Re: [core] Comments and questions on draft-jarvinen-core-fasor-02

Christer Holmberg <christer.holmberg@ericsson.com> Thu, 28 November 2019 11:55 UTC

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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Carsten Bormann <cabo@tzi.org>
CC: "core@ietf.org" <core@ietf.org>
Thread-Topic: [core] Comments and questions on draft-jarvinen-core-fasor-02
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Subject: Re: [core] Comments and questions on draft-jarvinen-core-fasor-02
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HI,



    >>>>> I don’t think that is the intention.

    >>>>> If the message-id of a received message is the same as the one the server just processed, just discard.

    >>>>

    >>>>  Are you saying that retransmissions of the same message may have different message-id values???

    >>>

    >>> No, I was trying to say that a recipient discards duplicates, which they detect by them having the same message-id.

    >>

    >> …which means the recipient would miss any updated data conveyed in the retransmission.

    >

    > Yes.  Hence the warning that the server should not consider the updated data conveyed.



Where is this "warning" documented?



Section 4.5 of 7252 says:



   "The recipient SHOULD acknowledge each

   duplicate copy of a Confirmable message using the same

   Acknowledgement or Reset message but SHOULD process any request or

   response in the message only once."



Based on that, to me it looks weird that we then define functionality which is based on actually processing retransmissions of requests/responses…





    >>>>>> In addition, if a retransmission contains updated information, retransmissions will have to be exposed to the application, rather than being handled by the protocol stack.

    >>>>>

    >>>>> Right.  That is not the intention.

    >>>>

    >>>> Well, if one is allowed to update information in retransmissions, that would be the case…

    >>>

    >>> Again, the point is that a duplicate is not processed, so the sender could not rely on the updated information being seen (in the case the ACK was lost).

    >>

    >> I think it is weird to define functionality that is based on the information being updated, and at the same time say that the sender can not

    >> rely that the receiver will see the updated information…

    >

    > The receiver is getting a more accurate max-age.  This is useful.

    > If data are updated as well, the receiver gets more timely data.

    > Also useful.



Yes, but the sender will not know if the receiver will get the updated data, and that can cause problems, depending on what data is updated.



    > Since we don’t have reliable ACKs, we can’t go beyond that.



Not sure what you mean.



Regards,



Christer