Thomas,
Thank you very much for liking the points that I raised, and including
a slide for discussion during the interim call. Appreciate for initiating a
lively discussion :)
Out of the three cases, I am wondering if the second case of achieving
fairness
among competing requests that arrive can be handled better without
reclaiming
cells. One possible method that comes to mind is pooling multiple requests
before responding, rather than serving requests as and when they arrive
in the
FCFS basis. Of course, there could be other alternatives. What do you say ?
Anand
On Friday 11 March 2016 07:23 PM, Thomas Watteyne wrote:
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. > >
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