地址格式？

看了RFC6052和RFC6219里面的介绍。（6052看的多）
6052的地址格式
2.2.  IPv4-Embedded IPv6 Address Format

   IPv4-converted IPv6 addresses and IPv4-translatable IPv6 addresses
   follow the same format, described here as the IPv4-embedded IPv6
   address Format.  IPv4-embedded IPv6 addresses are composed of a
   variable-length prefix, the embedded IPv4 address, and a variable-
   length suffix, as presented in the following diagram, in which PL
   designates the prefix length:

    +--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
    |PL| 0-------------32--40--48--56--64--72--80--88--96--104---------|
    +--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
    |32|     prefix    |v4(32)         | u | suffix                    |
    +--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
    |40|     prefix        |v4(24)     | u |(8)| suffix                |
    +--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
    |48|     prefix            |v4(16) | u | (16)  | suffix            |
    +--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
    |56|     prefix                |(8)| u |  v4(24)   | suffix        |
    +--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
    |64|     prefix                    | u |   v4(32)      | suffix    |
    +--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
    |96|     prefix                                    |    v4(32)     |
    +--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+


6219里面的又是
3.1.  Address Format

   The IVI address format is defined based on an individual ISP's IPv6
   prefix, as shown in the following figure

     | 0                 |32 |40                   |72             127|
     ------------------------------------------------------------------
     |                   |ff |                     |                  |
     ------------------------------------------------------------------
     |<-     PREFIX        ->|<-  IPv4 address   ->|   <- SUFFIX ->   |

                       Figure 4: IVI Address Mapping

   where bit 0 to bit 31 are the prefix of ISP(i)'s /32 (e.g., using
   document IPv6 address IPS6=2001:db8::/32) in the CERNET
   implementation, bit 32 to bit 39 are all ones as the identifier of
   the IVI addresses, and bit 40 to bit 71 are embedded global IPv4
   space (IVIG4), presented in hexadecimal format (e.g.,
   2001:db8:ff00::/40).  Note that based on the IVI mapping mechanism,
   an IPv4 /24 is mapped to an IPv6 /64, and an IPv4 /32 is mapped to an
   IPv6 /72.

   The IETF standard for the address format is defined in [RFC6052].

怎么都是关于IVI地址翻译的，会出来两个地址格式呢？没太明白。
是依据新出来的为准嘛？

RFC6052中的地址格式是供Stateless NAT64和Stateful NAT64方案使用的地址格式吧,貌似和IVI并没有直接联系或对应关系吧？
而IVI对应的有自己独立的IVI地址转换算法，就是IVI相关的RFC文档6219了，这里才是真正定义IVI地址格式的地方哦！
不要把二者搞混吧？
请看RFC6219的Page 5
   The IVI is an early design deployed in the CERNET for the stateless
   translation.  The IETF standard IPv4-IPv6 stateless and stateful
   translation mechanisms are defined in [RFC6144], [RFC6052],
   [RFC6145], [RFC6146], and [RFC6147].
已经说明二者是独立的了。

恩恩，看来得详细看6219的东西了。

今天大概扫了一眼6219，基本就是和stateless NAT64没太大的区别，如果你搞懂了statelss NAT64，则IVI也基本懂了！
PS:主要是其中的地址关系，这也是stateless中稍微复杂一点的地方。
如果你学习stateless NAT64，建议参考RFC6145中的Appendix A.  Stateless Translation Workflow Example
这个流程描述的很详细了，然后你用这个类似的思路去思考IVI中的地址映射关系