The Challenge of Challenged Networks

S. Keshav

University of Waterloo

Dharamshala, September 8, 2010

Waterloo?

Where is that?

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The Challenge of Challenged Networks

S. Keshav University of Waterloo

Dharamshala, September 8, 2010

A Fundamental Problem

Technology operates in a social, cultural and economic context

Real-world success depends on both the technology and the context

Nearly impossible to determine context in advance– and it may change

Challenged networks

Challenging conditions create unique requirements and also place strong constraints including:– Environmental– Infrastructural– Social– Cultural– Legal– Economic

How to proceed?

Iterative process of design, deployment, and refinement

Context: requirements, constraints, and alternatives

Design

Implement

Test

Deploy

Monitor

Redefine requirementsand constraints

Context: the SoftBridge stack

Power

Network

Media

Device

Synch

UI

People

Power

Network

Media

Device

Synch

UI

People

Tucker and Blake, University of the Western Cape, South Africa

Design

Design every layer of the SoftBridge stack, not just the network!

DTN offers alternatives but is not a panacea

Don’t underestimate cellular networks– economies of scale– femtocells

Implement

Challenged networks limit options– avoid lock-in

Don’t build on unproven technology– ‘error 22’ (?)

Build in monitoring

Test

Don’t skimp on testing, painful though it may be

Build test harnesses Always investigate unexpected results

– What you cannot explain is at the heart of new knowledge

Deploy

Always start with a pilot Feet on the street Start small

Monitor

Monitor everything Visualize data graphically Don’t skimp on analysis Insist on formal reporting

Refine

Use monitoring data to refine assumptions, constraints, and requirements

Be prepared to throw away the first and second systems– ruthlessness is essential

The rule of three

The first system is too naïve The second system is too ambitious The third system is usable

Another rule of three

The first system is too simple The second system is too complex The third system is simple in just the

right ways

Strive to achieve the second simplicity!

Summary so far

Contextualize Iterate Simplify

Case study: KioskNet

KioskNet (2005-2008)

Trade delay for cost

Power

Network

Media

Device

Synch

UI

People

Experiences

Single-board Linux-based computers are not mass-market– hard to debug and maintain by locals

Vehicular environment is harsh– failure– theft

Difficult to get agreement from transportation providers

VLink (2009)

Addresses problems with KioskNet– Reuses existing Windows and Linux desktops– Software-only solution– No computer in vehicle– No need for buy in from transportation authorities– and MUCH cheaper!

Leverages USB memory sticks (KeyLink) and SMS (SMSLink)

Applications

Email VSync

– keeps two directories in sync

Outcome?

Probably a failure NGOs do not want unsupported

software SMS/voice communication on mobiles

appears adequate– 3G is coming

Case study: TIER/Aravind

Power

Network

Media

Device

Synch

UI

People

Conclusions

Designing any successful network is difficult; challenging environments exacerbate this

Contextualize using the SoftBridge stack Iterate to build at least three solutions Simplify the system systematically and

ruthlessly Success is not assured

Thank you!

Grad students : S. Liang, A. Seth, N. Ahmed, M. Ghaderi, S. Guo, M.H. Falaki, S. Ur Rahman, E. A. Oliver, U. Ismail, S. Rahbar

Graduate interns: R. Luk, Z. Koradia

Staff Programmer: D. Kroeker, M. Derakhshani, A. Ganjali

Undergrads :  M.Zaharia, P. Darragh,  N. Arora, Y. Yin, G. Salmon, G. Wang, M. Liang, M. Thomas, A. Agarwal,Y. Xu, Y. Hu, S. Dube, R. Sethi, C. Ho,  C. Tan, A. Leong

Affiliated Faculty:  T. Brecht (UW), U. Hengartner (UW), S. Prasad  (IIT Delhi), H. Saran (IIT Delhi)

Staff support:  G. Chopiak