Disconnected islands in a sea of connectivity Ciaran Fisher 1 st - - PowerPoint PPT Presentation

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Disconnected islands in a sea of connectivity Ciaran Fisher 1 st - - PowerPoint PPT Presentation

Feb 01, 2023 234 likes •646 views

Disconnected islands in a sea of connectivity Ciaran Fisher 1 st Year PhD University of Sussex Dan Chalmers Ian Wakeman Steve Naicken Jon Rimmer Overview Digital Stadium Project EPSRC Produce a working DTN useable in the real

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Disconnected islands in a sea of connectivity

Ciaran Fisher 1st Year PhD University of Sussex Dan Chalmers Ian Wakeman Steve Naicken Jon Rimmer

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Overview

  • Digital Stadium Project
  • EPSRC
  • Produce a working DTN useable in the real

world

  • Engage with the public to make the DTN

something they want to use

  • Stadium scenario chosen
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The Solution

  • Pocket Switched Network

– Subset of Delay Tolerant Networks – Phones network with phones sharing data producing a distributed cache of common content – Previous attempts have relied on tethering – Overlay network

  • Based on Android
  • Other solutions targeted just one android

version or required root

Our Solution

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The Solution

  • Operating System based on the Linux kernel

by Google

  • Programmed in Java

– Every app runs in its own VM – Strict permissions model – Easy App sideloading

What is Android?

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The Solution Android Fragmentation

Data collected during a 14-day period ending on June 3, 2013. Source: http://developer.android.com/about/dashboards/index.html

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The Solution Android Fragmentation

Gingerbread Ice Cream Sandwich Jelly Bean 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35

Count Android Version

SDK: 2.3.3 2.3.4 2.3.5 2.3.6 4.0.3 4.0.4 4.1.1 4.1.2 4.2.2

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The Solution

  • Bluetooth

– Poor manufacture implementations

  • Wi-Fi via tethering

– Unrestricted internet access for all

  • Ad Hoc Wi-Fi

– Not part of standard API – requires root

  • Wi-Fi Direct + Legacy Mode

– The solution!

Connectivity

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The Solution

  • API added in Ice Cream Sandwich – Oct 2011
  • Allows Ad Hoc Phone to Phone Connection
  • Unfortunately requires user input

Wifi Direct

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The Solution

  • Creates a “normal” access point visible to all

wifi devices

  • DHCP
  • No internet connection - Advantage
  • Random SSID and password
  • Major differences between ICS, JB 4.1 and JB

4.2 implementation

Wifi Direct Legacy Mode

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The Solution Bootstrapping

Phone becomes Access point

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The Solution Bootstrapping

Sends data to rendezvous server Web Service

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The Solution Bootstrapping

Client Phone downloads the AP details from rendezvous server Web Service AP Client

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The Solution Bootstrapping

Client connects to AP with no external prompts needed using a “normal” Wi-Fi connection Web Service AP Client

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The Solution Bootstrapping

Phones Exchange cache information Web Service AP Client AP receives client requests and delivers responses

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System Architecture

User Interface Background Services

Asynchronous Data Request Response

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System Architecture

  • Background Services:

– LRU Cache of JSON containing http pages – Asset Request list – Network Service – AP Service

  • Brings up the Access point for clients to connect to
  • Switches to client mode after 6 minutes

– Client Service

  • Switches to AP mode (if supported) if it has no

connection within 1 minute

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System Architecture

Example Request: {url: “…/latestscores”, modified: 1370553092000} Example Response: {url: “…/latestscores”, modified: 1370553092000, content:”<html></html>”}

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UI Update

User enters view in app, E.g. Twitter

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UI Update

Asynchronous message sent to backend service with last updated time. LRU Cache Asset Request

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UI Update

  • Cache Hit - Data is broadcast
  • Received by listener in the UI
  • Data is type is checked to see if matches current

view

  • If it matches UI is updated

LRU Cache Asset Response

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UI Update

Cache Hit but stale data Data is broadcast and received by listener in the UI Asset request also generated LRU Cache Asset Request List Asset Request Asset Response

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The Solution Supporting GET

Web Service AP Request: scores newer than x Client Requests scores

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The Solution Supporting GET

Web Service AP AP checks cache, distributes request Request Request Request Request

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The Solution Supporting GET

Web Service AP AP resolves the request Marks request resolved Request Request Request Request Response

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The Solution Supporting GET

Web Service AP AP distributes response Request Request Request Response Response Response Response

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The Solution Supporting GET

Web Service AP Marks Requests as resolved Request Request Request Response Response Response Response

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The Solution Supporting GET

Web Service AP UI update broadcast Response Response Response Response

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The Solution Supporting POST

Web Service AP User posts Tweet

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The Solution Supporting POST

Web Service AP AP floods POST to other nodes ensuring delivery

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The Solution Supporting POST

Web Service AP AP delivers post Unique message ID is logged by server

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The Solution Supporting POST

Web Service AP Subsequent posts with the same unique ID are ignored

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The Solution Supporting POST

Web Service AP AP distributes message telling any node that connected that the post was successful, removing it from connected nodes

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The Solution Data Dissemination

  • Epidemic routing tried to ensure requests are

spread far through the network to increase the likelihood of a node getting a connection

  • DTN client nodes connect to different AP’s

helping to disseminate data

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Additional University benefits

  • Successful deployment at the BHAFC vs

Wolves

  • Over the DTN: 40MB between 67 participants

Results

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Additional University benefits Results

Views Page 1524 LiveScores 608 Twitter 362 LeagueTable 156 Status 81 CurrentMatch 38 Placeholder 31 Preferences 25 Trains 22 About 17 Results 13 Traffic 8 Bus 6 News 6 Fixtures 4 Feedback 1 Store

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30 40 50 60 70 11:00 12:00 13:00 14:00

Time (GMT) Battery Level

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0.00 0.25 0.50 0.75 1.00 103 105 107

Time (ms) P(X≤x)

Network dtn mob

Cumulative Distribution Function of RTTs

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Additional University benefits

  • Drop support for older phones enabling the

rendezvous server to be removed as users upgrade

  • Work on routing requests to nodes likely to

have a connection – My PhD

  • Work on making AP more intelligent

– Don’t be an AP if many are nearby

  • Further research latest API changes allowing

fixed access point names and passwords

Future Work

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Questions?