Re: [Roll] [roll] #128: Trickle multicast could be considered in other applications?

[Michael Richardson <[e-mail]>]

{answering some old emails, and trying to bring about some consensus to
close this ticket} 

>>>>> "lynn" == roll issue tracker <[e-mail]> writes:
    lynn>  Apart from the fact that this draft is introduced in ROLL to
    lynn> address a problem inherent in multi-link subnets, I see
    lynn> nothing in the proposal that limits it to such networks.  It
    lynn> seems to me that trickle multicast could be considered in
    lynn> other applications, e.g. homenet, if it compares favorably
    lynn> with PIM-xM in complexity.

I agree that it could be used elsewhere, and I think it's important to
remember that it's going to run over all sorts of media, as ROLL runs
over all sorts of links.

    adrian>  From Adrian Farrel about section 3 Applicability Statement

    adrian>  - can this be run over a wired (non-lossy, non-constrained
    adrian> environment) - should this be contained at the LBR,  

Yes, it can be gatewayed at the LBR, the because the LBR is the edge of
the LLN, not necessarily the edge of the DODAG.    The DODAG may be
extended across one or more wired segments to link(*) different parts of
the LLN together. 

(*) (I wrote "bridge" initially, and that's meaningful in a colloquial
    term, but I don't want to confuse people into thinking it's related
    to 802 concepts)
	
    adrian> and if
    adrian> so, can mcast traffic be gatewayed into the Internet

define "Internet" :-)
If you are asking if it can escape into an ISP uplink due to
misconfiguration of scope-3 interfaces, yes it could do that.  
At which point, it would face non-MPL routers, and traffic would die.
I can see a potential risk on cable networks where it some combination
of misconfigured home gateways might permit MPL traffic from one home to
enter another home's network. 

If you are asking if mcast traffic could be gatewayed into the PIM
multicast space, I supposed with the emission of the right IGMPs onto
the link with the PIM routers, and then decapsulation/encapsulation of
the packets, such a thing could occur. I don't see it as desireable.
The inner packets are expected to scope-2 (link) packets, so really, no 
compliant PIM router would do anything with them.

Are you asking for some Security Considerations here?

    adrian> - can
    adrian> MPL operate in a mixed environment where not all routers are
    adrian> MPL capable?  

No, I don't think so.  Non-MPL routers will not forward things.

    adrian> - do the hosts need to be in any way aware
    adrian> that their mcast is supported by MPL?

At some point the answer has been yes and at other points it has been
no, and I guess I have to back to the document to remember what we
concluded.

-- 
Michael Richardson
-on the road-