Subject: RE: [mobile-ip] 0.0.0.0 src address

From: Matt Impett <[email-masked]>
Date: Thu, 6 Dec 2001 09:56:57 -0500

Alper,

> -----Original Message-----
> From: Alper E. YEGIN [mailto:[email-masked]]
> Sent: Thursday, December 06, 2001 12:59 AM
> To: [email-masked]
> Subject: Re: [mobile-ip] 0.0.0.0 src address
> 
> 
> Matt,
> 
> 
> > > For example, what if any MN configures itself with a 
> temporary address
> > > to send the reg-req with home-addr=0, to get it's
> > > newly-assigned homeaddr?
> > >
> > > >    -  If the mobile node does not have a home address, 
> the IP source
> > >        address MUST be 0.0.0.0.
> > >
> >
> > I also question why this is a MUST.  It is entirely 
> possible that the MN's
> > interface over which it is going to send the RREQ has an IP address
> > (established via DHCP), while the mobile does not yet have 
> a MIP home
> > address.  In this case, shouldn't it be able to send the 
> RREQ with the
> > interface's address as the IP source address, but with a 
> zero home address
> > in the RREQ??
> 
> You cannot make this assumption. This works only if we are using
> co-located care-of address. In case of FA-located care-of
> address, mobile node has only home address.

I was not making the assumption that this was always the case.  I was merely
asking: when this is the case, shouldn't the mobile be able to set the
source IP address on its RREQ equal to the interface's address over which
the RREQ is going out??  Currently this is not allowed by the MIP draft, as
the mobile MUST set the source address of its RREQs to 0.0.0.0 if it has no
home address.

Furthermore, why can't the mobile have a local interface address which is
different than its home address without using co-located care-of-addresses??

matt

---

From: "Charles E. Perkins" <[email-masked]>
Date: Thu, 06 Dec 2001 09:06:58 -0800

Matt Impett wrote:

>>> I also question why this is a MUST.  It is entirely possible that
>>> the MN's interface over which it is going to send the RREQ has an IP
>>> address (established via DHCP), while the mobile does not yet have
>>> a MIP home address.  In this case, shouldn't it be able to send the
>>> interface's address as the IP source address, but with a zero home
>>> address in the RREQ??

I think your suggestion is reasonable.  It is currently a MUST for
historical reasons, and nobody ever suggested that the mandate be
softened.  Now that the document has already gone through IETF Last
Call, changes would have to go into a Mobile IP version 3 document
of some sort, and this matter doesn't seem to warrant such action.

> different than its home address without using co-located care-of-addresses??

I don't think there is any prohibition against the mobile node
getting more addresses, but that is a different question.

Regards,
Charlie P.

---

From: "Alper E. YEGIN" <[email-masked]>
Date: Fri, 7 Dec 2001 12:15:07 -0800

Matt,

> asking: when this is the case, shouldn't the mobile be able to set the

oh, ok. I thought you were suggesting this as a solution.

> the RREQ is going out??

that should be ok.

> Currently this is not allowed by the MIP draft, as

I don't know why it has to be like that. I cannot think of any reason.

I think the mobile node should be able to send the registration request
with the care-of address as the source address. After all, the reg. req. can
carry home address in a separate field.

In the case of co-located care-of address and dynamic home address
allocation, how can the mobile node send the registration request with
an unspecified source address (and receive a response)?

I think this is an important problem.

> different than its home address without using co-located
care-of-addresses??

I guess you can do that. It is just that one of the reasons of not
having a co-located care-of address is that mobile might be unable to
get a topological address (no dhcp, no ppp, or not enough IPv4
address). And resort to FA-located care-of address.

If it can get an address, it can use co-located care-of address. But, then
again it doesn't have to.

I agree.

> matt
alper

---

From: Sivasundar Ramamurthy <[email-masked]>
Date: Fri, 7 Dec 2001 13:57:26 -0800 (PST)

Hello,

> an unspecified source address (and receive a response)?

section 3.6.1.1 defines the rules for what address the MN should use
when sending out requests. My interpreation of this section is that
the first rule that applies to the situation must be used. That is, if
the MN has a co-located COA, it must use that as the src of a
registration request, EVEN if it does not have a home address.

The reason I interpret it so is due the issue brought up by Alper, and
these specific words in rule #3:

	"In all other cirsumstance....."

It is clear that rule #3 applies only if rules #1 and #2 do not. But
the question is, does rule #2 apply only if rule #1 does not? I
interepret it so; the MN can use the co-location COA as the src of its
request even when it has no home address....

Following this interpretation, rule #2 is used only if rule #1 does
not apply, thus not involving the "0.0.0.0 src address" issue in the
case of MN with co-located COA!

Is my interpretation too imaginative? :-)

If it is, then the problem described by Alper is serious. If the MN
sends a request (co-located COA and address allocation) to the HA with
0.0.0.0 as src address, the chances of getting the reply back to the
MN seem bleak. (could it be null??)

Anyway, even if my interpreation holds, the "0.0.0.0 src address"
issue still lives as in the case when the MN does not use a co-located
COA and does not have a home address....(rule #2).

thanks!

Siva

---

From: Joe Lau <[email-masked]>
Date: Fri, 7 Dec 2001 14:07:14 -0800 (PST)

>                                                     ..... If the MN

Right.  A co-located COA MN _must_ not send a registration request with a 
0.0.0.0 source address.  There is no way to get a reply back even if the 
registration request itself made it to the HA.

Joe

---

From: Peter Lei <[email-masked]>
Date: Fri, 07 Dec 2001 14:54:35 -0600

> I think this is an important problem.

So, wouldn't this solve this issue in 3.6.1.1 in 2002bis-08 (Note, this
merely "moves" the added requirement in -08):

    -  When registering on a foreign network with a co-located care-of
       address, the IP source address MUST be the care-of address.

    -  In all other circumstances, the IP source address MUST be the
       mobile node's home address.  If the mobile node does not have a
       home address, the IP source address MUST be 0.0.0.0.

Was this not the original intent of adding the 0.0.0.0 "homeless" text
in the first place; i.e. clarifying behavior for the homeless MN
registering through a FA, yet still allowing the homeless MN using
a colocated COA.

--peter

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