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Dear Wesley,
Thanks for your valuable comments.
Please find the inline answers (marked as LT >>) for your comments in the below email.
Happy to receiver your further inputs ...
Thanks & Regards
Lijo Thomas
On September 19, 2018 at 10:02 AM Wesley Eddy <wes@xxxxxxxxxxxxxxx> wrote: Reviewer: Wesley Eddy Review result: Ready with Issues The draft is easily readable and can be understood and should be simple to implement by someone working in the area. I only have one technical issue that I think should definitely need to be resolved, and a few small editorial comments. Technical issues: - The point of the D-bit is confusing. It is supposed to indicate whether the packet MUST be dropped when the deadline is exceeded. However, if the D-bit is zero, the document says that a 6LR "MAY" forward the packet anyways. Since this uses MAY rather than "MUST" or "MUST NOT", it seems like there should be some example use case, scenario, or rationale for why an implementer would choose one way or the other, or how they would include logic to make the decision when the D-bit is 0. Fundamentally though, I'm also unsure why a sender would include a deadline and then set the D-bit to 0 .... is it maybe something like they still want the packet to be delivered so that network measurements of current latency or other properties can be measured using the packet? If the deadline is missed due to congestion/contention causing increased delays, then it seems prudent to always drop the packet, in which case the D-bit would not be needed.
>> LT :
As you rightly noted, the primary reason for giving an option 0 for 'D' bit is for making delay measurements, and also to perform packet delay analysis on the bottleneck segments that are causing the deadline to exceed and take remedial action if possible.
Will the below additional text substantiate the usage of D bit set to 0 case: " The usage of D bit set to 0 implies the packet MAY be forwarded on an exception basis, if the forwarding node is NOT in a situation of constrained resource, and if there are reasons to suspect that downstream nodes might find it useful (delay measurements, interpolations, etc.) " Kindly let me know your inputs .. Editorial comments: - In Section 1, 2nd paragraph, it would probably be good to explain what an elective RH is and define 6LoRHE as an elective 6LoRH here, before "6LoRHE" is used in the Deadline-6LoRHE name.
>> LT : Will update the draft with the corrections
- In Section 1, last paragraph, it would be good to add informative references for the last two sentences mentioning Bluetooth and Wi-SUN work in this area.
>> LT : Will put the informative references.
- In Section 4, last paragraph, it might be worth mentioning for clarity that there are also potentially long serialization delay and MAC layer contention delays in some of the relevant network types. These could dominate propagation and queueing that are mentioned, in some feasible cases.
>> LT : Nice suggestion, will update the draft.
- The "Length of DT field" and "Length of OT field" descriptions seem a bit light, although from the examples it is clear, but they could be replaced with something more clear like "Length of DT field as an unsigned 3-bit integer, encoding the length of the field in octets, minus one."
>> LT : Will modify the draft and make the corrections based on the inputs provided.
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