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

[Rémi Després <[e-mail]>]

Satoru-san,
Sorry for the late answer.

Le 17 oct. 2011 à 15:17, Satoru Matsushima a écrit :

> Hi Remi-san,
> 
>> 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.
> 
> Not enough. The original TTL value in IPv4 header must be carried.

It isn't clear to me that mapping the IPv4 TTL into the IPv6 Hop limit isn't sufficient.
Have you a reference to suggest about this requirement?

Thanks,
RD


> 
> cheers,
> --satoru
> 
> 
> On 2011/10/17, at 21:36, Rémi Després wrote:
> 
>> 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
>