Subject: [nemo] Section 8 comment in IESG review

From: "Soliman Hesham" <[email-masked]>
Date: Wed, 31 Mar 2004 20:32:11 -0500

I saw Steve Bellovin's comment on this section below.
Since I've been wanting to raise the same point, I have 
a short comment.

8:      This text is unclear:

           When the Mobile Router and the Home Agent exchange routes
           through a dynamic routing protocol, the Mobile Router
           should be careful in including the same Mobile Network
           Prefixes in the Binding Update to the Home Agent and in
           the routing protocol updates.  The Home Agent depending
           on its configuration might not add routes based on the
           prefix information in the Binding Updates at all, and
           might use only the routing protocol updates.  Moreover,
           including the same prefix information in both the Binding
           Update and the routing protocol update is redundant.

        Do you mean "be careful to include the same information in
        both places" -- redunancy is sometimes good.  Or do you
        mean "be careful to avoid doing this"?  Personally, I think
        the former is more appropriate, because it allows a check
        on the validity of the routing information.  Note that the
        prefixes announced via binding updates are checked for
        authorization; routing data generally is not.  I would thus
        suggest that routing advertisements MUST NOT contain any
        prefixes not known to the home agent by either implicit
        mode configuration or explicit mode announcement.

=> Basically I think we need to make sure that the HA
checks the routing information exchanged and matches it 
against the prefix information that it already knows from
the MNP table/manual config/BCEs ..etc to make sure that
MRs are authorised to advertise such prefix(es). 
So we need tight coupling between the routing protocol
content and the content in the BU/manual config.
Otherwise Bad Guy could send a vaild BU and start announcing
someone else's prefix. 

Note that in many cases today IGPs are authenticated with
a single "domain key". To maintain this type of security
we need to verify that the MRs are authorised to advertise
reachability to the prefixes in question. 

I think a text change for this section will suffice.

Hesham

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