Re: [RRG] NTP and various proposals.

["William Herrin" <bill@herrin.us>]

On Tue, Feb 26, 2008 at 2:58 AM, Tony Li <tli@cisco.com> wrote:
>  Entirely possible.  The real question is how much state needs to be
>  stored.  That depends on the scope of the mapping resolution box.
>  Having a DNS server with a cache that's more than 18 minutes deep
>  doesn't sound so horrible to me, if the scope of that server is
>  constrained to some smallish [say O(1000)] number of hosts.

Hi Tony,

It's not just state, it's churn. It's 18 minutes that you have to keep
receiving and asking to receive map updates for the destination even
though there's no associated user-level traffic.

That or the ITR has to do some sort of probability assessment as to
whether the expired data is still valid so that it can use the expired
data for the next NTP packet while it goes out and refreshes the
cache. I've explored this possibility a little with TRRP. It gets
hairy fast.

You can't simply extend the cache validity of course. 18 minutes is
too long for multihoming, let alone mobility.

Regards,
Bill Herrin




-- 
William D. Herrin herrin@dirtside.com bill@herrin.us
3005 Crane Dr. Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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