Subject: Re: IKEv2 Correction (editorial)

From: Radia Perlman - Boston Center for Networking <[email-masked]>
Date: Tue, 14 Oct 2003 16:50:27 -0400 (EDT)

I don't understand why reserved fields shouldn't be "MUST be sent
as zero". At least for implementations of this draft. There might be
a future version that uses the bits, but that spec would no longer
say "MUST be sent as zero". Instead it would say "MUST be set to the
grobnitz filter value" or whatever the reserved bits get used for.

If the spec for this version of IKE says SHOULD, doesn't that allow
a vendor to use the bits for some proprietary purpose?

Radia

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From: Paul Koning <[email-masked]>
Date: Tue, 14 Oct 2003 17:38:54 -0400

>>>>> "Radia" == Radia Perlman <- Boston Center for Networking <[email-masked]>> writes:

 Radia> I don't understand why reserved fields shouldn't be "MUST be
 Radia> sent as zero". At least for implementations of this
 Radia> draft. There might be a future version that uses the bits, but
 Radia> that spec would no longer say "MUST be sent as zero". Instead
 Radia> it would say "MUST be set to the grobnitz filter value" or
 Radia> whatever the reserved bits get used for.

 Radia> If the spec for this version of IKE says SHOULD, doesn't that
 Radia> allow a vendor to use the bits for some proprietary purpose?

Two reasons.

1. "SHOULD" on send rules is the standard rule.
2. If you say "MUST send as zero" that creates a strong temptation in
   receivers to check for zero and reject the packet if a non-zero is
   found.  If that is done, the whole version thing breaks.

	   paul

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From: "Lakshminath Dondeti" <[email-masked]>
Date: Tue, 14 Oct 2003 17:47:15 -0400

Hi Paul,

I just checked 2407 and 2408:

2407 says MUST be zero
2408 says Unused, set to 0.  :-)

Could you please point me to a reference that says "SHOULD on send is 
the standard rule."

thanks,
Lakshminath

PS:  CW, quoted several times elsewhere says: "be conservative in what 
you send and generous in what you receive"; that might simply work!