DHCP/UDP performance tuning..

Bruce Hudson Bruce.Hudson at Dal.Ca
Tue Mar 27 17:40:06 UTC 2007

> Mathematically I'm figuring that the server should be getting about 24
> requests per second. This is figured out with 47110 current leases with a
> 7200 sec default lease time with a 14400 max-lease.  Additionally I have 531
> leases that have a 30 sec lease time.  Since we use a MAC address
> registration system the pool with the 30 sec leases are for unregistered MAC
> addresses.

    To start, your math is wrong. Remember that with a 30 second lease, a
client will renew every 15 seconds (at the half-way point for another 30
seconds). Assuming nobody specifies a lease period, your 47110 clients,
renewing once an hour will generate 13 requests per second. The actual
number will probably be closer to twice that since I supsect your maximum
lease time will dominate. Your 531 clients, renewing every 15 seconds
generate 35 requests per second; by far the dominant load. 

    I would serious reconsider your 30 second leases. Even the 2-4 hour
leases are fairly severe. What do you gain from keeping your leases this
short? Are your pools so small they cannot handle the address churn if
they are longer?
Bruce A. Hudson				| Bruce.Hudson at Dal.CA
UCIS, Networks and Systems		|
Dalhousie University			|
Halifax, Nova Scotia, Canada		| (902) 494-3405

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