[bcop] IPv6 deployment for small residential providers

Hi Nathalie,

> This should be made clear, as I notice in our training courses, a lot of engineers seem to think that the router ID MUST be an IPv4 address, while it normally is, it is not mandatory. 0.0.0.1 is a valid router-ID, I believe. In an IPv6-only network, for example, when you have no IPv4 addresses, you can just make something 32-bitty up and use that as the router ID. 

True, but it has to be unique a least between a router and all its neighbours. So if everybody on an internet exchange starts using 0.0.0.x then there will be trouble :)

> On the address assignment: What we see and hear in practice in our courses, is assign something on 4-bit boundary, big enough to cater for the next 10 years. 
> So: a /64 only if you are absolutely sure that the customer will never come back for one more subnet (not likely).
> a /60 (if you are conservative)

Don't be :)

> a /56 (most common for residential users)
> a /52 (we see this in some cases for both residential customers and business customers)
> a /48 (for business customers, or for residential customers if you are generous, and have a one-size-fits-all-approach)

I would phrase this as "a /48 (for business customers, and for residential customers if you are not stingy, and/or have a one-size-fits-all-approach)"

But those are minor details. The most common advice is
- give a /48 or a /56 to residential customers
- give a /48 to business customers
- in case of doubt err in the direction of /48

There are not much advantages in giving other sizes to users.

Cheers!
Sander