Re: [6tisch] MSF adapts to traffic only for secured packets

Yasuyuki Tanaka <yasuyuki.tanaka@inria.fr> Fri, 06 December 2019 22:24 UTC

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From: Yasuyuki Tanaka <yasuyuki.tanaka@inria.fr>
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Date: Fri, 6 Dec 2019 23:24:35 +0100
Cc: Yasuyuki Tanaka <yasuyuki.tanaka@inria.fr>, "Pascal Thubert (pthubert)" <pthubert@cisco.com>, 6tisch <6tisch@ietf.org>
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To: Tengfei Chang <tengfei.chang@gmail.com>
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Subject: Re: [6tisch] MSF adapts to traffic only for secured packets
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Thank you, Tengfei.

> On Dec 6, 2019, at 22:49, Tengfei Chang <tengfei.chang@gmail.com> wrote:
> 
> Handling DSCP value will be a per-packet process. Can we pass DCSP value 
> to the TSCH layer using the interface for transmission defined by 
> IEEE802.15.4? I don't think so.
>  
> TC: Not sure this is a standard way to do so. For implementing, tut this value or a flag could have a default value.
> TC: If this value is not given, i.e. frame from IEEE802.15.4 layer, just use the default value.

What we would do are:

- 1. don't update NumCellsUsed for AF43 packets, otherwise update them
- 2. don't update NumTX/NumTxAck for AF43 packets, otherwise update them

The first one may cause undesirable deallocations. If a node has relayed join request continuously for a certain period of time, the computed cell utilization (NumCellsUsed / NumCellsElapsed) goes down, then a negotiated TX cell will be deleted, even if the negotiated TX cell was scheduled to handle application traffic to forward. This behavior may degrade end-to-end reliability.

The second one may prevent the node from monitoring link PDRs on scheduled cells correctly. This could affect the scheduling collision detection.

Best,
Yatch