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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/