Re: [tcpm] Review (Re: WGLC for draft-ietf-tcpm-rack-08)
Theresa Enghardt <ietf@tenghardt.net> Sat, 25 July 2020 00:10 UTC
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Date: Fri, 24 Jul 2020 17:10:04 -0700
From: Theresa Enghardt <ietf@tenghardt.net>
To: Yuchung Cheng <ycheng@google.com>
Cc: tcpm IETF list <tcpm@ietf.org>
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Subject: Re: [tcpm] Review (Re: WGLC for draft-ietf-tcpm-rack-08)
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Hi Yuchung, See inline: On 2020-07-24 16:45, Yuchung Cheng wrote: >> On 2020-07-13 15:06, Yuchung Cheng wrote: >> […] >> Reading the new Section 3.3.2, I'm wondering about the following >> though: >> >> "If the sender has not observed any reordering since the >> connection was established, then the RACK reordering window >> SHOULD be zero in either of the following cases: […] >> >> 1. After learning that three segments have been delivered out of >> order (e.g. receiving 3 DUPACKs per [RFC5681]); in turn, this >> will cause the RACK loss detection logic to trigger fast >> recovery. >> >> 2. During fast recovery or RTO recovery." >> >> Does this SHOULD mean that the implementation should set the >> reordering >> window to 0 under either of the listed conditions? > yes > >> Because I fail to see how the two listed conditions mean that that >> "the >> sender has not observed any reordering". >> Or SHOULD the sender set the reordering window to 0 if either it >> hasn't >> observed any reordering, or one of the listed conditions are true. > > agree this can be better clarified. do you think the following is more > clear: > > 1. The reordering window SHOULD be zero if no reordering has been > observed on the connection so far, plus either (a) > three segments have been delivered out of order since the last > recovery or (b) the sender is already in fast or RTO recovery. > Otherwise the reordering window SHOULD start from a small fraction of > the > round trip time, or zero if no round trip time estimate is available. > > 2. The RACK reordering window SHOULD adaptively increase if the > sender receives the Duplicate Selective Acknowledgement (DSACK) > [RFC2883], > suggesting the window is too small which causes spurious > retransmission. > > 3. The RACK reordering window MUST be bounded and this bound SHOULD > be SRTT. > > (The text after this needs to be adjusted for the new bullet numbers). This is much clearer, thanks! Additionally, I suggest to change "The reordering window SHOULD be zero" to "The reordering window SHOULD be set to zero", or to prefix the entire list with a sentence like "More specifically, the sender sets the reordering window as follows:". >> In Section 3.3.2, I fail to understand or parse the following >> sentence: >> The RACK reordering window SHOULD leverage that to >> adaptively >> estimate the duration of reordering events, if the receiver >> uses >> Duplicate Selective Acknowledgement (DSACK) [RFC2883]. >> >> The RACK reordering window SHOULD leverage what? (If "that" refers to >> the sentence before, SRTT, then the connection to DSACK is not obvious >> to me. So I think it's good to substitute "that" here.) > sorry that=DSACK. sentence got cut out accidentally. Does the proposed > new text in my earlier comment look better? Yes, this is clearer to me now. I would suggest the following slight changes to this sentence though: OLD: "The RACK reordering window SHOULD adaptively increase if the sender receives the Duplicate Selective Acknowledgement (DSACK) [RFC2883], suggesting the window is too small which causes spurious retransmission." NEW: "The RACK reordering window SHOULD adaptively increase if the sender receives a Duplicate Selective Acknowledgement (DSACK) [RFC2883], suggesting the window is too small, which causes spurious retransmission." Best, Theresa
- [tcpm] WGLC for draft-ietf-tcpm-rack-08 Michael Tuexen
- [tcpm] Review (Re: WGLC for draft-ietf-tcpm-rack-… Theresa Enghardt
- Re: [tcpm] WGLC for draft-ietf-tcpm-rack-08 Mirja Kuehlewind
- Re: [tcpm] WGLC for draft-ietf-tcpm-rack-08 Gorry Fairhurst
- Re: [tcpm] WGLC for draft-ietf-tcpm-rack-08 - 3 i… Gorry Fairhurst
- Re: [tcpm] [EXTERNAL] WGLC for draft-ietf-tcpm-ra… Praveen Balasubramanian
- Re: [tcpm] WGLC for draft-ietf-tcpm-rack-08 Yuchung Cheng
- Re: [tcpm] Review (Re: WGLC for draft-ietf-tcpm-r… Yuchung Cheng
- Re: [tcpm] WGLC for draft-ietf-tcpm-rack-08 Yuchung Cheng
- Re: [tcpm] [EXTERNAL] WGLC for draft-ietf-tcpm-ra… Yuchung Cheng
- Re: [tcpm] Review (Re: WGLC for draft-ietf-tcpm-r… Theresa Enghardt
- Re: [tcpm] Review (Re: WGLC for draft-ietf-tcpm-r… Yuchung Cheng
- Re: [tcpm] Review (Re: WGLC for draft-ietf-tcpm-r… Theresa Enghardt
- Re: [tcpm] Review (Re: WGLC for draft-ietf-tcpm-r… Yuchung Cheng