Re: Comments on draft-ietf-ipoib-link-multicast-04.txt

Jerry,

I believe you mean that the packet MUST be forwarded to the routers if
they exist using one of all-router MGID or the broadcast-MGID. It at
present could convey the meanning that one SHOULD forward the packet ie.
decide not to forward the packet in some cases. How about rewriting it
along the following lines:


<snip...>
>
> See my response to Roy (sorry for the delay). I'd suggest the following
> paragraph:
>
>    A) An IB multicast group must be explicitly created through the SA
>    before it can be used.
>
>    This implies that in order to send a packet destined for an IP
>    multicast address, the IPoIB implementation must check with the SA on
>    the outbound link first for a "MCMemberRecord" that matches the MGID.
>    If one does exist, the MLID associated with the multicast group is
>    used as the DLID for the packet. Otherwise, it implies no member
>    exists on the local link.  If the scope of the IP multicast group is
>    beyond link-local, and routers exist on the local subnet, the packet
>    SHOULD be forwarded to locally connected IP routers through the use
>    of the all-router multicast group or the broadcast group. This is to



"...Otherwise, it implies no member exists on the local link. If the scope
of the IP multicast packet is beyond link-local, the packet MUST be sent
to the on-link routers to forward using one of (a) MGID mapped from the IP
all-routers group (b) the Broadcast-GID. It is RECOMMENDED that the sender
forward the packet using the MGID derived from the IP all-router multicast
address.

The all-router MGID is created as a result of the router's joining the
all-router IP group. If such a group does not exist then the sender can
assume that there are no routers on the link. Therefore if the sender has
failed to IB_join the all-routers MGID or otherwise determined that the
MGID doesn't exist the sender SHOULD NOT attempt to send the packet on the
broadcast GID. Alternatively, as noted above, a sender MAY choose to
transmit the packet directly on the broadcast-GID without checking the
presence of the all-routers MGID."



Thoughts?


Vivek



>    allow local routers to forward the packet to multicast listeners on
>    remote networks. The all-router multicast group is preferred over the
>    broadcast group for better efficiency


<snip>...


Vivek