Subject: [MEXT] DS-MIPv6 IPv4 HoA configuration from home link

From: Vijay Devarapalli <[email-masked]>
Date: Wed, 12 Mar 2008 10:26:33 -0700

Hello folks,

I am going to try and describe the issues one bye on. The first
one was the home link detection issue. The second one is on
configuring the IPv4 home address from the home link.

draft-ietf-mext-nemo-v4traversal-01.txt describes a mechanism
for the mobile node to configure an IPv4 home address. This is
based on the mobile node sending a binding update with a request
for the IPv4 home address. The home agent then responds with
the IPv4 home address in the binding ack.

When the mobile node boots up on the home link, it does not
send a binding update to the home agent. So we need to describe
another mechanism for the mobile node to configure an IPv4 home
address. There are two options possible.

- When the mobile node performs an IKEv2 exchange with the home
agent when it is attached to the home link it requests for an
IPv4 address using the configuration payloads. The home agent
responds with the IPv4 home address. We might need some sort
of indication that this address is usable as the IPv4 home
address, similar to what we say in RFC 4877 about the IPv6 home
address configured through the INTERNAL_IP6_ATTRIBUTE. Domagoj
mentioned this on the mailing list.

- The mobile node configures an IPv4 address using a p2p
link-specific mechanism. The link-specific mechanism could be
DHCPv4 too. When the mobile node goes away from the home link
and attaches to a visited link, it configures the IPv4 address
on the Mobile IP virtual interface and then sends the IPv4
address in the Binding Update to the home agent. Basically
instead of requesting for an IPv4 home address by setting it
to 0.0.0.0, it requests for the IPv4 address already configured
to be treated as a home address. draft-ietf-mext-nemo-v4traversal
allows for the mobile node to request for a particular home
address, instead of setting the address to 0.0.0.0.

I am fine with either of two options listed above. But, IMO, we
need to decide on one and document that in the IETF.

Vijay
_______________________________________________
MEXT mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/mext

---

From: Julien Laganier <[email-masked]>
Date: Tue, 18 Mar 2008 13:36:11 +0100

Hello Vijay,

<WG chair hat off>

Some comments below:

> mentioned this on the mailing list.

I think when the MN concludes it is at home (by comparing prefixes in 
MIP6_HOME_PREFIX and RAs) it can simply use standard IPv4 address 
configuration mechanism, e.g. DHCP as you suggest below. 

> need to decide on one and document that in the IETF.

I am not sure why anything new needs be specified. DSMIPv6 allows a MN 
to register a given IPv4 HoA, and does not mandate Dynamic IPv4 home 
address allocation. If the MN already has configured an address 
acquired by whatever mean (e.g. DHCP) then it can register that address 
with the HA when it moves away from home. What's missing?

--julien

---

From: Vijay Devarapalli <[email-masked]>
Date: Tue, 18 Mar 2008 16:16:40 -0700

> configuration mechanism, e.g. DHCP as you suggest below. 

Not if there are separate address pools for the IPv4 address
obtained via DHCP as part of the p2p link setup and for the
IPv4 home address allocation at the home agent. The home
agent is still a separate functional entity from the network
entity that terminates the p2p link. In any case, I think the
home agent needs to be aware of the IPv4 address configured
by the mobile node when the mobile node boots up on the home
link.

> with the HA when it moves away from home. What's missing?

If the home agent was not involved in the original IPv4
address allocation, then there is no guarantee that the mobile
node will get the IPv4 home address it requested for. In most
of the specifications done so far in the MIP6/MEXT WG, we have
assumed that the home agent is always involved in the home
address allocation.

Vijay

---

From: Julien Laganier <[email-masked]>
Date: Thu, 27 Mar 2008 14:33:27 +0100

Hello Vijay,

<WG chair hat off>

On Wednesday 19 March 2008, Vijay Devarapalli wrote:
> > I think when the MN concludes it is at home (by comparing prefixes
> > in MIP6_HOME_PREFIX and RAs) it can simply use standard IPv4
> > address configuration mechanism, e.g. DHCP as you suggest below.
>
> IPv4 home address allocation at the home agent. 

I think it is common sense that the same address pools need to be 
configured on one hand for the IPv4 address obtained by DHCP, and on 
the other hand for the IPv4 home address allocated by the home agent. 
Otherwise it's obvious the thing doesn't work.

> The home agent is still a separate functional entity from the network

I disagree the HA needs to be aware of the IPv4 address configured by 
the MN when it is at home. Since the MN already had an IPv4 allocated 
while at home, that's its home address, it does not need to use dynamic 
IPv4 address allocation with DSMIPv6. It simply uses that IPv4 home 
address in BU sent to the HA when it leaves home. The HA would then 
record that IPv4 address in the MN's BCE and that's it.

When a MN returns home, whether its IPv4 home address has been allocated 
via DHCP while at home, or via DSMIPv6's dynamic IPv4 address 
allocation while away from home, the MN can ask the DHCP server to 
allocate that same address, it will work if the address pools are the 
same.

If that is unclear and needs to be clarified, I guess it is better to 
clarify that in the DSMIPv6 specification rather than in a different 
spec.

What do you think?

--julien