Re: [Softwires] Unified Softwire CPE: draft-bfmk-softwire-unified-cpe

[Simon Perreault <[e-mail]>]

Le 2012-11-30 20:36, Ole Trøan a écrit :
>> Med: The rationale we adopted in this draft is as follows:
>>
>> * there are three major flavors: full stateful, full stateless, and binding mode
>> * all these modes can support assigning a full or a shared IPv4 address
>
> now you got me thinking, are these really the right modes from a CPE perspective?
>
> let me try to explain, with my CPE implementor hat on, what "modes" would make sense?
>
> - NAT placement. do I need a NAT on the CPE or not?
>    (no NAT && no IPv4 address == DS-lite)
> - full IPv4 address assigned.
>    I can assign the IPv4 address to the tunnel endpoint interface, and use that address for
>    local applications, and as the outbound address of the NAT
>    (mechanisms: MAP, Public 4over6)
> - IPv4 prefix assigned:
>    I need to disable the CPE NAT, and use the assigned IPv4 prefix as my LAN side DHCPv4 pool
>    (mechanism: MAP)
> - Shared IPv4 address.
>    I must enable a local NAT, I cannot assign the IPv4 address on the "WAN" interface, but only use it
>    for the outbound side of the NAT.

Interesting... But note that even just implementing MAP alone would 
generate three of these "implementation modes". I would still like to 
see this list added to an "implementation considerations" section. Stuff 
like "you can't assign a partial address to a tunnel interface" may not 
be obvious to implementers.

> then there might be a sub-modes for "tunnel endpoint determination" i.e. how to determine an IPv6 tunnel end point address given an IPv4 destination address and port.
> 1) algorithmic (MAP)
> 2) configured (Public 4over6, LW46, DS-lite)
>
> and a sub-mode for IPv4 address configuration:
> 1) As "native IPv4"
>      (Public4over6, LW46)
> 2) Embedded Address
>      (MAP)
> 3) None
>     DS-lite
>
> does this make sense?

Totally appropriate for an "implementation considerations" section IMHO.

Simon
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