Hi David,

On May 18, 2015, at 17:09 , dpr...@reed.com wrote:

> I'm curious as to why one would need low priority class if you were using 
> fq_codel?  Are the LEDBAT flows indistinguishable?  

        Well, as far as I can tell fq_codel treats all flows the same, but we 
want LEDBAT flows to basically scavenge the left-overs, not get their fair 
share on the table ;). Updates by the way are not the best example for this 
kind of problem as some updates are urgent enough to post-pone everything else 
for.

> Is there no congestion signalling (no drops, no ECN)? The main reason I ask 
> is that end-to-end flows should share capacity well enough without magical 
> and rarely implemented things like diffserv and intserv.

        As far as I can tell bit torrent tries to do two things: 1) open up 
quite a number of parallel ingress and egress flows and 2) keep that traffic 
out of the way of other traffic. fq_codel interferes with how 2) is 
implemented. Currently, the best of the flawed work-arounds is to have bit 
torrent tell the network that it should be treated as LEDBAT using TOS bits. 
This is flawed as we have no gurateee whatsoever on the sanity of TOS bits on 
our networks ingress (and often networks will re-map the TOS bits anyway, so on 
ingress the LEDBAT TOS signal might not be in the packets any more, and since 
one man’s ingress is another man’s egress, basically using TOS bits for keeping 
bit torrent in the background is a loosing proposition). That said I watched a 
ripe talk by Peter Lothberg where he proposed for the carriers (DTAG in his 
case) to encode their TOS bits into the IPv6 addresses and simply ignore the IP 
TOS bits, so they will not need to re-map those as they are totally neutral for 
DTAG planned internal network. (And interestingly in DTAG’s IPv6 network RRUL 
test packets from sweden keep their TOS bits fully intact).

Best Regards
        Sebastian

> 
> 
> On Monday, May 18, 2015 8:30am, "Simon Barber" <si...@superduper.net> said:
> 
> I am likely out of date about Windows Update, but there's many other programs 
> that do background downloads or uploads that don't implement LEDBAT or 
> similar protection. The current AQM recommendation draft in the IETF will 
> make things worse, by not drawing attention to the fact that implementing AQM 
> without implementing a low priority traffic class (such as DSCP 8 - CS1) will 
> prevent solutions like LEDBAT from working, or there being any alternative. 
> Would appreciate support on the AQM list in the importance of this.
> 
> Simon
> 
> Sent with AquaMail for Android
> http://www.aqua-mail.com
> 
> On May 18, 2015 4:42:43 AM "Eggert, Lars" <l...@netapp.com> wrote:
> 
> On 2015-5-18, at 07:06, Simon Barber <si...@superduper.net> wrote:
> Windows update will kill your Skype call.
> 
> Really? AFAIK Windows Update has been using a LEDBAT-like scavenger-type 
> congestion control algorithm for years now.
> Lars
> _______________________________________________
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