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SPF:None; LANG:en; PTR:InfoNoRecords; A:1; MX:1; received-spf: None (protection.outlook.com: telekom.de does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: 87gu36q1vu6kzb0u/dvjVqkmsZDP3kZzWix3Ea512ZF5f57ceQZmiSd/IGc2931mzdOjfYXYFldsYtwpnUG2ceqZwicxy5d07KQAkCfhTqfYvJ1ujY59neYBan6W+9SwH+PMkkH57NB74ZiO4IvQ7kQsB8zrX/Xi4TbL/7ekHzDK4trLJEv8QtRgByAKTcRL7bAY/kOofrKhyBA1JDi2W1Dp17u0lq4SikKWqtOLRK/BTNHlHCKRC6YuuXtcxnsMBJ8M9oEwNdvLuqvMxnpnLUXOqqzxMO6ux5LOmqQOkymSRIO+PLrIc5qKqVNDnMs4C3zi9U4DSDPW7EcE8oXg9B4R6TI+aMxjc6/Pn5oSV9qrnWWFFq6g5MJnCbrVcTumXxFRVzzb5TBqSDSWLP2SM4cQWTz3WneAgAlTYe6T2AI= Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: ec9e52cc-9016-4cb2-e613-08d717238b5c X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Aug 2019 08:29:32.4540 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: bde4dffc-4b60-4cf6-8b04-a5eeb25f5c4f X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: Ruediger.Geib@telekom.de X-MS-Exchange-Transport-CrossTenantHeadersStamped: FRXPR01MB0582 X-OriginatorOrg: telekom.de X-Mailman-Approved-At: Fri, 02 Aug 2019 06:22:53 -0400 Subject: Re: [Ecn-sane] [tsvwg] ECN CE that was ECT(0) incorrectly classified as L4S X-BeenThere: ecn-sane@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Discussion of explicit congestion notification's impact on the Internet List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 02 Aug 2019 08:29:36 -0000 Hi Jonathan, could you provide a real world example of links which are consecutively nar= rower than sender access links? I could figure out a small campus network which has a bottleneck at the Int= ernet access and a second one connecting the terminal equipment. But in a s= mall campus network, the individual terminal could very well have a higher = LAN access bandwidth, than the campus - Internet connection (and then there= 's only one bottleneck again). There may be a tradeoff between simplicity and general applicability. Aware= ness of that tradeoff is important. To me, simplicity is the design aim.=20 Regards, Ruediger=20 -----Urspr=FCngliche Nachricht----- Von: tsvwg Im Auftrag von Jonathan Morton Gesendet: Dienstag, 9. Juli 2019 17:41 An: Bob Briscoe Cc: tcpm IETF list ; ecn-sane@lists.bufferbloat.net; tsvwg I= ETF list Betreff: Re: [tsvwg] [Ecn-sane] ECN CE that was ECT(0) incorrectly classifi= ed as L4S > On 13 Jun, 2019, at 7:48 pm, Bob Briscoe wrote: >=20 > 1. It is quite unusual to experience queuing at more than one > bottleneck on the same path (the available capacities have to > be identical). Following up on David Black's comments, I'd just like to note that the abov= e is not the true criterion for multiple sequential queuing. Many existing TCP senders are unpaced (aside from ack-clocking), including = FreeBSD, resulting in potentially large line-rate bursts at the origin - es= pecially during slow-start. Even in congestion avoidance, each ack will tr= igger a closely spaced packet pair (or sometimes a triplet). It is then ea= sy to imagine, or to build a testbed containing, an arbitrarily long sequen= ce of consecutively narrower links; upon entering each, the burst of packet= s will briefly collect in a queue and then be paced out at the new rate. TCP pacing does largely eliminate these bursts when implemented correctly. = However, Linux' pacing and IW is specifically (and apparently deliberately= ) set up to issue a 10-packet line-rate burst on startup. This effect has = shown up in SCE tests to the point where we had to patch this behaviour out= of the sending kernel to prevent an instant exit from slow-start. - Jonathan Morton