Re: 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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----- Original Message ----- 
From: Jayanth Chennamangalam 
To: [email protected] 
Sent: Thursday, February 08, 2007 9:32 PM
Subject: RE: [magma] some questions about RFC4605 -- IGMP/MLD multicast proxy
 
Hi Yu-Jung,

I have given my answers to your questions inline in your mail attached below. Hope you will find it useful.

Regards,

Jayanth Chennamangalam



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From: Yu-Jung Lee [mailto:[email protected]] 
Sent: Thursday, February 08, 2007 5:57 PM
To: [email protected]
Subject: [magma] some questions about RFC4605 -- IGMP/MLD multicast proxy


Hi,

I have a few questions regarding RFC 4605.

(1) In RFC 4605, it defines that a proxy device has a single upstream interface and one or more downstream interfaces. What's the reason for the restriction of only one upstream interface? 
>> If there are more than one upstream port, it would result in upstream looping. For the proxy device to work, the network should be a tree, with the upstream interface pointing towards the root of the tree.

(2) It is said in the RFC that the proxy device MUST NOT perform the router portion of IGMP/MLD on its upstream interface. There's no restriction on performing the host portion of IGMP/MLD on the downstream interfaces. Does that mean it's okay to send out reports which are received from one downstream interface to other downstream interfaces? Wouldn't it cause problems if the hosts attached to downstream interfaces support report suppression? 
>> The reason behind the lack of restriction on performing the host portion of IGMP/MLD proxying on the dowstream is to support querier election. The host functionality does not involve forwarding received MLD Reports. Besides, if the proxy device sends Reports on the downstream, it might lead to Report suppression.

(3) What should the proxy device do except for querier election if it receives MLD query on downstream interfaces? Shuold it send out MLD report on downstream interfaces? (This question is related to (2) though.)
>> If querier election is not implemented, the proxy device should discard the MLD Query received on the downstream interface. Even if querier election is implemented, MLD Reports should not be sent in response to MLD Queries received on the downstream.

It's not clear about the protocol behaviors in RFC 4605 and I'm quite confused. Thanks in advance if anybody have explanations.



BR,
Yu-Jung

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