Re: [Roll] RPLInstanceID parameter from Source Routing Header is missing in RFC6554

Could the answer be: all the instances that have Y in the source route to D?

Thanks
Mukul

----- Original Message -----
From: "Dario Tedeschi" <dat@exegin.com>
To: "Jonathan Hui" <jonhui@cisco.com>
Cc: roll@ietf.org
Sent: Thursday, June 21, 2012 11:05:09 AM
Subject: Re: [Roll] RPLInstanceID parameter from Source Routing Header is missing in RFC6554

Hi Jonathan 

Sorry, for late response to your email. 

Consider the scenario where a DODAG root node supports two or more RPL instances under one prefix. Each instance providing different routing objectives (i.e. different objective functions). Potentially, the source-route to a destination under one instance can be different to the source-route to the same destination under a different instance. For example: Instance 1 could have a source-route R-->X-->Y-->D, while instance 2 could have a source-route R-->X-->Z-->D. Lets say node Y sent a Destination Unreachable ("Error in source-route") back to R, because D was unreachable from Y. How would R know which source-route needed repair and, consequently, which instance needed a DTSN update? 

Regards 
Dario 

On 01/06/2012 7:46 PM, Jonathan Hui wrote: 

I don't understand the need for knowing the RPLInstanceID when handling an ICMP Destination Unreachable error.  The SRH does not follow any RPL Instance, just the IPv6 addresses listed in the SRH.  Receiving an ICMP Destination Unreachable error from a node S simply means that S could not forward to the next IPv6 address in the SRH.  The inability of S to forward to the specified next hop would be true regardless of what RPL Instance the SRH was constructed from. 

-- 
Jonathan Hui 

On Jun 1, 2012, at 7:21 PM, Dario Tedeschi wrote: 

Yes, I noticed this as well. It is unfortunate because as you say, there is now no way to identify which instance a Error in SRH is for, and subsequently the root node can't just remove that routing entry in a specific instance. Instead it must either remove that entry from all instances or do nothing and wait for the next DAO to update the entry. 

Dario 

On 30/05/2012 1:58 AM, Tecuceanu Andreea-Dana-B10623 wrote: 

Hello, 

I have observed that the RPLInstanceID field from Source Routing header (present in  draft-ietf-6man-rpl-routing-header-07) was removed in RFC6554. 

Are there particular reasons for this? This field is necessary at the DODAG Root when it receives a   Destination Unreachable with code "Error in Source Routing Header" to identify the instance with the problem (only if there are two instances with the same prefix and if the node is Root in both of them). 

Andreea Tecuceanu 
(Freescale Semiconductor) 

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