Hey all,

 

ESP Header Compression (EHC, [1]) defines a set of rules how to compress ESP 
for specific scenarios, e.g. IoT and [2] describes how to negotiate this rules 
with IKEv2.

Due to some suggestions we defined a new IPsec mode (COMPRESSION_MODE), which 
is necessary in order to prevent decompression failures in certain maybe 
unforeseen situation (e.g. IP fragmentation, or the use UDP options).

 

With the new mode, the sender can decide to send certain packets “uncompressed” 
if the receiver may not be able to decompress properly.. The sender notifies 
the receiver by using a different SA and thus a different SPI.

We believe this is more clean than defining something like a “compressed” bit 
in the ESP packet. 

 

That’s why we also thought about how to negotiate this new mode with IKEv2.

We believe that a clean way to negotiate this new mode is with a new Notify 
Payload, namely “USE_COMPRESSED_MODE”.

The question is, do we need an explicit agreement of the COMPRESSED_MODE or is 
the negotiation of using EHC [1] enough to figure out that the two peers have 
to use COMPRESSED_MODE anyways?

 

More specifically here are the following possibilities

A) Negotiating 2 IPsec SAs with EHC parameters and specifying. with 
USE_COMPRESS_MODE the SA that compress payload (using EHC). The other SA 
*without* USE_COMPRESS_ MODE will not proceed to compression. In other words, 
EHC is activated if and only if USE_COMPRESS_MODE is active for the SA.

B) Negotiation of 2 IPsec SAs. One with EHC parameters which assumes 
compression is requested and one without EHC in which case no compression is 
performed.

 

During the last IETF we had a brief discussion in the meeting which we would 
like to bring to the list now.

We’re looking forward to any opinions or suggestions.

 

Regards

Tobias

 

[1] https://tools.ietf.org/html/draft-mglt-ipsecme-diet-esp-06 

[2] https://tools.ietf.org/html/draft-mglt-ipsecme-ikev2-diet-esp-extension-01

 

 

-- 

         _  _ _  _ _  _          Tobias Guggemos M.Sc.

         |\/| |\ | |\/|          Institut für Informatik / Dept. of CS

         |  | | \| |  |          Ludwig-Maximilians-Universität München

      ======= TEAM =======       Oettingenstr. 67, 80538 Munich, Germany

                                 Room E 010, Phone +49-89-2180-9209 

Munich Network Management Team   Email: [email protected] 
<mailto:[email protected]>   

Muenchner Netz-Management Team   http://www.nm.ifi.lmu.de/~guggemos 

 

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