Re: some questions about RFC4605 -- IGMP/MLD multicast proxy

Hi, Jayanth:

You're right. I see why the proxy device should not forward MLD reports received from one downtream interface to another downstream interface. That's because of report suppression. Now my question is, could a proxy device send out MLD reports on downstream interface if the downstream interface itself is interested in a multicast group?

BR,
Yu-Jung

  ----- Original Message ----- 
  From: Jayanth Chennamangalam 
  To: [email protected] 
  Sent: Friday, February 09, 2007 9:41 PM
  Subject: Re: [magma] some questions about RFC4605 -- IGMP/MLD multicast proxy


  Hi Yu-Jung,

  Consider the following scenarios:

  1. Querier election is implemented: If the proxy device receives an MLD Query on a downstream, it should process it for finding out who the querier should be.

  ---------       ---------
  | Proxy |       | Proxy |
  ---------       ---------
      |               |
      |               |
      -----------------
              |
              |
       Downstream Tree

  2. Querier election is not implemented: If the proxy device receives an MLD Query on a downsream, it should not process it, as it should be the only querier on the network, and no other device should send queries on the downstream tree.

           ---------
           | Proxy |
           ---------
               |
               |
        Downstream Tree

  In both these cases, MLD Reports received on the downstream should not be forwared to any other downstream port, as this is not required for any purpose. Consider the case of an MLD Report from one dowstream interface (Interface 1) being forwarded on another downstream interface (Interface 2). Any host on Interface 2 interested in that particular multicast group will suppress its own MLD Report. So, when the group table is downloaded to the hardware in the proxy device, it will not have Interface 2 in the forwarding entry corresponding to that group. This will result in multicast data not being forwarded to hosts connected to Interface 2.

  MLD Reports are sent by the proxy device only on the upstream.

  Regards,

  Jayanth

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------------------------------------------------------------------------------
  From: Yu-Jung Lee [mailto:[email protected]] 
  Sent: Friday, February 09, 2007 11:02 AM
  To: Jayanth Chennamangalam; [email protected]
  Subject: Re: [magma] some questions about RFC4605 -- IGMP/MLD multicast proxy


  Hi, Jayanth:

  Thanks for your response.
  Regarding the answer about (3), MLD Reports should not be sent in response to MLD Queries received on the downstream. I suppose it means that the proxy device does not forward received MLD reports on downstream interfaces. However, the proxy does send out unsolicited reports on its downstream interfaces whenever the interface itself has multicast address of interest, and also send out solicited reports with group of interest in response to MLD Queries received on the downstream interface. Is it right?


  BR,
  Yu-Jung

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