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List:       ipng
Subject:    RE: Stateless autoconf and dial-on-demand
From:       Richard Draves <richdr () microsoft ! com>
Date:       2000-06-28 20:06:00
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> > If your dialup router is in command of the whole process, what
> > happens if it holds the first outbound packet for a while, then
> > advertises the new global prefix, *then* sends the initiator an ICMP
> > "beyond scope of source address"?  Will the initiator's stack then
> > retry with the new global-scope address?
> 
> Matt,
> 
> I guess what we are worried about is the source address 
> selection in the
> host implementations on the network. If a host needs to send 
> a packet to a
> global scope destination address and only has a link local address to
> supply as the source, are we guaranteed that the packet will 
> be put on the
> wire in the first place?

According to the draft source address selection rules, yes the packet will
be sent with a global destination and link-local source if there is no
better choice.

But then there's Matt's question of whether the initiator's stack would
retry with a new global source address after getting the ICMP error. The MSR
stack would *not* do this when establishing a TCP connection.

Backing up, I don't understand the approach. In this dial-on-demand
scenario, why not "permanently" allocate a global prefix to the dial-up
site? So router with the modem advertises this global prefix. And when the
router gets a packet that it wants to send over the modem, then it dials.

> A dumb question: Where is the "beyond scope of source address" ICMPv6
> message defined? I see it mentioned in RFC2765 (SIIT) as 
> "host unreachable,
> code 2", but the location of the definition eludes me.

draft-ietf-ipngwg-icmp-v3-00.txt, which seems to have expired.

Rich
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