Re: Choosing length of lease

[Mark Sirota <[e-mail]>]

John M. Wobus wrote:
> (1) At your own site, how long do you make leases and why did you
>     choose this time?

Initially, our leases in the residential dorms were made one year long.
That way, students were guaranteed to have the same address all year,
which is very important to them.  Furthermore,  those few who stay
in the dorms year-round get the same address indefinitely.

We have since reduced it to four months, long enough to cover the
summer.  If a student renews near the end of the academic year, and
gets back early, and lives in the same dorm, they'll get the same
address the following year, but we will survive the big September
crunch.

In non-Resnet networks, we generally do one-day leases, with a maximum
of one week.

> (2) Are there lease-lengths that you would consider to be a
>     lower-bound or upper-bound for any ALL practical uses?  If so,
>     what would you be trying to avoid by staying above/below this
>     bound.

One concern I have about the very short lease times that some people
have reported is, what about load on the server and the network
to which the server is connected?  In a large installation, with
thousands of addresses being served by a single central server, this
seems like it could be a consideration.

On the flip side, it looks like just about everything communicates with
the server when it boots, even if the lease is fresh, so maybe short
leases (as long as they are one day or more) don't introduce that much
extra traffic.
-- 
Mark Sirota, Network Systems Engineer
University of Pennsylvania, Information Systems and Computing
[e-mail], 215/573-7214