Subject: [dhcwg] RE: meta thoughts on m/o bits

From: [email-masked]
Date: Mon, 23 May 2005 12:24:05 +0300

Jari & Hesham,

> >=> :) I don't want them to charge users for Ralph's implementation :)
> >But seriously, charging is one thing, inefficient use of power is 
> >another serious problem which can actually reduce revenue because
> >a device doesn't go dormant long enough and runs out of battery 
> >instead of using that battery power for what the user actually wants
> >to do.
> >  
> >
> I tend to agree with Hesham that we should attempt to design
> our protocols so that unnecessary periodic probing over wireless
> is minimized. One thing that should be kept in mind is that most
> people want their devices to be always on and reachable, but yet
> they might actually use them for something only a very small
> fraction of the time. Even a tiny amount of traffic during the
> inactive period may thus result in a relatively large impact
> when you compare it to actual useful traffic. This in turn
> translates to battery lifetimes and cost for the users.

Basically, what I think we'd like is that if a device has a working
address and is 'attached' to a network, it should probably use that
address and only probe upon some failure event.  When the device
shows up to a new network, it can probe and if it gets a DHCP address,
then use it, and update the address before the lease expires.  If
the device gets a valid address via autoconfig, then it should continue
to use that.  It doesn't make much sense that a node should continually
verify if it should use a DHCP address if it has an otherwise working
address.

Note that many applications will run sometime of watchdog or heartbeat
to ensure that application is still alive on both ends.  If this fails,
that might be a clue to check if the IP address is still valid.  I
agree that having probing at multiple layers is a bad design, IMO.

John

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From: Ralph Droms <[email-masked]>
Date: Mon, 23 May 2005 07:46:37 -0400

John - My understanding is that the selection of SLAAC addresses is
separate from the use of DHCP; that is, a host may be in a scenario in
which it uses both an address chosen through SLAAC and an address
assigned through a DHCP message exchange.  So, the availability of a
SLAAC address should not affect the use of DHCP.

- Ralph

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From: Ralph Droms <[email-masked]>
Date: Mon, 23 May 2005 07:50:58 -0400

John - I agree that in lieu of some failure or otherwise special
condition, devices should use the mechanisms built into SLAAC and DHCP
(address lifetimes) to control the use and assignment of addresses.

I think the DNAv6 work may have some impact on this discussion as
providing a more reliable mechanism for detecting when a host has
changed links and should therefore consider re-checking its addresses.

- Ralph