Re: RAO for IPv4

>From the draft:

> 4.2.  IANA Considerations for IPv6 Router Alert Option Values
> 
>    The registry for IPv6 Router Alert Option Values should continue to
>    be maintained as specified in [RFC2711].  However, when a new
>    allocation is made in this registry an identical registration MUST be
>    made in the IPv4 Router Alert Option Values registry, or that value
>    MUST be reserved.  In the case that it is reserved rather than
>    allocated, the registry entry should say "Reserved (not to be
>    allocated) - Note: This value is allocated in the IPv4 Router Alert
>    Options registry".


Why exactly is it necessary to have the IPv4 and IPv6 number space be
consistent? What is the technical requirement/benefit here?

My own sense is that this would be "nice to have", but it is certainly
not required, and I don't see that having the numbering space be strictly
synchronized as providing compelling technical benefit.

What am I missing?

Thomas