RE: I-D ACTION:draft-coene-multi6-sctp-00.txt

[Coene Lode <Lode.Coene@siemens.com>]

-----Original Message-----
From: marcelo bagnulo [mailto:mbagnulo@ing.uc3m.es] 
Sent: donderdag 5 februari 2004 18:51
To: Coene Lode; john.loughney@nokia.com
Cc: multi6@ops.ietf.org
Subject: RE: I-D ACTION:draft-coene-multi6-sctp-00.txt


Hi Coene,

> A section in the draft on SCTP multihoming issues deals with that:
> - if the host is able to fill in the IP address of the interface on which
> the msg is send out, then the return msg will arrive back on that same
> interface, not on the others. That mean that for the initial outgoing
> message, the source address will belong to the network to which
> the host is
> sending it, thus any ingress filtering within that network should let it
> pass(it is after all the address given out by that network(via DHCP,
> fixed...))
> - if the host allows to fill in the IP address of ANY interface as the
> source addres of the msg(example : source = IP1, addres of interface on
> which msg was actually send out was IP3) then ingress filter
> should drop the
> message(as should be expected)
> This is  basically implementation dependant in the host.

>What happens when there are multiple addresses (with different prefixes)
>assigned to the same interface?


Then the IP layers can take a pick of each of the source addresses assigned
to the interface.
The problem for selecting the "correct" link is then move to the first
router which has 2 different links toward the destination. That router has
then to route the packet towards the link where the packet won't be dropped
by the ingress filtering. Thus the router would be doing its routing based
on the source address. If ISP1 gave out IP1(or the prefix for IP1), then if
a packet shows up with source address = IP1 it must route the packet onto
the link to ISP1. If on the other hand IP3 was the source of the packet,
then the packet must be routed through the ISP which supplied the IP
address/prefix for IP3. Once again, that is something that SCTP cannot do,
it is routing which has to do this. 
It is maybe a rule that needs to be described more in detail.

Yours sincerely,
Lode