Congestion Control for Real-time Communication[edit]
Congestion control for Real-Time media communication (Video-conferencing, Voice over IP) over the Internet is currently being addressed in IETF
and W3C bodies aiming at standardizing a set of inter-operable protocols and APIs to enable real-time communication between Web browsers.
The IETF working group (WG) RTP Media Congestion Avoidance Techniques (RMCAT) has been established in 2012 to propose the standardization of congestion control algorithms using the RTP. We are developing a congestion control algorithm for Web Real-time Communication (WebRTC). The proposed algorithm is used in Google Chrome and Google Hangouts.
Google Faculty Research Award
Google Faculty Award 2014 for designing a congestion control algorithm for real-time communication within the WebRTC framework to enable video conference among Web browsers.
- Principal investigator: S. Mascolo
- Title:Congestion Control for Web Real-Time Communication (WebRTC)
- August 2014
- Press coverage: Link
A description of the algorithm is provided in the IETF RMACT draft.
- S. Holmer, H. Lundin, G. Carlucci, L. De Cicco, and S. Mascolo
A Google Congestion Control Algorithm for Real-Time Communication
IETF draft RMCAT wg, draft-ietf-rmcat-gcc-01, Oct 2015 (Web: Link)
Google Congestion Control for WebRTC[edit]
- G. Carlucci, L. De Cicco, S. Holmer, and S. Mascolo
Congestion Control for Web Real-Time Communication
IEEE/ACM Transactions on Networking, vol. 25, no. 5, pp. 2629-2642, Oct. 2017. doi: 10.1109/TNET.2017.2703615 (PDF)
- L. De Cicco, G. Carlucci, and S. Mascolo
Congestion Control for WebRTC: Standardization Status and Open Issues
IEEE Communications Standards Magazine, Feature topic 'Real Time Communications in the Web', June 2017
- G. Carlucci, L. De Cicco, and S. Mascolo
Controlling Queuing Delays for Real-Time Communication: Interplay of E2E and AQM Algorithms
ACM SIGCOMM Computer Communication Review, July 2016 (PDF)
- G. Carlucci, L. De Cicco, S. Holmer, and S. Mascolo
Making Google Congestion Control robust over Wi-Fi networks using packet grouping
ACM, IRTF & ISOC , Applied Networking Research Workshop 2016, Berlin, Germany, July 2016 (PDF)
- G. Carlucci, L. De Cicco, C. Ilharco, and S. Mascolo
Congestion Control for Real-time Communications: a comparison between NADA and GCC
24th IEEE Mediterranean Conference on Control & Automation, Athens, Greece, June 2016 (PDF)
- G. Carlucci, L. De Cicco, S. Holmer, and S. Mascolo
Analysis and Design of the Google Congestion Control for Web Real-time Communication (WebRTC)
Proc. ACM Mmsys 2016, Klagenfurt, Austria, May 2016 (PDF)
- L. De Cicco, G. Carlucci, and S. Mascolo
Understanding the Dynamic Behaviour of the Google Congestion Control for RTCWeb
Packet Video Workshop, San Jose, CA, USA, 2013 (PDF) (Slides:PDF)
- L. De Cicco, G. Carlucci, and S. Mascolo
Experimental Investigation of the Google Congestion Control for Real-Time Flows
ACM SIGCOMM 2013 Workshop on Future Human-Centric Multimedia Networking, Hong Kong, China, August 2013 (PDF)
Our experimental investigation has shown that the first version of GCC gets starved when a TCP flow joins the bottleneck (see Fig. below (a)). Moreover, we have found that starvation also occurs when two coexisting GCC flows share a bottleneck (see Fig. below (b) (c)).
