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

Hi, Gang, Maoke

2011/10/6 Maoke <fibrib@gmail.com>

> hi Gang,
>
> trying to understand your point, may i follow your message inline? sorry if
> my questions are trial/naive.
>
>  2011/10/6 GangChen <phdgang@gmail.com>
>
>> Hello Congxiao,
>>
>> Thanks for the discussion.
>> Please see my reply inline.
>>
>> 2011/10/5, Congxiao Bao <cx.cernet@gmail.com>:
>> >> > There are no necessary to put IPv4 and Port-set ID information in
>> last
>> >> > 64 bits.
>> >>
>> >> The CE Pv6 prefix included in the /64 Subnet prefix isn't self
>> delimited,
>> >> so that the length of the CE index can't be determined in this part of
>> the
>> >> address.
>> >> Having the length of the A or A+P prefix in the IID completes what is
>> >> needed to derive the CE port-set.
>> >
>> > Besides, if a medium or large size ISP can’t get short enough IPv6
>> prefix
>> > (ex. /24), the first 64 bits can not contain the whole IPv4 32 bits,
>> which
>> > cannot make the double translation successful.
>>
>> I guess that is depending on a specific algorithm. I don't see such
>> limitation in 4v6
>> translation(
>> http://tools.ietf.org/html/draft-murakami-softwire-4v6-translation-00)
>>
>>
> i couldn't understand why we "don't see such limitation in 4v6
> translation". 4via6 translate the private ipv4 address with 4rd mapping rule
> while the public ipv4 address with RFC6052 algorithm, right? can the both
> case work fine if an ISP can only get a fairly long IPv6 prefix, like /40 or
> even longer?
>

Yes, if ISP has /32 IPv6 address, then how to embed 32 bits IPv4 address and
PSID in the first 64 bits?

>
>
>>
>> > The ISP is not able to achieve per-host traffic control without a
>> standard
>> > defining last 64 bits. If the ISP does, why not use IPv4+psid in suffix
>> > naturally instead of other new bits definition?
>>
>> First off, I'm not sure per-host traffic control is a common case for
>> network operations
>>
>
> i think it is common for, maybe, not any network operators but at least
> some operators. especially for those running middle-to-small ISP services
> (like my company), the capability of per-host traffic control is definitely
> needed. a specific but not rare case is suppressing the pathologically
> greedy download/upload behavior of bot-net boxes.
>

Agree.

>
>  Secondly, it could be possible to use first 64 bits differentiating
>
>  hosts. Please see Max PSID usage in
>
> http://tools.ietf.org/html/draft-despres-softwire-4rd-addmapping-01#page-15
>>
>
> 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?
> again, what if an ISP can only get a fairly long IPv6 prefix?
>
>
 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.

Congxiao

>
>>  Many thanks
>
>
>> Gang
>>
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