Motivation Internet in Pakistan Developed Developing Facts of - PDF document

Overview Information Access and � Poor Man’s Broadband Communication Networks in the – Poor Man’s Cache Developing-world – Packet Containment � TEK Internet Search Umar Saif � Inverse Multiplexing of Cellular LUMS, Pakistan Connections umar@lums.edu.pk | umar@mit.edu � Teleputer (Time permitting) Motivation Internet in Pakistan Developed Developing � Facts of life in the developing world Digital Divide W orld W orld – Expensive International Bandwidth 2 MB I nternet 2 MB I nternet Connection Connection – No real peering points < $ 4 0 > $ 4 0 0 0 – Internet used over dialup Bulk Data Bulk Data Transfer on Transfer on • Poor “Scratch card” provisioning the I nternet the I nternet > 7 0 % < 1 5 % Average End- Average End- user user Bandw idth via Bandw idth I SP via I SP > 1 0 0 kb/ sec < 1 0 kb/ sec Internet in Pakistan How I Stumbled Upon this? � Average Dialup Bandwidth � “Good research solves real problems in a – Less than 10 kb/sec practical way” � Almost Never Used for – Started last year when I wanted to exchange a 3.5 MB PDF file with my dad – Exchanging – Two laptops sitting next to each other – Disseminating – No way to exchange data if you don’t have portable – Accessing storage! …. Content larger than a couple of hundred • We actually went our and bought a CDR to exchange data…. kilobyes 1

Problem Solution <10kb/sec Bypass the Internet when exchanging large Internet Internet ~ 56kb/sec ~ 56kb/sec Not a Last Mile Problem Email Attachments Disruptive Technology � Time to exchange a 3.5 MB file on the � Of course Internet also started as an Internet ~ 1 hours (16 Kb/sec) overlay over the phone lines – 30 mins upload and download � A new kind of Internet – Assuming no disconnections � Reminiscent of Pre-Internet days � Time now (40 kb/sec) – FidoNet – 12 mins!! – UUCP Dialup P2P-ISP Interleaving Why is this Practical? Key Idea: Use Internet as a directory service, not as digital pipe Internet � Phone bills are becoming “Flat” – Rs 199/month -- free nation-wide calls � But cannot always connect to the server � As long as one can identify a “close-by” host, “broadband access” is free Line-speed � P2P systems already follow a similar (~40kb/s) dialup connections model Peer-to-peer dialup – Incentive-based BitTorrent connections Interleaving of ISP- Dialup P2P dialup Underlay connections 2

Dialup BitTorent Other Challenges BitTorrent in a � Overhead of Peer connections: ~30 sequential mode sec � Offline Block Discovery � Last Block Problem � Flash Crowds (Backoff for congestion control) � Budget-based Download Peer Connection Overhead Offline Block Discovery DitTorrent(Greedy) Worst Case(N-Calls) Best Case(lgN-Calls) A 2 3 7 9 B 1 3 6 8 Virally Spread 6 Knowledge of File Blocks 1 3 6 8 A B 2 3 7 9 Offline Block Discovery Last Block Problem • Grab rare blocks first Downloading Time • Favor those who will finish at the end of the connection Online Block Discovery Offline Block Discovery 100.00 90.00 Globally Rarest First(GRF) Scheme 80.00 3500.00 70.00 ) in 3000.00 (m 60.00 n e 2500.00 k 50.00 a T 2000.00 e 40.00 im T 1500.00 30.00 20.00 1000.00 10.00 500.00 0.00 0.00 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 0.00 1000.00 2000.00 3000.00 4000.00 5000.00 6000.00 File Size(KB) File Size(MB) 3

Flash crowds Budget-based Download • Each busy-tone costs ~10 secs Incomplete Nodes (%age) Data Acquired(%age) • Wait between calls (nominal) • Back-off in times of congestion (busy tones) Optimum Choking Interval WBC=1 WBC=25 1600.00 1400.00 ) 1200.00 in (m 1000.00 aken 800.00 T e 600.00 im T 400.00 200.00 0.00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Choking Interval Three Evolving Applications Can we do the same on the “Internet” � Contain packets within the developing- � P2P file-sharing world � Web-browsing – Routing paths are screwed up � Large Email attachments • “All roads lead to Rome” i.e. transit out of the country � Low cache hit-rates – Too many small ISPs, no sharing of cached content http://dittorrent.sourceforge.net – Misconfigured “Proxies” – Hit rates < 30% (instead of >60%) � Poor DNS support Work-in-progress ChoupalLink � Indirect Routing – Force routing paths by vectoring messages through intermediate nodes – Initial results show improvement across all traffic metrics Inverse multiplexing High-bandwidth Virtual Channel over GSM/GPRS/ � An ISP-independent distributed cache – Similar to CoralCDN � An ISP-independent DNS Inverse Multiplexing over cellular connections 4

TEK: Time Equals Knowledge TEK � Internet in the developing-world � Web Search for Low-bandwidth, – Expensive intermittently connected users – Intermittent � One of the first examples of mainstream ICTD research ~circa � An Email-based Internet Search Facility 2000 – Asynchronous Dialup model – Search optimized for bandwidth and latency � Renewed interest with DTNs coming rather than speed in vogue – Heavy client-side caching TEK TEK Server � Remove Duplicate Content � Cluster results � Distinguish Content from links � Remove images � Remove background code � Compress results Rationale Our Teleputer � Lower operational costs – Caching vs internet download – ISP-host connection • Reliable • Higher Bandwdith • Cheaper: email-only account – Better utilization of Internet Connection 5

Multi-user devices Teleputer � Zero-configuration � Text-free Interface � Sensor-actuator � Cell-phone integrated � Shared Computing � Server-style processing Teleputer Sensors Teleputer Operation Network connected to teleputer device Workstation Workstation Workstation Television Workstation Workstation Workstation Mobile Device Workstation Workstation Workstation Laptop computer Built on MOTE Based Teleputer Device Berkeley MOTE Thank you! umar@lums.edu.pk http://www.dritte.org 6