Hemant, On 8/17/10 11:37 AM, Hemant Singh (shemant) wrote: > -----Original Message----- > From: Brian Haberman [mailto:br...@innovationslab.net] > Sent: Tuesday, August 17, 2010 8:59 AM > To: Ole Troan > Cc: Hemant Singh (shemant); Sri Gundavelli (sgundave); Suresh Krishnan; > IPv6 WG Mailing List > Subject: Re: Consensus call on > adopting:draft-krishnan-6man-rs-mark-06.txt > > >> Correct. The MLD snooping functionality only looks at L3 information > if >> the L2 destination address is a multicast address. In this case, L2 > has >> a unicast address and the MLD snooping function will never see the >> packet (it will be forwarded using standard L2 logic).
I do not grok this scenario. Let me see if I can understand what you are concerned about. > > Brian, I changed the subject back to the Gundavelli document. I am > saying a host sent an MLDv2 Report to a router. There is no network > switch between this host and the router. Now with the rule in the > Gundavelli document, the host sent the MLDv2 Report with the L3 > multicast destination but L2 unicast destination. The L2 sniffer on the > router fails to capture this packet and fails to forward the packet to > its ULP (Upper Layer Protocol) for multicast. So now the packet is > shipped to the unicast ULP. Why can't the unicast ULP barf that it > received a packet with a L3 destination when it's a unicast ULP? Why > shouldn't we test such a case with a router and a host sending such a > doctored MLDv2 Report? One should use more than one router to test such > a case. Or am I missing something - if yes, my humble apologies. A host generates an MLDv2 Report message that expresses interest in receiving multicast traffic on group X. The destination address in the IPv6 header will be the All-MLDv2-Routers address (FF02::16). However, the Gundavelli draft allows the node to set the destination L2 address to a unicast address of the only router on the link. The host transmits this message. Now, what I see you arguing above is that the router will receive this message, but may try and pass it to a *different* ULP. I think we agree that the router will receive the packet since it is addressed to one of its L2 addresses. Now, when it is parsing this message I don't see how the L2 destination address will have any impact on which protocol this message is handed to. All the routing platforms I am familiar with follow a coarse (and high-level) logic like: 1. Verify L2 validity (e.g., checksum) 2. Pass packet to protocol handler based on e.g., ethertype 3. For IPv6, parse Next Header field 4. Process MLDv2 Report So, I can't see a scenario where the L2 destination address interferes with the proper handling of the L3 information. Regards, Brian -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
