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From: Jonathan Morton <chromatix99@gmail.com>
To: Sebastian Moeller <moeller0@gmx.de>
Cc: Jonathan Foulkes <jf@jonathanfoulkes.com>,
	bloat <bloat@lists.bufferbloat.net>
Subject: Re: [Bloat] [Bug 1436945] Re: devel: consider fq_codel as the default qdisc for networking
Date: Tue, 5 Jun 2018 22:31:30 +0300	[thread overview]
Message-ID: <6AD85E99-BCD8-4548-AAA4-F5B08599C7AD@gmail.com> (raw)
In-Reply-To: <9675C88A-FCC0-43EB-9C71-CBEFD67408CB@gmx.de>

> On 5 Jun, 2018, at 9:34 pm, Sebastian Moeller <moeller0@gmx.de> wrote:
> 
> The rationale for that decision still is valid, at low bandwidth every opportunity to send a packet matters…

Yes, which is why the DRR++ algorithm is used to carefully choose which flow to send a packet from.

> …and every packet being transferred will increase the queued packets delay by its serialization delay.

This is trivially true, but has no effect whatsoever on inter-flow induced latency, only intra-flow delay, which is already managed adequately well by an ECN-aware sender.

May I remind you that Cake never drops the last packet in a flow subqueue due to AQM action, but may still apply an ECN mark to it.  That's because dropping a tail packet carries a risk of incurring an RTO before retransmission occurs, rather than "only" an RTT delay.  Both RTO and RTT are always greater than the serialisation delay of a single packet.

Which is why ECN remains valuable even on very low-bandwidth links.

 - Jonathan Morton


  reply	other threads:[~2018-06-05 19:31 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <152717340941.28154.812883711295847116.malone@soybean.canonical.com>
2018-05-24 15:38 ` [Bloat] Fwd: " Jan Ceuleers
2018-06-04 11:28   ` Bless, Roland (TM)
2018-06-04 13:16     ` Jonas Mårtensson
2018-06-04 17:08       ` Dave Taht
2018-06-04 18:22         ` Jonas Mårtensson
2018-06-04 21:36           ` Jonathan Morton
2018-06-05 15:10             ` [Bloat] " Jonathan Foulkes
2018-06-05 17:24               ` Jonathan Morton
2018-06-05 18:34               ` Sebastian Moeller
2018-06-05 19:31                 ` Jonathan Morton [this message]
2018-06-06  6:53                   ` Sebastian Moeller
2018-06-06 13:04                     ` Jonathan Morton
2018-06-12  6:39                       ` Dave Taht
2018-06-12  6:47                         ` Dave Taht
2018-08-11 19:17                           ` Dave Taht
2018-08-13 22:29                   ` [Bloat] ecn redux Dave Taht
2018-06-06  7:44                 ` [Bloat] [Bug 1436945] Re: devel: consider fq_codel as the default qdisc for networking Bless, Roland (TM)
2018-06-06  8:15                   ` Sebastian Moeller
2018-06-06  8:55                     ` Mario Hock
2018-06-05  0:22           ` [Bloat] Fwd: " Michael Richardson
2018-06-05  6:21             ` Jonas Mårtensson
2018-06-06  4:14               ` Mikael Abrahamsson
2018-06-07 12:56               ` [Bloat] Fwd: [Bug 1436945] -> What other options/bufferbloat-advice ... ? Simon Iremonger (bufferbloat)
2018-06-04 23:00     ` [Bloat] Fwd: [Bug 1436945] Re: devel: consider fq_codel as the default qdisc for networking David Lang
2018-06-05  7:44       ` Mario Hock
2018-06-05  7:49         ` Jonathan Morton
2018-06-05 11:01           ` Mario Hock
2018-08-16 21:08           ` Dave Taht
     [not found] <mailman.3.1527177601.17575.bloat@lists.bufferbloat.net>
2018-05-24 16:31 ` [Bloat] " Rich Brown

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