Subject: Prefix delete RA behaviour

From: "Basavaraj Unnibhavi" <[email-masked]>
Date: Wed, 8 Aug 2001 20:38:10 +0530

Hello,
If prefixes in the router are deleted by admin, what should be the behaviour
of RA (Router advertisement). I think Neighbor discovery spec doesn't
specify about this.

Thanks in advance for clarification.

Basavaraj

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From: Francis Dupont <[email-masked]>
Date: Wed, 08 Aug 2001 18:35:02 +0200

In your previous mail you wrote:

=> they are no more in RAs so hosts will deprecate and invalidate them
at experations of lifetimes. Usually the router admin has an easy way
to send some RAs with 0 lifetimes in case of an error (a router plugged
on the wrong Ethernet for instance). You may have troubles with the two
hour rule but in this case you can authenticate RAs too ...

Regards

[email-masked]

PS: my neighbor (the guy who plugged a router on the wrong socket)
is smiling because no current implementation has the two hour rule
enabled by default (read never :-), look at  Arkko's drafts to know why.
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From: Erik Nordmark <[email-masked]>
Date: Fri, 10 Aug 2001 01:37:55 +0200 (CEST)

> of RA (Router advertisement). I think Neighbor discovery spec doesn't

It depends on what the semantics are of the administrative
"delete" operation.

There are 2.5 possible interpretations:
 - Immediately remove the prefix.
   To do this robustly for nodes that are not connected to the link
   the hole time the router(s) need to advertise the prefix with zero
   lifetimes until the end of the original lifetime has expired.
 - Remove the prefix by stopping to extending the lifetime.
   This can be done by either
	- stop advertising the prefix. This causes existing nodes
	  to decrement the lifetime in real time.
	- advertiseing the prefix with a lifetime decrementing in real time.
	  This is the same as the "stop" except that newly arriving nodes
	  will configure the addresses with a short lifetime.

So you are correct that RFC 2461 doesn't specify the semantics of such
*management operations* and how they map to the routers configuration
information. But the spec does specify how this configuration information
is advertised in the protocol and how the information received in the
protocol affects the configuration on the hosts.

  Erik