Subject: Stateless autoconf and dial-on-demand

From: Morten Heiberg Rasmussen <[email-masked]>
Date: 26 Jun 2000 11:19:54 +0200

Hi

I have a question regarding IPv6 stateless address autoconfiguration in
combination with dial-on-demand network access.

Suppose I have a network configured using only stateless address
autoconfiguration. At this point all hosts have a link local address but
nothing with wider scope. When a connection to the outside world is opened
the gateway node starts to receive router advertisements from our ISP with
a globally routable prefix. This prefix is distributed to the hosts on the
local network so that they can form complete, global IP addresses.

How does one implement dial-on-demand in such a setting? The gateway for
the network needs an outbound packet to trigger the dialing process, but at
that time the emitting host does not have a global address to select as the
packet source address. Hence the packet cannot be sent.

Is there any way to avoid having to rewrite the first outbound packets in
the gateway? If it is not acceptable to open the connection when no traffic
is being sent and if we cannot assume that everybody uses DNS I don't
really see how it could be done.

Best regards

Morten Heiberg

-- 
Morten Heiberg Rasmussen              System Developer, M. Sc. 
Ericsson Telebit A/S                  Tel: +45 86 28 81 76
Fabrikvej 11                          Fax: +45 86 28 81 86
DK-8260 Viby J, Denmark               E-mail: [email-masked]

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From: "Matt Crawford" <[email-masked]>
Date: Mon, 26 Jun 2000 14:43:21 -0500

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 Crawford

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From: Jim Bound <[email-masked]>
Date: Tue, 27 Jun 2000 09:24:21 -0400

Morten,

We have not developed specs for this operation.  Whether we will is TBD.
I do believe we should be able to do router renumbering from the ISP
though.

But initially I would imagine that there is some SLA with ones ISP to
develop the entire relationship and with that customer.  At that time an
IPv6 Prefix would be part of that SLA.  Once you have that prefix the
connection between the ISP and the customer can be set up over the
medium to the ISP site and customer site.

I believe you will see products on the market for IPv6 to do this very
soon.

regards,
/jim

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From: Morten Heiberg Rasmussen <[email-masked]>
Date: 28 Jun 2000 10:23:48 +0200

> 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?

It not, the dialup router will never know that a host wants to open the
connection.

If the packet _is_ sent with a link local source address at first I believe
the initiator will have to retry with the new global-scope address when the
ICMP message is sent. Provided, of course, that any duplicate address
detection algorithms have completed and so on.

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.

Thanks!

        /Morten

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From: Margaret Wasserman <[email-masked]>
Date: Wed, 28 Jun 2000 15:28:28 -0400

Hi Matt,

>retry with the new global-scope address?

I don't think that this would work well for many application
and/or transport layer protocols.  Once the remote host has
been identified as having a particular address, it may not
be possible to change that address in mid-session.

Margaret