('''Skype Congestion Control''')
('''Skype Congestion Control''')
Riga 13: Riga 13:
 
In the next figures we stress the main issues we have found in our investigation.
 
In the next figures we stress the main issues we have found in our investigation.
  
* Skype adapts to the available bandwidth very slowly.
+
* '''Skype adapts to the available bandwidth very slowly.'''
  
 
[[Immagine:skype_on_off.png|right|thumb|400px|''One Skype flow on a square wave form available bandwidth pattern'']]
 
[[Immagine:skype_on_off.png|right|thumb|400px|''One Skype flow on a square wave form available bandwidth pattern'']]
  
 
The figure shows the input rate, the drop rate and the available bandwidth. It can be noticed that Skype adapts its sending rate when the available bandwidth decreases but it takes 40s to match it, thus leading to high packet losses.
 
The figure shows the input rate, the drop rate and the available bandwidth. It can be noticed that Skype adapts its sending rate when the available bandwidth decreases but it takes 40s to match it, thus leading to high packet losses.

Revisione 17:13, 13 Mar 2007

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 such as Skype for VoIP applications and RealNetworks video on demand applications. We have found that both applications don't employ an efficient congestion control scheme.

Multimedia application

Helix Player Congestion Control (RealPlayer by RealNetworks)

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 experiences up to 30% of packet losses when another helix flow enters the link at 30s and exits at 90s.

Two Helix flows sharing a bottleneck

Skype Congestion Control

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.

In the next figures we stress the main issues we have found in our investigation.

  • Skype adapts to the available bandwidth very slowly.
One Skype flow on a square wave form available bandwidth pattern

The figure shows the input rate, the drop rate and the available bandwidth. It can be noticed that Skype adapts its sending rate when the available bandwidth decreases but it takes 40s to match it, thus leading to high packet losses.

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 such as Skype for VoIP applications and RealNetworks video on demand applications. We have found that both applications don't employ an efficient congestion control scheme.

Multimedia application

Helix Player Congestion Control (RealPlayer by RealNetworks)[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 experiences up to 30% of packet losses when another helix flow enters the link at 30s and exits at 90s.

Two Helix flows sharing a bottleneck

Skype Congestion Control[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.

In the next figures we stress the main issues we have found in our investigation.

One Skype flow on a square wave form available bandwidth pattern

The figure shows the input rate, the drop rate and the available bandwidth. It can be noticed that Skype adapts its sending rate when the available bandwidth decreases but it takes 40s to match it, thus leading to high packet losses.