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

[James Kempf <kempf@docomolabs-usa.com>]

Brett,

> 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.
>

It really depends on how the L2 software exposes this capability to the IP
stack. In certain sense, this technology already exists with CDMA soft
handover, but the problem is that the driver does not expose the outstanding
soft handover legs to the IP layer. The soft handover legs look like a
single link from the IP layer's perspective, and are handled as such by the
network.

I think Flarion's OFDM also allows the terminal to have outstanding links to
two base stations at a time, but I do not know how these are exposed to the
IP stack. I believe they use the forward link (to the new base station) to
perform Mobile IPv4 CoA registration while still receiving packets on the
backward link (to the old base station).

If the L2 software hides the L2 handover latency, then "Link Up" and Link
Down" never occur during handover, although they may occur at other times,
for example, if the terminal moves out of range of any base stations.

            jak