Re: [lp-wan] re-order header field request

[Arun <[e-mail]>]

Hi Carles,

 Having the uniform header format seems to be an ideal solution but
Tx'ing additional bit without any significance seems contentious.
Will wait for more feedbacks or comments :)

thanks,
Arun

On 20/06/2017 18:01, Carles Gomez Montenegro wrote:
> Hi Arun,
>
> Thanks for pointing this out.
>
> Your proposal seems fine to me, except for the (possibly minor) detail
> that in your proposal "R" would comprise a number of header fields for the
> last fragment that would be different from the number of fields in
> previous fragments.
>
> Maybe we could also consider another solution: adding the W bit in the
> header of the last fragment of the packet.
>
> I haven't found examples of scenarios where the W bit is actually needed
> in the last fragment (i.e. fragment with "all ones" CFN). However, I'm
> wondering if there is an actual benefit or a related use case that may
> require *not* having a W bit in the last fragment header. (If anyone has
> any in mind, please chime in!)
>
> On the other hand, if we have the W bit also in the last fragment header,
> header format will be more uniform across all fragments.
>
> Thoughts?
>
> Cheers,
>
> Carles
>
>
>
>
>> Hi all,
>> Absence of window bit in the last fragment of the packet makes it tricky
>> to unmarshall the header at the receiver.
>> As I see it, the receiver up front shall know the length of the CFN
>> field depending on the Window size configured but doesn't know to
>> anticipate the last fragment unless indicated by CFN.
>> So I think,  we need to maintain same order on all fragment headers.
>>
>> existing;
>>
>>       		<------------ R ---------->
>>                           <--T--> 1 <--N-->
>>                +-- ... --+- ... -+-+- ... -+
>>                | Rule ID | DTag  |W|  CFN  |
>>                +-- ... --+- ... -+-+- ... -+
>>
>> shall be;
>>      		<------------ R ---------->
>>                           <--T--> <--N--> 1
>>                +-- ... --+- ... -+- ... -+-+
>>                | Rule ID | DTag  |  CFN  |W|
>>                +-- ... --+- ... -+- ... -+-+
>>
>> and for the last fragment
>>    		<------------ R ---------->
>>                           <--T--> <--N-->
>>                +-- ... --+- ... -+- ... -+-+
>>                | Rule ID | DTag  |  CFN  |MIC
>>                +-- ... --+- ... -+- ... -+-+
>>
>>
>> what do you think?
>>
>>
>> thanks,
>> Arun
>>
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>
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