Re: [Roll] Eliding-Info: Abbreviated Option and RCSS of an Option

[Rahul Jadhav <[e-mail]>]

Please find my response inline [RJ].



RCSS can identify whole options in DIO, but it may be not flexible.

Imagine the case that some reduced function device which don’t support MOPex/GCO, when root only update MOPex/GCO, even though RCSS increment, DIO can carry AOO and advertise the updated options, these RFDs could ignore the RCSS increment.


[RJ] I would argue on the contrary that for an RFD the complexity of AOO is even less useful. Assuming that the protected options change rarely, how big is the utility for an RFD to know that only one of the protected options is changed and syncing it individually.



Is it possible to add mode for RCSS? Simple mode means RCSS can only be a common counter for all the options. Complex mode means AOO can identify individual protected options?


[RJ] I understand that the draft supports simple mode and complex mode (using AOO) is only an extension. But what I intend to say is that the complex mode may be a deterrent to anyone reading the draft. More importantly, I could not figure out much utility. The purpose of this draft is to reduce runtime network overhead. I would argue that complex mode will reduce the control overhead by a fraction of a percentage but requires more flash/ram.








From: Roll <[e-mail]> on behalf of Rahul Jadhav <[e-mail]>
Reply-To: Routing Over Low power and Lossy networks <[e-mail]>
Date: Thursday, June 4, 2020 at 15:45
To: Routing Over Low power and Lossy networks <[e-mail]>
Subject: [Roll] Eliding-Info: Abbreviated Option and RCSS of an Option



Hello All, Pascal,



Based on my understanding currently, the draft serves three purposes:

1. Helps elide common DIO options which rarely change

2. Helps elide common DAO options during route refresh cycles

3. Allow sync for individual protected options by assigning RCSS to an option (this implies the use of new AOO)



Points 1 and 2 are quite clear and easy to follow.



The whole complexity of the proposal lies in point 3 and from what I understand I believe the utility is not convincing enough for the amount of complexity it introduces.



My understanding is that with AOO, it is possible that a Root assigns a different RCSS to individual protected options such that the downstream nodes can individually query and synchronize with any of that option on change.



My rationale is that PIO/RIO/DODAG Configuration/MOPex/GCO options rarely change. IMO, if either of it changes then it is no big deal to advertise all the options. Rather than managing versions for each of these options, the RCSS can only be a common counter for all the options.



I understand that RCSS of an option is "an extension" and it is possible to only use common RCSS. But I believe the whole RCSS of an option as an extension is adding to the complexity of the draft (introducing more scenarios to handle), and also making it difficult for the reader.



Best,

Rahul