Scalability and Development of Space Networks

Vincenzo Liberatore, Ph.D.

Disclaimer: the views expressed here are solely the author’s, not the presenter’s

Scalability

Definition• Ability of a system to sustain seamless

operations when certain parameters increase

Dimensions• Specified across four dimensions

Scalability: DimensionsDimension Definition

Numerical Increased number of users, resources, and services

Geographical Users and resources that lie far apart

Administrative Easy to manage even if it encompasses multiple administrative domains

Functional Increasingly more complex functionality

Scalability: Terrestrial BackgroundDimension Definition

Numerical Increased number of users, resources, and services

Geographical Users and resources that lie far apart

Administrative Easy to manage even if it encompasses multiple administrative domains

Functional Increasingly more complex functionality

Terrestrial concern

Exponential increase in number of users, data volume, services, resources

Worldwide network

Rapid increase in administrative domains (e.g., autonomous systems)

Complex distributed applications

Scalable Terrestrial NetworksScalability is Primary Concern

• Exponential increases of key parameters• Quality Assurance

– “If it scales, it must be working” [O’Dell]Expandable and Reusable Solutions

• Convergence layers– E.g., Internet Protocol (IP)– Support multiple link, transport layers

• Middleware – E.g., Resource Discovery– Simplifies design, development, and

deployment of complex distributed applications – Reduces costs – Improves system quality

Scalable Space Networks

Assumption• Combined approach more powerful

than each in isolation• Leverage on high readiness terrestrial

technology• Only a working hypothesis

Gap Analysis• Terrestrial assumptions may be

inappropriate for space networks

Gap AnalysisDimension Definition

Numerical Increased number of users, resources, and services

Geographical Users and resources that lie far apart

Administrative Easy to manage even if it encompasses multiple administrative domains

Functional Increasingly more complex functionality

Terrestrial concern

Exponential increase in number of users, data volume, services, resources

Worldwide network

Rapid increase in administrative domains (e.g., autonomous systems)

Complex distributed applications

Space approach

Sparser set of assets

Earth, Moon, Mars and beyond

Smaller number of administrative domains

Flexible, sustainable, affordable, and autonomousHighly optimized

Gap Analysis

Example• Numerical scalability

– Vast numbers of terrestrial assets– Fewer and sparser space assets

Objective• Reconcile gaps

Process

Resolve Gaps• Needs explicit process

Spiral Development• Cycle steps to resolve gaps• Cycle steps to evaluate alternatives• Milestones to resolve gaps

Spiral Development

Reprinted from [Bohem 89]

Hypothetical Example: Development ScalabilityDetermine Objectives

• Flexibility• Sustainability • Affordability • Autonomy• Others?

Determine Constraints• Computation• Power• Delays and errors• Others?

Hypothetical Example: Development ScalabilityDetermine alternatives

• Terrestrial Networks– Sensor Networks– Common architectures, interfaces, substrates

(on-going at NSF NeTS)• Alternative Approach I

– Highly optimized systems– Hooks for flexibility

• Alternative Approach II– Reference model:

Common architectures, interfaces, and substrates Compile into highly optimized implementation

Analogy: distributed shared memory• Alternative Approach III

– Anyone?

Hypothetical Example: Development ScalabilityRemaining spiral stages

• Evaluate alternatives, identify resolve risk

• Develop, verify next level product• Plan next phases

Conclusions

Concern with scalability central to terrestrial networks

Reconcile with space objectives• Identify and resolve gaps• Process: Theory W spiral