title: Techniques for Failure Recovery in a Software-Defined Network

authors: Lorier, Christopher Martin

subjects: Software-Defined Networking

abstract: As our lives become ever more dependent on network connectivity, it becomes increasingly more important for networks to be able to overcome the failure of individual components and continue to function. This thesis examines approaches to fault tolerance in software defined networks, and how the global viewpoint that Software-Defined Networking provides can be leveraged to create more reliable networks.

In order to continue operation after the failure of a network component, the failure must first be detected, and then the network must automatically change its behaviour to mitigate any adverse consequences.  This thesis evaluates a variety of fault detection methods and potential responses. Based on these evaluations the design for a fault tolerance system for software defined networks is presented. This system builds protected paths using Ring Based Forwarding, an algorithm for creating a full mesh of paths between switches in a network where each path has a fail-over path at each hop. The system monitors the network for faults using Traffic Colouring, a technique for passively monitoring network traffic.

text: Techniques for Failure Recovery in a Software-Defined Network As our lives become ever more dependent on network connectivity, it becomes increasingly more important for networks to be able to overcome the failure of individual components and continue to function. This thesis examines approaches to fault tolerance in software defined networks, and how the global viewpoint that Software-Defined Networking provides can be leveraged to create more reliable networks.

In order to continue operation after the failure of a network component, the failure must first be detected, and then the network must automatically change its behaviour to mitigate any adverse consequences.  This thesis evaluates a variety of fault detection methods and potential responses. Based on these evaluations the design for a fault tolerance system for software defined networks is presented. This system builds protected paths using Ring Based Forwarding, an algorithm for creating a full mesh of paths between switches in a network where each path has a fail-over path at each hop. The system monitors the network for faults using Traffic Colouring, a technique for passively monitoring network traffic.

year: 2014

title: Late Quaternary climate variability and change from Aotearoa New Zealand speleothems: Progress in age modelling, oxygen isotope master record construction and proxy-model comparisons

authors: Lorrey, Andrew M.

abstract: We re-evaluated speleothem isotope series from Aotearoa New Zealand that were recently contributed to the Speleothem Isotopes Synthesis and AnaLysis (SISAL) database. COnstructing Proxy Records from Age Models (COPRA) software was used to produce Bayesian age models for those speleothems. The new age modelling helped us examine Late Quaternary temporal coverage for the national speleothem network, and also supported our exploration of three different isotope master record generation techniques using Holocene δ¹⁸O data from Waitomo. We then applied the output from one of the isotope master record techniques to test an application case of how climate transfer functions can be developed using climate model simulated temperatures. Our results suggest Holocene δ¹⁸O trends at Waitomo capture air temperature variations weighted toward the primary season of soil moisture (and epikarst) recharge during winter. This interpretation is consistent with the latest monitoring data from the Waitomo region. Holocene δ¹⁸O millennial-scale trends and centennial-scale variability at Waitomo likely reflect atmospheric circulation patterns that concomitantly vary with surface water temperature and the isotopic composition of the Tasman Sea. A climate model simulation context for the Holocene millennial-scale trends in the Waitomo δ¹⁸O isotope master record suggest that site is sensitive to changes in the subtropical front (STF) and the Tasman Front. Our comparison of isotope master record techniques using Waitomo δ¹⁸O data indicate that caution is needed prior to merging δ¹⁸O data series from different caves in order to avoid time series artefacts. Future work should incorporate more high-resolution cave monitoring and climate calibration studies, and develop new speleothem data from northern and eastern regions of the country.

text: Late Quaternary climate variability and change from Aotearoa New Zealand speleothems: Progress in age modelling, oxygen isotope master record construction and proxy-model comparisons We re-evaluated speleothem isotope series from Aotearoa New Zealand that were recently contributed to the Speleothem Isotopes Synthesis and AnaLysis (SISAL) database. COnstructing Proxy Records from Age Models (COPRA) software was used to produce Bayesian age models for those speleothems. The new age modelling helped us examine Late Quaternary temporal coverage for the national speleothem network, and also supported our exploration of three different isotope master record generation techniques using Holocene δ¹⁸O data from Waitomo. We then applied the output from one of the isotope master record techniques to test an application case of how climate transfer functions can be developed using climate model simulated temperatures. Our results suggest Holocene δ¹⁸O trends at Waitomo capture air temperature variations weighted toward the primary season of soil moisture (and epikarst) recharge during winter. This interpretation is consistent with the latest monitoring data from the Waitomo region. Holocene δ¹⁸O millennial-scale trends and centennial-scale variability at Waitomo likely reflect atmospheric circulation patterns that concomitantly vary with surface water temperature and the isotopic composition of the Tasman Sea. A climate model simulation context for the Holocene millennial-scale trends in the Waitomo δ¹⁸O isotope master record suggest that site is sensitive to changes in the subtropical front (STF) and the Tasman Front. Our comparison of isotope master record techniques using Waitomo δ¹⁸O data indicate that caution is needed prior to merging δ¹⁸O data series from different caves in order to avoid time series artefacts. Future work should incorporate more high-resolution cave monitoring and climate calibration studies, and develop new speleothem data from northern and eastern regions of the country.

year: 2020

title: A newly-available resource for historians of early New Zealand: The Marist Missionary Letters (1838-54)

authors: Jennings, William

abstract: The 7000 pages of primary documents of the Lettres reçues d’Océanie constitute a vast new source for the study of the Pacific during the period 1838-54. Published in 2009 after sixteen years of transcription, the Lettres are the collected correspondence of the first French Marist missionaries to New Zealand and other Pacific islands. In the words of Pacific historian Hugh Laracy, they are ‘the single most important foundational contribution to Pacific history in its fullest extent since J. C. Beaglehole’s magisterial editions of James Cook’s Journals. About 2000 of those pages are transcripts of letters written in New Zealand that open up a fresh perspective of life before the wars of the 1860’s. This paper will locate the early French Marist Māori mission within the context of New Zealand public history before exploring how the Lettres reçues d’Océanie can complement existing views of early colonial New Zealand. To better contextualise the correspondence, it would be useful to begin with a brief background of the Marists’ presence in New Zealand.

text: A newly-available resource for historians of early New Zealand: The Marist Missionary Letters (1838-54) The 7000 pages of primary documents of the Lettres reçues d’Océanie constitute a vast new source for the study of the Pacific during the period 1838-54. Published in 2009 after sixteen years of transcription, the Lettres are the collected correspondence of the first French Marist missionaries to New Zealand and other Pacific islands. In the words of Pacific historian Hugh Laracy, they are ‘the single most important foundational contribution to Pacific history in its fullest extent since J. C. Beaglehole’s magisterial editions of James Cook’s Journals. About 2000 of those pages are transcripts of letters written in New Zealand that open up a fresh perspective of life before the wars of the 1860’s. This paper will locate the early French Marist Māori mission within the context of New Zealand public history before exploring how the Lettres reçues d’Océanie can complement existing views of early colonial New Zealand. To better contextualise the correspondence, it would be useful to begin with a brief background of the Marists’ presence in New Zealand.

year: 2012