RE: [Autoconf] Multicast confusion between MANET Arch and AUTOCONFProblem Statement

Hi Alex, 

> -----Original Message-----
> From: Alexandru Petrescu [mailto:alexandru.petrescu@gmail.com] 
> Sent: dinsdag 20 november 2007 16:20
> To: autoconf@ietf.org
> Subject: [Autoconf] Multicast confusion between MANET Arch 
> and AUTOCONFProblem Statement
> 
> I think there may be a confusion with respect to the 
> interpretation of multicast in 
> draft-ietf-autoconf-manetarch-07.txt vs 
> draft-ietf-autoconf-statement-02.txt.
> 
> It seems as if the manetarch accepts that link-layers have a 
> well defined multicast behaviour whereas the problem 
> statement doesn't.
> 
> autoconf-statement:
> > Traditional solutions assume that a broadcast directly 
> reaches every 
> > router or host on the subnetwork, whereas this generally is not the 
> > case in MANETs (see [2]).
> 
> So a broadcasted message (a special case of multicast) will 
> not reach every host on the MANET subnet.

"link" versus "subnetwork" are distinct notions, aren't they? What is
left of a "subnetwork" in an environment where \128 (\32 for IPv4)
prefixes are configured on MANET interfaces? If your local interface is
the only one in the subnet, then all interfaces in the subnet are
trivially reachable :-) "Link" is something else...

> 
> [2] autoconf-manetarch:
> > Link-local Multicast/Broadcast Scope On a MANET interface, a packet 
> > sent to a link-local multicast or all-ones broadcast 
> address reaches 
> > the MANET interfaces of neighboring MANET routers...
> 
> So it actually does.
>

No, not all interfaces of all MANET routers. Just those of the
*neighbo(u)ring* MANET routers. See MANET architecture for a definition
of neighbo(u)r.

> I personally think that the autoconf-manetarch definition is 
> more inline with how I see relationships between link-layer 
> multicast and IP multicast.
> 
> Or maybe we could define 'subnet' to be a set of hosts and 
> routers linked together by the same link-layer technology 
> where a multicast behaviour is well defined.  Or similar?
> 
> What do you think?
> 
> Alex

Just my 2 cents,
Ronald

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