Subject: Device to GGSN as point to point (was: MLD comments on cellular h ost drafts - seeking feedback)

From: Craig Dunk <[email-masked]>
Date: Fri, 24 May 2002 16:56:28 -0400

Someone may need to correct this, but, 

I think the misunderstanding comes from the nature of the link between the
mobile and the GGSN. Conceptually it is more like the device making a phone
call to the ggsn: it doesn't matter how many phone switches are between the
endpoints, they don't come into play in the packet forwarding, only the GGSN
does. However, in this case the "phone calls" are called pdp contexts and
pass through the SGSN.

In that case I think the answer to your question about scope is that the
addresses of the SGSN can be any scope, but they are conceptually below the
point to point relationship that exists between the device and GGSN. 

Craig.

-----Original Message-----
From: Dr. Subrata Goswami [mailto:[email-masked]]
Sent: May 24, 2002 2:58 PM
To: [email-masked]
Subject: RE: MLD comments on cellular host drafts - seeking feedback

I do not think we can ignore the rest of the network. The SGSN needs a 
mechanism to populate its forwarding table with mcast addresses - 
that is where MLD snooping comes in. 

Is the following a good representation of a cellular network ?

        IPL1               IPR1
Mobile 1--------(SGSN)------\
                            (GGSN)-->
Mobile 2--------(SGSN)------/
        IPL2               IPR2

I am saying IPR1 = IPR2 , hence IPL1, IPL2, IPR1 all are on the same
link as SGSN are L2 devices. So if Mobile 1 subscribes to a link-local 
group and so does Mobile 2, then we need mcast forwarding between 
them. Next question would be what are IPL1, IPL2, and IPRx - global,
site-scope,link-local unicat addresses ?

Subrata.
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