Hi Thomas and Tero, Thank you for your responses! Yes, Tero's answered my question!!
To summarize: [For TX] - Any destination address is accepted in a cell if and only if its macNodeAddress is the broadcast address (or the short broadcast address). - A unicast frame is sent over a cell whose macNodeAddress matches its destination address or is the broadcast address. [For RX] - macNodeAddress has nothing to do with RX. - Any frame, regardless of the combination of its source and destination address, can be received through a cell. In this sense, the purpose of macNodeAddress is only to make something like a priority cell for outgoing frames to a certain MAC address other than the broadcast address. And, we cannot allocate a cell exclusively used for sending broadcast frames. I wish IEEE 802.15.4-2015 could elaborate what is expected to do with macNodeAddress... Everybody may have no confusion about these things except me... With regard to Link Options or Cell Options, I believe I have the same understanding as Tero's. I'm relieved here. :-) But, I have one thing I want to confirm about this. If a cell is "shared", this means that there is a possibility of contention or collision as you mentioned. This attribute, shared or not, is orthogonal to which type of communication, unicast and/or broadcast, to be done, isn't it? Therefore, in theory, we may have a dedicated (non-shared) TX cell whose macNodeAddress is the broadcast address. In this case, a node having such a TX cell is supposed to be the unique sender in its neighborhood. We may also have a shared TX cell whose macNodeAddress is a unicast address. In this case, more than one pairs of devices could share such a cell for their communication. How does that sound...? Best, Yatch On 2016/11/15 5:06, Thomas Watteyne wrote:
Yatch, Can you confirm Tero has answered your question? Thomas On Tue, Nov 15, 2016 at 12:02 PM, Tero Kivinen <kivi...@iki.fi <mailto:kivi...@iki.fi>> wrote: Yasuyuki Tanaka writes: > To my understanding, the scheduled cell in 6tisch-minimal can be used > for both of unicast and broadcast. The destination address of a frame > to be sent with the cell may have the MAC address of a particular > neighbor or the broadcast address. > > But I'm not sure how we can handle that use case with the MAC Layer > defined by IEEE 802.15.4-2015. > > According to IEEE 802.15.4-2015, each scheduled cell has a node > address associated with it, which is called "macNodeAddress" and > listed as a TSCH MAC PIB attribute in Table 8-85. By definition, this > is "(an) address of neighbor device connected to this link or the > broadcast address." It sounds like we cannot use a single cell for > unicast and broadcast at the same time; more generally, a cell cannot > be associated with more than one distinct MAC address. This also > implies that a node has to know the address of a correspondent > beforehand to receive frames from it. In 802.15.4-2015 there is 3 bits that affect this. TxLink, RxLink and SharedLink. SharedLink means that the link is used by multiple senders at the same time, and senders need to use different retransmission mechanims on the link, as there might be collisions. If the link is not SharedLink, it is dedicated link, thus node can send to it without caring about collsions. SharedLink only has real mening on the TxLinks. In addition to that the TxLink might either have one mac address assigned to it, or it might be breadcast address. This affects whether this node can be used to send to that node. I.e. if node is trying to send node xxx, it can either wait for TxLink having macNodeAddress of xxx, or it can wait TxLink having macNodeAddress of broadcast. macNodeAddress does not really have any meaning for the RxLinks (unless they also have TxLinks). There is nothing in the 802.15.4-2015 which says how macNodeAddress is for RxLinks (i.e., the section 6.7.2 does not have any filter rules based on that. > I thought there might be a special MAC address for internal use which > matches any address, like 0.0.0.0 or ::/0, and we could set the > address to "macNodeAddress." However, I cannot find such an address... > > In practice, is the broadcast address used for "any" as well as for > "broadcast"? Do you have any thoughts? Yes, I think you can use broadcast for NodeAddress for RxLinks. -- kivi...@iki.fi <mailto:kivi...@iki.fi> _______________________________________________ 6tisch mailing list 6tisch@ietf.org <mailto:6tisch@ietf.org> https://www.ietf.org/mailman/listinfo/6tisch <https://www.ietf.org/mailman/listinfo/6tisch> -- _______________________________________ Thomas Watteyne, PhD Research Scientist & Innovator, Inria Sr Networking Design Eng, Linear Tech Founder & co-lead, UC Berkeley OpenWSN Co-chair, IETF 6TiSCH www.thomaswatteyne.com <http://www.thomaswatteyne.com> _______________________________________ _______________________________________________ 6tisch mailing list 6tisch@ietf.org https://www.ietf.org/mailman/listinfo/6tisch
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