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

From: "Martin Johnsson (ERA)" <[email-masked]>
Date: Wed, 29 Mar 2000 12:39:55 +0200

Regarding the use of DHCP in corporate environment, the idea would be to have the possibility to configure "everything" from the beginning, i.e. both the address of the HA as well as MN's IP address corresponding to the home network, and possibly also the address corresponding to the visited network. This means that tunneling via the HA (And FA) won't begin until you have all this configured in the MN.

We have done this in actual implementation, and it works fine, though there is a need to make some modifications in the DHCP client when you request the IP addresses for both home + visited.

Cheers,
  /Martin

-----Original Message-----
From: Pete McCann [mailto:[email-masked]]
Sent: den 29 mars 2000 08:21
To: Martin Johnsson (ERA)
Cc: [email-masked]
Subject: Re: [MOBILE-IP] Dynamic Address Assignment in Mobile IP

"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

---

From: Vipul Gupta <[email-masked]>
Date: Wed, 29 Mar 2000 10:34:20 -0800

> Date: Tue, 28 Mar 2000 01:19:33 -0600
> From: Pete McCann <[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:

> 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.

  I agree. As people start using Mobile IP in other scenarios, the mobile
  node will need to acquire additional parameters (e.g. it might need
  an "internal" DNS server when using private addresses) and it makes
  sense to reuse DHCP for this purposes. The PPP WG has already been
  down the path of first trying to add lots of DHCP-like functionality
  to PPP and then deciding on reusing DHCP (through the DHCP inform
  message) as the preferred approach.

  [Interestingly enough, the IPSRA working group (IPSec for remote access)
  is also going through a similar debate -- reusing DHCP v/s extending
  IKE for negotiating network parameters relevant to the
  "internal network". For some background on why the former is better,
  see draft-ietf-ipsec-dhcp-04.txt.]

  vipul