Subject: Re: [6tisch] 6P Timeout in MSF

From: <[email-masked]>
Date: Mon, 2 Sep 2019 01:15:18 +0000

Hi Tengfei,

I'm not sure if this is really a problem, but maybe we can start
with a small timeout and extend it exponentially every time we
observe 6P Timeout. In that case, the current definition of
TIMEOUT can be the upper bound of the timeout.

Best regards,
Toshio Ito

From: 6tisch <[email-masked]> On Behalf Of Tengfei Chang
Sent: Friday, August 23, 2019 9:49 PM
To: 6tisch <[email-masked]>
Subject: [6tisch] 6P Timeout in MSF

Hi All,

For the current version (06) of MSF,  we defined the 6P Timeout as the result of following equation:

6PTIMEOUT = ((2^MAXBE)-1)*MAXRETRIES*SLOTFRAME_LENGTH

   o  MAXBE is the maximum backoff exponent used

   o  MAXRETRIES is the maximum retransmission times

   o  SLOTFRAME_LENGTH represents the length of slotframe

What I believed is this is the right timeout value according the definition of RFC8480:

The value of the 6P

   Timeout should be greater than the longest possible time it takes to

   receive the 6P Response or Confirmation.

However, this value could be super large depending the value of MAXBE and SLOTFRAME_LENGTH.

For example, MAXBE = 5, MAXRETRIES=8 (to get a better reliability), SLOTFRAME_LENGTH=101.
for 10 ms slot duration, the 6P timeout is more than 4 minutes. This could cause large delay for 6P transaction, for example at network forming phase.

So my concerns on the 6P Timeout are

- do you think this is an issue or not

- if yes,  what's your suggestion?

Thanks!

Tengfei

--
Chang Tengfei,
Postdoctoral Research Engineer, Inria