Bandwidth Consumed by DHCP Message
dhcp1 at thehobsons.co.uk
Thu Mar 27 07:46:09 UTC 2008
Aggarwal Vivek-Q4997C wrote:
>I v a network of 150,000 clients requiring an IP Address simultaneously
>from the ISC-DHCP Server (3.0.6). Can anyone please help me in guiding
>that how much bandwidth will be required?
When you say "... requiring an IP Address simultaneously ...", is
that simply the total of all your clients, or do you mean that you
might want to service them all obtaining a lease at the the same
point in time ? It makes a big difference !
The packets themselves are small, perhaps 100 to 150 bytes - it
depends on what options you use. Discover and Request are the
It takes a two packet handshake to renew an existing lease, four
packets to obtain a lease from cold. So worst case, assume all
clients need to do do Discover-Offer-Request-Ack - that's going to be
about 1/2k total traffic. For 150,000 clients that's going to be
around 75,000k, or 75MByte of traffic. It will be split at about 30MB
client-server and 45MB server-client.
However, the server would not handle that number of requests in a
short space of time, check the archives for a number of threads
related to supporting large numbers of clients.
More normally, many of your clients will already have a lease, they
just want to renew it - so that halves the traffic. Worst case for
them in a business environment is the 'morning rush hour' as users
come in and switch on their PCs. I would guess that with 150,000
clients they are not all going to be switched on at once, and will
more likely be spread over at least an hour, more likely several
If your devices are left on permanently, then the load will be spread
over whatever lease time you use - or more correctly half the lease
time as most clients will renew at somewhere around half the lease
time. If your leasetime is (say) 15 days, then that's going to be
20,000 clients/day renewing, or about one every 4 seconds on average.
So, there's your parameters, you'll need to do the sums for your
particular setup and operating regime.
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