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

["Hemant Singh (shemant)" <shemant@cisco.com>]

Remi and Alain,

It's a very general statement to refer to broken RFC3484 implementations and I agree with that sentiment.  However, please note that our source address selection behavior for ULA and GUA coexisting on the LAN interface is really simple - odds of broken CPE Router implementations are less.  We are pointing to Rule#2 in RFC3484 for scope comparison.  Here is some relevant text from our draft:

[After this process, every LAN interface has a link-local unicast address, a ULA, and a global unicast address (GUA). Therefore, the interface has to apply source address selection to determine which address to use as a source for outgoing packets. Since the GUA has a larger scope than the link-local address, or the ULA (rule #2 of [RFC3484], the GUA will be used as a source address of outgoing packets that are not subject to rule #1.].

Also, if ULA is not used, what choice does one have to configure an IPv6 address on the CPE Router for manual configuration in a standalone CPE Router?

Thanks.

Hemant 

-----Original Message-----
From: Rémi Denis-Courmont [mailto:rdenis@simphalempin.com] 
Sent: Monday, July 21, 2008 10:58 AM
To: Alain Durand
Cc: Hemant Singh (shemant); v6ops@ops.ietf.org; Wes Beebee (wbeebee)
Subject: Re: New (-02) version of IPv6 CPE Router draft is available for review

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/