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Re: Why can't ESP authenticate IP header?
Title: Re: Why can't ESP authenticate IP
header?
At 7:11 PM +0530 9/25/01, lokesh wrote:
----- Original Message -----
From: Stephen
Kent
To: lokesh
Cc: ipsec@lists.tislabs.com
Sent: Tuesday, September 25, 2001 6:13
PM
Subject: Re: Why can't ESP authenticate IP
header?
At 10:25 AM +0530 9/25/01, lokesh wrote:
As noted, ESP coverage of selected header fields would
increase complexity and reduce performance. It also would create even
more circumstances where NAT could interfere with IPsec use. Today,
using ESP in tunnel mode can be made to work with NAT, but if the
outer S/D IP addresses were covered, that capability (I hesitate to
call it a feature) would go away.
Steve,
As for as I know, in
many implementations, NAT is done prior to ipsec processing at the
sending end, and Ipsec processing is done before NAT at the receiving
end.
Are there situvations where
NAT would interfere in ipsec processing ? if so, kindly will you brief
them?
Assuming there will be
situations where NAT will interfere with IPsec processing, how AH in
transport mode will work there?
I get the feeling that you have not been reading this list
for very long.
Yes, a combined IPsec/NAT implementation in a security
gateway avoids the problems I cited. The NAT problems I refer to arise
when NAT takes place at a device that is between the IPsec
implementation and the Internet. For example, I am in a hotel room in
London now and if I had IPsec on my laptop, it would have to deal with
the NAT box that the hotel has deployed. Same problem arises in many
cable modem nets, and for desktop IPsec implementations in corporate
environments where NAT is performed at the
gateway/firewall.
Steve,
yes , I have subscribed it
very recently,
in such scenarios, as the one
you mention above, I think AH in transport mode should not be used
right?
Thanks
-Lokesh
AH in any mode will break in these contexts, as will ESP in
transport mode, but ESP in tunnel mode is less problematic.
Steve
References: