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: Dimensions DimensionDefinition NumericalIncreased number of users, resources, and services GeographicalUsers and resources that lie far apart AdministrativeEasy to manage even if it encompasses multiple administrative domains FunctionalIncreasingly more complex functionality

Scalability: Terrestrial Background DimensionDefinition NumericalIncreased number of users, resources, and services GeographicalUsers and resources that lie far apart AdministrativeEasy to manage even if it encompasses multiple administrative domains FunctionalIncreasingly 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 Networks Scalability 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 Analysis DimensionDefinition NumericalIncreased number of users, resources, and services GeographicalUsers and resources that lie far apart AdministrativeEasy to manage even if it encompasses multiple administrative domains FunctionalIncreasingly 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 autonomous Highly 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 Scalability Determine Objectives Flexibility Sustainability Affordability Autonomy Others? Determine Constraints Computation Power Delays and errors Others?

Hypothetical Example: Development Scalability Determine 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 Scalability Remaining 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