Re: [lp-wan] Flow validation in ACK-on-error Mode

[Rodrigo Muñoz <[e-mail]>]

Thanks Juan Carlos for your response.

My comments below:

In your flow, you are showing a “Retransmission Timer” time between the
retransmitted Reg Frag 1 and the All-1.
[Rodrigo]: Yes. This timer is definided
in draft-petrov-lpwan-ipv6-schc-over-lorawan document. In the 5.5.1 said:
"If this ACK is not received the end-device sends an all-0 (or an all-1)
fragment with no payload to request an SCHC ACK retransmission. The
periodicity between retransmission of the all-0/all-1 fragments is
device/application specific and may be different for each device (not
specified).

If the All-1 is the fragment that would have normally followed Reg Frag 4,
there is no need for the sender to wait between retransmitting Reg Frag 4
and the All-1.
[Rodrigo]: I don't understand this. Could you explain it in more detail
please? Remember that in my diagram, fragment 1 is lost, but fragments 2, 3
and 4 correctly reach the receiver. In addition, I assume that these
fragments are not in the last window, therefore an All-1 SCHC message
should not be sent

This All-1 would trigger again the receiver to send a SCHC ACK, which would
notify the sender of the correct (or not) reception of all the previous
fragments.
[rodrigo]: Yes, I also agree with you

The problem is: what happens when the sender relays the Frag 1 message and
this message is lost. Neither the sender nor the receiver have timers to
start retransmissions again, or do they have them?

I corrected the diagram to give more clarity

El lun., 16 sept. 2019 a las 13:06, Juan Carlos Zuniga (<
[e-mail]>) escribió:

> Hello Rodrigo,
>
>
>
> Thanks for your enquiry.
>
>
>
> In your flow, you are showing a “Retransmission Timer” time between the
> retransmitted Reg Frag 1 and the All-1.
>
>
>
> If the All-1 is the fragment that would have normally followed Reg Frag 4,
> there is no need for the sender to wait between retransmitting Reg Frag 4
> and the All-1.
>
>
>
> This All-1 would trigger again the receiver to send a SCHC ACK, which
> would notify the sender of the correct (or not) reception of all the
> previous fragments.
>
>
>
> I hope this helps.
>
>
>
> Best,
>
>
>
> Juan Carlos
>
>
>
> *From:* lp-wan <[e-mail]> *On Behalf Of *Rodrigo Muñoz
> *Sent:* September 16, 2019 10:42 AM
> *To:* [e-mail]
> *Cc:* Sandra Cespedes <[e-mail]>
> *Subject:* [lp-wan] Flow validation in ACK-on-error Mode
>
>
>
> Dear Author,
>
>
>
> I am working on the implementation of the SCHC standard for Sigfox and
> LoRaWAN. I have the following doubt regarding the data flow when there is a
> failure in the transmission of a SCHC fragment in the ACK-on-error Mode.
>
>
> In this email, I attach my draft compression. Is this flow ok?
>
>
> I have assumed the following:
>
>    - The SCHC Ack is sent immediately by the receiver at the end of the
>    window.
>
> Regards
>
> --
>
> -------------------------------------------
> *Rodrigo Muñoz Lara*
>


-- 
-------------------------------------------
*Rodrigo Muñoz Lara*