BASS Application Sharing System

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BASS Application Sharing System
Omer Boyaci September 10, 2008 www.cs.columbia.ed
u/boyaci/appshare
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Overview

• Introduction
• Demo
• Architecture
• Challenges
• Features
• Conclusion

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Application Sharing Models

• Application specific
• Efficient
• - Participants need application
• - Application has to be modified
• Generic
• - Inefficient (sometimes)
• Participants don't need application
• All applications are supported

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Application Sharing Models

• Application specific
• Efficient
• - Participants need application
• - Application has to be modified
• Generic
• - Inefficient (sometimes)
• Participants don't need application
• All applications are supported

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Overview

• Introduction
• Demo
• Architecture
• Challenges
• Features
• Conclusion

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Application Sharing

• Sharing an application with multiple users
• There is only one copy of the application
• Participants do not need application itself
• Briefly, participants
• receive screen updates
• send keyboard and mouse events
• Desktop sharing is also supported.

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Screenshot
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Screenshot (2)
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Screenshot (Overlapped Windows)
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Screenshot (Multicast App. Tool)
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2
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Screenshot (Ultra VNC)
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Screenshot (BASS)
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2
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Supported Platforms/OS
Client is Java based.
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Overview

• Introduction
• Demo
• Architecture
• Challenges
• Features
• Conclusion

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Demo

• Demo

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Overview

• Introduction
• Demo
• Architecture
• Challenges
• Features
• Conclusion

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System Architecture

• Client/Server Software Architecture

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System Architecture

• Client/Server Software Architecture

Screen Updates
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System Architecture

• Client/Server Software Architecture

Keyboard Mouse Events
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Client (Viewer) Architecture

• Client can
• Connect to server
• Wait for incoming connections
• Client supports
• TCP
• UDP (Multicast)

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Client (Viewer) Architecture

• Client receives these commands
• Open new window
• Window size changed
• Pixel update
• Close window
• Client sends
• BFCP (Binary Floor Control Protocol) commands
• Keyboard and mouse events

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BASS Windows Server Architecture
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BASS Windows Server Architecture
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BASS Windows Server Architecture
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BASS Windows Server Architecture
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Overview

• Introduction
• Demo
• Architecture
• Challenges
• Features
• Conclusion

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Challenges

• Different client bandwidths/speeds
• Late Joiner
• The effects of packet loss
• Reliable multicast

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Multimedia Support (Movies)
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Multimedia Support (Movies)

• Our system uses PNG to compress and transmit the
  region updates
• PNG is lossless and effective for computer
  generated images but ineffective for real world
  captures like pictures or movies
• JPG is more suitable for photographic images
• However, JPG is lossy and not effective for
  computer generated images (text, line,
  shapes,...)
• Our system should use both

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Multimedia Support (Movies)

• Composite image comparing JPEG and PNG notice
  artifacts in JPEG versus solid PNG background.

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Multimedia Support (PNG vs JPG)
Size x 360x150 162K Size 4x 720x300 648K
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Multimedia Support (PNG vs JPG)
Ethernet (60Mb/s)
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Multimedia Support (PNG vs JPG)
Wireless (4Mb/s)
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PNG/JPG Detection Algorithm
Regiongt 40,000px ?
-1,0,1
coordinates
PNG Size
counter
YES
Time Stamp
New Region ?
Create a record Start Checking
Region record
YES
NO
Detected ?
Use Detected Format
Continue Checking
NO
YES
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Sharing a Movie (Media Player)
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Sharing a Movie File

• Capturing from the Frame Buffer is expensive.
• Instead
• Transcode the movie to Theora beforehand
• Then stream the theora directly to participants
• Java client supports theora playback
• Negligible CPU usage during playback on the
  server

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Sharing a Movie (Our Method)
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Sharing a Movie File
Movie File (wmv,mpg,divx)
Movie File (wmv,mpg,divx)
FFMpeg2Theora
Java Client
Theora Movie
Java Streaming Server
Java Client
UDP/Multicast
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Challenges

• Different client bandwidths/speeds
• Late Joiner
• The effects of packet loss
• Reliable multicast

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Different Client Bandwidths/Speeds
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Different Client Bandwidths/Speeds

• Possible Solutions
• Slowest one
• Average speed
• Fastest one

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Different Client Bandwidths/Speeds

• Possible Solutions
• Slowest one
• Problem Penalize everybody except the slowest
• Average speed
• Fastest one

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Different Client Bandwidths/Speeds

• Possible Solutions
• Slowest one
• Problem Penalize everybody except the slowest
• Average speed
• Possible solution
• Fastest one

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Different Client Bandwidths/Speeds

• Possible Solutions
• Slowest one
• Problem Penalize everybody except the slowest
• Average speed
• Possible solution (Can we do better?)
• Fastest one

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Different Client Bandwidths/Speeds

• Possible Solutions
• Slowest one
• Problem Penalize everybody except the slowest
• Average speed
• Possible solution (Can we do better?)
• Fastest one
• The best solution
• Client bandwidths are fully utilized

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Different Client Bandwidths/Speeds
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Different Client Bandwidths/Speeds
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Challenges

• Different client bandwidths/speeds
• Late Joiner
• The effects of packet loss
• Reliable multicast

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Late Joiner

• Force server to generate full screen update

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Late Joiner

• Force server to generate full screen update
• Problems
• Misbehaving clients can degrade performance
• If Join/Leave rate is high, too much burden on
  server
• Solution
• Generate full screen updates if really necessary
• Otherwise start the new client from last full
  screen update

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Different Client Bandwidths/Speeds
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Different Client Bandwidths/Speeds
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Different Client Bandwidths/Speeds
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Different Client Bandwidths/Speeds
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Different Client Bandwidths/Speeds
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Different Client Bandwidths/Speeds
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Different Client Bandwidths/Speeds
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Different Client Bandwidths/Speeds
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Challenges

• Different client bandwidths/speeds
• Late Joiner
• The effects of packet loss
• Reliable multicast

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The effects of Packet Loss

• This problem applies to
• Multicast
• UDP
• The PNG images can be large
• Regular desktop can be 900KB
• 600 Ethernet packets
• One packet loss wastes all PNG image

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The effects of Packet Loss

• Solution
• Small PNG images
• Around 1500 bytes
• Consist of a few scanlines
• Disadvantages
• Increased CPU usage (clientserver)
• Lower compression ratio (20 lower)
• Advantages
• One packet loss no update for a few scanlines

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The effects of Packet Loss
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Challenges

• Different client bandwidths/speeds
• Late Joiner
• The effects of packet loss
• Reliable multicast

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Reliable Multicast

• RTP Library stores last N rtp packets
• Clients send NACK for lost packets
• RTP Library resend the requested packets

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The effects of Packet Loss
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Overview

• Introduction
• Demo
• Architecture
• Challenges
• Features
• Conclusion

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Recording

• Clients can record the whole/part session
• Anybody can play these files locally
• These files can be streamed to receivers via
  streaming server
• Streaming server supports multiple receivers
• Also late joiners

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Listening Client

• Client waits for incoming connections
• It can display windows from multiple user
• Can be used for RGB cable replacement

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Overview

• Introduction
• Demo
• Architecture
• Challenges
• Features
• Conclusion

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Conclusion

• Application sharing allows users to share a
  single application with multiple participants.
• Participants don't need the application.
• It is not specific to a single application.
• Extra features like recording is added.

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Thanks

• Questions?