ICN on top of Ad hoc network, approach compares to the one based on infrastructure, that is less resilient in the case of disaster. In addition, we compare the performance of different message forwarding strategies in VANETs (Vehicular Adhoc Networks) using ICN. Our results show that ICN strategy outperforms the infrastructure-based approach as it is 100 times faster for 63\% of total messages delivered. Then we look into the case where we have the cellular network infrastructure, but it is being pressured due to rapid increase in volume of network traffic (as seen during a major event) or it has been replaced by low capacity mobile tower. In this case we look at offloading as much traffic as possible from the infrastructure to device-to-device communication. However, the host-oriented model of the TCP/IP-based Internet poses challenges to this communication pattern. A scheme that uses an ICN model to fetch content from nearby peers, increases the resiliency of the network in cases of outages and disasters. We collected content popularity statistics from social media to create a content request pattern and evaluate our approach through the simulation of realistic urban scenarios. Additionally, we analyze the scenario of large crowds in sports venues. Our simulation results show that we can offload traffic from the backhaul network by up to 51.7\%, suggesting an advantageous path to support the surge in traffic while keeping complexity and cost for the network operator at manageable levels. Finally, we look at adaptive bit-rate streaming (ABR) streaming, which has contributed significantly to the reduction of video playout stalling, mainly in highly variable bandwidth conditions. ABR clients continue to suffer from the variation of bit rate qualities over the duration of a streaming session. Similar to stalling, these variations in bit rate quality have a negative impact on the users’ Quality of Experience (QoE). We use a trace from a large-scale CDN to show that such quality changes occur in a significant amount of streaming sessions and investigate an ABR video segment retransmission approach to reduce the number of such quality changes. As the new HTTP/2 standard is becoming increasingly popular, we also see an increase in the usage of HTTP/2 as an alternative protocol for the transmission of web traffic including video streaming. Using various network conditions, we conduct a systematic comparison of existing transport layer approaches for HTTP/2 that is best suited for ABR segment retransmissions. Since it is well known that both protocols provide a series of improvements over HTTP/1.1, we perform experiments both in controlled environments and over transcontinental links in the Internet and find that these benefits also “trickle up” into the application layer when it comes to ABR video streaming where HTTP/2 retransmissions can significantly improve the average quality bitrate while simultaneously minimizing bit rate variations over the duration of a streaming session. Taking inspiration from the first two approaches, we take into account the resiliency of a multi-path approach and further look at a multi-path and multi-stream approach to ABR streaming and demonstrate that losses on one path have very little impact on the other from the same multi-path connection and this increases throughput and resiliency of communication.

Modern web-applications often need to be able to handle multi-window views that are dynamically synchronized depending on user input, as well as continuous and rapid data transfer between the client and the server. The WebSocket protocol has seen widespread industry use when it comes to bidirectional, real-time communication. However, its inherent security flaws make the prospect of other adequate alternatives highly relevant. SSE combined with XHR is a technology that has been overlooked by developers due to the shortcomings of the HTTP/1.1 protocol regarding efficiency. However, the HTTP/2 protocol expands upon and streamlines the core features of HTTP/1.1 while also providing full-duplex functionality. The introduction of the HTTP/2 protocol has given rise to speculations regarding a potential comeback for SSE as a viable contender for the WebSocket protocol. The aim is to evaluate whether the combination of SSE and XHR over HTTP/2 could be an equally or more efficient alternative to the WebSocket protocol for real-time data synchronization between multiple web-application views. This is done through the design and creation of two proof-of-concepts supported by the theoretical foundation established by conducting a literature review. The literature in this area indicates a lack of existing research concerning SSE over HTTP/2. The proof-of-concepts has produced empirical data, consisting of average data transmission times, that points to SSE/XHR performing as well as, if not better than the WebSocket counterpart. The results confirm that a combination of XHR and SSE over HTTP/2 is an adequate alternative to WebSockets within the scope of this study.

This diploma thesis focuses on theoretical and practical comparison of webpage transport protocols such as HTTP/HTTPS (Hypertext Transfer Protocol) v1.1, SPDY, HTTP/2 and QUIC using UDP (User Datagram Protocol), TCP (Transmission Control Protocol) and SCTP (Stream Control Transmission Protocol) as transport protocols. This work also contains design and manual for practical laboratory tasks on which can students verify theoretical assumptions. These tasks compares protocols in different conditions such as packet loss, latency and jitter.

