Re: [Softwires] MAP Open issues: Interface-id

[Rémi Després <[e-mail]>]

Le 8 nov. 2011 à 09:36, Ole Troan a écrit :

>>> 1. Checksum neutrality being an open question, it is relevant here.
>>> 2. It is useful AFAIK to distinguish CE addresses from BR addresses.
>>> 
>>> The best proposal I know so far is as follows (with CNP = Checksum
>>> neutrality preserver)
>>> 
>>> CE ADDRESS
>>> 
>>> <- - - - - - IPv6 Unformatted  address (104 bits) - - - ->
>>> +-------------------+----------+----------+---------------+
>>> | Rule IPv6 prefix  |IPv4 suff.| Max PSID |  Padding = 0  |
>>> +-------------------+----------+----------+---------------+
>>> :
>>> :<- - - - - - - - - 64  - - - - - >:<- - - - 40 - - - - ->:
>>> :                                  :\                      \
>>> :                                  <8>                      :<- 16 ->
>>> :                                  : :                      :        :
>>> +----------------------------------'-'----------------------+--------+
>>> | IPv6 unformatted address (part 1)|V|                      |   CNP  |
>>> 
>>> +----------------------------------+-+----------------------+--------+
>>> <- - - - - - - - - - -  IPv6 address (108 bits)  - - - - - - - - - - >
>>> 
>>> 
>>> 
>>> BR ADDRESS
>>> 
>>> +------------------------------------+-+-----------------+-+-------+
>>> |              BR IPv6 prefix        |V|   IPv4 address  |0|  CNP  |
>>> +------------------------------------+-+-----------------+-+-------+
>>> < - - - - - - - - - 64  - - - - - - ><8><- - -  32 - - -><8><  16  >
>>> 
>> 
>> +1
>> The checksum neutrality is desirable for translation case.
>> I suggest to take above format into consideration
> 
> the consequence of that is that the destination IPv6 address will change for every flow.

If a source ignores the destination PSID length, yes, IPv6 addresses of two flows going to the same CE may differ.
But so what?
- The IPv4 packet submitted to the CE NAT is the same as the source IPv4 packet
- The final destinations behind the NAT may differ too


> the MAP node cannot any longer listen to a single IPv6 address for MAP traffic, but has to intercept packets for a whole prefix.

- BR's of double translation have always had this property.
- Talking with Mark townsley, I got the understanding that this wasn't a real problem, at least with IOS.
=> Clarifying this point would IMHO be useful. 

Cheers,
RD



> 
> cheers,
> Ole