passing values to client: how big?

Simon Hobson dhcp1 at
Tue Jan 13 12:42:06 UTC 2009

Carl Karsten wrote:
>Someone just suggested passing a public key.
>Is there a limit on how big the parameters, and the over all dhcp response is?

Yes, there is.

The UDP packet is limited to 576 bytes, unless the client indicates 
that it can accept larger. 312 bytes are allowed for the variable 
option part - but don't forget that each option value is preceded by 
a byte for option code and a byte for option length - eg a 4 byte 
option would take 6 bytes the packet.

There is also a facility to redefine the server and file fields as 
option space, this gives an extra 192 bytes for options.
Simon Hobson

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