To overcome these issues, we have proposed the adaptive threshold mechanism which sets the threshold used by the over-use detector. More details can be found in the following papers:
- G. Carlucci, L. De Cicco, S. Holmer, and S. Mascolo
Analysis and Design of the Google Congestion Control for Web Real-time Communication (WebRTC)
Proc. ACM Mmsys 2016, Klagenfurt, Austria, May 2016 (PDF)
- Gaetano Carlucci, Luca De Cicco,Saverio Mascolo
Modelling and Control for Web Real-Time Communication
Proc. of 53rd IEEE Conference on Decision and Control, Los Angeles, California, USA, December 2014 (PDF)
Fig. below shows how rate flows dynamics along with one way delay variations are nicely set after the introduction of the adaptive threshold.
Skype Video Congestion Control Responsiveness to Bandwidth Variations[edit]
This paper investigates Skype Video in order to discover at what extent this application is able to throttle its sending rate to match the unpredictable Internet bandwidth while preserving resource for co-existing best-effort TCP traffic.
- L. De Cicco, S. Mascolo, V. Palmisano
Skype Video Responsiveness to Bandwidth Variations
ACM NOSSDAV '08, Braunschweig, Germany, May, 2008 (PDF)
Skype VoIP 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.
Next figures summarize main findings (more can be found in the paper: "An Experimental Investigation of the Congestion Control Used by Skype VoIP" pdf and slides).
Skype implements some mechanism to adapt the input rate to the available bandwidth[edit]
One Skype flow over a square waveform available bandwidth
The figure shows the sending rate, the loss rate and the available bandwidth. It can be noticed that Skype adapts its sending rate when the available bandwidth decreases but this adaptation takes 40s, thus leading to high packet loss rates.
Skype adapts to the available bandwidth very slowly[edit]
For the before mentioned reason Skype is not able to cope with sudden bandwidth variations as it can be seen in the next figure.
One Skype flow over a square waveform available bandwidth (higher frequency than before)
Skype is not TCP friendly[edit]
Skype's response to bandwidth variation is sluggish and leads to unfriendliness with respect to TCP flows.
One Skype flow versus one TCP flow
The Figure above shows that TCP connection suffers a large number of timeouts.
Skype is not able to guarantee fairness either[edit]
Two Skype calls have been placed flowing in the same bottleneck in order to investigate if Skype's congestion control is able to guarantee fairness.
Two Skype flows sharing the same bottleneck
Relevant bibliography[edit]
- L. De Cicco, S. Mascolo, V. Palmisano
Skype Video Congestion Control: an Experimental Investigation
Computer Newtorks, Elsevier, in press, doi 10.1016/j.comnet.2010.09.010, 2010
- L. De Cicco, S. Mascolo
A Mathematical Model of the Skype VoIP Congestion Control Algorithm
IEEE Transactions on Automatic Control, to appear, 2010
- L. De Cicco, S. Mascolo, V. Palmisano
A Mathematical Model of the Skype VoIP Congestion Control Algorithm
in Proc. of IEEE Conference on Decision and Control 2008, Cancun, Mexico, Dec, 2008 (PDF)
- L. De Cicco, S. Mascolo, V. Palmisano
Skype Video Responsiveness to Bandwidth Variations
NOSSDAV '08, Braunschweig, Germany, May, 2008 (PDF) (Slides:PDF)
- L. De Cicco, S. Mascolo, V. Palmisano
An Experimental Investigation of the End-to-End QoS of the Apple Darwin Streaming Server
Wired/Wireless Internet Communications (WWIC) 2008, May, 2008 (PDF)
- L. De Cicco, S. Mascolo and V. Palmisano
An Experimental Investigation of the Congestion Control Used by Skype VoIP
Wired/Wireless Internet Communications (WWIC) 2007, Coimbra, Portugal, May, 2007 (PDF) (Slides:PDF)
- L.A. Grieco, S. Mascolo,
Adaptive Rate Control for Streaming Flows over the Internet
ACM Multimedia Systems Journal, Regular paper, Volume 9, Issue 6, pp. 517 - 532, Jun. 2004