Illustrating Networking Concepts with Wireless Handheld Devices

Brad Richards & Nate WaisbrotComputer Science DepartmentVassar College

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Project Overview• Writing custom apps for Cybiko

– “PDA for Kids”– Wireless communication

• Illustrate selected topics via hands-on lab sessions

• Students interact with each other through Cybiko apps – Each has a Cybiko– Participate by sending routing

info, data, etc.– Process orchestrated by an

administrator

• Funded by NSF CCLI grant

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Overview of Talk• Motivation & Example• Cybiko Details• Project Status• Experiences• Ongoing Work

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Motivation• Wanted easy way to introduce routing details• Had traditionally been a lecture-only topic• Was difficult to hold students’ interest

– Hard to respond quickly to “what if” questions

• Considered using simulator– Lots of good tools available– Often much more detailed than required– Non-trivial learning curve

• Cybiko applications– Students enjoy interactive nature– Can arrange students to match virtual topology– Can be used in any setting

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Example: Distance-Vector RoutingStudents can:• Send short text msgs• Send DVs to neighbors• Ping neighbors• Display routing table• Clear routing table• Toggle msg forwarding

Also displays:• Incoming text msgs• Arriving DVs• Details on forwarding

Administrator can:• Change parameters:

– Split Horizon– Split w/poison reverse– Triggered Updates

• Force optimal routes• “Kill” nodes• Change NW topology

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Cybiko Details• Basic PDA applications• Wireless RF communications (19.2 Kbps)• Cheap! (US $30 for Classic)• Full QWERTY keyboard• Grayscale LCD display• 1 MB memory (expandable)• Tethers to PC to download apps, etc.• Free Software Development Kit– Book also available

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Project Status• Routing applications finished– Flooding, Distance-Vector, Link-State

• Lab materials available for faculty – Source code as well

• Materials used with several groups:– My undergraduate Networks course, Fall 2001– High-school students, Fall 2001– Max Hailperin’s Networks course, Spring 2002

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Experiences• Did controlled study in Fall 2001

– Total of only 17 students (7 women, 7 of color)

• Introduced routing algorithms in lecture• Gave assessment exam

– Some concepts, some specific routing questions

• Randomly split group into two halves– 8 Students got additional, more specific lecture– 9 Students covered same material via Cybiko

• Gave same assessment exam again• Both groups improved, Cybiko more

– Cybiko: 83103 (24%), 33% on detailed probs.– Lecture: 86100 (16%), 15% on detailed probs.

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Experiences (cont’d)

• Cybiko group wanted more examples– Both groups were asked

if they wanted more– Could specify Flooding,

DV, Link-State Routing– Most popular answer in

lecture group: zero– Two and three were

popular with Cybiko group

0%

10%

20%

30%

40%

50%

0 1 2 3

Cybiko

Lecture

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Experiences (cont’d)• My conclusion:– Cybiko students learned at least as well– Had more fun doing it

• Max Hailperin’s experiences less positive– Used with 24 students– Had some hardware, user-interface difficulties

• We’ve worked to address most concerns– Concluded that it didn’t add anything – Still, did say:

“ability to match our collective wits against reality was the strongest positive aspect”

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Ongoing Work• Currently working on apps for wireless NW• Demonstrate contention for shared channel• Hope to illustrate– Traditional Ethernet– ALOHA– WiFi (802.11)

• Progress slower than anticipated…

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Summary• Using inexpensive wireless devices• Demonstrate concepts interactively• Can incorporate by:– Using our applications in lab– Removing some of our code, students supply– Extend our framework in new directions

• See www.cs.vassar.edu/cybiko• Demonstration on Wednesday

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