Placement of IPCOMP header in IPSEC Tunnel mode

"Strahm, Bill" <bill.strahm@intel.com> Thu, 18 November 1999 00:15 UTC

Message-ID: <7DAA70BEB463D211AC3E00A0C96B7AB20344B38B@orsmsx41.jf.intel.com>
From: "Strahm, Bill" <bill.strahm@intel.com>
To: ipsec@lists.tislabs.com
Subject: Placement of IPCOMP header in IPSEC Tunnel mode
Date: Wed, 17 Nov 1999 13:32:25 -0800
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I am confused about the placement of the IPComp header when used in Tunnel
mode.

>From RFC 2393 Section 2.1
   In IP version 4 [RFC-0791], the compression is applied to the upper
   layer protocol (ULP) payload of the IP datagram.  No portion of the
   IP header or the IP header options is compressed.

Now in Tunnel mode I am building an IP packet that looks like this

IP(outer)- IPSEC transform - IP(inner) - data

I am convinced that the correct placement of a tunnel mode compression
header is

IP(outer) - IPSEC transform - IPCOMP - IP(inner) - data

However from section 2.1 I can see a reading that says I am not to compress
the IP header or options, so a packet would be built like this

IP(outer) - IPSEC transform - IP(inner) - IPCOMP - data

If this later packet is correct I would have a hard time determining if I
should unapply compression at the gateway or the end host.

Can I get some clarification on this point please ?

Bill

______________________________________________
Bill Strahm        Programming today is a race between
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Placement of IPCOMP header in IPSEC Tunnel mode Strahm, Bill
RE: Placement of IPCOMP header in IPSEC Tunnel mo… rmonsour