Hi Pete,
I really don't think we should force DHCP to re-run on every handover.
I thought one of the motivations for network-based mobility was to
minimize the signaling to the MN during handover.
In the current mobility models we have two DHCP deployment models. a.)
DHCP server in the access. b.) DHCP Relay in the access
For #a, it is the dominant model. The DHCP server is collocated on the
access gateway; the interworking between the DHCP server and the mobility
function in the access gateway allows the network to offer the same IP
address to the mobile node. After each handoff and based on DNA
considerations, the MN may go into DHCP INIT-REBOOT followed by
Request/reply. I don't know if I should call this as complete Re-Run after
each handoff, but at least the current data suggests the handoff latency
related to this same-link validation is insignificant. Now, from coloring
perspective, the DHCP server in the access network can potentially change
the properties of the address. MN is on a new world, new access network,
new link and hence some changes to the properties.
For #b, we continue to route the DHCP lease renewal messages back to the
network where the MN obtained its address. Typically its tunneled to the
anchor. Here I see your point of not impacting the DHCP state machine by
changing properties based on MN's movement. But, if the DHCP server is
aware of changes to properties, can it not send the updated properties ?
We have to look at properties as meta-data that goes with an IP
address/prefix. This meta-data should not have any relation to the DHCP
state machine. But, some properties of that address do change, based on
MN's movement, mobility state changes ..etc. If the DHCP server is aware
of these property change, IMO, it should reflect the updated properties.
I'm more interested in #a and not deal with this issue at all. But, if we
insert a property element in PIO, we should do that consistently and have
that in DHCP as well.
Regards
Sri
On 3/20/14 5:37 PM, Peter McCann peter.mcc...@huawei.com wrote:
Hi, Sri,
Sri Gundavelli (sgundave) wrote:
On 3/20/14 5:54 AM, Peter McCann peter.mcc...@huawei.com wrote:
I think our extensions should be to the prefix information option and
not DHCP.
The properties of an address may change after a handover and we should
not couple the DHCP state machine (which is about lease renewal) to the
handover state machine.
Hi Pete,
This is a good comment. If we are making any assumption that even
after a handover, the DHCP transactions are still hitting the same
DHCP server node, this may be a valid concern. But, if DHCP
transactions are locally terminated after handover (Ex: RFC5844/MAG),
then the updated properties can be provided as part of the new DHCP
transaction. Some parameters such as MTU settings do change after an
handover and so we can probably agree that address properties can
change as well.
Regards
Sri
I really don't think we should force DHCP to re-run on every handover. I
thought
one of the motivations for network-based mobility was to minimize the
signaling
to the MN during handover.
-Pete
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