ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / The National Oceanic and Atmospheric Administration (NOAA) Jason Ground System (NJGS) is a consolidated next-generation ground system that will support the simultaneous operation of the OSTM/Jason-2 and Jason-3 ocean surface topography missions. The NJGS will consist of several independent subsystems for spacecraft command and control, telemetry processing, and data archiving and distribution. The existing NOAA Jason-2 Ground System (J2GS) was designed around the concept of subsystem "strings", in which two complete sets of subsystems acted in primary and standby roles. For the NJGS, this concept is replaced with subsystem-level redundancy, in which two or more instances of each subsystem independently provide redundant capabilities. This paper discusses the design elements involved in the provision of a ground system architecture providing redundancy at the subsystem level. The paper focuses on the interaction between primary and standby subsystems and the mechanism through which failover capabilities are provided across the ground system.

The mass popularization of telecommunication services in recent years have resulted in a heavily loaded signaling network. The Signaling System number 7 (SS7) is used in fixed and wireless networks and is needed for call control and services such as caller ID, roaming, and for sending SMS. The traditional SS7 networks are expensive to lease and to expand, hence a new suite of protocols have been designed to carry signaling messages over IP. This suite contains a transport protocol called Stream Control Transmission Protocol (SCTP) and various user adaptation layer protocols such as M2PA, M2UA, M3UA, and SUA. To transport the highly loss and delay sensitive signaling messages over IP, it is mandatory that the transport protocol meets the high performance requirements of SS7. Not before the IP-solution has been tested in detail, will it replace significant parts of the national telephone network. In this thesis, the failover duration in the case of link failure was tested using the feature of SCTP called multi-homing. The results suggest that carrying SS7 signaling traffic over IP is possible, since the failover duration does not exceed the required limit. / Under de senaste åren har telekommunikationstjänster blivit allt mer populära, vilket har lett till ett tungt belastat signaleringsnätverk. The Signaling System number 7 (SS7) används i fasta och trådlösa nätverk och behövs för att kontrollera telefonsamtal och för tjänster såsom caller ID, roaming och för att skicka SMS. De traditionella SS7- nätverken är dyra att hyra och att expandera, varför en ny grupp av protokoll har designats för att bära signaleringsmeddelanden över IP. De nya protokollen innehåller ett transportprotokoll som heter Stream Transmission Control Protocol (SCTP) och flera adaptionslagerprotokoll, bl.a. M2PA, M2UA, M3UA och SUA. För att transportera de förlust- och förseningskänsliga signaleringsmeddelandena över IP, måste transportprotokollet möta de höga krav som SS7 har. Inte förrän IP-lösningen har testats ingående, kommer den att ersätta betydelsefulla delar av det nationella telefonnätet. I detta examensarbete har failovertiden mätts då en nätverkslänk mellan två noder har utsatts för ett avbrott. Resultaten pekar på att det är möjligt att bära SS7-trafik över IP eftersom failovertidskraven inte överstigs.

Historically virtual machines have been the backbone of the cloud-industry, allowing cloud-providers to offer virtualized multi-tenant solutions. A key aspect of the cloud is its flexibility and abstraction of the underlying hardware. Virtual machines can enhance this aspect by enabling support for live migration and failover. Live migration is the process of moving a running virtual machine from one host to another and failover ensures that a failed virtual machine will automatically be restarted (possibly on another host). Today, as containers continue to increase in popularity and make up a larger portion of the cloud, often replacing virtual machines, it becomes increasingly important for these processes to be available to containers as well. However, little support for container live migration and failover exists and remains largely experimental. Furthermore, no solution seems to exists that offers both live migration and failover for containers in a unified solution. The thesis presents a proof-of-concept implementation and description of a system that enables support for both live migration and failover for containers by extending current container migration techniques. It is able to offer this to any OCI-compliant container, and could therefore potentially be integrated into current container and container orchestration frameworks. In addition, measurements for the proof-of-concept implementation are provided and used to compare the proof-of-concept implementation to a current container migration technique. Furthermore, the thesis presents an overview of the history and implementation of containers, current migration techniques, and metrics that can be used for measuring different migration techniques are introduced. The paper concludes that current container migration techniques can be extended in order to support both live migration and failover, and that in doing so one might expect to achieve a downtime equal to, and total migration time lower than that of pre-copy migration. Supporting both live migration and failover, however, comes at a cost of an increased amount of data needed to be transferred between the hosts.

