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

Satoru Matsushima <satoru.matsushima@gmail.com> Tue, 11 October 2011 11:25 UTC

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From: Satoru Matsushima <satoru.matsushima@gmail.com>
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Date: Tue, 11 Oct 2011 20:25:27 +0900
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To: Leaf yeh <leaf.y.yeh@huawei.com>
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Cc: Softwires-wg <softwires@ietf.org>, "fine_sz@huawei.com" <fine_sz@huawei.com>
Subject: Re: [Softwires] Proposed Unified Address Mapping for encapsulation and double-translation
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On 2011/10/11, at 20:00, Leaf yeh wrote:

>> 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 |
>>>> +--------------------------+----+---------------+------------+---+
> Leaf -> 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.
> Satoru -> I think we could have it.
> 
> What is the definition of the IPv4 address in the above format? Is it the destination IPv4 address of any hosts outside 4rd IPv4 domain in the internet?

I believe that the embedded IPv4 address should be an IPv4 address of a host on outside the domain.

cheers,
--satoru

> 
> 
> Best Regards,
> Leaf
> 
> 
> -----Original Message-----
> From: Satoru Matsushima [mailto:satoru.matsushima@gmail.com] 
> Sent: Tuesday, October 11, 2011 4:30 PM
> To: Leaf yeh
> Cc: Satoru Matsushima; Rémi Després; Ole Troan; Softwires-wg; fine_sz@huawei.com
> Subject: Re: [Softwires] Proposed Unified Address Mapping for encapsulation and double-translation
> 
> 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: softwires-bounces@ietf.org [mailto:softwires-bounces@ietf.org] 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
>>> 
>>> 
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