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. -- [email protected] _______________________________________________ 6tisch mailing list [email protected] https://www.ietf.org/mailman/listinfo/6tisch
