| Main index | Section 4 | Options |
During delay-based operation, CDG uses a delay-gradient based probabilistic backoff mechanism, and will also try to infer non congestion related packet losses and avoid backing off when they occur. During loss-based operation, CDG essentially reverts to cc_newreno(4)-like behaviour.
CDG switches to loss-based operation when it detects that a configurable number of consecutive delay-based backoffs have had no measurable effect. It periodically attempts to return to delay-based operation, but will keep switching back to loss-based operation as required.
| version | |
| Current algorithm/implementation version number. | |
| beta_delay | |
| Delay-based window decrease factor as a percentage (on delay-based backoff, w = w * beta_delay / 100). Default is 70. | |
| beta_loss | |
| Loss-based window decrease factor as a percentage (on loss-based backoff, w = w * beta_loss / 100). Default is 50. | |
| exp_backoff_scale | |
| Scaling parameter for the probabilistic exponential backoff. Default is 2. | |
| smoothing_factor | |
| Number of samples used for moving average smoothing (0 means no smoothing). Default is 8. | |
| loss_compete_consec_cong | |
| Number of consecutive delay-gradient based congestion episodes which will trigger loss-based CC compatibility. Default is 5. | |
| loss_compete_hold_backoff | |
| Number of consecutive delay-gradient based congestion episodes to hold the window backoff for loss-based CC compatibility. Default is 5. | |
| alpha_inc | |
| If non-zero, this enables an experimental mode where CDG's window increase factor (alpha) is increased by 1 MSS every alpha_inc RTTs during congestion avoidance mode. (Setting alpha_inc to 1 results in the most aggressive growth of the window increase factor over time. Use higher alpha_inc values for slower growth.) Default is 0. | |
, , Networking 2011 Proceedings, Part II, 328-341, Revisiting TCP Congestion Control using Delay Gradients, May 2011.
http://caia.swin.edu.au/reports/121113A/CAIA-TR-121113A.pdf, , CAIA Technical Report 121113A, Minimising RTT across homogeneous 802.11 WLANs with CAIA Delay-Gradient TCP (v0.1), November 2012.
The module was first released in 2011 by David Hayes whilst working on the NewTCP research project at Swinburne University of Technology's Centre for Advanced Internet Architectures, Melbourne, Australia. More details are available at:
| CC_CDG (4) | July 2, 2013 |
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