Re: [6tisch] Link Options bitmap in 6P Cell format

[Xavier Vilajosana <[e-mail]>]

Hi Qin,

the LinkOptions makes it more flexible for future uses (as it opens more
options). I see the priority field for example also interesting.

I agree however that we use 5-extra bits per requested cell and that the
timekeeping and priority fields are not in the scope as of today. Maybe
even 8 if we leave some reserved bits as 15.4.

thoughts?
X


2016-10-05 17:27 GMT+02:00 Qin Wang <[e-mail]>:

> Hi Tero,
>
> Thank you for the update.
>
> According to my understanding, the flag used in 6P is trying to define the
> communication direction of scheduled cell(s). So, I wonder if 2 bits flag
> is enough.
>
> Thanks
> Qin
>
>
> On Wednesday, October 5, 2016 11:03 AM, Tero Kivinen <[e-mail]>
> wrote:
>
>
> Qin Wang writes:
> > In IEEE802.15.4e, LinkOptions is defined as follows.
>
> This was changed in the 802.15.4-2015, i.e., the MLME and he PIB no
> longer specify bit numbers for those infrmation, they provide the same
> information in separate parameters (TxLink, RxLink, SharedLink,
> TimekeepngLink, PriorityLink), or spearate PIB entries (macTxType,
> macRxType, macLinkTimekeeping and macPriorityType).
>
> The TSCH Slotframe and Link IE do define field called Link Options and
> splits it to bits as follows:
>
> +---------+---------+-------------+-------------+----------+----------+
> | Bits: 0 |    1  |      2      |      3      |    4    |  5-7    |
> +---------+---------+-------------+-------------+----------+----------+
> | TX Link | RX Link | Shared Link | Timekeeping | Priority | Reserved |
> +---------+---------+-------------+-------------+----------+----------+
>         Figure 7-54 --Link Options field format
>
> Note, that there is new bit for Priority in there too. And as normally
> this is LSB first so care should be taken when written to the IETF
> draft...
>
>
> > Is it what you are going to use? Then, another way is to use two bits to
> > express TX/RX/Share. I'm not sure which way is better than another.
>
>
> Two bits is not enough to define all different link types. The text in
> 802.15.4-2015 defining the bits is:
>
>     The TX Link field shall be set to one if it is a TX link and
>     shall be set to zero otherwise.
>
>     TX Shared links, indicated by the TX link field and Shared
>     Link field both set to one, may be used by a joining device to
>     send an Association Request command or higher layer message to
>     the advertising device.
>
>     The RX Link field shall be set to one if the link is an RX
>     link and shall be set to zero otherwise. RX links are used by
>     a joining device to receive an Association Response command or
>     higher layer message from an advertising device.
>
>     The Shared Link field shall be set to one if the link is a
>     shared link and shall be set to zero otherwise. A shared link
>     is one that uses contention to access the medium.
>
>     A link may be used as both a TX shared link and RX link.
>
>     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.
>
>     The Priority field shall be set to one if the link is a
>     priority channel access, as defined in 6.2.5.2, and shall be
>     set to zero otherwise.
> --
> [e-mail]
>
>
>
>