From: Sebastian Moeller <moeller0@gmx.de>
To: Michael Richardson <mcr@sandelman.ca>
Cc: cerowrt-devel@lists.bufferbloat.net
Subject: Re: [Cerowrt-devel] Ideas on how to simplify and popularize bufferbloat control for consideration.
Date: Fri, 1 Aug 2014 20:28:56 +0200 [thread overview]
Message-ID: <70BB6CDF-5A8C-4F44-A308-8681536BB085@gmx.de> (raw)
In-Reply-To: <11000.1406866900@sandelman.ca>
HI Michael,
On Aug 1, 2014, at 06:21 , Michael Richardson <mcr@sandelman.ca> wrote:
>
> On symmetric links, particularly PPP ones, one can use the LCP layer to do
> echo requests to the first layer-3 device. This can be used to measure RTT
> and through some math, the bandwidth.
Sure.
>
> On assymetric links, my instinct is that if you can measure the downlink
> speed through another mechanism, that one might be able to subtract, but I
> can't think exactly how right now.
> I'm thinking that one can observe the downlink speed by observing packet
> arrival times/sizes for awhile --- the calculation might be too low if the
> sender is congested otherwise, but the average should go up slowly.
If you go this rout, I would rather look at the minimum delay between incoming packets as a function of the size of the second packet.
>
> At first, this means that subtracting the downlink bandwidth from the uplink
> bandwidth will, I think, result in too high an uplink speed, which will
> result in rate limiting to a too high value, which is bad.
But given all the uncertainties right now finding the proper shaping bandwidths is an iterative process anyway, but one that is best started with a decent initial guess. My thinking is that with binary search I would want to definitely see decent latency under load after the first reduction...
>
>
> But, if there something wrong with my notion?
>
> My other notion is that the LCP packets could be time stamped by the PPP(oE)
> gateway, and this would solve the asymmetry.
If both devices are time synchronized to a close enough delta that would be great. Initial testing with icmp timestamp request makes me doubt the quality of synchronization (at least right now).
> This would take an IETF action
> to make standard and a decade to get deployed, but it might be a clearly
> measureable marketing win for ISPs.
But if the “grown ups” can be made to act wouldn’t we rather see nice end-user query-able SNMP information about the current up and downlink rates (and in what protocol level, e.g. 2400Mbps down, 1103Kbps up ATM carrier) (For all I know the DSLAMs/BRASes might already support this)
Best Regards
Sebastian
>
> --
> Michael Richardson
> -on the road-
>
>
>
> _______________________________________________
> Cerowrt-devel mailing list
> Cerowrt-devel@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/cerowrt-devel
next prev parent reply other threads:[~2014-08-01 18:29 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-24 14:03 R.
2014-07-25 18:37 ` Valdis.Kletnieks
2014-07-25 21:03 ` David Lang
2014-07-26 11:30 ` Sebastian Moeller
2014-07-26 20:39 ` David Lang
2014-07-26 21:25 ` Sebastian Moeller
2014-07-26 21:45 ` David Lang
2014-07-26 22:24 ` David Lang
2014-07-27 9:50 ` Sebastian Moeller
2014-07-26 22:39 ` Sebastian Moeller
2014-07-26 22:53 ` David Lang
2014-07-26 23:39 ` Sebastian Moeller
2014-07-27 0:49 ` David Lang
2014-07-27 11:17 ` Sebastian Moeller
2014-08-01 4:21 ` Michael Richardson
2014-08-01 18:28 ` Sebastian Moeller [this message]
2014-07-25 20:48 ` Wes Felter
2014-07-25 20:57 ` David Lang
2014-07-26 11:18 ` Sebastian Moeller
2014-07-26 20:21 ` David Lang
2014-07-26 20:54 ` Sebastian Moeller
2014-07-26 21:14 ` David Lang
2014-07-26 21:48 ` Sebastian Moeller
2014-07-26 22:23 ` David Lang
2014-07-26 23:08 ` Sebastian Moeller
2014-07-27 1:04 ` David Lang
2014-07-27 11:38 ` Sebastian Moeller
2014-08-01 4:51 ` Michael Richardson
2014-08-01 18:04 ` Sebastian Moeller
2014-08-02 20:17 ` Michael Richardson
2014-08-01 4:40 ` Michael Richardson
2014-07-26 11:01 ` Sebastian Moeller
-- strict thread matches above, loose matches on Subject: below --
2014-05-24 14:12 R.
2014-05-24 17:31 ` Sebastian Moeller
2014-05-24 19:05 ` David P. Reed
2014-05-20 22:11 Frits Riep
2014-05-20 23:14 ` Dave Taht
2014-05-21 11:42 ` Frits Riep
2014-05-21 14:51 ` dpreed
2014-05-21 15:19 ` Dave Taht
2014-05-21 16:03 ` dpreed
2014-05-21 16:30 ` Dave Taht
2014-05-21 17:55 ` dpreed
2014-05-21 17:47 ` Jim Gettys
2014-05-21 17:53 ` Dave Taht
2014-05-21 17:56 ` dpreed
2014-05-21 17:57 ` Jim Gettys
2014-05-21 18:31 ` Dave Taht
2014-05-21 15:07 ` Dave Taht
2014-05-21 16:50 ` Michael Richardson
2014-05-21 17:58 ` David Lang
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