Subject: [Mip4] RFC3024 on multicasting

From: "Bjorn Andersson" <[email-masked]>
Date: Thu, 10 May 2007 14:32:55 +0300

RFC3024 states: "Mobile nodes that wish to send either broadcast or
multicast packets MUST use the Encapsulating Delivery Style." Is this
really a MUST? On point-to-point links the encap delvivery style does
not seem to give any added value. On the contrary it adds unnecessary
overhead.

Also, on links such as ethernet couldn't the MN send the packet with
the unicast FA link address and multicast/broadcast IP address? Or
would this behaviour violate some other specification? I have vague
feeling that some spec says that IP multicast/broadcast packets MUST
use multicast/broadcast L2 addresses, but I am not sure. Is it so?

  Bjorn

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From: "Kent Leung \(kleung\)" <[email-masked]>
Date: Sat, 12 May 2007 14:09:36 -0700

Hi Bjorn.  Comments below.

-----Original Message-----
From: Bjorn Andersson [mailto:[email-masked]] 
Sent: Thursday, May 10, 2007 4:33 AM
To: [email-masked]
Subject: [Mip4] RFC3024 on multicasting

KL> I agree with you that it should not be a MUST from the practical
perspective for p2p links.    

Also, on links such as ethernet couldn't the MN send the packet with the
unicast FA link address and multicast/broadcast IP address? Or would
this behaviour violate some other specification? I have vague feeling
that some spec says that IP multicast/broadcast packets MUST use
multicast/broadcast L2 addresses, but I am not sure. Is it so?

KL> I'm not so clear why MN needs to use multicast/broadcast IP address
of the FA (besides Agent Solicitation)?  MN should learn the FA's
address via Agent Advertisement and use that address for registration
and data packets.  If you are asking the other way around (i.e. FA
sending to MN with broadcast IP address and unicast L2 address), then
there are cases when this happen.

Kent

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From: "Bjorn Andersson" <[email-masked]>
Date: Mon, 14 May 2007 10:10:14 +0300

Should we write an updated reverse tunneling RFC were the encap
delivery for multicast MUST is removed? At least I think there will be
consensus for p2p links. What about other links?

Kent Leung:
> I'm not so clear why MN needs to use multicast/broadcast IP address

I meant that if the MN wants to send a multicast/broadcast packet to
(or via) the home network. The FA could tunnel all broadcast/multicast
to the home network except agent solicitations. Or maybe that's the
reason why encap delivery MUST always be used, so that the FA can
differentiate between multicast packets that are destined for the home
network and the one for the local network? On the other hand the FA
could do this differentiation by looking at the L2 address: if it is
the FA L2 address tunnel the packet to the home network, else do
nothing. Perhaps there are some problems with this that I am not aware
of or come to think of?

  Bjorn