Re: Comments on draft-yourtchenko-colitti-nd-reduce-multicast

[Erik Nordmark <[e-mail]>]

On 2/21/14 6:03 AM, Hemant Singh (shemant) wrote:
> ErikN has commented on section 4.7.   I have additional comments.   ND as defined in RFC 4861 has no means to specify a prefix as off-link.  Thus the L-bit equals zero is not a valid means to signal an off-link prefix to SLAAC hosts.
It is correct that L=0 doesn't mean anything. For instance, if a prefix 
P1 has been advertised in a PIO with L=1 and later the host receives a 
PIO with P1 and L=0, that doesn't change anything. (But section 6.2.7 in 
RFC 4861 would flag it if routers advertise the same prefix that way - 
Oops - 6.2.7 doesn't explicitly list the PIO flags which I think is an 
omission.)

However, ND does indicate that prefixes are off link. That is done by 
never advertising them, or only advertising them with L=0. That can be 
overridden by having individual IPv6 addresses be considered on-link 
through a redirection where target==destination.
> The only means in ND to specify all destinations as off-link is to have the RA include no PIO and have the A-bit cleared.   The hosts use DHCPv6 for address assignment.   This is the NBMA ND link model.  The router also supports a DAD Proxy.
That isn't correct. PIO with L=0 works. SLAAC can be used even if L=0 - 
the case when L=0 and A=1.

Regards,
    Erik