Re: [6lo] working group last call (wg lc) on https://datatracker.ietf.org/doc/draft-ietf-6lo-deadline-time/

["Lijo Thomas" <[e-mail]>]

Dear Georgios,

 

Thanks for the feedback, responding to your query : 

 

Deadline Time (DT) by itself does not guarantee deterministic behaviour, but its information enables intermediate nodes to implement delay sensitive scheduling and routing algorithms towards achieving deterministic behaviour.

 

As a use case application of our draft,  we implemented a basic EDF policy in OpenWSN 6tisch stack. 

 

Please find the link for our openwsn implementation

 

https://github.com/openwsn-berkeley/openwsn-fw/tree/develop/openapps/uexpiration

 

 

Thanks & Regards,

Lijo Thomas 

 

From: 6lo [mailto:[e-mail]] On Behalf Of Georgios Z. Papadopoulos
Sent: 24 July 2018 13:49
To: Lijo Thomas
Cc: [e-mail]; [e-mail]; Malati Hegde; Samita Chakrabarti; Gabriel Montenegro; lo; Charlie Perkins; [e-mail]
Subject: Re: [6lo] working group last call (wg lc) on https://datatracker.ietf.org/doc/draft-ietf-6lo-deadline-time/

 

Hello Lijo,

 

Thank you so much for your detailed comments. I appreciate it very much.

I am happy with your response, I just have one last clarification point, see below:

 

 

On Jul 24, 2018, at 09:38, Lijo Thomas <[e-mail] <mailto:[e-mail]> > wrote:

 

Dear Georgios,

 

Thanks for your valuable suggestions and we really appreciate for taking your valuable time for the review .

 

Please find our comments inline below marked as (*** [LT]) 

 

We will be happy to receive your further inputs !!!

 

 

Thanks & Regards,

Lijo Thomas 

 

From: 6lo [ <mailto:[e-mail]> mailto:[e-mail]] On Behalf Of Georgios Z. Papadopoulos
Sent: 17 July 2018 21:40
To:  <mailto:[e-mail]> [e-mail]
Cc:  <mailto:[e-mail]> [e-mail];  <mailto:[e-mail]> [e-mail]; Malati Hegde; Samita Chakrabarti; Gabriel Montenegro; lo; Charlie Perkins;  <mailto:[e-mail]> [e-mail]
Subject: Re: [6lo] working group last call (wg lc) on  <https://datatracker.ietf.org/doc/draft-ietf-6lo-deadline-time/> https://datatracker.ietf.org/doc/draft-ietf-6lo-deadline-time/

 

Dear Lijo and co-authors,

 

I went through the draft, please find my comments below:

— — 

 

High level comments:

*/ [GP] The draft defines the Deadline Time (DT), but it is not clear to me how the arrival of the datagram within this pre-defined DT period is guaranteed?

Indeed, the draft provides the necessary DT information, however, the only action I could observe is the delay-sensitive datagram to be dropped if the indicated DT is elapsed.

 

 

*** [LT] Yes, the Deadline Time (DT) specifies the maximum allowable delay

before which the packet should be delivered to the destination. The proposed

draft provides a mechanism for transporting the DT information. By incorporating

deadline based scheduling/routing mechanisms within the intermediate nodes

using DT, one could guarantee deterministic behavior in terms of delay. 

 

 

[GP] Would you agree that this draft do not guarantees deterministic behavior in terms of delay, but it provides

the information of maximum allowable delay for a packet to be delivered to the destination?

 

To be more precise, for instance, lets us consider the following multi-hop network A—> B —> C.

According this draft, it will required 2 timeslots (or 20ms) for a packet to be delivered at the DODAG Root C.

However, if there is an external interference from A to B, then A may need to retransmit multiple times

in order the datagram to be received by B. Then there are two options according to the draft:

a) the datagram is dropped, to reduce the traffic, energy consumption.

b) the datagram is delivered even if the deadline time is crossed, i.e., as you said in your e-mail “in some scenarios where the intention is also to know the total delay experienced by the packets in a network”

 

In both bases, a and b, there is no guarantee that the datagram will be delivered in predefined time, i.e., in deterministic behavior. 

 

— — 

Thank you so much,

Georgios

 

____________________________________

 

Georgios Z. Papadopoulos, Ph.D.

Associate Professor, IMT Atlantique, Rennes

 

web:     www.georgiospapadopoulos.com <http://www.georgiospapadopoulos.com> 
twitter:            @gzpapadopoulos <https://twitter.com/gzpapadopoulos?ref_src=twsrc%5Etfw&ref_url=http://georgiospapadopoulos.com/> 

____________________________________

 

 

 


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