Subject: RE: Question on draft-ietf-l2tpext-security-02.txt

From: "Chen, David" <[email-masked]>
Date: Thu, 24 May 2001 17:40:53 -0400

Since the L2tp depands on the IPSec's transport mode which is
an "eval" among IPSec community and
they prefer IPSec tunnel mode that more secure but has headache.
Why this WG does not draw up a few AVP exchanges to implement
DH key exchange, Public key certification, and encryption algorithm to
satisfy both IPSec's tunnel mode and l2tp's security requirement?

--- David

-----Original Message-----
From: Skip Booth [mailto:[email-masked]]
Sent: Thursday, May 24, 2001 1:22 PM
To: Jhilmil Kochar
Cc: W. Mark Townsley; [email-masked]
Subject: Re: Question on draft-ietf-l2tpext-security-02.txt

Jhilmil Kochar writes:
> Hi,
>     I had 2 questions on this draft.
> 1.section 7.1
> "The L2TP security protocol MUST provide authentication, integrity and
> replay protection for control packets. In addition, it SHOULD protect
> confidentiality of control packets. It MUST provide integrity and replay
> protection of data packets, and MAY protect confidentiality of data
> packets. An L2TP security protocol MUST also provide a scalable approach
> to key management."
> The draft does not talk of requirement of authentication of data packets.
Why?

"It MUST provide integrity and replay protection of data packets"

I believe integrity at least in the sense of IPsec implies authentication.
Would it make you happy if this sentence where worded:

"It MUST provide authentication, integrity and replay protection of data
packets"

> 
> 2. what happens to control plane security as defined in L2TP draft using H
> bit, Random vector and MD5 hashing in the presence of IPSEC security? The
> draft does not talk of this. Taking care of  both would mean duplicating
the
> effort so that should mean that data hiding in control plane should be
> disabled by default when IPSEC is enabled.

I personally don't think this is an area that the draft needs to focus
on. Just because the L2TP packets are being protected by IPsec doesn't rule
out the need to do AVP hiding.  For instance, the IPsec SA may only be
providing authentication/integrity checking of the control packets and thus
it's still desirable to use AVP hiding for confidentiality of AVPs.

-Skip

> 
> Thanks in advance
> Jhilmil Kochar
> 
> --
> 
> ------------------------------
> Jhilmil Kochar
> Technical Manager
> Globespan India
> E-mail:mailto:[email-masked]
> Web: http://www.globespan.net
> 
> 
> 
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---

From: "W. Mark Townsley" <[email-masked]>
Date: Thu, 24 May 2001 18:07:01 -0400

> satisfy both IPSec's tunnel mode and l2tp's security requirement?

We did (well, some of us did) a long time ago, before the L2TPEXT WG
existed, but it was rejected. 

Also, many contend that IPsec tunnel mode is *not* more secure than L2TP
secured by IPsec.

- Mark