RE: Some Comments on ID/Loc Separation Proposals

[Erik Nordmark <Erik.Nordmark@Sun.COM>]

> An IP address can be used, for example, to allow ULPs to indicate 
> which physical interface to use for outbound packets by explictly 
> choosing a source address.  This can be useful for multicast traffic 
> and specialized ULPs such as routing protocols. 

I heard this asserted elsewhere yersterday but I haven't seen any IPv* stacks 
that do such a thing.
The outbound interface is selected based on the destination IP address
independently of the source address.
Thus if the application specifies the source address for if2 and sends
a packet to some destination where the routing table for the destination
says to use if1, then the packet will go out if1 with the source of if2.

Are there host stacks that do something different when there
are multiple (equal?) routes that match the destination?

> The use of IP addresses as interface identifiers may or may not
> have any implications for NOID, as it seems that NOID will allow
> ULP access to the real local IP addresses (??) -- the document
> doesn't specifically say this, but I'm assuming that is how SCTP
> would run over NOID, for example. This is a larger potential issue 
> for other proposals, such as HIP.

In NOID there is a choice (don't know the tradeoffs) whether the
application gets all locators (i.e. all potential AIDs for the peer)
from the getaddrinfo() API it uses, or whether getaddrinfo()
would pick one AID to return to the app.
If the app gets all of them *and* if source addresses imply interface selection
in the stack, then the application would have control over the interface that
is used.

  Erik