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

["Dijk, Esko" <[e-mail]>]

> I asked a question, how does a node know if it should forward/rebroadcast a packet in an identified MPL domain.

Ah, ok. Maybe both question and answer become easier once we have an update of the I-D text? My simple view is:
For 'node' being an MPL forwarder, there's no decision to make: it will anyway forward packets (with the MPL Option) on the same interface at which it was received, following the MPL protocol. Only a single MPL domain is assigned to any one network interface (assumption).

If an MPL forwarder wants to send/forward to other interfaces and/or into other MPL domains it knows, that's possible - but needs to be explicitly configured/implemented on the forwarder. MPL states a forwarder MAY do this.

> ...how, when the MPL domain is less than the LLN, the packets are pruned to just the MPL domain.
The pruning happens automatically if there is only one MPL domain configured within an LLN.
Specifically, the non-MPL-forwarders that are inside the LLN but outside the MPL domain won't forward the packets by definition.

For other cases (i.e. 2 or more MPL domains within the subnet) I have the same question as you - it seems impossible to do the 'pruning' correctly based on the current MPL -02 text, for unencapsulated multicast packets at least.

Esko

-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf Of Michael Richardson
Sent: Friday 14 December 2012 3:36
To: [e-mail]
Cc: Dijk, Esko; [e-mail]
Subject: Re: [Roll] [roll] #105: trickle-mcast: how to determine scope of MPL domain


Dijk, I do not feel that you understood the question.

>>>>> "Dijk," == Dijk, Esko <[e-mail]> writes:
    Dijk> Just to check our current understanding of scope:

    >> How does a node determine what the scope of the MPL domain?

    Dijk> From the I-D -02, it is "multicast scope of the IPv6
    Dijk> Destination Address of an MPL multicast packet". So it can be
    Dijk> derived from the mcast address(es) that MPL uses which are
    Dijk> defined in application code or in a config file or so.

You answered the question:
    "how does a node determine the MPL domain of a multicast packet"

I asked a question, how does a node know if it should forward/rebroadcast a packet in an identified MPL domain.

    >> Is this an intrinsic (provisioned) property of a node?

    Dijk> - if encapsulation is used, I expect the outer IP address is
    Dijk> configured in the node (e.g. FF05::MPL)


    Dijk> - if encapsulation is not used, the IP address where to send
    Dijk> to or to receive on would be set by the application code
    Dijk> i.e. it's also configured on the node (e.g. FF05::1234)


I do not feel that I have a good understanding of how, when the MPL domain is less than the LLN, how the packets are pruned to just the MPL domain.


--
Michael Richardson <[e-mail]>, Sandelman Software Works
IETF ROLL WG co-chair.    http://datatracker.ietf.org/wg/roll/charter/


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