Re: [tcpm] History of ECN's use of TCP header bits vs. TCP option
Jonathan Morton <chromatix99@gmail.com> Mon, 25 November 2019 14:57 UTC
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From: Jonathan Morton <chromatix99@gmail.com>
In-Reply-To: <28cdf725-546f-6d0f-516e-1c8f19a00749@bobbriscoe.net>
Date: Mon, 25 Nov 2019 16:57:04 +0200
Cc: tcpm IETF list <tcpm@ietf.org>
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References: <28cdf725-546f-6d0f-516e-1c8f19a00749@bobbriscoe.net>
To: Bob Briscoe <ietf@bobbriscoe.net>
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Subject: Re: [tcpm] History of ECN's use of TCP header bits vs. TCP option
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> 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
- [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