Subject: Re: [MOBILE-IP] Dynamic Address Assignment in Mobile IP

From: "Martin Johnsson (ERA)" <[email-masked]>
Date: Tue, 28 Mar 2000 10:22:50 +0200

Dear all,

I'm happy to see that this discussion continues as there is, I would say obvious, a need to support dynamic address assignment also in Mobile IP. And yes the NAI draft gives this possibility, and which would be quite suitable to use in remote access.

In the corporate environment, DHCP is the king (in most networks), and it should definitely be possible to assign address(es) using DHCP, especially as this is the means by which many network administrators like to manage their IP address space.
Using DHCP is by the way not limited just to the corporate environment, also ISPs are using it.

Sorry to say, but I haven't read your draft, but I hope it is possible to also have this option for IP address assignment covered in your draft (and perhaps it already is?).

Cheers,
  /Martin

-----Original Message-----
From: Pete McCann [mailto:[email-masked]]
Sent: den 28 mars 2000 09:20
To: [email-masked]
Subject: [MOBILE-IP] Dynamic Address Assignment in Mobile IP

In light of the discussion following my presentation today, does
anyone want to talk about address assignment?  Here are the issues
as I understand them:

1) The NAI draft allows for a home address to be dynamically assigned
   to the MN if the MN puts 0.0.0.0 as its home address.
2) There is currently no way to specify additional information to the
   home agent that might guide it in choosing an address pool or
   performing other device-specific tasks upon receiving the registration
   request.  Also there is currently no way to keep the address after
   returning home.  Our draft attempts to fix these problems.
   (See draft-mccann-mobileip-sessionid-00.txt).
3) There was a lot of discussion about the proper role of DHCP in a
   Mobile IP network.  My personal feeling is that it is perfectly
   fine to use Mobile IP for address assignment, but any other parameters
   should be configured via DHCP after the registration has completed.
   This is analagous to the way DHCP would be used over a PPP link,
   for example.  That way the MN could be registered and have an address
   in one quick round trip for most cases.
4) For consistency, MNs should be able to get an address from an HA
   even while at home.  This eliminates the confusion about which server
   is managing the state for the address in case the MN later moves to
   a different network but wants to keep the assigned address.  I want
   to add this to the draft.

Comments?

-Pete

---

From: Pete McCann <[email-masked]>
Date: Wed, 29 Mar 2000 00:20:50 -0600

"Martin Johnsson (ERA)" <[email-masked]> (MJ) writes:

MJ> I'm happy to see that this discussion continues as there is, I
MJ> would say obvious, a need to support dynamic address assignment
MJ> also in Mobile IP. And yes the NAI draft gives this possibility,
MJ> and which would be quite suitable to use in remote access.

Good - I hope we have agreement on that.

MJ> In the corporate environment, DHCP is the king (in most networks),
MJ> and it should definitely be possible to assign address(es) using
MJ> DHCP, especially as this is the means by which many network
MJ> administrators like to manage their IP address space.  Using DHCP
MJ> is by the way not limited just to the corporate environment, also
MJ> ISPs are using it.

There is nothing in the draft that precludes the Home Agent from using
DHCP to manage the address pool.  However I think there is a problem
if the MN tries to use DHCP directly to acquire an address.  The problem
is that the MN's DHCP DISCOVER message needs to be reverse-tunneled
to the home network *before* the MN has even acquired an IP address,
and the response needs to be properly encapsulated by the HA - essentially,
the FA and HA are acting in concert as a BOOTP relay, which I am not
sure is supported.  Any comments from DHCP experts?

MJ> Sorry to say, but I haven't read your draft, but I hope it is
MJ> possible to also have this option for IP address assignment
MJ> covered in your draft (and perhaps it already is?).

Assignment of an address by DHCP is outside the scope of the draft.  I
hope we can build upon the NAI-based address assignment, and use DHCP
later for configuring other things.

-Pete