RE: How to distinct the V2 and V3 IGMP query for asnoopingswitch?

i.e In case of IGMP, the length is taken from length in IP header. It
does not matter if the Ethernet frame includes padding. In case of
IGMP/IP frames Ethernet length/type is type.

Warm Regards,
Ashish

-----Original Message-----
From: Ashish Yadav [mailto:[email protected]] 
Sent: Wednesday, January 10, 2007 10:49 AM
To: [email protected]; [email protected]
Cc: [email protected]
Subject: RE: [MAGMA]How to distinct the V2 and V3 IGMP query for
asnoopingswitch?

In my view, IP does not include the padding of Ethernet in the length.

Warm Regards,
Ashish

-----Original Message-----
From: [email protected] [mailto:[email protected]] 
Sent: Tuesday, January 09, 2007 7:39 PM
To: [email protected]
Cc: [email protected]
Subject: Re: [MAGMA]How to distinct the V2 and V3 IGMP query for a
snoopingswitch?

> According to the 7.1 of RFC3376 (IGMP V3)
> 7.1. Query Version Distinctions
>   The IGMP version of a Membership Query message is determined as
>   follows:
>      IGMPv1 Query: length = 8 octets AND Max Resp Code field is zero
>      IGMPv2 Query: length = 8 octets AND Max Resp Code field is
>                    non-zero
>      IGMPv3 Query: length >= 12 octets
> I have a question about that. For Ethernet the IGMP V2 Query is 
> always encapsulated in a 64 bytes packet.  da+sa+tpid+ip header+IGMP
> query+padding+fcs=64 bytes,that means after 8 bytes Query fields,there

> are some padding "zeros".For this packet the TOTAL LENGTH filed of IP 
> header is 46.  So it seems that it's impossible for a snooping 
> switch to tell the IGMP QUERY 
> version from the IP header length. ...

In my experience, the length in the Ethernet header does not include the
padding bytes but I've found conflicting documentation on the web.

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