Re: [Roll] Error flows, which ICMP errors and to which root

["Huimin She (hushe)" <[e-mail]>]

Hi Pascal,

RFC 6550 section 11.1 says the ICMPv6 error in SRH should be sent to the source of the packet.

Best regards,
Huimin

    Message: 2
    Date: Fri, 27 Nov 2020 07:47:22 +0000
    From: "Pascal Thubert (pthubert)" <[e-mail]>
    To: Routing Over Low power and Lossy networks <[e-mail]>
    Subject: [Roll] Error flows, which ICMP errors and to which root?:
    	[extends] IETF 109 open Questions on P-DAO
    Message-ID:
    	<[e-mail]>

    Content-Type: text/plain; charset="us-ascii"

    Hello Li

    This is the wrong thread. I created a new one.

    > Section 7.9 of pdao-draft defines a new code for  ICMPv6 error message "Error in Projected Route". Does it only work for ICMP errors sent to the main Root?

    Section 5 says "


       In case of a forwarding error along a Projected Route, an ICMP error

       is sent to the Root with a new Code "Error in Projected Route" (See

       Section 7.9<https://tools.ietf.org/html/draft-ietf-roll-dao-projection-14#section-7.9>).  The Root can then modify or remove the Projected

       Route.  The "Error in Projected Route" message has the same format as

       the "Destination Unreachable Message", as specified in RFC 4443<https://tools.ietf.org/html/rfc4443>

       [RFC4443<https://tools.ietf.org/html/rfc4443>].

    "

    So yes the intention was to send the ICMP to the main Root. But as you point out the packet does not indicate it is following a P-route. This was related to storing mode P DAO. In non-storing the node does not know it's a P-route.


    > In non-storing PDAO, forwarder can't recognize whether data packet is in PDAO instance. Forwarder should send ICMP Destination Unreachable error to root (the source of the packet), then root generates ICMPv6 error message with "Error in Projected Route" to main Root.  Is it correct?

    That would work. Seems neat. The alternate would be to signal it is a P route in the RPI. That's item 2) in the list in this thread. If we do that the current text works. What makes more sense to you?

    > In storing PDAO, forwarder can recognize the PDAO instance from the RPI. It can send "Error in Projected Route" or  "Destination Unreachable error" to root. Maybe we need more claims for which code forwarder should use.

    We have to decide if we send it to the main root as written in the current draft or to the Track Root. If the P route is reversible could be done that way. But that's added complexity. I'm not very convinced either way. The Okham razor could be to do the simplest.

    Keep safe!

    Pascal