[c-nsp] MLD snooping

[Multicast maillist]

As per RFC 4541 (Considerations for Internet Group Management Protocol
(IGMP)and Multicast Listener Discovery (MLD) Snooping Switches), it is
inferred that forwarding criteria for all multicast IPv6 address (except
ff02::1) is always based on group database as MLD is mandated for all the
multicast v6 address.

As per this, there is no special consideration for solicited multicast
addresses or multicast addresses used for protocol control traffic.

I feel this could cause issues in protocol adjacency maintenance or DAD
process.

Below is the link discussing about CISCO mld snooping breaking DAD
functionality.

http://networking.itags.org/networking-tech/148011/

OSPFv3 adjacency could break if MLD snooping is enabled on a L2 switch
between two OSPFv3 neighbors. (If the enable configuration happens just
after a MLD query in the network, It would take another 120+ seconds to get
the MLD report for FF02::5. OSPFv3 hello packets will not be forwarded by
the MLD snooping enabled switch till report for FF02::5 is received and
adjacency will break).

There was a draft draft-pashby-magma-simplify-mld-snooping-01.txt stating
that multicast traffic for solicited addresses and control packet reserved
addresses should be forwarded to all ports. But that draft was not taken
forward and has expired.

Shouldn’t the MLD snooping enabled switch forward the traffic for solicited
multicast address and protocol control packets to all the ports of VLAN?


Regards,

Magna.