Re: [Roll] P2P-RPL: Data-Option in P2P-DIO

[Mukul Goyal <[e-mail]>]

Hi Joseph

Please see inline.

Thanks
Mukul


[Joseph1]
Section 9.4
Bullet 1: 
Under what conditions would a router receive the same DIO and a Data-Option with higher sequence number? I assume that only the Originator can include a Data-Option ? Same question also arises for section 9.5 ( para 1 )

[Mukul1]
Yes, only the origin can include a data option for delivery to the target(s). In theory, the origin might have newer data to convey to the target(s) while the route discovery is still going on. Sequence numbers accounts for that possibility. Note that Data option did not have a sequence number earlier (before the first LC). Then, Pascal raised the possibility what if origin changes the data option. How would intermediate routers and target know that this is the newer data? Hence, we introduced the sequence number.

[Joseph2]
I don’t think the Origin should able to this. In fact, the Origin must not make any changes to the contents of the DIO and retransmit it without updating the version number. If the Origin wants to send data, it should simply wait until the p2p route is setup and then use it. 

The whole idea of sending UDP Data messages in the ICMP message payload itself doesn’t seem quite right. It is also not simple from an implementation perspective to make this kind of cross layer interactions. 

[Mukul2]

I think that implementation concerns (regarding sending UDP data inside ICMP message) might be valid and would like to hear more opinions in this regard. But, I also think that LLNs need cross layer interactions and this experimental RFC might be the perfect place to check if this works or not. Certainly, the need to piggyback data on route discovery packets is real in many LLN applications. In my opinion, we should allow this unless there are overpowering reasons why this is a bad idea.