Re: [tcpm] Francesca Palombini's No Objection on draft-ietf-tcpm-rfc793bis-25: (with COMMENT)
Benjamin Kaduk <kaduk@mit.edu> Thu, 30 September 2021 20:12 UTC
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Date: Thu, 30 Sep 2021 13:12:03 -0700
From: Benjamin Kaduk <kaduk@mit.edu>
To: Francesca Palombini <francesca.palombini@ericsson.com>
Cc: The IESG <iesg@ietf.org>, draft-ietf-tcpm-rfc793bis@ietf.org, tcpm@ietf.org, michael.scharf@hs-esslingen.de, tcpm-chairs@ietf.org
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Subject: Re: [tcpm] Francesca Palombini's No Objection on draft-ietf-tcpm-rfc793bis-25: (with COMMENT)
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On Wed, Sep 22, 2021 at 02:19:17PM -0700, Francesca Palombini via Datatracker wrote: > 4. ----- > > FP: This is surely me missing something but, in section 3.5 I see: > > 4. ESTABLISHED --> <SEQ=101><ACK=301><CTL=ACK> --> ESTABLISHED > > 5. ESTABLISHED --> <SEQ=101><ACK=301><CTL=ACK><DATA> --> ESTABLISHED > > which is followed by: > > Note that the sequence number of the segment in line 5 is the same as > in line 4 because the ACK does not occupy sequence number space (if > it did, we would wind up ACKing ACKs!). > > However, later on, in Figure 13: > > 2. (Close) (Close) > FIN-WAIT-1 --> <SEQ=100><ACK=300><CTL=FIN,ACK> ... FIN-WAIT-1 > <-- <SEQ=300><ACK=100><CTL=FIN,ACK> <-- > ... <SEQ=100><ACK=300><CTL=FIN,ACK> --> > > 3. CLOSING --> <SEQ=101><ACK=301><CTL=ACK> ... CLOSING > <-- <SEQ=301><ACK=101><CTL=ACK> <-- > ... <SEQ=101><ACK=301><CTL=ACK> --> > > I am confused why in this case, in line 3, ACK does in fact occupy sequence > number space. What am I missing? It is the FIN that occupies sequence number space, not the ACK. Both steps 2 and 3 show messages being sent "in parallel", i.e., the "..." in the respective column shows that the event is not currently occuring at that endpoint. So in (2), left sends SEQ=100,FIN, and right sends SEQ=300,FIN; since those sequence numbers are thus committed, in (3) left has to send SEQ=101 and right has to send SEQ=301. -Ben
- [tcpm] Francesca Palombini's No Objection on draf… Francesca Palombini via Datatracker
- Re: [tcpm] Francesca Palombini's No Objection on … Jeremy Harris
- Re: [tcpm] Francesca Palombini's No Objection on … Benjamin Kaduk
- Re: [tcpm] Francesca Palombini's No Objection on … Francesca Palombini
- Re: [tcpm] Francesca Palombini's No Objection on … Benjamin Kaduk
- Re: [tcpm] Francesca Palombini's No Objection on … Francesca Palombini
- Re: [tcpm] Francesca Palombini's No Objection on … Wesley Eddy
- Re: [tcpm] Francesca Palombini's No Objection on … David Borman