Bandwidth Consumed by DHCP Message
dhcp1 at thehobsons.co.uk
Thu Mar 27 11:43:17 UTC 2008
Aggarwal Vivek-Q4997C wrote:
>Can you please help me with actual figures?
>As per the RFC I guess DHCP Message size is 576 bytes. And lets take the
>worst case scenario that all 150,000 clients require IP at the same
>time. Then according to you how much bandwidth will be required.
Sorry, that's a nonsensical question !
If taken literally, and all 150,000 clients transmitted a 576 byte
packet at the very same microsecond in time, then you could be
looking at filling a gigabit link for as long as it takes to transmit
150,000 x 576 byte packets !
It won't happen, and the server won't deal with it<period>.
You need to work out what are your normal scenarios (including actual
packet sizes), and what abnormal scenarios are reasonably likely to
happen. We cannot do that based on the limited information you've
provided which does not go beyond "150,000 clients" !
What sort of clients ? Desktop PCs (what OS ?) Clients router
appliances ? Something else altogether ?
What sort of network ? All devices in one building ? One corporate
WAN across one or two timezones ? A corporate WAN across many
timezones ? Random customers of an ISP ?
What sort of startup strategy can you **REASONABLY** expect as a
'normal worst case' ? OK, if all the clients are in one building then
it's feasible to see them all suffering a common power outage - but
if they are ISPs customers spread across half of the North American
continent then a common power outage is going to be VERY rare indeed
(but yes I know they do happen - just VERY rarely)
What sort of startup spread would be sensible to expect after a
widespread power outage ? Even if you switched off the whole of the
USA and turned it back on at once (doesn't happen !), then the
clients will have a spread of startup times. ADSL lines will take
different times to sync, different makes/models of hardware router
will take different times to boot, users using a directly connected
PC will take different times to turn them on, and then the PCs will
take differing times to boot.
In a really worst case scenario, what is a realistic target recovery
time - 'instant' is not realistic and you'll simply spends lots of
unneccessary cash not achieving it !
If you cannot answer ALL of those questions for yourself, then no-one
else can do it for you - we don't know what your network is, and what
your requirements are.
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