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Re: New (-02) version of IPv6 CPE Router draft is available for review

The only time the CPE router needs to use GUA is if it has never received a delegated prefix. Prefix delegation uses the same leasing mechanism as address assignment; if the WAN interface on the CPE router is not up, the CPE router can still use the previously delegated prefix on the subscriber network.
So, as long as the CPE router has been connected to the ISP network at least once and has obtained a delegated prefix, there is no need for GUA. To avoid unnecessary complexity, I would strongly recommend that the CPE router be required to complete an initial prefix delegation operation when first connected to the ISP before enabling any downstream interfaces. Once that prefix delegation takes place, it is immaterial whether the LAN or WAN interface comes up first.
This discussion brings up the problem of subscriber network operation - is it an explicit goal of this document that the subscriber network be able to operate even if the WAN interface is not up? What are the expectations for that unconnected operation and what services must the CPE router provide to meet those expectations?
According to the spec, the requesting router can only use the delegated prefix until the lease on the prefix expires. We hadn't thought about relaxing that restriction to allow the requesting router to continue to use the delegated prefix until it has a WAN connection back to the delegating router. 

- Ralph


On Jul 21, 2008, at Jul 21, 2008,10:57 AM, Rémi Denis-Courmont wrote:


Le vendredi 18 juillet 2008 19:25:54 Alain Durand, vous avez écrit :
Supporting both ULA & GUA at the same time is also a source of complexity 
and confusion. The key problem I see is with external referrals in
multi-party communications where some of the hosts are inside, and some are 
outside. Mixing ULA & GUA can have complex consequences, and again
generates service call.
Yeah. Broken RFC3484 implementations will do just that. But all nodes (broken and non-broken RFC3484 implementations alike) will *break* without ULA, until we have *instantaneous* 100%-reliable and 100%-available upstream connections (which we will NEVER have). Without this, the network will simply not work 
until the ISP connection is established (if ever), which is a total
non-starter. Therefore, it seems like a total non-question that ULA is the 
way to go.
Also, if I read the text correctly, if the WAN interface gets configured first, no ULA are generated. Which leads to confusing situation depending 
on whether the customer turns its modem on before or after its CPE.


You may have a point here.
I would rather like the text to recommend to only use ULA when nothing else 
is available and immediately renumber to GUA when those are acquired.


And break existing connections on the local network? Total no go.

--
Rémi Denis-Courmont
http://www.remlab.net/