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[Softwires] 4rd-U complement - e2e transparency to IPv4 TOS

Rémi Després <despres.remi@laposte.net> Mon, 17 October 2011 12:36 UTC

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From: Rémi Després <despres.remi@laposte.net>
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Date: Mon, 17 Oct 2011 14:36:27 +0200
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To: Satoru Matsushima <satoru.matsushima@gmail.com>
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Cc: Softwires WG <softwires@ietf.org>
Subject: [Softwires] 4rd-U complement - e2e transparency to IPv4 TOS
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Hi Satoru-san,

Thank you for identifying a limitation of the 4rd-U  
You are right, as currently specified, "it doesn't support diff-serv tunneling model, pipe and short-pipe".
All these need e2e transparency to the IPv4 Type of Service.

Fortunately, this is easy to fix: in the Identification field of the IPv6 Fragment header, copy not only the DF bits but also the IPv4 TOS.
  
The proposed 4r-U packet format becomes:


   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Vers=6 |   TrafClass   |            Flow Label                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Payload Length        |Next Header=44 |   Hop Limit   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                  IPv6 Source Address                          +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                IPv6 Destination Address                       +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Next Header  |    Reserved   | IPv6  Fragment Offset   | 0 |M|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |D|      0      |    IPv4 TOS   |       IPv4 Identification     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                        IPv4 Payload                           |
   |                                                               | 

With this added, I believe that 4rd-U is a real progress over previously proposed Double translation and Encapsulation.
It can make IMHO a valuable unified standard.

Yet, I may have missed something else. 
New justified objections are therefore most welcome..


Regards,
RD

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