Re: [6tsch] set DAGRank to Join Priority

Qin Wang <qinwang@berkeley.edu> Fri, 27 September 2013 21:20 UTC

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Date: Sat, 28 Sep 2013 05:20:18 +0800
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From: Qin Wang <qinwang@berkeley.edu>
To: Xavier Vilajosana Guillen <xvilajosana@eecs.berkeley.edu>
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Subject: Re: [6tsch] set DAGRank to Join Priority
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Xavi,

You mean:
if rank <= 0x3f then JoinPriority=rank else JoinPriority=0x3f

Correct? I think it could be a solution.

Thanks
Qin


On Sat, Sep 28, 2013 at 5:07 AM, Xavier Vilajosana Guillen <
xvilajosana@eecs.berkeley.edu> wrote:

> Hi Qin,
>
> my suggestion is to use JoinPriority[5:0] = (rank[15:8]&0x3F) or 0x3F if
> bigger -- having a 0x3F would be like having INFINITE Join Priority as in
> the case of RPL with ranks>65535.
>
> would that not work?
> X
>
>
> On Fri, Sep 27, 2013 at 1:44 PM, Qin Wang <qinwang@berkeley.edu> wrote:
>
>> Xavi,
>>
>> Let's take the example in your draft to see what the problem is. Please
>> point out if I'm wrong.
>> +-------+
>>      |   0   | R(0)=0
>>      |       | DAGRank(R(0)) = 0
>>      +-------+
>>          |
>>          |
>>      +-------+
>>      |   1   | R(1)=R(0)+683=683
>>      |       | DAGRank(R(1)) = 2
>>      +-------+
>>          |
>>          |
>>      +-------+
>>      |   2   | R(2)=R(1)+683=1366
>>      |       | DAGRank(R(2)) = 5
>>      +-------+
>>          |
>>          |
>>      +-------+
>>      |   3   | R(3)=R(2)+683=2049
>>      |       | DAGRank(R(3)) = 8
>>      +-------+
>>          |
>>          |
>>      +-------+
>>      |   4   | R(4)=R(3)+683=2732
>>      |       | DAGRank(R(4)) = 10
>>      +-------+
>>          |
>>          |
>>      +-------+
>>      |   5   | R(5)=R(4)+683=3415
>>      |       | DAGRank(R(5)) = 13
>>      +-------+
>>
>> From the example, you can see R(n) is a 2-byte integer, and DAGRank is
>> always the higher byte of the 2byte integer, because minHopRankIncrease =
>> 256.
>>
>> If set JoinPriority = DAGRank, then it is possible JoinPriority> 0x3f
>> (although it unlikely happens often), out of its range.
>> If set JoinPriority[5:0] = DAGRank[7:2], (Is it your suggestion?), a new
>> node may found many existing nodes with same JoinPriority in received EB.
>> In another word, the JoinPriority can not provide information about
>> preferring joining. Right?
>>
>> I haven't had good solution for it. So, I hope the range 0x00~0x3f is not
>> a "MUST" in IEEE802.15.4e.
>>
>> What  do you think?
>> Qin
>>
>>
>>
>>
>> On Sat, Sep 28, 2013 at 2:30 AM, Xavier Vilajosana Guillen <
>> xvilajosana@eecs.berkeley.edu> wrote:
>>
>>> Hi Qin,
>>>
>>> after thinking a little bit on that maybe we can use the higher byte of
>>> the rank for that. that is  rank>>8, the higher byte is a monotonically
>>> increasing counter. As each hop is <<8 (due to minhopRankIncrease) we can
>>> have the sense of higher join priority as higher the rank.
>>>
>>> In addition having if we have the limitation of 0x3F, this means that we
>>> will support Join priorities up to 0x3F that translated to ranks are
>>> 0x3F<<8 (big number) ..
>>>
>>> just thoughts...
>>> X
>>>
>>>
>>> On Fri, Sep 27, 2013 at 10:30 AM, Qin Wang <qinwang@berkeley.edu> wrote:
>>>
>>>> Hi Thomas,
>>>>
>>>> I think with OF0 the DAGRank is uint8. But, in the Table 52b of
>>>> IEEE802.15.4e, the range of Join Priority is 0x00~0x3f. If the range is a
>>>> "MUST", we have to have a function mapping a DAGRank in 0x00~0xff to a
>>>> JoinPriority in 0x00~0x3f. Correct?
>>>>
>>>> Would you please confirm with some expertise in IEEE802.15.4e if the
>>>> range 0x00~0x3f is a MUST or not?
>>>>
>>>> Thanks
>>>> Qin
>>>>
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>>>>
>>>
>>
>