Re: [Cerowrt-devel] Ideas on how to simplify and popularize bufferbloat control for consideration.

[Sebastian Moeller <moeller0@gmx.de>]

Hi Wes,


On Jul 25, 2014, at 22:48 , Wes Felter <wmf@felter.org> wrote:

> The Netgear stock firmware measures bandwidth on every boot or link up (not sure which) and I would suggest doing the same for CeroWRT.
> 
> Do you need to measure Internet bandwidth or last mile bandwidth?

	I think you want the bandwidth of the usual bottleneck, on DSL that typically is the actual DSL-link to the DSLAM (even though the DSLAM is oversubscribed typically its upstream link is not congested…). I think with DOCSIS it is the same. Realistically bandwidth measurement are going to be sporadic, so this will only help with pretty constant bottlenecks anyway, no use in trying to track, say the DSLAM congestion that transiently happens during peak use time...


> For link bandwidth it seems like you can solve a lot of problems by measuring to the first hop router.

	And that would be sweet, but with DT’s network  the first hop does not respond to ICMP probes, nor anything else under end user control, also the bottleneck might actually be in the BRAS, which can be upstream of the DSLAM. What would be great is if all CPE would return the current link rates per SNMP or so… Or if DSLAMs and CMTSs would supply data sinks and sources for easy testing of good-put.

> Does the packer pair technique work on TDMA link layers like DOCSIS?

	Toke and Dave dug up a paper showing that packet pair is not an reliable estimator for link bandwidth, So one could send independent packet of differing size, but then one needs to synchronize the clocks somehow… 

Best Regards
	Sebastian

> 
> -- 
> Wes Felter
> 
> 
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