Re: [Softwires] Proposed Unified Address Mapping for encapsulation and double-translation

[Satoru Matsushima <[e-mail]>]

Leaf, thanks for the summary.

On 2011/10/10, at 20:34, Leaf yeh wrote:

> Remi - >> a1- If the CE has an exclusive or shared IPv4 address:
>>> <--------- 64 ------------><8 ><------ L >= 32 -------><48-L><8 >
>>> +-------------+--------+---+---+----------------+------+-----+---+
>>> | IPv6 prefix |CE index| 0 | V |  IPv4 address  | PSID |  0  | L |
>>> +-------------+--------+---+---+----------------+------+-----+---+
> Ole - > putting the IPv4 address / port information at the end of the interface identifier will allow for > /64 support. > what's the L?
> Remi - Don't see what you found unclear.
> 
> 
> Question: Supposed the question is on the last field, named 'L', in the new address format.
> 

Since Remi's draft doesn't specify 'CE IPv6 prefix length', IPv6 prefix can't be self delimiting to extract IPv4 address and port-set ID in the case of double translation. That's my understanding. Is that correct?
As '4rd-a', and 4via6(draft-murakami-softwire-4v6-translation), the 'L' bits are not necessary because 'CE IPv6 prefix length' is defined through a domain, instead of 'L'.


> 
> Remi - >> A Destination address from a CE to the outside IPv4 Internet is:
>>> <--------- 64 ------------>< 8 ><----   32 ----><--- 16 ----><8 >
>>> +--------------------------+----+---------------+------------+---+
>>> |     BR subnet prefix     | V  |  IPv4 address |      0     |32 |
>>> +--------------------------+----+---------------+------------+---+
> Ole - this is a big change for encapsulation, where prior to this encapsulation means sending to a single destination.
> Remi - Copying an available IPv4 address at a fixed place isn't IMHO a "big change".
> 
> 
> Concern: Supposed the replacement of the 1st 64bits of the BR address with a subnet prefix is not for the tunnel case if the field of IPv4 address can be variable, right?

I think that it could be a case where the BR address with a subnet prefix for the tunnel case. My concern rather than the BR address is that a CE should pick packets up which have 'V' in IID, even destined prefixes are delegated to nodes which are behind of the CE.


> 
> In fact, I doubts we could have the same address mapping for both tunnel and translation. Supposed the address of tunnel end-points is preferred to be fixed, but the address for the translation could be variable.
> 

I think we could have it.