With the rise of microservice architectures, there is a need for an orchestration tool to manage containers. Kubernetes has emerged as one of the most popular alternatives, adopting widespread usage. But managing multiple Kubernetes clusters on its own have proven to be a challenging task. This difficulty has given rise to multiple cloud based alternatives which help streamline the managing process of a cluster environment and helps maintain an extreme high availability environment that is hard to replicate in an on premise environment. Using these cloud based platforms for hosting and managing ones system is great, but alleviating control of a system to a cloud provider masquerades any illicit behaviour performed on or through the system. The scope of this thesis is on examining optional designs that will automate the process of executing a geographical failover between different locations to better sustain an on premise fault tolerant kubernetes environment. There already exists multiple tools in the area of kubernetes service mesh, but their focus is not primarily on increasing system resilience but to increase security, observability and performance. Linkerd is a sidecar oriented service mesh which supports geographical failover by manually announcing individual services between cluster(s) mirror gateways. Cilium offers an Container Networking Interface (CNI) which performs routing through eBPF and allows for seamless failover between clusters by managing cross cluster service endpoints. Both of the mentioned service mesh providers handle failover from inside the kubernetes cluster. The contributions includes two new peer-to-peer designs that focus on external cluster geographical failover - both designs are compatible with preexisting kubernetes clusters without internal modifications. A fully repli-cated design was then realised into a proof of concept (POC), and tested against a Cilium multi cluster environment on the metric of north to south traffic latency. Due to the nature of the underlying hardware, the tests showed that the POC can be used for external geographical failover and it showed potential performance capabilities in a limited lab scale. As the purpose of this thesis was not to determine the traffic throughput of a geographical failover solution; but to examine different approaches automatic geographical failover can be implemented, the tests were a success. Therefore, this thesis can conclude that there exists several working solutions, and the POC have shown that there are still undiscovered and unimplemented solutions to explore.

Computer systems can fail for a vast range of reasons, and handling failures is crucial to any critical computer system. Many modern computer systems are migrating to public clouds, which provides more flexible resource consumption and in many cases reduced costs, while the migration can also require system changes due to limitations in the provided cloud environment. This thesis evaluates a few methods of achieving failover when migrating a system to a public cloud, with the main goal of finding a replacement for failover mechanisms that can only be used in self-managed infrastructure. A few different failover methods are evaluated by looking into different aspects of how each method would change an existing system. Two methods using \textit{etcd} and \textit{Apache ZooKeeper} are used for experimental evaluation where failover time is measured in two simulated scenarios where the primary process terminates and a standby process needs to be promoted to the primary status. In one scenario, the primary process is not able to notify other processes in the system before terminating, and in the other scenario, the primary process can release the primary status to another instance before terminating. The etcd and ZooKeeper solutions are shown to behave quite similarly in the testing setup, while the ZooKeeper solution might be able to achieve lower failover time in low-latency environments.

In recent years, Internet and IP technologies have made inroads into almost every commu- nication market ranging from best-effort services such as email and Web, to soft real-time applications such as VoIP, IPTV, and video. However, providing a transport service over IP that meets the timeliness and availability requirements of soft real-time applications has turned out to be a complex task. Although network solutions such as IntServ, DiffServ, MPLS, and VRRP have been suggested, these solutions many times fail to provide a trans- port service for soft real-time applications end to end. Additionally, they have so far only been modestly deployed. In light of this, this thesis considers transport protocols for soft real-time applications. Part I of the thesis focuses on the design and analysis of transport protocols for soft real- time multimedia applications with lax deadlines such as image-intensive Web applications. Many of these applications do not need a completely reliable transport service, and to this end Part I studies so-called partially reliable transport protocols, i.e., transport protocols that enable applications to explicitly trade reliability for improved timeliness. Specifically, Part I investigates the feasibility of designing retransmission-based, partially reliable transport protocols that are congestion aware and fair to competing traffic. Two transport protocols are presented in Part I, PRTP and PRTP-ECN, which are both extensions to TCP for partial reliability. Simulations and theoretical analysis suggest that these transport protocols could give a substantial improvement in throughput and jitter as compared to TCP. Additionally, the simulations indicate that PRTP-ECN is TCP friendly and fair against competing congestion- aware traffic such as TCP flows. Part I also presents a taxonomy for retransmission-based, partially reliable transport protocols. Part II of the thesis considers the Stream Control Transmission Protocol (SCTP), which was developed by the IETF to transfer telephony signaling traffic over IP. The main focus of Part II is on evaluating the SCTP failover mechanism. Through extensive experiments, it is suggested that in order to meet the availability requirements of telephony signaling, SCTP has to be configured much more aggressively than is currently recommended by IETF. Fur- thermore, ways to improve the transport service provided by SCTP, especially with regards to the failover mechanism, are suggested. Part II also studies the effects of Head-of-Line Blocking (HoLB) on SCTP transmission delays. HoLB occurs when packets in one flow block packets in another, independent, flow. The study suggests that the short-term effects of HoLB could be substantial, but that the long-term effects are marginal.

