title: Identifying equivalent SDN forwarding behaviour

authors: Sanger, Richard

subjects: computer science

abstract: Software-Defined Networking (SDN) enables network operators the flexibility to program their own forwarding rules, providing more than one way to achieve the same behaviour. Verifying equivalence between rulesets is a fundamental analysis and verification building block for SDN as it can be used to: (1) confirm a ruleset optimised for power efficiency or table occupancy remains equivalent, (2) verify a ruleset modified for new hardware, (3) regression test an SDN application to detect bugs early.
We present a practical and novel canonical Multi-Terminal Binary Decision Diagram (MTBDD) representation of OpenFlow 1.3 ruleset forwarding behaviour which can be trivially compared for equivalence. Basing our representation on an MTBDD provides a proven canonical form which is also compact. In this paper, we present the algorithms required to correctly flatten multi-table pipelines into an equivalent single-table, resolve equivalences in OpenFlow actions, and build the final MTBDD representation from a priority ordered ruleset. OpenFlow rulesets can typically be converted to an MTBDD within tens of seconds. We release our opensource implementation to the SDN community.

text: Identifying equivalent SDN forwarding behaviour Software-Defined Networking (SDN) enables network operators the flexibility to program their own forwarding rules, providing more than one way to achieve the same behaviour. Verifying equivalence between rulesets is a fundamental analysis and verification building block for SDN as it can be used to: (1) confirm a ruleset optimised for power efficiency or table occupancy remains equivalent, (2) verify a ruleset modified for new hardware, (3) regression test an SDN application to detect bugs early.
We present a practical and novel canonical Multi-Terminal Binary Decision Diagram (MTBDD) representation of OpenFlow 1.3 ruleset forwarding behaviour which can be trivially compared for equivalence. Basing our representation on an MTBDD provides a proven canonical form which is also compact. In this paper, we present the algorithms required to correctly flatten multi-table pipelines into an equivalent single-table, resolve equivalences in OpenFlow actions, and build the final MTBDD representation from a priority ordered ruleset. OpenFlow rulesets can typically be converted to an MTBDD within tens of seconds. We release our opensource implementation to the SDN community.

year: 2019

title: Quantifying relationships between land-use gradients and structural and functional indicators of stream ecological integrity

authors: Clapcott, Joanne E.

subjects: boosted regression

abstract: 1. Modification of natural landscapes and land-use intensification are global phenomena that can result in a range of differing pressures on lotic ecosystems. We analysed national-scale databases to quantify the relationship between three land uses (indigenous vegetation, urbanisation and agriculture) and indicators of stream ecological integrity. Boosted regression tree modelling was used to test the response of 14 indicators belonging to four groups – water quality (at 578 sites), benthic invertebrates (at 2666 sites), fish (at 6858 sites) and ecosystem processes (at 156 sites). Our aims were to characterise the ecological response curves of selected functional and structural metrics in relation to three land uses, examine the environmental moderators of these relationships and quantify the relative utility of metrics as indicators of stream ecological integrity.
2. The strongest indicators of land-use effects were nitrate + nitrite, delta-15 nitrogen value (δ15N) of primary consumers and the Macroinvertebrate Community Index (a biotic index of organic pollution), while the weakest overall indicators were gross primary productivity, benthic invertebrate richness and fish richness. All indicators declined in response to removal of indigenous vegetation and urbanisation, while variable responses to agricultural intensity were observed for some indicators.
3. The response curves for several indicators suggested distinct thresholds in response to urbanisation and agriculture, specifically at 10% impervious cover and at 0.1 g m−3 nitrogen concentration, respectively.
4. Water quality and ecosystem process indicators were influenced by a combination of temperature, slope and flow variables, whereas for macroinvertebrate indicators, catchment rainfall, segment slope and temperature were significant environmental predictor variables. Downstream variables (e.g. distance to the coast) were significant in explaining residual variation in fish indicators, not surprisingly given the preponderance of diadromous fish species in New Zealand waterways. The inclusion of continuous environmental variables used to develop a stream typology improved model performance more than the inclusion of stream type alone.
5. Our results reaffirm the importance of accounting for underlying spatial variation in the environment when quantifying relationships between land use and the ecological integrity of streams. Of distinctive interest, however, were the contrasting and complementary responses of different indicators of stream integrity to land use, suggesting that multiple indicators are required to identify land-use impact thresholds, develop environmental standards and assign ecological scores for reporting purposes.

text: Quantifying relationships between land-use gradients and structural and functional indicators of stream ecological integrity 1. Modification of natural landscapes and land-use intensification are global phenomena that can result in a range of differing pressures on lotic ecosystems. We analysed national-scale databases to quantify the relationship between three land uses (indigenous vegetation, urbanisation and agriculture) and indicators of stream ecological integrity. Boosted regression tree modelling was used to test the response of 14 indicators belonging to four groups – water quality (at 578 sites), benthic invertebrates (at 2666 sites), fish (at 6858 sites) and ecosystem processes (at 156 sites). Our aims were to characterise the ecological response curves of selected functional and structural metrics in relation to three land uses, examine the environmental moderators of these relationships and quantify the relative utility of metrics as indicators of stream ecological integrity.
2. The strongest indicators of land-use effects were nitrate + nitrite, delta-15 nitrogen value (δ15N) of primary consumers and the Macroinvertebrate Community Index (a biotic index of organic pollution), while the weakest overall indicators were gross primary productivity, benthic invertebrate richness and fish richness. All indicators declined in response to removal of indigenous vegetation and urbanisation, while variable responses to agricultural intensity were observed for some indicators.
3. The response curves for several indicators suggested distinct thresholds in response to urbanisation and agriculture, specifically at 10% impervious cover and at 0.1 g m−3 nitrogen concentration, respectively.
4. Water quality and ecosystem process indicators were influenced by a combination of temperature, slope and flow variables, whereas for macroinvertebrate indicators, catchment rainfall, segment slope and temperature were significant environmental predictor variables. Downstream variables (e.g. distance to the coast) were significant in explaining residual variation in fish indicators, not surprisingly given the preponderance of diadromous fish species in New Zealand waterways. The inclusion of continuous environmental variables used to develop a stream typology improved model performance more than the inclusion of stream type alone.
5. Our results reaffirm the importance of accounting for underlying spatial variation in the environment when quantifying relationships between land use and the ecological integrity of streams. Of distinctive interest, however, were the contrasting and complementary responses of different indicators of stream integrity to land use, suggesting that multiple indicators are required to identify land-use impact thresholds, develop environmental standards and assign ecological scores for reporting purposes.

year: 2012

title: Hei Āwhina Mātua: A kaupapa Māori response to behaviour

authors: Berryman, Mere

abstract: Hei Āwhina Mātua (strengthening parents and other adults), a kaupapa Māori research and development project, sought to capitalise on the strengths available within both whānau and teachers so that both groups could take joint responsibility for students' learning and behaviour. This required professionals trained in delivering learning and behavioural programmes for individual students working in culturally responsive and collaborative ways with adults, whānau, teachers and community members, This chapter returns to this study to reconsider the key findings.

text: Hei Āwhina Mātua: A kaupapa Māori response to behaviour Hei Āwhina Mātua (strengthening parents and other adults), a kaupapa Māori research and development project, sought to capitalise on the strengths available within both whānau and teachers so that both groups could take joint responsibility for students' learning and behaviour. This required professionals trained in delivering learning and behavioural programmes for individual students working in culturally responsive and collaborative ways with adults, whānau, teachers and community members, This chapter returns to this study to reconsider the key findings.

year: 2015