# Presentation: 139618

## An XML Schema for NMWGGGF8 - June 2003

- Yee-Ting Li (UCL)
- Presented by
- Richard Hughes-Jones (University of Manchester)

## Requirements and Goals

- Different network monitoring architectures represent their results in different formats
- Unify output to common format to aid consumer interaction
- Ability to describe all characteristics and underlying measurement methodologies
- Make it future proof
- Does not replace current technologies
- Idea is to cast network data to a suitable format for intercommunication
- For use in Web Services and OGSA Technologies
- Fits in with idea of a Web Service front end

## ‘Features’ – What does XML give us

- XML Schemas describe the structure and content of XML document
- Uses meta data to describe virtually anything through document structure
- Extensible and flexible – can use XSLT’s to format the data in any other way (schema conversion)
- Can store both historical (lists) and ‘single’ measurements in same document
- Makes it easier for consumers to parse information
- Includes all necessary information to repeat a test
- Embodies measurement methodology as a fundamental necessity

## NMWG - Overview

- Results gathered into an Observation
- Realised by a Measurement Methodology
- Which measures a Characteristic
- Which describes a Network Entity

## NMWG Schema Goal

- To be able to fully describe network metrics/characteristics
- In complete and extensible way
- Able to store as much information as required
- Able to have as little information as required
- To be used in a real system with real results
- Capable to describing WHAT a tool measures and HOW and WHERE
- Focusing actually implementing what the NMWG document says... and doesn’t say...
- With view on actually using it to retrieve results...
- As a results doesn’t always exactly match what NMWG says/suggests 

## NMWG Schema - Overview

- networkEntity is root document
- Described by:
- target
- Describes the source and sink nodes
- measurementMethodology
- Used to describe the application used to gather the results
- The network used
- The results (observations) of the characteristics

- Each box – XML element = chunk of meta data

## Schema – measurementMethodology

- Name / version / cmd ...

- Key – value pairs

- Char – numeric only

- hoplist

**Notes:**
- Whether the methodology is raw of derived is an attribute in <measurementMethodology/>, also a brief desciption of the methodology in attr ‘method’.
The realisation of a measurement methodology is the tool (name, version, accucy), extended with key/value pairs in the parameter element
A layer element used to formally describe the OSI layer and protcol used for test; includes TCP types and packet sizes.
Path: endToEnd (most tools) and hops (traceroute/pipechar etc): endtoend would only have one path entry (black box), hops would have an entry for each hop end to end.
Characteristic describes each path that its nested under. Benefit; can describe many characteristics for each path; eg, ping can give both loss and delay for same path.

## NMWG Schema - Characteristic

- BW type
- Use XML attribute

- Characteristics:
- make uniform representation
- – all at same level

- Missing:
- Patterns – in statistical part
- Non - numeric

**Notes:**
 - no defintion of sub classes of characteristics – all high level
 - idea is to be uniform in the descriptions, so used <observationSample/> (next)

## Schema - observationSample

- Tried to incorporate method of describing more than one observation at once
- When we retrieve historical information of the bandwidth for the last month
- May have singleton values as well as statistical values
- Collate all ping singletons for last year!
- Or just get a the averages for each week..
- Some tools may report more than one characteristic
- Eg ping: 2WD and loss, traceroute: rtt and path, pipechar: capacity and path etc.

## NMWG Schema - observationSample

- Aim to represent Singleton or Statistical in the same way.
- observation can be: Singleton or Statistical or Singleton(s) and Statistical
- observationSample is allows for a series of observations

**Notes:**
Every Characterstic has an observationSample underneath
Singletons and statisticals have attributes to describe the value, units and error.
Can have singletons and or statisticals. The statisticals in same observation are statistical descriptions of its peered singletons.
Problem is that we have now defined that only charactersitcs that are numerical can exist in schema (can’t have ForwardTable, etc).
Statistical also has ‘type’ attribute; eg average, percentile etc.
Statisticals can also be extended to represent patters; just use eg. LossAverage as type
Interval summarises the time period of when the underlying elements take place: under observation we have the pattern of when the singletons take place, under observationSample, it describes the pattern of observatiosn.
A observationSample can have lots of observations => historical information.

## Example Of Ping Schema : target

## Example Of Ping Schema : measurementMethodology

## Example Of Ping Schema : observation

## Summary

- A useable implementation of XML Schema for Network Monitoring
- Can report single observations or a group of observations in a single document
- Demonstrated suitability for most common monitoring tools
- Easily extended to *most* tools
- Also includes non-network information that may contribute to poor network performance
- Host configuration, kernel parameters etc.
- However doesn’t quite fit into NMWG framework
- Needs further refinement of both the Schema and what NMWG define