Re: [tcpm] History of ECN's use of TCP header bits vs. TCP option
Bob Briscoe <ietf@bobbriscoe.net> Tue, 26 November 2019 08:02 UTC
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To: Jonathan Morton <chromatix99@gmail.com>
Cc: tcpm IETF list <tcpm@ietf.org>
References: <28cdf725-546f-6d0f-516e-1c8f19a00749@bobbriscoe.net> <4F389E20-C5A7-441D-89CE-5F32A3629151@gmail.com>
From: Bob Briscoe <ietf@bobbriscoe.net>
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Date: Tue, 26 Nov 2019 08:02:06 +0000
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Subject: Re: [tcpm] History of ECN's use of TCP header bits vs. TCP option
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Done - in the offline copy. On 25/11/2019 22:57, Jonathan Morton wrote: >> On 25 Nov, 2019, at 2:55 pm, Bob Briscoe <ietf@bobbriscoe.net> wrote: >> >> In Appendix B.1 of the AccECN draft it says: >> It is not recorded why ECN originally used this [header flags] >> approach instead of the more orthodox use of a TCP option. >> >> Having dug into the history, I propose we change this to: >> >> ECN originally used header flags rather than a TCP option because it was considered more efficient to use a header flag for 1 bit of feedback per ACK, and this bit could be overloaded to indicate support for ECN during the handshake. During the development of ECN, 1 bit crept up to 2, in order to deliver the feedback reliably and to work round some broken hosts that reflected the reserved flags during the handshake. > This seems like a reasonable improvement to me. > > - Jonathan Morton -- ________________________________________________________________ Bob Briscoe http://bobbriscoe.net/
- [tcpm] History of ECN's use of TCP header bits vs… Bob Briscoe
- Re: [tcpm] History of ECN's use of TCP header bit… Jonathan Morton
- Re: [tcpm] History of ECN's use of TCP header bit… Bob Briscoe