(Congestion Control for Multimedia Applications)
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[[Category:Research]]
 
=Congestion Control for Multimedia Applications=
 
=Congestion Control for Multimedia Applications=
 
The congestion control for multimedia applications (Voice over IP, video on demand) is an open issue. We have evaluated the congestion control strategies employed by leading multimedia applications that is Skype for the VoIP application and RealNetworks for the video on demand applications. We have found out that both applications doesn't employ a valuable congestion control scheme.
 
The congestion control for multimedia applications (Voice over IP, video on demand) is an open issue. We have evaluated the congestion control strategies employed by leading multimedia applications that is Skype for the VoIP application and RealNetworks for the video on demand applications. We have found out that both applications doesn't employ a valuable congestion control scheme.

Revisione 15:45, 21 Set 2006

Congestion Control for Multimedia Applications

The congestion control for multimedia applications (Voice over IP, video on demand) is an open issue. We have evaluated the congestion control strategies employed by leading multimedia applications that is Skype for the VoIP application and RealNetworks for the video on demand applications. We have found out that both applications doesn't employ a valuable congestion control scheme.

Multimedia appliaction

Helix Player (RealNet)

We have evaluated how Helix Player behaves when available bandwidth reductions take place in order to find out how it reacts to congestion episodes. The figure below shows how the throughput of an helix connection experiencess up to 30% of packet losses when another helix flow enters the link (between ~30s and 90s).

Two Helix flows sharing a bottleneck

Skype

Skype is the most popular VoIP application with over 250 million userbase spread all over the world. It is important to study how skype reacts to packet losses in order to infer if a huge amount of skype calls can result in a congestion collapse.

Towards this end we have evaluated Skype generated flows in a local testbed. We have routed the traffic of two Skype users hosted on the same machine through a virtual machine where "tc" and "netem" have been configured in order to add delays and and to control link capacity (see figure below).

Testbed employed to test Skype

The figure below shows how Skype behaves when the link suffers drops in capacity. We have set up the link capacity to vary between 20 Kbyte/s and 2 Kbyte/s as a square wave with 50% duty cycle and 30s period. The figure clearly shows (see the loss percentage) that Skype is not able to react to link capacity drops leading to very high packet loss rates (up to 80%) when the link capacity is reduced.

Skype connection

Congestion Control for Multimedia Applications[edit]

The congestion control for multimedia applications (Voice over IP, video on demand) is an open issue. We have evaluated the congestion control strategies employed by leading multimedia applications that is Skype for the VoIP application and RealNetworks for the video on demand applications. We have found out that both applications doesn't employ a valuable congestion control scheme.

Multimedia appliaction

Helix Player (RealNet)[edit]

We have evaluated how Helix Player behaves when available bandwidth reductions take place in order to find out how it reacts to congestion episodes. The figure below shows how the throughput of an helix connection experiencess up to 30% of packet losses when another helix flow enters the link (between ~30s and 90s).

Two Helix flows sharing a bottleneck

Skype[edit]

Skype is the most popular VoIP application with over 250 million userbase spread all over the world. It is important to study how skype reacts to packet losses in order to infer if a huge amount of skype calls can result in a congestion collapse.

Towards this end we have evaluated Skype generated flows in a local testbed. We have routed the traffic of two Skype users hosted on the same machine through a virtual machine where "tc" and "netem" have been configured in order to add delays and and to control link capacity (see figure below).

Testbed employed to test Skype

The figure below shows how Skype behaves when the link suffers drops in capacity. We have set up the link capacity to vary between 20 Kbyte/s and 2 Kbyte/s as a square wave with 50% duty cycle and 30s period. The figure clearly shows (see the loss percentage) that Skype is not able to react to link capacity drops leading to very high packet loss rates (up to 80%) when the link capacity is reduced.

Skype connection