RE: ULAs [Re: draft-ietf-v6ops-ipv6-cpe-router-03.txt WGLC]

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

  >-----Original Message-----
>From: Dan Wing (dwing) 
>Sent: Tuesday, January 05, 2010 3:16 PM
>To: 'Brian E Carpenter'
>Cc: Fred Baker (fred); v6ops@ops.ietf.org; kurtis@kurtis.pp.se;
rbonica@juniper.net; draft-ietf-v6ops-ipv6-cpe-router@tools.ietf.org
>Subject: RE: ULAs [Re: draft-ietf-v6ops-ipv6-cpe-router-03.txt WGLC]

>I'm asking for text to provide motivation for the existing L-1 
>requirement (which reads "The IPv6 CE router MUST support ULA 
>addressing [RFC4193]").

About two years back Brian Carpenter gave the dentist's office as one
motivation for use of ULA in the home with the CE Rtr. The dentist's
office network is setup once and that's how it runs for a long time.  If
the Internet WAN link of the dentist's office CE Rtr goes down, the
dentist can still print from his office PC to his printer which are both
using ULA.  The other motivation that is also in emails of v6ops
archives is that what does one do for configuration of the CE Rtr right
out of shrink-wrap?  The user bought the device from retail and powered
it up in the home before attaching the CE Router to any WAN.  Without a
GUA (Globally Unique Address), how does one configure the CE Rtr if
using link-local is spotty at best to access a device with a link-local
URL.  You see, the link-local can be common to all LAN ports of the CE
Rtr and that is why it's not a good address to use to configure the CE
Rtr in a web browser.  So that leaves only the GUA (auto-configured on
the CE Rtr on power up) to configure the device with using a web
browser.  Auto-configuration of the CE Rtr is part of the Phase II
document, so any more details in the current CE Rtr doc (Phase I) will
be skipped.

If none objects that motivation for use of ULA needs to be included as
text in the CE Rtr doc, what we can do is work on a formal version of
what I have summarized above.

Further, in an earlier version of the CE Rtr we also said the ULA and
the GUA coexist on a LAN network interface.  Since the addresses
coexist, here is what our earlier version said about RFC 3484.  

"... every LAN interface has a link-local unicast address, a ULA, and a
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 and ULA have a larger scope than the link-local address (rule #2
of [RFC3484]), the GUA or ULA will be used as a source address of
outgoing packets that are not subject to rule #1.  For source address
selection between a GUA and ULA, rule #8 of [RFC3484] will be used."

In the -03 version we have removed such text.

Thanks,

Hemant