Mobile handset manufacturers have begun to include wireless LAN (WLAN) interfaces in their cellular handsets. This allows users to access WLAN networks when they are available and to revert to conventional cellular communications otherwise. In this way the handset can dynamically use the "best" available network, by switching connections between the two network interfaces. This switching is referred to as a vertical handoff (VHO). When handling real-time connections, handsets must be capable of performing a seamless vertical handoff. This occurs when the interface switching does not disrupt the quality of service requirements of the active connections. Vertical handoffs are generally time consuming, and this delay creates a difficult problem since WLAN coverage can be lost very abruptly. In this thesis, we propose and investigate several methods of mitigating this problem. A solution based on using a Vertical Handoff Support Node (VHSN) is proposed. When the WLAN link is lost, the VHSN is able to quickly redirect packets through the local cellular base-station during the time that handoff is taking place. This approach can eliminate VHO link loss. It is shown that the act of WLAN-to-cellular handoff can result in a severe bandwidth deficit problem on the WLAN. A novel bandwidth reservation and securing mechanism is proposed which overcomes this problem and performs significantly better than schemes based on modified versions of the static guard channel scheme used in cellular networks. The work is characterized by simulation and analytic models which investigate the key performance aspects of this type of system. / Thesis / Doctor of Philosophy (PhD)

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京都大学 / 新制・課程博士 / 博士(医学) / 甲第24831号 / 医博第4999号 / 新制||医||1067(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 山本, 洋介, 教授 武藤, 学, 教授 永井, 純正 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

The rapid increase in the number of IoT devices and their widespread applications demands secure and scalable solutions for managing and executing IoT workflows. This thesis investigates the security of IoT workflows created in Node-RED, an open-source visual programming tool, and deployed on untrusted hosts managed by a major cloud service provider, Azure. The hypothesis was that the security of IoT workflows could be improved by utilizing a trusted execution environment, such as Intel SGX. Additionally, an assessment of consequent performance degradation was proposed. A threat model for an IoT workflow system scenario was established using the STRIDE threat modeling framework. An evaluation of the security guarantees provided by the prototype system was performed using an analysis comparing the security guarantees of underlying technologies, predominantly Intel SGX, and aggregating them to establish the security promises of the final system. The performance evaluation of the system was conducted using a set of experimental workflows, executed both natively on Linux and inside Intel SGX. The proposed prototype system was deemed to be capable of mitigating 15 out of 18 potential threats defined in the threat model, which indicates a significant threat risk reduction. However, the added security resulted in degraded performance, which was considerable when executing system calls and significantly noticeable for workflows requiring multi-threading. The results showed that node execution time inside SGX was 4.8 times slower and the mean round trip time for workflow execution was 6 times slower than the native execution. The thesis aims to provide a starting point for estimating performance degradation for potential future applications requiring secure IoT workflow deployment on untrusted hosts. / Den snabba ökningen av antalet IoT-enheter i dagens samhälle och deras breda användningsområden kräver säkra och skalbara lösningar för exekvering av IoT-arbetsflöden. Detta examensarbete undersöker säkerheten för IoT-arbetsflöden skapade i Node-RED, ett öppen källkodsverktyg för visuell programmering, i kontexten att dessa arbetsflöden exekveras på opålitliga enheter som hanteras av molntjänstföretag, som i detta fall är Azure. Hypotesen var att säkerhetsgarantin för IoT-arbetsflöden kunde förbättras genom att använda en betrodd exekveringmiljö, såsom Intel SGX. Dessutom krävdes en utvärdering av påföljderna på systemets prestanda som en konsekvens av den betrodda exekveringmiljöns användning. En hotmodell för ett IoT-arbetsflödesystem etablerades med hjälp av ramverket STRIDE. En bedömning av säkerhetsgarantierna som tillhandahålls av prototypsystemet genomfördes med hjälp av en kvalitativ analys som jämförde säkerhetsgarantier för underliggande teknologier, främst Intel SGX, och aggregerade dessa för att etablera säkerhetsgarantin för det slutgiltiga systemet. Prestandautvärderingen av systemet genomfördes med hjälp av ett antal experimentella arbetsflöden, som exekverades både direkt på Linux och inuti den betrodda exekveringsmiljön Intel SGX. I det föreslagna prototypsystemet ansågs 15 utav 18 potentiella hot som definierats i hotmodellen vara försumbara, vilket indikerar en signifikant reduktion av hotbilden. Dock resulterade den ökade säkerheten i en försämrad prestanda, som var betydande när systemanrop användes och synnerligen märkbar för flöden som krävde parallellisering. Resultaten visade att nodexekveringstiden inuti SGX var 4,8 gånger långsammare och medelvärdet för rundturstiden för exekvering av ett arbetsflöde var 6 gånger långsammare än den direkta exekveringen. Examensarbetet syftar till att ge en utgångspunkt för att bedöma prestandaförsämringen för potentiella framtida applikationer som kräver säkra IoT-arbetsflöden exekverade på opålitliga enheter.

According to the classical paradigm, CCR7 is a homing chemokine receptor that grants normal lymphocytes access to secondary lymphoid tissues such as lymph nodes or spleen. As such, in most lymphoproliferative disorders, CCR7 expression correlates with nodal or spleen involvement. Nonetheless, recent evidence suggests that CCR7 is more than a facilitator of lymphatic spread of tumor cells. Here, we review published data to catalogue CCR7 expression across blood cancers and appraise which classical and novel roles are attributed to this receptor in the pathogenesis of specific hematologic neoplasms. We outline why novel therapeutic strategies targeting CCR7 might provide clinical benefits to patients with CCR7-positive hematopoietic tumors.

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