Subject: Re: [dhcwg] Minimum size of a dhcp message

From: Richard Johnson <[email-masked]>
Date: Wed, 15 Oct 2003 22:36:51 -0700

Interesting!  I just finished taking care of an incompatibility between 
our DHCP client and one particular ISP and (after trying various 
changes to get it to work) found the change which finally fixed the 
problem was to *remove* the additional padding of the packets to a 
minimum of 312 bytes.  If I padded the DISCOVER packets, I never got 
any responses.  They were showing me packet traces of a Windows system 
which did *not* do this padding and which got responses just fine.  
Removing our padding got a response as well.  I guess you can take this 
as proof that there exists at least one ISP with a configuration which 
will NOT work if the packets are padded.

/raj

On Tuesday, October 14, 2003, at 07:37 PM, Rob Stevens wrote:

> Barr Hibbs and I are working on an update to RFC2131 and many of the
> issues will be described in the draft
> "draft-ietf-dhc-implementation-01" (forthcoming).
>
> Our recommendation there is that the minimum size of a DHCP packet
> MUST be 300 octets.
> This is based solely on the stated design goal that DHCP be largely
> compatible with BOOTP, and this requirement was imposed on BOOTP
> (RFC951).
>
> Why the original BOOTP stipulated this requirement is hard to say, but
> in the past certain routers were known to drop BOOTP packets with a
> smaller size. I have no idea whether this is true today, but I think
> we should stick with the historical requirement.
>
> Rob Stevens
>
>
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> [email-masked]
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