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NPM NM-WG Object Model JRA4 F2F, Edinburgh, 12-13 July 2005

NPM NM-WG Object Model JRA4 F2F, Edinburgh, 12-13 July 2005. Alistair K Phipps (A.Phipps@ed.ac.uk) University of Edinburgh. Background. NM-WG interface is defined as an XML schema Two alternatives for writing software to adhere to this interface:

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NPM NM-WG Object Model JRA4 F2F, Edinburgh, 12-13 July 2005

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  1. NPM NM-WG Object ModelJRA4 F2F, Edinburgh, 12-13 July 2005 Alistair K Phipps (A.Phipps@ed.ac.uk) University of Edinburgh

  2. Background • NM-WG interface is defined as an XML schema • Two alternatives for writing software to adhere to this interface: • Directly parse XML using an XML parser library • Writing XML parsing code tricky and prone to errors • Use software such as Apache Axis to generate "stub" classes • Stub classes mirror the schema elements and carry out the XML parsing internally (and automatically) • However, they are automatically generated and are often quirky and awkward to use JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  3. Object model • What is it? • A set of objects that encapsulate part of the NM-WG schema (just what we use) in a sensible way • A 'mapper' to translate these objects into the form of Axis stub objects (though the mapper could also do direct XML parsing) • Designed with reference to the draft schema • Who is it useful for? • Implementers of services and clients that have to 'talk' the schema • Why not just use Axis stubs directly? • Would tightly bind the 'business logic' to the interface; instead, the business logic uses the object model objects which do not vary with (minor, at least) interface changes - only the mapper changes • As noted previously, the Axis stubs are generated automatically and are awkward to use JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  4. About this presentation • Covers: • NM-WG features covered by the object model in the draft design • Design overview (for those implementing components that will be making use of the object model) • Objectives: • Reach agreement on the NM-WG (v1 and v2) features covered by the object model, e.g.: • Do we need to request or report packet gap information? • Do we need separate classes for the different types of result (e.g. AvailableBandwidth including bottleneck information)? • Gather design improvements / corrections JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  5. Design • Current status: • Draft design document written: http://edms.cern.ch/document/606702/ • Implementation of this to happen soon after F2F • Will not go through entire design in detail - instead give overview, then draw attention to specific areas which merit discussion JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  6. NM-WG Request • Request has: • List of hop addresses. Addresses include IP/hostname, type (IPv4, IPv6), optional 'friendly' name (string) • TimeInformation. Time focus, optional lower and upper bounds. • Characteristic. Includes enumerated characteristic type. (e.g. ONE_WAY_DELAY) • List of Statistics • Set of Parameters JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  7. NM-WG Statistics • Statistic includes an enumerated StatisticType (e.g. MAX) • StatisticInterval specialisation also includes a time interval over which the statistic should be applied, in milliseconds • StatisticPercentile includes a time interval and also a percentile value, in percent JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  8. NM-WG Parameters • Parameter includes whether the parameter is required • ParameterPacketType specialisation also includes a packet type (TCP, UDP, ICMP) • ParameterPacketSize specialisation also includes a packet size (in bytes) • ParameterDSCP specialisation also includes a DSCP value byte JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  9. NM-WG Report • A Report consists of an array of Measurements; NM-WG object model does not encapsulate the Report explicitly • Measurement has: • List of hop addresses, Characteristic, Set of Parameters • TimeInterval - lower and upper bounds on time for the whole measurement • List of Results • List of tools (strings) JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  10. NM-WG Result • Result has: • Value (double) • Unit • Statistic (as for Request) • TimeInterval - upper and lower bound on time for this specific Result JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  11. NM-WG Unit • Unit has: • Numerator and denominator unit (e.g. byte, bit, second) • Numerator and denominator prefix (e.g. kilo, micro, kebi) • Supports conversions between Units and to/from strings JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  12. NM-WG Fault • Fault has: • Enumerated fault type • Fault message • Extends (Java) Exception - can be thrown JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  13. Mapper • A mapper class translates between NM-WG object model entities and NM-WGv1 stubs generated by Axis • It should be possible to write similar mappers to translate to NM-WGv2 stubs (GN2:JRA1 TL?) • AxisMapper is a singleton (only one instance created) that provides methods to convert back and forth, e.g.: • axis.report.NetworkMeasurementReport measurementArrayToAxisNetworkMeasurementReport( Measurement[] measurementArray ) • Measurement[] axisNetworkMeasurementReportToMeasurementArray( axis.report.NetworkMeasurementReport report ) JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  14. Enumerations (1) • Faults: any more? • System • No Data • Communication • Authorisation • Request • Units: any more? • Only "unit" or "unit1/unit2" permitted • Data: bit, byte • Time: second, minute, hour • Probability: percent, probability • Misc: none • Prefixes: micro to tera (steps of 1000), kibi to tebi (steps of 1024) JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  15. Enumerations (2) • Parameters - any more? • Packet Type • Packet Size • DSCP • Packet types - any more? • TCP • UDP • ICMP • Address types - any more? • IPv4 • IPv6 JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  16. Enumerations (3) • Statistics - any more? • Raw • Count • Min • Max • Mean • Median • Standard deviation • Percentile JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  17. Enumerations (4) • Characteristics - any more? • Path delay one-way • Path delay round-trip • Path bandwidth achievable • Path loss one-way • Path loss round-trip • Path bandwidth capacity • Hop bandwidth utilised • Path delay one-way jitter • Path packet reordering JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

  18. NM-WG Object Model • Any other issues? Questions? Comments? JRA4: http://egee-jra4.web.cern.ch/EGEE-JRA4/

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