From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-x441.google.com (mail-wr1-x441.google.com [IPv6:2a00:1450:4864:20::441]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 57E833CB37 for ; Sat, 23 Mar 2019 11:03:46 -0400 (EDT) Received: by mail-wr1-x441.google.com with SMTP id p1so5364099wrs.8 for ; Sat, 23 Mar 2019 08:03:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=JhDlOZ+1G9nWMDnHWi2Z2Vu8kGoxJdsC+Hvpfyvw860=; b=aOoigDoo4XKv8VaNPxIRoM4OLrTn0VDjv3P5vwWz+ZqzPFM5uttDq+UrCW9Hi9BwEb TFZvTGEWC1VrEBIIoBZNtn8FNPO+Krq4+5FJ187kyfir82Ai3HozWcM7/LRBQfwdp5OW c060lF7XshHtfAEvzu4eRkTzkRcYvuk++ly8FXG3KZecrb+l3l8tEDjt5L/3aPt9aTe5 n7C3YZwyM0oq8QbIeUhHYDcsHBNXf196Wwo9wpB3p1Ph1qUFiEzOMyg1fBqdAvDH+Voj RvHGS27BXzJ0iMstZe55QvWaq0s2M3R7dB8aZVMNiUODqBAYOLgmWNjRb9t1mRQKS2t/ iIvA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=JhDlOZ+1G9nWMDnHWi2Z2Vu8kGoxJdsC+Hvpfyvw860=; b=jtbINvrBVJpCG+vxRjOD5wU/K0U05VwkvpLDEp26sYuPt7yD6r3nXSIz+lq6S/kscr 3NshXm05CqvPLZ0n2LYmIZ4Gupb/1tT9Tz/0g874UPDp6CfqSJxJUImS7XfGF5oQPdIZ arPmL13rekbJUdRHW8tmi/pn9LM1ZNL9Te2ashfeBuF+A7flf/jTClPkOpj7R7mD6o8H loLMf24yE9Ff/reqosIpLc0nK2yZAQi37avTVa2qvB7xT3fqyeOEsIcjBPh2QNTbjz4N 7nHEsL26fnLUxKKItV0UWMe+5NGs+v3k1zoe6T5X+VQas+lUPz2b4h+RBA0Ny8pYzLSP AN5g== X-Gm-Message-State: APjAAAUtRhkTWL4fUKci1do709E41T3ph4wix2vrrWzzkaqApbvSrxSf 4ct3Rs7a5gHwqMU4Q2yTsUM= X-Google-Smtp-Source: APXvYqyQuGM9d7izYVjJbvgI+DvUIntWVCg0hr8+awFzIP8vw0kTWvMD7f4IxVbB/dP5aswQd55rZw== X-Received: by 2002:a5d:69c7:: with SMTP id s7mr9724673wrw.71.1553353425549; Sat, 23 Mar 2019 08:03:45 -0700 (PDT) Received: from [10.0.0.135] ([82.202.112.231]) by smtp.gmail.com with ESMTPSA id e9sm3628083wrp.35.2019.03.23.08.03.44 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 23 Mar 2019 08:03:44 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.1\)) From: Jonathan Morton In-Reply-To: Date: Sat, 23 Mar 2019 16:03:43 +0100 Cc: Roland Bless , Victor Hou , bloat@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: <8C8DEC20-2995-4B2E-BB56-CE74B4FA5BAE@gmail.com> References: <2c8ad5fe4be5c52ad1a3c2bf7f91a09a@mail.gmail.com> <00674bef-877b-3ccc-9c8e-e7e06ee8e1cd@kit.edu> To: Mikael Abrahamsson X-Mailer: Apple Mail (2.3445.9.1) Subject: Re: [Bloat] [Ecn-sane] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104 X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 23 Mar 2019 15:03:46 -0000 > On 23 Mar, 2019, at 11:02 am, Mikael Abrahamsson = wrote: >=20 > On Sat, 23 Mar 2019, Roland Bless wrote: >=20 >> I suggest to use an additional DSCP to mark L4S packets. >=20 > DSCP doesn't work end-to-end on the Internet, so what you're = suggesting isn't a workable solution. An interesting question, in this context, is "precisely what happens if = the DSCP is lost?" With a notional L4S using DSCP instead of ECT(1) as an identifier, that = really is a serious problem; the L4S flow will flood out TCP-friendly = flows *unless* its failsafe kicks in. But with SCE, what happens is that the L4S flow gets treated the same as = any other, if the bottleneck where the distinction matters is downstream = of the DSCP corruption. The L4S flow reacts properly to CE in this = scenario, because its been designed around SCE semantics, so it is = TCP-friendly. Flow-isolating AQMs don't need to know the DSCP in the = first place. So the worst case is when a single or dual-queue AQM bottleneck is = involved, and the L4S flow is affected by queuing induced by other flows = who aren't quite so enlightened. The damage is only to the L4S flow, = and within reasonable bounds. This of course ignores the overwhelmingly most common situation on = today's Internet, where the bottleneck queue is completely unmanaged. = But then, losing the DSCP has no effect there. - Jonathan Morton