Re: [magma] Version of General Query sent by a V3 Querier in thepresence of lower version hosts

[Brian Haberman <brian at innovationslab.net>]

Suvendu,
      An IGMPv3 router can still send IGMPv3 formatted General Query 
messages.  The extended size Query should be handled by older IGMP hosts 
since they will only parse as much of the message as they recognize. 
Please take a look at section 2.5 of RFC 2236 (IGMPv2) for the exact 
text description of forward compatibility in IGMP.

Regards,
Brian


Suvendu Mozumdar wrote:
> Thanks for the reply Ashish, but the section talks about the group 
> compatibility mode, but does not say anything regarding what should be 
> the version of the general queries sent. The compatibility mode is kept 
> per group, but what should be the compatibility mode of the general 
> queries which is not related to any particular group, this is not 
> mentioned clearly.
> 
>  
> 
> Regards,
> 
> Suvendu.
> 
> ------------------------------------------------------------------------
> 
> *From:* Ashish Yadav [mailto:Ashish.Yadav at conexant.com]
> *Sent:* Monday, March 24, 2008 3:00 PM
> *To:* Suvendu Mozumdar; magma at ietf.org
> *Cc:* Rhitwick Mookherjee
> *Subject:* RE: [magma] Version of General Query sent by a V3 Querier in 
> thepresence of lower version hosts
> 
>  
> 
> Hi,
> 
>  
> 
> The querier should send version 1 queries, as mentioned in the section 
> 7.3.2 of RFC 3376.
> 
> “IGMPv3 routers may be placed on a network where there are hosts that
> 
>    have not yet been upgraded to IGMPv3.  In order to be compatible with
> 
>    older version hosts, IGMPv3 routers MUST operate in version 1 and
> 
>    version 2 compatibility modes. 
> 
>    IGMPv3 routers keep a compatibility mode per group record.  
> 
>    A group's compatibility mode is determined
> 
>    from the Group Compatibility Mode variable which can be in one of
> 
>    three states:  IGMPv1, IGMPv2 or IGMPv3.  This variable is kept per
> 
>    group record and is dependent on the version of Membership Reports
> 
>    heard for that group as well as the Older Version Host Present timer
> 
>    for the group.
> 
> ”
> 
> Regards,
> 
> Ashish
> 
> =================================================================================================
> 
> Don't complain about others; Change yourself if you want peace. It is 
> easier to protect your feet with slippers than to cover the entire earth 
> with carpet.
> 
> ------------------------------------------------------------------------
> 
> *From:* magma-bounces at ietf.org [mailto:magma-bounces at ietf.org] *On 
> Behalf Of *Suvendu Mozumdar
> *Sent:* Monday, March 24, 2008 2:25 PM
> *To:* magma at ietf.org
> *Cc:* Rhitwick Mookherjee
> *Subject:* [magma] Version of General Query sent by a V3 Querier in 
> thepresence of lower version hosts
> 
>  
> 
> Hi
> 
>    I have this following doubt for which RFC 3376 has no clear 
> directive. In a LAN there is a v3 querier and three hosts each of 
> version 1, 2 and 3 respectively. What should be the version of the 
> general queries sent by the querier, will it send v1 queries, v2 queries 
> or v3 queries?? Logically thinking it should send queries with the 
> lowest version present in the LAN. Please advise.
> 
>  
> 
> Regards,
> 
> Suvendu.
> 
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