Subject: I-D ACTION:draft-ietf-l2tpext-security-05.txt

From: [email-masked]
Date: Thu, 06 Sep 2001 06:45:51 -0400

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Layer Two Tunneling Protocol Extensions Working Group of the IETF.

	Title		: Securing L2TP using IPSEC
	Author(s)	: B. Patel, B. Aboba, W. Dixon, G. Zorn, S. Booth
	Filename	: draft-ietf-l2tpext-security-05.txt
	Pages		: 27
	Date		: 05-Sep-01
	
This document discusses how L2TP may utilize IPSEC to provide for tunnel
authentication, privacy protection, integrity checking and replay
protection. Both the voluntary and compulsory tunneling cases are
discussed.

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From: Mark Duffy <[email-masked]>
Date: Fri, 07 Sep 2001 15:02:47 -0400

Hi,

It has been my understanding that the approach described in
draft-ietf-l2tpext-security-xx.txt involved using IPsec in *transport mode*
with l2tp.  However, I do not see anything in this draft that explicitly
states that.  Am I just missing it?  Or is it implied somehow?  Or does the
draft purposely leave transport/tunnel mode unspecified?

Thanks, Mark

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From: Skip Booth <[email-masked]>
Date: Fri, 7 Sep 2001 15:06:30 -0400

Most implementations do use transport mode, however it is not mandated or
suggested by the draft.  There are some situations where tunnel mode would
be prefered, i.e. when you are behind a NAT, that's why the isn't any
language which specifies which mode is required.  From a security
perspective, there is no value using one or the other.  The only
optimization in transport mode is the reduction in header size.

If folks feel strongly about this we could add text that clarifies this.

-Skip

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From: Mark Duffy <[email-masked]>
Date: Fri, 07 Sep 2001 18:24:21 -0400

Thanks Skip.  I guess my concern would be about interoperability.  If one
implementation does only transport mode and the other only tunnel mode,
bummer!  Since transport mode is widespread, would it make sense to make
that a MUST and make tunnel mode a MAY?

--Mark

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From: Bernard Aboba <[email-masked]>
Date: Sat, 8 Sep 2001 15:06:30 -0700 (PDT)

Yes, I think that this needs to be made explicit or else inteorperability
will be difficult.

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From: Thomas Narten <[email-masked]>
Date: Thu, 13 Sep 2001 10:08:35 -0400

> Yes, I think that this needs to be made explicit or else inteorperability

Please post the exact text that is being proposed. The IESG is
reviewing the document, and they need to know what the final text is
(i.e., they won't approved documents that are still being revised).

Thomas

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From: Bernard Aboba <[email-masked]>
Date: Thu, 13 Sep 2001 08:03:10 -0700 (PDT)

Here is the text (reflected in the -06 version), added to section 2.1:

"Transport mode MUST be supported, tunnel mode MAY be supported."

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From: Thomas Narten <[email-masked]>
Date: Fri, 14 Sep 2001 12:26:50 -0400

> "Transport mode MUST be supported, tunnel mode MAY be supported."

Great. I misread the thread as saying another text change was needed
to the existing 06 document. Looks like we're set then.

Thomas