Re: [Softwires] Thoughts on provisioning and universal CPE

[Cong Liu <[e-mail]>]

Dear Tom and all,

I think this discussion is significant.

2013/10/18 Tom Taylor <[e-mail]>

> (1) DHCP Provisioning of IPv4 Options
> ==============================**======
>
> The conclusion out of Berlin is that the best general solution to
> provisioning of IPv4 and transition-specific options is to use DHCPv4 over
> DHCPv6 as documented in draft-ietf-dhc-dhcpv4-over-**dhcpv6-01.txt. The
> authors of draft-ietf-softwire-map-dhcp-**05.txt argue that that document
> is sufficient to meet the needs of MAP, but it is not a general solution
> and leaves the other techniques uncovered.
>

[Cong] I agree with this conclusion that DHCPv4 over DHCPv6 shoud be used
as the IPv4 provisioning protocol in IPv6 network.
I think it's clear that DHCPv4 is designed for IPv4 address provisioning,
and DHCPv6 is designed for IPv6 address provisioning. I don't understand
what the benefit is to use DHCPv6 for IPv4 address provisioning.


> (4) Summary of Provisioned Information
> ==============================**=======
>
> Common to multiple methods
> --------------------------
>
> Every method requires signalling of the IPv6 tunnel endpoint addresses at
> the CPE and the BR. It is assumed that this is done as a preliminary step,
> as illustrated in draft-ietf-softwire-public-**4over6-10.txt Figure 2.
> That document assumes the provisioning of both addresses is done by DHCPv6,
> if it is done by DHCP at all.
>
> Note that RFC 6334 provides the AFTR-Name option, which is an FQDN.
>

[Cong] map-dhcp-05 defines a new DHCPv6 option OPTION_S46_BR to provide
BR/lwAFTR address. The draft requires both MAP-E and lw4o6 to use this
option.
If a unified tunnel-end option is needed, OPTION_AFTR_NAME in RFC6334
should be used. If this option is not good enough, we should update it.
If OPTION_S46_BR is not going to cover DS-Lite, it should not include lw4o6
either. Then we should define seperate options for each mechanism.
http://tools.ietf.org/html/draft-sun-softwire-lw4over6-dhcpv6-00 describes
such scenario.


> Light-Weight 4over6
> -------------------
>
> An object to specify the assigned port set is required. This would be
> carried via DHCPv4overDHCPv6.
>

[Cong] I agree and think it's a consensus that the recommended provisioning
mechanism for lw4o6 is DHCPv4 over DHCPv6, not DHCPv6.

Best Regards,
Cong