From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lj1-x22e.google.com (mail-lj1-x22e.google.com [IPv6:2a00:1450:4864:20::22e]) (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 EDFF33B29E; Sat, 30 Nov 2019 17:23:08 -0500 (EST) Received: by mail-lj1-x22e.google.com with SMTP id m4so35593897ljj.8; Sat, 30 Nov 2019 14:23:08 -0800 (PST) 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=79lInzbpTGQ50pFJXcia7+B5hVqNKzIM24W0CuUmqtQ=; b=Pbjv2exV14ry3zIkysIvZCCezjKGYVOwtUA1dfHLIO2+HLPF4m2kpMCGfJOvE5jTQI mQd63adPUunjk7lTXe/AGx+hyeMKs6k5tHmzwE4RkCZIYJyicgv92AH6CKRVyCQmh71k fyMJf20qoWmpJrfMrNLESLKc8KjkkbAv1FlwwHRMV4LO7a9VAF/EcNmCFLv4eIXSTlLC MCAaFv40Gda6LSxO30rBA3kVrVxlHwIDRtEYErAl7n+SmUNP0MpKewfU2MUbe1VMzYLC a0vztsrc9OlEDqKG6n/Ech22eF54AUX845IjNno5uRcHXuVPJyHbS2Pd001JnYNCYHhL VXbw== 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=79lInzbpTGQ50pFJXcia7+B5hVqNKzIM24W0CuUmqtQ=; b=QTz/K0EbtIFkJvpVJhf3ghyu+nu6sLyUogHrcYgi5ojkKd7a1if5TkbIijQHKet1SY U0yJ1qGASF/SFrVwq252GQTnWjvzC/mWofmxqw/JC0L6nWvvSWUrUzNeaW50ayDWKouz 05iGLSTHn1h6PmNCXaj/uz+hNn9S1vHvy6YiKbAxOnF+Z5nZ104dfwRy3g2ASa9GZnby bOO053BBEib8M3M3CmqfofWQmTdzP0uXsBCcA4ABo5J8NVw2pvB9gcmsJiWWrZYf+2Z0 kUSTFvHCsKn91fl4DWwdzppM5GSJ9zk2t2BfVnho1lWa2feuQc2FBMl5AAv2PzgaQugd 73Ug== X-Gm-Message-State: APjAAAUZ6Ij8ahY7jFuEk5CgdoaAKQLvwkma7pinfX6DSvA5HtQl9z+D sSxZsirdo1B5RwXRgJqjG3g= X-Google-Smtp-Source: APXvYqzpaz8GGafJkibKmQKPjjrkM1IJBZbBgCNtbloksYW8wW/GQO4bSZZZ+mSYm3ZRfptqdWHY7g== X-Received: by 2002:a2e:8695:: with SMTP id l21mr41053688lji.53.1575152587902; Sat, 30 Nov 2019 14:23:07 -0800 (PST) Received: from jonathartonsmbp.lan (83-245-229-102-nat-p.elisa-mobile.fi. [83.245.229.102]) by smtp.gmail.com with ESMTPSA id t9sm12320390ljj.19.2019.11.30.14.23.06 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 30 Nov 2019 14:23:07 -0800 (PST) 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: Sun, 1 Dec 2019 00:23:05 +0200 Cc: Sebastian Moeller , ECN-Sane , bloat Content-Transfer-Encoding: quoted-printable Message-Id: <8C5FD2CE-D24F-4998-A636-8F85279C67BA@gmail.com> References: <63E9C0E4-C913-4B2F-8AFC-64E12489BC65@gmail.com> <297503679.4519449.1575069001960@mail.yahoo.com> <54C976BC-DEC7-4710-9CFF-0243559D9002@gmail.com> <156EA284-C01D-4FAA-89F4-DB448795F7FC@gmx.de> <385CF47C-17AD-4A62-9924-068E1485FFD5@gmail.com> To: Carsten Bormann X-Mailer: Apple Mail (2.3445.9.1) Subject: Re: [Bloat] [Ecn-sane] sce materials from ietf 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, 30 Nov 2019 22:23:09 -0000 > On 1 Dec, 2019, at 12:17 am, Carsten Bormann wrote: >=20 >> There are unfortunate problems with introducing new TCP options, in = that some overzealous firewalls block traffic which uses them. This = would be a deployment hazard for SCE, which merely using a spare header = flag avoids. So instead we are still planning to use the spare bit - = which happens to be one that AccECN also uses, but AccECN negotiates in = such a way that SCE can safely use it even with an AccECN capable = partner. >=20 > This got me curious: Do you have any evidence that firewalls are = friendlier to new flags than to new options? Mirja Kuhlewind said as much during the TCPM session we attended, and = she ought to know. There appear to have been several studies performed = on this subject; reserved TCP flags tend to get ignored pretty well, but = unknown TCP options tend to get either stripped or blocked. This influenced the design of AccECN as well; in an early version it = would have used only a TCP option and left the TCP flags alone. When it = was found that firewalls would often interfere with this, the three-bit = field in the TCP flags area was cooked up. - Jonathan Morton