More and more so-called soft real-time traffic is being sent over IP-based networks. The bursty, data-limited traffic pattern as well as the latency requirements from this traffic present challenges to the traditional communication techniques, designed for bulk traffic without considering latency. To meet the requirements from soft real-time traffic, in particular from telephony signaling, the Stream Control Transmission Protocol (SCTP) was designed. Its support for connectivity to multiple networks, i.e., multihoming, provides robustness and opens up for concurrent multipath transfer (CMT) over multiple paths. Since SCTP is a general transport protocol, it also enables for handover of media sessions between heterogeneous networks. Migrating an ongoing session to a new network, as well as CMT with minimal latency, requires tuning of several protocol parameters and mechanisms. This thesis addresses latency reduction for soft real-time traffic using SCTP multihoming from three perspectives. The first focus is on latency for signaling traffic in case of path failure, where a path switch, a failover, occurs. We regard quick failure detection as well as rapid startup on the failover target path. The results indicate that by careful parameter tuning, the failover time may be significantly reduced. The second focus in the thesis is on latency for signaling traffic using CMT. To this end, we address sender-side scheduling. We evaluate some existing schedulers, and design a dynamic stream-aware scheduler. The results indicate that the dynamic stream-aware scheduler may provide significantly improved latency in unbalanced networks. Finally, we target multihomed SCTP to provide for handover of a media session between heterogeneous wireless networks in a mobile scenario. We implement a handover scheme and our investigation shows that SCTP could provide for seamless handover of a media session at walking speed. / So-called soft real-time traffic may be sent over IP-based networks. The bursty, data-limited traffic pattern and the latency requirements from this traffic present a challenge to traditional communication techniques. The Stream Control Transmission Protocol (SCTP), with support for multihoming, was designed to better meet the requirements from soft-real time traffic. Multihoming provides for robustness and for concurrent multipath transfer (CMT) as well as for handover of sessions between heterogeneous networks. Still, to meet the timeliness requirements, tuning of protocol parameters and mechanisms is crucial. This thesis addresses latency reduction for soft real-time traffic using SCTP multihoming. The first focus is on signaling traffic in case of path failure, where a path switch, a failover, occurs. We show that careful parameter tuning may reduce the failover time significantly. The second focus is on signaling traffic using CMT. We address sender-side scheduling and show that dynamic stream-aware scheduling may reduce latency when data is transmitted over asymmetric network  paths. The third focus is multihomed SCTP for handover between heterogeneous networks, where we show that SCTP could provide for seamless handover of a media session at walking speed. / <p>Paper 3 (Efficient Scheduling to Reduce Latency...) ingick i avhandlingen som manuskript med samma namn.</p>

This thesis describes development and verification of application for support of HACMP clustering education in IBM AIX OS. In fact, development of this application can help students to understand basic functions of this type of cluster. Users, eventually, can verify full function of input configuration cluster in real environment. Ultimately, it can simulate basic cluster function and create basic configuration file, which can be direct apply to operational installation of HACMP software of version 5.3.

Klustring innebär att flera servrar arbetar tillsammans och på så sätt klarar av en uppgift som en ensam server inte skulle klara. Klustring kan också användas för att säkra drift med hjälp av en eller ett flertal servrar som väntar i startgropen om den aktiva servern som tillhandahåller tjänsten går ner.   Detta examensarbete utfördes genom att först undersöka vilka kluster­lösningar som fanns tillgängliga. Därefter utfördes intervjuer med företag som använde sig av olika typer av klustring. Laborationer gjordes för vidare undersökning av några av de mjukvaror som de intervjuade företagen använde.   Det upptäcktes att variationen av lösningar hos de intervjuade företagen inte var så stor som förväntat innan arbetet påbörjades.   Efter genomförd litteraturstudien och intervjumaterialet, för att sedan ge rekommendationer på vilka lösningar som bör väljas av exempelföretag utifrån vilka krav och kriterier som finns hos dessa.

This thesis deals with the routing of data traffic to multiple gateways with a network operating system MikroTik RouterOS, which has become widespread in the small firms and home users. It is aimed to describe the problem with using multiple gateways. RouterOS description itself and its core components needed to solve this issue, such as routing, packet marking and quality assuranceservices. It also deals with the description of the particular design and testing. The proposedsolution is verified on the example of a real situation. Finally, the proposed solution is compared to alternative solutions, commonly used in practice.