Subject: Re: [magma] Multicast Group Membership Discovery MIB questions

From: Julian Chesterfield <[email-masked]>
Date: Sun, 31 Jul 2005 12:41:42 -0400

Apologies for the delay in replying, many thanks for your feedback. 
I'll go over some of the points everyone has made so I can clarify the 
situation:

1. The hostInterface table should also provide a robustness value 
applicable to the state-change reports in IGMPv3, but does not apply to 
v2 or v1. This should probably be a writeable object (?).

2. mgmdRouterInterfaceQueryInterval, 
mgmdRouterInterfaceQueryMaxResponseTime, and 
mgmdRouterInterfaceLastMembQueryIntvl need to have max values adjusted 
to reflect floating point calculations

3. mgmdRouterCacheExpireTime should represent the Group Membership 
Interval state in the router, not an indication of the filter time => 
needs clarification in the text.

4. A source expiry timer needs to be added to the Srclist entries to 
indicate when a source include entry is to expire. Value >0 means entry 
is include mode, value == 0 means entry in exclude mode. Similarly need 
to remove the SourceFilterMode value from cache table to allow for 
mixed table of exclude and include entries.

5. Values for  last-member-query-count (default robustness variable), 
startup-query-count (default robustness variable) and 
startup-query-interval (default 1/4 the query interval) should be added 
to the RouterInterface table.

6. Host compatibility mode variable for hostinterface table and for 
routercache table should be added.

Please let me know if any of these points are incorrect, or if I've 
missed any of the requests.

Thanks!
Julian

On 28 Jul 2005, at 01:10, kishore P wrote:

> Hi Karl,
>
> Regarding the group timer, it is right to say it is being used as the 
> filter timer ( RFC explaination) to change from exclude mode to 
> include mode. It was a misnomer in my explanation to place group timer 
> for the mgmdRouterCacheExpiryTime, instead a seperate timer is 
> maintained (for sake, call it) groupExpiryTimer which is updated using 
> Group Membership Interval (GMI), it is set whenever membership report 
> is received, and also reset to small value (last member query 
> interval) when sending  group-specific messages to find out any 
> interested hosts on the network. This is the parameter that needs to 
> be associated with the mgmdRouterCacheExpiryTime.
>
> May be it is right to add the filterTimer too to the 
> mgmdRouterCacheTable so that this info can be viewed by the user to 
> know when the filter mode would change from exlude to include. This is 
> valid for routers that are configured as IGMPv3 or MLDv2.
>
> Rgds,
> Kishore
>
>
>
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---

From: Karl Schmidt <[email-masked]>
Date: Mon, 1 Aug 2005 11:13:25 -0500

Hi Julian,

Thanks for the response and the summary looks good to me. I have a few 
comments on a couple of the points.

1. In point 1 (host robustness) the robustness should be writeable. Host 
robustness can be learned but I don't think this addressed in the IGMPv3 
spec. Even if learning occurs, the robustness needs to be set to a value 
used until the first IGMPv3 query is received.

2. In point 3 (router cache exp time) I think you are stating that the 
expire time is the highest expiration time for the group timer and any 
source timers. I like this, but would also request an additional object 
representing the group timer so that the time left in exclude mode is 
known. I guess we could call this the exclude mode timer which would only 
be applicable for IGMPv3 and MLDv2.

3. In point 4 (router source list) you suggest removing the cache 
SourceFilterMode object. If I understand what you are saying about the 
router cache expire time the router cache should live even if the group is 
in include mode. This is what I would prefer. If this is the case, the 
SourceFilterMode is very important to have around but the description 
needs to be changed to not imply what entries should be in the source 
list.

Regards,
Karl

Julian Chesterfield <[email-masked]> 
Sent by: [email-masked]
07/31/2005 11:41 AM

To
"kishore P" <[email-masked]>
cc
[email-masked]
Subject
Re: [magma] Multicast Group Membership Discovery MIB questions

Thanks!
Julian