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Re: [Roll] [roll] #105: trickle-mcast: how to determine scope of MPL domain

"Jonathan Hui (johui)" <johui@cisco.com> Thu, 01 November 2012 18:54 UTC

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From: "Jonathan Hui (johui)" <johui@cisco.com>
To: Michael Richardson <mcr+ietf@sandelman.ca>
Thread-Topic: [roll] #105: trickle-mcast: how to determine scope of MPL domain
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Date: Thu, 01 Nov 2012 18:54:47 +0000
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Subject: Re: [Roll] [roll] #105: trickle-mcast: how to determine scope of MPL domain
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On Nov 1, 2012, at 10:10 AM, Michael Richardson <mcr+ietf@sandelman.ca> wrote:

> Is there a reason to encapsulate other than the Path MTU discovery issue?
> I think it has to do with getting the packet to the seed, but I'm
> unclear on this.

The other reason to encapsulate is for clean removal of the MPL Option.  Removing the MPL Option would be fairly straightforward if that were the only IPv6 Option contained in an IPv6 Hop-by-Hop Option header.  But things get a bit hairy when other IPv6 Options exist.

> Am I understranding correctly: if the packet originates in the LLN from
> an MPL aware node, then encapsulation is not necessary: the originator
> knows about the Hop-by-Hop option, and takes that into account for Path
> MTU calculations.
> 
> Is this Peter's concern?


Peter's primary concern is to eliminate any header overhead caused by encapsulation.  But you are correct that a MPL-aware node can take the MPL Option into account in Path MTU calculations.

--
Jonathan Hui

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