Subject: [nemo] draft-wakikawa-nemo-v4tunnel-01.txt

From: Brian Haley <[email-masked]>
Date: Tue, 08 Mar 2005 15:37:14 -0500

Hi Ryuji,

Comment about the v4tunnel draft.

In Section 4.3, second paragraph:

   "If the Home Agent that receives the Binding Update is a legacy Mobile
    IPv6 Home Agent and does not understand the new IPv4 Care-of Address
    option, it ignores the Binding Update."

But Section 6.2.1 of RFC 3775 says:

   "Implementations MUST silently ignore any mobility options that they
    do not understand."

So a legacy HA will ignore the option, but treat the BU as a de-reg as 
stated later in that paragraph, right?

I guess it's not that important as anyone deploying a MR that supports 
v4 tunnels will certainly update the HA as well.

-Brian

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From: Ryuji Wakikawa <[email-masked]>
Date: Wed, 9 Mar 2005 22:47:14 +0900

Hello Brian

Thanks for comments. You observation is right.

However, this case is rarely happened.
Before sending BU with IPv4 CoA sub-opt, MN must have IPv4 address of 
HA and establish SA (IPv4) with HA.
If HA can not process the new sub-option, it is likely misconfiguration.
In addition, MN can know this misconfiguration due to lack of BA.

What MN can do after the absence of BA is
1. MN tries to get v6 CoA by the use of general v4 traversal mechanism
2. MN gives up due to no IPv6 address.

regards,
ryuji