Post on 15-Jan-2016
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Application and Desktop SharingApplication and Desktop SharingOmer Boyaci, Henning Schulzrinne, Department of Computer Science, Columbia University
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Participant ParticipantHost
Application specific+ Efficient- Participants need application- Application has to be modifiedGeneric- Inefficient (sometimes)+ Participants don't need application+ All applications are supported
•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
Related Work
UltraVNC
MASTMulticast ApplicationSharing ToolX 320,340
Y 100,200Kernel space
User space X 320,340Y 100,200
X 320,340Y 100,200
X 320,340Y 100,200
Mirror Driver
2X 300,500Y 200,600
Server Main Thread
Window coordinates
•Participants may have different bandwidths•Some participants may join lately.•The effects of packet losses•Reliable multicasting (NACK)•Some regions require different encoding
Region>40,000px
?
YES
New Region
?
NO
Use DetectedFormat
YES
-1,0,1
coordinates
PNG Size
Time Stamp
counter
Region recordCreate a record&
Start Checking
Detected?
Continue Checking
NO YES
PNG/JPG Detection Algorithm
What is Application Sharing?
ChallengesWindows Server Architecture
Application Sharing Models
Multimedia Support The effect of Packet Loss
RetransmissionsNACK mechanism for lost packetsNACK suppression for multicasting
Minimizing the loss effectSmall PNG imagesAround 1500 bytesSeveral scan lines