Subject: [mobile-ip] FA vs COA

From: Sivasundar Ramamurthy <[email-masked]>
Date: Thu, 11 Apr 2002 17:29:45 -0700 (PDT)

Hello,

I have a couple simple questions wrt to registration via with
co-located COA (R bit in advertisement).

1. If they share a SA, MUST the FA and HA include the FA-HA auth ext
when exchanging control packets? 

2. Can the FA request a HA-FA key if it does not have a SA with
the HA, even though it is not the COA?

thanks,

Siva

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From: "Kevin Purser" <[email-masked]>
Date: Fri, 12 Apr 2002 11:46:32 -0700

Hello All,

A few questions regarding the use of the 'R' bit with a mobile node using a
co-located CoA:

Section 2.1.1 states:

"   R        Registration required.  Registration with this foreign
               agent (or another foreign agent on this link) is required
               even when using a co-located care-of address."

 and section 2.4.1 states:

"   When the mobile node receives an Agent Advertisement with the 'R' bit
   set, the mobile node SHOULD register through the foreign agent, even
   when the mobile node might be able to acquire its own co-located
   care-of address.  This feature is intended to allow sites to enforce
   visiting policies (such as accounting) which require exchanges of
   authorization.

   If formerly reserved bits require some kind of monitoring/enforcement
   at the foreign link, foreign agents implementing the new
   specification for the formerly reserved bits can set the 'R' bit.
   This has the effect of forcing the mobile node to register through
   the foreign agent, so the foreign agent could then monitor/enforce
   the policy."

This brings up the following question:  If a mobile has obtained a
co-located CoA, and wishes to register through a FA who has set the 'R' bit
in his agent advertisement, does the MN have to relinquish the co-located
CoA (and instead use the FA as the CoA)?  At first read, it would appear as
though this is *not* necessary, which has brought up the following
questions:

Since we are using a co-located CoA (but still through a FA), is the FA-HA
authentication extenstion used, and if so, how, since the MN is the endpoint
of the MIP tunnel?  Or is it that we actually end up with IP-in-IP-in-IP
between the HA and FA, then IP-in-IP between the FA and MN, and the MN does
the final decapsulation?  (hope this question makes sense... :)

Thanks,
Kev & Tony