Anand, You are raising a good point. This would mean that a 6P transaction is started not by the the sender, but the receiver.
I have added a slide in the set for this afternoon's call, as a high-bandwidth discussion might be best approach here. Thomas On Mon, Mar 7, 2016 at 11:36 AM, S.V.R.Anand <[email protected]> wrote: > Hi Diego and others, > > Since we are discussing about the message transactions in SF0, this mail > is with > respect to the RPL parent, the cell donor. > > There are situations where the RPL parent might want to apply a cell > reclamation > and, depending on the context, a reallocation policy dynamically. This > results in one or more cells that > have been given to its children are reclaimed by the RPL parent due to > various > reasons as below. > > - The child node is out of the network, or child and parent cannot reach > each other, > after the 6P add cell transaction is complete, thereby delete cell > operation is not > being transacted. Cell reclamation helps in "cell garbage" collection. > > - As add cell requests arrive asynchronously from its children, an RPL > parent implementing certain fairness objective might re-appropriate the > cells > that have already alloted its children, especially during a resource > crunch. > > - Referring to the following text in 4.2.5 of the 6tisch architecture > document, > > "...Note that a PCE is expected to have precedence in the allocation, so > that an RPL parent > would only be able to obtain portions that are not in-use by the PCE." > > It may be that, an RPL parent might have to relinquish its own cells if > needed by PCE any time. In such a scenario, the RPL parent may be > forced to > reclaim the cells given to its children. > > While the first case is relatively less complex, the latter two cases are > problematic as these cases can lead to (i) potential race conditions, say > between PCE and SF0 operations, and (ii) a cascading effect across several > RPL > parents down the DODAG. Currently, there is no mechanism defined to address > this problem. > > I suppose the above text extends beyond SF0. > > In light of the above use cases and the associated problems, do you think > it is a > good idea to include an appropriate message in SF0 for reclaiming the > cells by > the RPL parent ? or are we inviting new set of problems by doing so ? > > Will be happy to receive your inputs. > > Anand > > > -- > This message has been scanned for viruses and > dangerous content by MailScanner, and is > believed to be clean. > > _______________________________________________ > 6tisch mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/6tisch >
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