According to the HTTP Archive, 75% of websites are using web fonts. Multiple conditions have to be met before modern web browsers like Chrome, Firefox and Safari decide to download the web fonts needed on a page. As a result, web fonts are late discovered resources that can delay the First Meaningful Paint (FMP). Improving the FMP is relevant for the web industry, particularly for performance-conscious web developers. This paper gives insight into how the resource prioritization approaches HTTP/2 Preload and HTTP/2 Server Push can be used to optimize the delivery of web fonts for first-time visitors. Five font loading strategies that use HTTP/2 Server Push and/or Preload were implemented on replicas of the landing pages from five real-world websites. The font loading strategies were evaluated against each other, and against the non-optimized version of each landing page. All the evaluated font loading strategies in this degree project improved the time it took to deliver the first web font content to the user’s screen, resulting in a faster FMP. It was also discovered that HTTP/2 Server Push, on its own, is not a more performance efficient resource prioritization approach than HTTP/2 Preload when it comes to delivering web font content to the client. Further, HTTP/2 Server Push and HTTP/2 Preload appears to be more efficient when used together, in the context of optimizing the delivery of web font content. However, all conclusions in this paper are based on the results gathered from testing the font loading strategies in an emulated environment and are yet to be confirmed on actual mobile devices with real network conditions.

New developments in web transport such as HTTP/2 and first and foremost QUIC promise fewer connections to track as well as shorter connection setup times. These protocols have proven themselves on modern reliable connections with a high bandwidth-delay-product, but how do they perform over cellular connections in rural or crowded areas where the connections are much more unreliable? A lot of new users of the web in todays mobile-first usage scenarios are located on poor connections. A testbench was designed that allowed for web browsing over limited network links in a con- trolled environment. We have compared the network load time of page loading over the protocols QUIC, HTTP/2 and HTTP/1.1 using a variety of different network conditions. We then used these measurements as a basis for suggesting which protocol to use during different conditions. The results show that newer is not always better. QUIC in general works reasonably well under all conditions, while HTTP/1.1 and HTTP/2 trade blows depending on connection conditions, with HTTP/1.1 sometimes outperforming both of the newer protocols.

Geographic Information Systems and Network Information Systems are important tools for our society, used for handling geographic spatial data and large information networks. It is therefore important to make sure such tools are of high quality. GIS/NIS applications typically deal with a lot of data, possibly resulting in heavy loads of network traffic. This work aims to evaluate two different communications protocols and serialization formats for client-server communications efficiency in GIS/NIS applications. Specifically, these are HTTP/1.1, HTTP/2, Java Object Serialization and Google's Protocol Buffers. They were each implemented directly into a commercial GIS/NIS environment and evaluated by measuring two signature server calls in the system. Metrics that were examined are call duration, HTTP overhead size and HTTP payload size. The results suggest that HTTP/2 and Google's Protocol Buffers outperform HTTP/1.1 and Java Object Serialization respectively. An 87% decrease in HTTP overhead size was achieved when switching from HTTP/1.1 to HTTP/2. The HTTP payload size is also shown to decrease with the use of Protocol Buffers rather than Java Object Serialization, especially for communications where data consist of many different object types. Concerning call duration, the results suggest that the choice of communications protocol is more significant than the choice of serialization format for communications containing little data, while the opposite is true for communications containing much data. / Geografiska informationssystem och nätverksinformationssystem är viktiga redskap för vårt samhälle, vilka används för hantering av geografisk data och stora informationsnätverk. Det är därför viktigt att se till att sådana system är av hög kvalitet. GIS/NIS-applikationer behandlar vanligtvis stora mängder data, vilket kan resultera i mycket nätverkstrafik. I det här arbetet utvärderas två olika kommunikationsprotokoll och serialiseringsformat för kommunikationseffektivitet mellan klient och server i GIS/NIS-applikationer. Specifikt är dessa HTTP/1.1, HTTP/2, Java Objektserialisering och Googles Protocol Buffers. De implementerades var och en i en kommersiell GIS/NIS-miljö och utvärderades genom mätningar av två signaturanrop i systemet. De aspekter som observerades är kommunikationstiden, mängden HTTP-overhead och mängden HTTP-payload. Resultaten tyder på att HTTP/2 och Googles Protocol Buffers presterar bättre än HTTP/1.1 respektive Java Objektserialisering. En 87% minskning av mängden HTTP overhead uppnåddes då HTTP/1.1 ersattes med HTTP/2. En minskning av mängden HTTP payload observeras också med användning av Protocol Buffers snarare än Java Objektserialisering, särskilt för kommunikationer där data innehåller många olika objekttyper. Gällande kommunikationstiden tyder resultaten på att valet av kommunikationsprotokoll påverkar mer än valet av serialiseringsformat för kommunikationer med små mängder data, medan motsatsen gäller för kommunikationer med mycket data.