Subject: RE: [DNA] Definition of "Link Up" and "Link Down" events?

From: "Tero Kauppinen (JO/LMF)" <[email-masked]>
Date: Wed, 25 May 2005 14:33:16 +0200

> Works for me.  My only concern would be about what would happen if an
L2
> technology comes along that can move its attachment point without any
> intermediate period of disconnection, perhaps through some out-of-band
> pre-establishmment of the new connection (and it would be good if such
a
> technology did!).
> 
> Perhaps it would just be a matter of using these definitions, but
> ensuring that a transition like above causes a matched pair of Link
Down
> / Link Up events to be generated.

Well ... actually, for example, an Orinoco Gold WLAN card doesn't signal
"link down" when switching from one AP to another. This means that in
some cases the driver sees just a sequence of "link up" events when the
node is roaming.

> 
> As an aside: for draft-pentland-dna-solution-00 we only really
> considered Link Up, because that is the point at which the network
> layer on that interface is able to take some action (sending an RS, in
> this case, to find out what the Link Up means).  Link Down is probably
> useful for coordinating between multiple interfaces, as are some of
> the events that might be able to be triggered by the intermediate
> connectivity situations that you described, but that is outside the
> scope of what we tried to achieve in the proposal.
> 
> Brett.

Tero

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From: Bernard Aboba <[email-masked]>
Date: Wed, 25 May 2005 05:56:31 -0700 (PDT)

> some cases the driver sees just a sequence of "link up" events when the

Right.  Note that some TCP implementations (foolishly) tear down connections
on receipt of a "Link Down" indication;  on such implementations the above
behavior will spare the user considerable pain.