Re: [6tisch] Benjamin Kaduk's Discuss on draft-ietf-6tisch-architecture-24: (with DISCUSS and COMMENT)

[Benjamin Kaduk <[e-mail]>]

On Fri, Aug 09, 2019 at 12:58:08AM +0300, Tero Kivinen wrote:
> Benjamin Kaduk via Datatracker writes:
> > ----------------------------------------------------------------------
> > DISCUSS:
> > ----------------------------------------------------------------------
> > 
> > Section 4.3.4 asserts:
> > 
> >    [...]                                      We'll note that the Join
> >    Priority is now specified between 0 and 0x3F leaving 2 bits in the
> >    octet unused in the IEEE Std. 802.15.4e specification.  After
> >    consultation with IEEE authors, it was asserted that 6TiSCH can make
> >    a full use of the octet to carry an integer value up to 0xFF.
> > 
> > I'm extremely reluctant to publish this text in the IETF stream without
> > a citation.
> 
> IEEE Std 802.15.4-2015 says:
> 
> ----------------------------------------------------------------------
> 7.4.4.2 TSCH Synchronization IE
> 
> The TSCH Synchronization IE Content field shall be formatted as
> illustrated in Figure 7-50.
> 
>           +-------------+---------------+
> 	  |  Octets: 5  |       1       |
>           +-------------+---------------+
> 	  |     ASN     |  Join Metric  |
>           +-------------+---------------+
> 
>      Figure 7-50 -- TSCH Synchronization IE Content field format
> 	   
> The ASN field contains the ASN corresponding to the timeslot in which
> the enhanced beacon is sent. The ASN is used as the Frame Counter for
> security operations if enabled.
> 
> The Join Metric field is an unsigned integer and shall be set to
> macJoinMetric.
> ----------------------------------------------------------------------
> 
> And
> 
> ----------------------------------------------------------------------
> 
> Section 8.4.2.2 TSCH-specific MAC PIB attributes
> 
> ...
> 
>        Table 8-83 -- TSCH-specific MAC PIB attributes
> 
> Attribute	Type     Range       Description                     Default
> ...
> macJoinMetric	Integer	 0x00–0xff   The sum of one and the	     1
> 			 	     value of the Join Metric
> 				     field from the TSCH
> 			 	     Synchronization IE, 7.4.4.2,
> 			 	     received in the Enhanced Beacon
> 			 	     frame used by the device
> 				     joining the network. If the
> 				     device is the an endpoint, the
> 				     value shall be set to zero.
> 
> ----------------------------------------------------------------------
> 
> So it is very clear that Join Metric can be any number between
> 0x00-0xff. 

Great news; I see that Pascal will update the text/reference.

> >    scheduled cell:  A cell which is assigned a neighbor MAC address
> >                (broadcast address is also possible), and one or more of
> >                the following flags: TX, RX, shared, timeskeeping.  A
> > 
> > "timeskeeping" does not seem to be defined anywhere.
> 
> Timekeeping comes from the IEEE Std 802.15.4-2015 Section 7.4.4.3 TSCH
> Slotframe and Link IE:
> 
> ----------------------------------------------------------------------
>    The Timekeeping field shall be set to one if the link is to be used
>    for clock synchronization and shall be set to zero otherwise. RX
>    links shall have the Timekeeping field set to one.

Ah, so it's just a typo and not a term of art.  Thanks!

-Ben