Subject: [Mip4] Doubts in RFC 3344

From: "K V Pradap-a22072" <[email-masked]>
Date: Tue, 16 Jan 2007 22:13:25 +0800

Hi All
I have got few questions that I have listed below with regard to MIPv4
as specified in RFC 3344

 
Question-1) In the case of Dynamic Home Agent Address Resolution as
described in RFC 3344, the mobile node does not know the address of Home
Agent and thus send a Registration Request as specified in Sec 3.6.1.1 ,
3.6.1.2 . 
 
sec 3.6.1.1
" If the mobile node is registering directly with its home agent,

         but does not know the IP address of its home agent, the mobile

         node may use dynamic home agent address resolution to

         automatically determine the IP address of its home agent

         (Section 3.6.1.2)"

sec 3.6.1.2

"

   The Home Agent field MUST be set to the address of the mobile node's

   home agent, if the mobile node knows this address.  Otherwise, the

   mobile node MAY use dynamic home agent address resolution to learn

   the address of its home agent."

sec 3.2

"

   Registration messages between

   a mobile node and its home agent MUST be authenticated with an

   authorization-enabling extension, e.g. the Mobile-Home Authentication

   Extension (Section 3.5.2).  

"

sec 3.5.2

"

The Mobile-Home Authentication Extension is

always an authorization-enabling for registration messages specified

in this document

"

What should be the authorization enabling extension should the message
be protected with, as here Mobile Node -Home Agent Authentication
Extension cannot be used as MN does not know its Home Agent?
 
Question-2)If the Mobile Node has the Key for HA, but HA does not have
the key of MN, can the HA get the Keys of MN by some other means.  as
sec 3.5.2 specifies
"Exactly one authorization-enabling extension MUST be present in all

   Registration Requests, and also in all Registration Replies generated

   by the Home Agent.  The Mobile-Home Authentication Extension is

   always an authorization-enabling for registration messages specified

    in this document"
Is there a way for HA to get the MSA dynamically from the AAA? I
understand that 3957 is way to do this,  I also understand that 4004
gives a Diameter based approach to the whole thing. But in this case,
where MN sends MN-HA auth ext, is there a way for HA to just lookup the
MSA from the AAA?
 
Question-3)if HA doesn't support simultaneous binding, for every
"accepted" registration , HA will send Registration reply with code set
to 1. if MN moves to new FA, and sends a Registration Request with "S"
bit set what should be the behavior of HA. 
        - Whether it should keep earlier binding and disallow the new
RRQ or
        - Delete the earlier binding and allow the new RRQ.
   as sec 3.8.2 specifies
"
3.8.2.2:

"
If the Lifetime is nonzero, the home agent adds an entry containing the
requested Care-of Address to the mobility binding list for the mobile
node. If the 'S' bit is set and the home agent supports simultaneous
mobility bindings, the previous mobility binding entries are retained.
Otherwise, the home agent removes all previous entries in the mobility
binding list for the mobile node.
"
But this does not specify what should the HA do if the S bit is set & HA
does not support the simultaneous bindings.
 
Question-4)In the case of non-co located Mobile Nodes requesting a copy
of Broadcast datagrams by setting B bit in Registration Request.  Does
HA while transmitting the broadcast datagrams, encapsulate inner and
outer datagrams with same mode (say, GRE or IP-IP)?
sec 3.6.1.2 specifies
"
         If the 'D' bit is NOT set, then the mobile node has indicated

         that it is using a foreign agent care-of address, and that the

         foreign agent will thus decapsulate arriving datagrams before

         forwarding them to the mobile node.  In this case, to forward

         such a received broadcast datagram to the mobile node, the home

         agent MUST first encapsulate the broadcast datagram in a

         unicast datagram addressed to the mobile node's home address,

         and then MUST tunnel this resulting datagram to the mobile

         node's care-of address.

         When decapsulated by the foreign agent, the inner datagram will

         thus be a unicast IP datagram addressed to the mobile node,

         identifying to the foreign agent the intended destination of

         the encapsulated broadcast datagram, and will be delivered to

         the mobile node in the same way as any tunneled datagram

         arriving for the mobile node.  The foreign agent MUST NOT

         decapsulate the encapsulated broadcast datagram and MUST NOT

         use a local network broadcast to transmit it to the mobile

         node.  The mobile node thus MUST decapsulate the encapsulated

         broadcast datagram itself, and thus MUST NOT set the 'B' bit in

         its Registration Request in this case unless it is capable of

         decapsulating datagrams.

"
Normally, if an MN uses FA CoA as tunneling end-point, it does not
matter what decapsulation capability the MN has. But in this case, looks
like, a decapsulation is being forced upon it & hence the capability
matters. 
 
Question-5) How does multi-homed mobiles register with the HA? Do they
use one CoA? or multiple CoAs? Do they acquire multiple HoAs?

I would be appreciable, if you can provide clarifications or references
to discussions(if any ) for the above mentioned issues.
 
Thanks and Regards
Pradap
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---

From: [email-masked]
Date: Tue, 16 Jan 2007 16:00:08 +0100

See inline my 2 cents for question 1)

K V Pradap-a22072 wrote:
> described in RFC 3344, the mobile node does not know the address of 
> Home Agent and thus send a Registration Request as specified in Sec 
> 3.6.1.1 , 3.6.1.2 .
>  
> sec 3.6.1.1
Later in the 3.6.1.2 section:

In this case, the mobile node MUST
   set the Home Agent field to the subnet-directed broadcast address of
   the mobile node's home network.  Each home agent receiving such a
   Registration Request with a broadcast destination address MUST reject
   the mobile node's registration and SHOULD return a rejection
   Registration Reply indicating its unicast IP address for use by the
   mobile node in a future registration attempt.

So then, registration has to be performed again using one the Home Agent 
addresses replied.

> Extension cannot be used as MN does not know its Home Agent?
The MN will choose one of the "in-error" registration reply to pickup 
the Home Agent Adress and process authorization with the chosen HA.

Regards, Bruno.

---

From: "K V Pradap-a22072" <[email-masked]>
Date: Tue, 16 Jan 2007 23:07:38 +0800

Hi Bruno
Thanks for the reply.
I have an added question that,
By what Authorization enabling extension will the Initial Registration
request(which is used for Home Agent Discovery)  will be protected with?
Thanks and regards
Pradap

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]
Sent: Tuesday, January 16, 2007 8:30 PM
To: K V Pradap-a22072
Cc: [email-masked]
Subject: Re: [Mip4] Doubts in RFC 3344

Regards, Bruno.

---

From: [email-masked]
Date: Tue, 16 Jan 2007 16:33:46 +0100

> request(which is used for Home Agent Discovery)  will be protected with?
Good question.
Not sure of my answer but let's try:

If co-located FA is used, i think the RFC assumes that the check for IP 
broadcast destination address is performed before authorization checks. 
If so the MN does not care about Authorization enabling extension in the 
initial request.

If FA is used, i guess the same assumption applies. The Foreign Agent 
authorization extension will be present while relaying the initial 
registration request i guess.

Not sure of this however!