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

["Hemant Singh (shemant)" <[e-mail]>]

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.  ND can only specify an ipv6 destination as off-link.   Here is the reason.  The RA sets the A-bit to have hosts use SLAAC for ipv6 address assignment.  The router also sets the L-bit to zero in the RA.   After address assignment the host has an incomplete entry in the Neighbor Cache for a packet destination where the packet destination matches the host address up to 64 bits.  Due to the A-bit set, all addresses within the /64 assigned to the host are on-link.  Does the host issue an address resolution NS because the packet destination is on-link or due to the L-bit cleared in the received RA, the host sends the packet to the default router(s)?  

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.

For multicast behavior in network switches, please see RFC 4541.  Additionally MLD snooping is old and a burden for consumer devices to implement.   New protocol work is needed to mark packets for specific multicast flows so that hosts don't have to snoop MLD. 

Additionally, section 4.6 mentions the avalanche effect.  The ND protocol randomizes and adds jitter when issuing messages to the link precisely to alleviate any avalanche effect.  Thus I am not convinced of the avalanche effect.    May I also know why the wifi nodes in a 100,000 clients link will have not of entries in the Neighbor Cache?  Each client talks to one or two clients at a time.  So what traffic causes the number of entries in a client to be large?  How large is large?

Thanks,

Hemant