Re: [tcpm] Opsdir telechat review of draft-ietf-tcpm-yang-tcp-07

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Date: Sun, 03 Jul 2022 21:44:46 -0700
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Subject: Re: [tcpm] Opsdir telechat review of draft-ietf-tcpm-yang-tcp-07
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> On Jul 3, 2022, at 9:04 PM, Gyan Mishra via Datatracker <> wrote:
> Reviewer: Gyan Mishra
> Review result: Not Ready
> This draft provides the Yang data mode for TCP.
> The draft is well written and is almost ready publication.  I verified the FSM
> state machine and all states are listed.
> Minor issues:
> None
> Major issues:
> None
> Nits:
> I reviewed the TCP Yang data model and has a question related to the FSM state
> machine.
> Would it be possible to specify the TCP Header flags SYN, FIN, ACK, RST of BFD
> FSM finite state machine Events and Transition.  I think this would be very
> helpful for the TCP Yang model FSM state machine.  For each state you could
> specify the flags set.

These issues appear to have been raised by you in March during last call review. Some have been addressed by others before; I’ll add my input.

The YANG model represents information about the current TCP connection. It is not (and should not be confused with) a specification of the protocol.

Further, flags are associated with messages that cause state transitions, not states (i.e., the FSM is a Mealy machine, not a Moore machine). There is no “flags set for each state”.


That page has errors and is not consistent with RFC793 (or it’s pending -bis update). E.g., FIN stands for “finis” (latin for “end”), not “finish”.

> I think the TCP TCB (TCP Control Block) is missing in the Yang model. This is
> important for troubleshooting TCP connection state.

RFC793 (and -bis) indicate that the STATUS command, which might return similar information, is optional. 

If there is connection information returned, I do not think it should be the TCB; that is an implementation-dependent parameter, not a universal property of TCP connections. As others have stated in previous responses to you review, the common subset of the TCB is already contained.

I.e., I think the YANG model represents TCP information. It is not - and should not be confused with - a troubleshooting tool.