[PATCH] udhcpc: add support IETF RFC2131 section-4.1 retransmission strategy

Frank TEO frank128 at ymail.com
Fri Sep 28 15:58:59 UTC 2012


A retry timeout of 40ms from large quantities of machines would 

create a DDoS to the dhcp server when recovery from large scale power failure.


If 40ms is the upper limit, it would be better off using static IP address.



----- Original Message -----
From: Rich Felker <dalias at aerifal.cx>

On Fri, Sep 28, 2012 at 03:04:02PM +0800, Frank TEO wrote:
> IETF RFC2131 section-4.1 retransmission strategy said
> 
> The client MUST adopt a retransmission strategy that incorporates a
> randomized exponential backoff algorithm...
> 
> first retransmission SHOULD be 4 seconds ...
> next retransmission SHOULD be 8 seconds ...
> retransmission delay SHOULD be doubled with subsequent
> retransmissions up to a maximum of 64 seconds.

Perhaps this should be the default, but as bad as dhcp servers tend to
be, I like starting at 40ms retry rather than 4s... Perhaps the RFC
should adopt language that the dhcp server MUST reply within 100ms..

Rich


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