Dear All,
I have few comments with respect to the draft-wang-6tisch-6top-protocol-00.
1) The draft includes 3-step transaction described in Section. 4.1.1,
for negotiation
of cells between two neighbours. In step 4 of 3-step transaction, there is
a mistake. “The SF running on node B selects 2 cells” is written. It should
have been “The SF running on node A selects 2 cells".
2) In 3-step transaction, the requester only specifies number of cells, and
the candidate list is not specified by the requester. I assume, the
neighbouring node is free to choose the candidate list.
When requester sends empty list, what is the motivation behind the
neighbouring node sending the candidate list in second step of 3-step
transaction ? Is it because the requester has better knowledge about the
cell quality, and therefore can pick the right ones ?
3) In the 3-step transaction, I foresee a problem when there are
concurrent requests
from different neighbours. Regarding concurrent requests, the
draft-wang-6tisch-6top-protocol-00 says “A node MAY support concurrent 6P
Transactions from different neighbors” in Section 4.3.3. A node would reply
BUSY to requester only when it does not have enough resources.
Problem: In the topology specified in the draft, consider node B and C
requires 2 cells each from node A. Node A has 4 or more cells. The SF
chooses 3-step transaction.
NumCells = 2,[]
Step 1: B -------------------------> A
[(1,2),(2,2),(3,5),(4,6)]
Step 2: B <------------------------- A
NumCells = 2, []
Step 3: A <------------------ C
At this step, if Node A specifies [(1,2),(2,2),(3,5),(4,6)] as candidate
list, there will be problem if both Node B and C choose same cells. What
should Node A do at this point ? This problem would not arise in 2-step
transaction.
Currently, if SF0 is used, node A would specify [(1,2),(2,2),(3,5),(4,6)]
as candidate list. Am I right? Then the problem mentioned above would occur.
In my opinion, there is no need for specifying the candidate list in step 2
of 3-step transaction. When requester is not particular about cells, the
neighbouring node can give any 2 cells instead of again asking the
requester to choose.
Regards,
Seema Kumar
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