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

[Maoke <[e-mail]>]

hi Gang,

2011/10/8 GangChen <[e-mail]>

> Hello Congxiao, Maoke,
>
> Please see my reply inline.
>
> 2011/10/6, Congxiao Bao <[e-mail]>:
> > Yes, if ISP has /32 IPv6 address, then how to embed 32 bits IPv4 address
> and
> > PSID in the first 64 bits?
> >
> 4v6 translation doesn’t need to embed whole 32 bits IPv4 address
> according to the algorithm. Please take look EA-bits usage in
> http://tools.ietf.org/html/draft-murakami-softwire-4rd-01 for more
> details
>
>
i suppose Ole and Congxiao have clarified this point, right? for the double
translation, full ipv4 address is needed.


> >> sorry but i may not yet understand the mapping algorithm. is the Rule
> IPv6
> >> prefix definitely short enough to take all Max CE in the first 64 bits?
>
> Yes, in padding case.
>
>
what do you mean with the "yes"? do you mean having a short-enough Rule-IPv6
is a prerequisite for deploying 4rd-pd?

for example, a small ISP has its Rule IPv4 prefix such as 10/8, while its
total IPv6 block is a /48 or a /56 prefix only. the ISP is deploying
stateless transition, possibly 4rd-pd. is such an ISP surely able to pad
necessary part of IPv4 address in the first 64 bits?


> >> again, what if an ISP can only get a fairly long IPv6 prefix?
>
> Can I interpret your question like how can we configure mapping
> parameter if ISP only gets a fairly long IPv6 prefix? Yes. I mean that
> could be possible for some ISP.


it *could* be *possible* for *some* ISP but not for any ISP, right?


> However, I find that is somewhat
> contradictory with requirement of prefix delegation deployment. (Note:
> there are also some statements for this requirement in
> draft-boucadair-softwire-stateless-requirements-00 REQ#1, REQ#4). At
> least, I see all current practices are trying to encoding the
> information in first 64 bits (e.g.
> draft-despres-softwire-4rd-addmapping-01
> draft-boucadair-behave-ipv6-portrange-04
> draft-murakami-softwire-4rd-00
> draft-murakami-softwire-4v6-translation-00
> draft-xli-behave-divi-pd-01
> draft-chen-softwire-4v6-pd-00)
>
>
i don't think all current practices are "trying to encode the information in
the first 64bits". to my humble understanding, at least divi-pd encodes the
IPv4 full address information, which identifies a specific user, not in the
first 64 bits.


>
> >  For per-host traffic, the prefix length of ACL should be /128. In this
> > case, you have to specify the value of the suffix. So different ISPs in
> the
> > IPv6 data path can implement IPv6 ACL without additional knowledge.
>
> Again. If there is a way to identify each user in first 64 bits, why not
> use.
>
>
in your proposal draft-chen-softwire-4v6-pd-00, you have

  Delegated IPv6 prefix = IPv6 prefix + Add set + Port set

where your Add-set is (32 - IPv4_pref_len) long, right? if the IPv4_pref_len
= 8 while the IPv6_prefix_len = 48, can your first 64bits identify a user?

thanks and regards,
maoke


> Many thanks
>
> Gang
>