Subject: [Monami6] MCoA and HAO dest. option

From: Romain KUNTZ <[email-masked]>
Date: Thu, 14 Dec 2006 23:16:51 +0900

Hello,

I have an issue with using HAO dest. option for multihomed MNs/MRs.

RFC 3775 says:
    Mobile nodes can include a Home Address destination option in a
    packet if they believe the correspondent node has a Binding Cache
    entry for the home address of a mobile node.

So a multihomed MN using the MCoA registration with its Home Agent may
include an HOA dest. option in the packets destinated to the HA instead
of reverse-tunneling them. The source address of the packet would thus
be the CoA of the interface from which the packet is sent.

At the Home Agent, according to RFC 3775:
    [...] the currently registered care-of address MUST be equal to
    the source address of the packet.  These tests MUST NOT be done for
    packets that contain a Home Address option and a Binding Update.

The MCoA draft does not say anything about the behavior the HA should
have in that case. As packets do not contain any information about the
BID binded to the CoA used to send the packet, the HA at this time would
have, for each packet, to check if the source address of the packet is
equal to *one of the CoA registered for the corresponding BCE*, thus to
parse the list of all the CoA registered for the node.

However I doubt about the efficiency of such tests if the number of CoA
registered of each node is great and if the traffic is heavy. One
solution could be to use reverse tunneling rather than HOA dest. option
when the node uses MCoA and wants to send packets (other than Mobility
Headers) to its HA.

Then, when the HA replies, it must put a RTH2 in the reply instead of
reverse-tunneling the packet. How does the HA select the source address
to put in the RTH2? As the RTH2 is included once the IP packet is forged
by upper layers, the HA has no way to maintain a state for each packet
received from a node to know which address to include in the RTH2 of the
reply. Picking up one randomly may result in a non-symmetric path
between the MN and the HA.

Thoughts?

regards,

-- 
Romain KUNTZ
[email-masked]

_______________________________________________
Monami6 mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/monami6