[e2e] Routing for multi-homed host traffic

[Xiaoming Fu]

Hi all,

I'm wondering how a multi-homed host can deliver such "special" data through
an alternative path while "normal" data through a default path toward the
same
destination. This has been originated by the following problems:

1) how to send a QoS signaling message (to check/re-establish QoS status)
through a potential path while the normal data traffic of the mobile node is
still
through the old path (suppose the MN already obtains a new Care-of-Adress
from the new subnet). With our trial based on MIPL Mobile IPv6 for Linux,
specifying the source IP address proved unable to achieve this. Our
(temporary?)
way was to use a routing header (first destination: the new Access Router
- nAR) but apparently it introduces certain overhead;

2) how to send a heartbeat message in SCTP.  It is stated in RFC3257 that
   "When the endpoint chooses a source address, it should always select the
    source address of the packet to correspond to the IP address of the
    Network interface where the packet will be emitted subject to the
    binding address constraint." However the routing rule in the endpoint
(which
    is not explicitly indicated in SCTP specs), may not support this.

RFC1122 sugests implementors may use either of two different conceptual
models for multihoming host (without preference):
   Strong ES Model:
                         route(src IP addr, dest IP addr, TOS)
                                                        -> gateway
   Weak ES Model:
                         route(dest IP addr, TOS) -> gateway, interface

It seems to me the Strong ES model holds as a (default) assumption for 2).
But I don't
understand why 1) doesn't work that way. Could some one clarify me, is the
Strong
ES Model ever the best practice / solution to routing for multi-homed host
traffic?

Thanks,
Xiaoming