On 12/21/2014 12:07 PM, Tom Henderson wrote: > If you are using ns-2 and RED queues, please help us to evaluate the > following proposed change. > > Mohit Tahiliani has been working on Adaptive RED in ns-2, and has > patched a few issues, including: > > - use of ARED in wireless networks leads to floating point exception > - the default value of Queue/RED set q_weight_ -1 is incorrect > - Queue/RED set adaptive_ 0: this must be set to 1, otherwise "max_p" > parameter never adapts. > > While the default values of some parameters (such as thresh_, > maxthresh_, q_weight_) were changed in 2001 to make ARED as the default > RED mechanism in ns-2, those of others parameters were > left unchanged. The resulting code defaults to something that is neither > RED nor ARED; this patch will fix the default to ARED. > > The proposed patch is in a tracker issue here: > > http://sourceforge.net/p/nsnam/patches/25/ > > I'm testing release candidates for ns-2.36, which are described here: > > http://nsnam.isi.edu/nsnam/index.php/Roadmap > > Mohit's patch is _not_ part of the first release candidate. If we move > forward with it, it will be merged as part of a later release candidate. > So to test it yourself, I recommend to download the release candidate > and apply the patch there. > > I've been through a couple of review cycles with Mohit on this patch. > We'll use lazy consensus to try to decide on its inclusion. Unless we > hear from the community that these changes should be reconsidered (let's > set a date, such as by January 10), I plan to work with Mohit to > evaluate the ns-2 validate trace changes and update the traces, and > commit this to ns-2 prior to the ns-2.36 release. > > Of course, even if you support this, it would be nice to hear > positive feedback if you read over this patch, test it, and like what > you see. > > Thanks, > Tom
Hi all, I've looked into this further and learned that we may not have a major problem to fix with RED in ns-2. It turns out that there is a distinction between what is the default in ns-2, and is called "automatic configuration of RED parameters", and what is called "adaptive RED". This is discussed in more detail on Sally Floyd's RED page: http://www.icir.org/floyd/red.html#parameters So, the claim that adaptive RED was made the default in ns-2 a while back is not correct. This wasn't very clear in the documentation. Accordingly, I updated the patch in the sourceforge tracker to fix the segmentation fault caused by mixing adaptive RED with wireless links, and to update the RED documentation about the ns-2 defaults. This patch does not cause any of the existing validation output to change. I'm planning to add it to the main tree if there are no other comments. https://sourceforge.net/p/nsnam/patches/25/ To respond to a ns-2 RED question on another mailing list, I decided to try to run the existing RED tests against the tests documented in this 1996 report, which was actually conducted using ns-1 (and tests later ported to ns-2): http://www.icir.org/floyd/red.html#ns I was able to pretty closely reproduce most of the figures in that report by running the existing ns-2 RED test suite, suggesting to me that the basic RED implementation in ns-2 has been stable for a long time. I expect to post a new ns-2 release candidate shortly, once I resolve some validation trace discrepancies that are showing up on a few platforms. - Tom
