[Cerowrt-devel] SQM Question #5: Link Layer Adaptation Overheads

Rich Brown richb.hanover at gmail.com
Sat Jan 4 13:16:37 EST 2014

QUESTION #5: I still don’t have any great answers for the Link Layer Adaptation overhead descriptions and recommendations. In an earlier message, (see https://lists.bufferbloat.net/pipermail/cerowrt-devel/2013-December/001914.html and following messages), Fred Stratton described the overheads carried by various options, and Sebastian Moeller also gave some useful advice.

After looking at the options, I despair of giving people a clear recommendation that would be optimal for their equipment. Consequently, I believe the best we can do is come up with “good enough” recommendations that are not wrong, and still give decent performance.  

In this spirit, I have changed Draft #3 of the “Setting up SQM” page to reflect this understanding. See http://www.bufferbloat.net/projects/cerowrt/wiki/Setting_up_AQM_for_CeroWrt_310

	ADSL/ATM link: Choose “ADSL/ATM", and set Per Packet Overhead to 40
	VDSL2 link: Choose “VDSL”, and set Per Packet Overhead to 8
	Other kind of link (e.g., Cable, Fiber, Ethernet, other not listed): Choose “None (default)”, and set Per Packet Overhead to 0

NB: I have changed the first menu choice to “ADSL/ATM” and the second to “VDSL” in the description. I would ask that we change to GUI to reflect those names as well. This makes it far easier/less confusing to talk about the options. 

As always, I welcome help in setting out clear recommendations that work well for the vast majority of people who try CeroWrt. Thanks.


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