Subject: Re: [Softwires] ***CAUTION_Invalid_Signature*** Re: On the topic of OPTION_S46_IPV4ADDRESS

From: <[email-masked]>
Date: Fri, 15 Nov 2013 13:23:29 +0100

Hi Ole,

>
>if optional, we have to think through the corner cases:
> - how does a CPE know when to initiate DHCPv4 (or PCP)?

[ian] Unified CPE is scoped to solve this.

> - can a CPE end up with an IPv4 address provisioned both with
>OPTION_S46_IPV4ADDRESS
>   and DHCPv4 (and PCP)?

[ian] Again, unified CPE describes how to deal with this, if it¹s possible
to happen.

> - what does the CPE do with IPv4 addresses with longer lifetimes than
>the softwire?

[ian] lw4o6 states that if the v6 prefix changes, it re-runs whatever v4
provisioning, so it would be up to the v4 config server to decide if the
same or new parameters were given out.
>
>I'm sure there are more.
>keeping choice down makes for a simpler solution.

[ian] the problem that we have here is that we¹re trying to solve hybrid
provisioning cases: If I get this parameter from DHCPv4 and this from
DHCPv6, then how do I deal with it?

The simple answer here is to say: don¹t do hybrid provisioning. If
option_s46_xx provides all the v4 conf you need, need, then use it. If it
doesn¹t, then use DHCPv4overDHCPv6.

Thinking further about Simon¹s original question, which sparked this
discussion: if you¹re implementing the OPTION_SW_CONT_LW46, then you have
to implement all of the sub-options that it needs including the
OPTION_S46_IPV4ADDRESS. Then it¹s a self-contained softwire provisioning
mechanism in it¹s own right.

Likewise, DHCPv4o6 and PCP need to provide self-contained softwire
provisioning mechanisms in their own right. DHCPv6 may be used to switch
them on, but all of the actual parameters that are necessary for
provisioning the softwire come through DHCPv4o6 or PCP.

If we go down this road, then adding the previously suggested priority
field as a sub option into OPTION_S46_XX,
OPTION_S46_DHCPV4OVERV6_ACTIVATE(?) and OPTION_S46_PCP_ACTIVATE(?) gives
both the CPE a way of indicating what it can do, and for the operator to
indicate what they would prefer without having to consider all 'Possible
Parameters' x Œavailable configuration protocols¹.

Cheers,
Ian

---

From: Ole Troan <[email-masked]>
Date: Fri, 15 Nov 2013 13:57:05 +0100

Ian,

confused, so please bear with me.

I thought the OPTION_SW_CONT_LW46 was going to be used to provision the softwire,
regardless of how IPv4 was provisioned on top of it.
you seem to indicate below, that is not the case?
if so, there would be no reason to make OPTION_S46_IPV4ADDRESS optional.

how would you then provision the softwires?
I think we need a complete picture to ensure we have the right thing in MAP DHCP.

cheers,
Ole