cheers,
--satoru


> 
> Best Regards,
> Leaf
> 
> 
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On Behalf Of Rémi Després
> Sent: Thursday, October 06, 2011 6:07 PM
> To: Ole Troan
> Cc: Softwires-wg
> Subject: Re: [Softwires] Proposed Unified Address Mapping for encapsulation and double-translation
> 
> 
> Le 6 oct. 2011 à 18:47, Ole Troan a écrit :
> 
>> Remi,
>> 
>> [...]
>> 
>>> 2.
>>> (a)
>>> The IPv6 Source address of an IPv4 packet from a CE is:
>>> 
>>> a1- If the CE has an exclusive or shared IPv4 address:
>>> 
>>> <--------- 64 ------------><8 ><------ L >= 32 -------><48-L><8 >
>>> +-------------+--------+---+---+----------------+------+-----+---+
>>> | IPv6 prefix |CE index| 0 | V |  IPv4 address  | PSID |  0  | L |
>>> +-------------+--------+---+---+----------------+------+-----+---+
>> 
>> putting the IPv4 address / port information at the end of the interface identifier will allow for > /64 support.
> 
> Could you explain more the requirement you have in mind?  
> 
>> what's the L?
> 
> On the picture, L is 32 bits + Length(PSID).
> Don't see what you found unclear. 
> 
>> 
>> you suggest that the first subnet of an allocation should be used for this purpose.
> 
> Did I do this?
> Please explain because that's not, IMHO,  something to be done.
> 
>> the first subnet is convenient to use for e.g. manual addressing (since it allows the :: short hand).
>> I do wonder if this has to be provisioned. e.g. some deployments may use the first subnet for the link between
>> CE and PE. (i.e. a /56 - 1 using the PD exclude option is used).
> 
> See just above.
> 
>> 
>>> a2- If the CE has an IPv4 prefix:
>>> 
>>> <--------- 64 ------------><8 ><-- L < 32 --><--- 48-L -----><8 >
>>> +-------------+--------+---+---+-------------+---------------+---+
>>> | IPv6 prefix |CE index| 0 | V | IPv4 prefix |         0     | L |
>>> +-------------+--------+---+---+-------------+---------------+---+
>>> 
>>> (b)
>>> V is the mark that characterizes IPv6 packets that are in reality IPv4 packets.
>>> Its value differs from any permitted value of this octet in IPv6 IIDs  (ref RFC 4291).
>>> 
>>> It is understood that, if double Translation coexists with single translation, concerned ISPs may notify their CEs to use the U octet of RFC 6052 instead of V.
>>> 
>>> An unambiguous mark is fortunately possible because currently permitted IIDs have in their first octet either bit6 = 0 (the "u" bit"), or bit6 = 1 and bit7= 0 (the "g" bit).
>>> With V having "u" = 1 (signifying Universal scope) AND "g" = 1, distinction is therefore deterministic.
>>> 
>>> The proposed V is = 00000011. 
>>> (With other values of this octet, other IID formats can be defined in case some would be useful in the future.)
>>> 
>>> Note that, if and when a consensus is reached in Softwire, an extension of RFC 4291 will have to be submitted to 6MAN. 
>> 
>> or rather IEEE?
> 
> IMHO, IEEE has nothing to do with a marker that is purposely an escape mechanism from the modified EUI-64 format of RFC 4291.
> 
>> I am not convinced that "V" is needed.
> 
> The point is more, IMHO, whether you have an objection to it (and in this case which one).
> Reason is that we are working for a consensus, and several are satisfied with the explanation that there are use cases where it is useful, and none where it is harmful.
> 
>> you could even use the IANA OUI if pretty printing was required.
> 
> The point is that it takes 32 bits which is too much to have IPv4 address + PSID in the IID.
> 
> 
>>> (c)                                   
>>> A Destination address from a CE to the outside IPv4 Internet is:
>>> <--------- 64 ------------>< 8 ><----   32 ----><--- 16 ----><8 >
>>> +--------------------------+----+---------------+------------+---+
>>> |     BR subnet prefix     | V  |  IPv4 address |      0     |32 |
>>> +--------------------------+----+---------------+------------+---+
>> 
>> this is a big change for encapsulation, where prior to this encapsulation means sending to a single destination.
> 
> Copying an available IPv4 address at a fixed place isn't IMHO a "big change".
> 
>> if we also allow for a BR subnet prefix of /128 I'm OK with this (I think).
> 
> I don't understand what you mean by "Subnet prefix of /128".
> 
> 
>>> Note that if double-translation CEs are notified to use U instead of V, the last octet becomes 0 per RFC  6052.
>> 
>> how would a CE know if it was single or double translating?
> 
> Presumably with a usual method, e.g. DHCPv6.
> Anything problematic with that?
> 
> 
>> e.g we could do:
>> 
>> <--------- 64 ------------><--- 24 ------><----- 32 -------><--8 >
>> +-------------+--------+---+--------------------+------+-----+---+
>> | IPv6 prefix |CE index| S | 00-00-5E    |  IPv4 address  | PSID |
>> +-------------+--------+---+---+----------------+------+-----+---+
>> 
>> we also need to handle the case where IPv6 prefix + CE index > 64.
> 
> Please explain more your understanding of this requirement.
> (I personally believe we should avoid that.)
> 
>> I suggest we then just put as much as the interface identifier that will fit.
> 
> 
> May I suggest that, to be more constructive, you could first express your objections to the proposed unified mapping, rather than making a number of new proposals whose justifications are sometimes hard to understand, 
> 
> Cheers,
> RD 
> 
> 
>> 
>> cheers,
>> Ole
>> 
>> 
> _______________________________________________
> Softwires mailing list
> [e-mail]
> https://www.ietf.org/mailman/listinfo/softwires
> _______________________________________________
> Softwires mailing list
> [e-mail]
> https://www.ietf.org/mailman/listinfo/softwires