v6 & DSL / Cable modems [was: Private use of non-RFC1918 IP space (IPv6-MW)]

TJ trejrco at gmail.com
Tue Feb 10 16:08:43 CST 2009

>> Your routers fail frequently?  And does your traffic continue to get
>> forwarded?  Perhaps through another router?
>More frequently than the DHCP server, but neither are "frequent" events.
>Cisco's software is not 100% perfect, and when you plug it into moderately
>unstable things like phone lines (DSL) and cable networks, those little
>cause reloads -- you'd think they'd have better error handling, but they
>don't. (I don't buy millions in equipment from Cisco so they don't care
>about my problems.)  While I could use backup links, flip-floping between
>ISPs with different addresses is not ideal (and that's as true for
>v6 as v4.)

But my real point was if the router is failed, traffic isn't being forwarded
regardless of how the host got the information ... correct?

And vendor support issues are a layer 8-11 problem ... no layer 3 fix for
(8-11 == people politics religion money ... in no particular order)

>> Why is there a problem with RAs being the first step, possibly
>> including prefix info or possibly just hinting @ DHCPv6?
>Because it doesn't fit the needs of *every* network.  In fact, it's only
>"good enough" for very few networks.  As such it just adds more useless
>layers of bloat.

Obviously we disagree, fundamentally.

>> Well, as it stands now the RA isn't useless.
>> Also, it is not true in every case that hosts need a "lot more" than
>> an address.
>> In many cases all my machine needs is an address, default gateway and
>> DNS server (cheat off of v4 | RFC5006 | Stateless DHCPv6).
>It's useless.  It does NOT provide enough information alone for a host to
>function.  In your own words, you need a DNS server.  That is NOT provided
>by RA thus requires yet another system to get that bit of configuration to
>the host -- either entered manually, DHCPv6, or from IPv4 network
>configuration (ie. DHCP!)  Forcing this BS on the world is a colossal
>We've had a system to provide *ALL* the information a host needs or wants
>the IPv4 world for years.  Why it's not good enough for IPv6 is beyond me.

Technically, that is a gap RFC5006 would fill - once supported, which should
have been long before now but too late for that, eh?

And I think we also disagree on a fundamental aspect, specifically - I see
it this way:
	1) the RAs are there primarily to allow a router to provide
information about itself to the hosts on the link
		a) which becomes the default gateway from the hosts'
	2) Everything after that is a separate thing, namely - host
addressing and "other" configuration
 		a) which could be SLAAC, by including a prefix in the RA ...
and maybe a DNS server option, someday.
			-) and maybe Stateless DHCPv6 as well, for the DNS
or other missing info
 		b) which could be DHCPv6, providing all of the addressing
and config info (but not router info)

I think the key factor to our disagreement is that I think it makes great
sense for the router to provide information about itself to the hosts, and
you'd rather it be centralized.  I don't really care either way, to be
honest - it just seems to make good sense (to me) the way it works now.  If
I understand correctly the answer, from your standpoint, would be to author
an RFC specifying a default gateway option for DHCPv6 (and maybe a prefix
length option as well?).  And then get DHCPv6 client functionality itself,
and this option, more widely supported (and in fact, "on by default").

As to "why it's not good enough" ... well, suffice it to say this debate has
raged for a LOOOONG time and apparently sufficient consensus (for reasons
good or ill) was reached at some point for the way it is now.  Build
consensus to change that (factoring in the pain it would cause to current
deployments) ... maybe starting off small, with just defining the option and
convincing a major vendor or two to implement it ... if the world agrees, it
will migrate to working that way ... isn't that how this whole open
standards process is supposed to work? 
(OK, that last question was a bit rhetorical and was not meant to spark a
debate about this being the IETF vs the IVTF vs the ______ etc. etc.

Failing that (or while that is ongoing?) ... we have what we have.  
And it does indeed work, today, for almost all * cases.  
So let's get deploying, go team!

* - as discussed at length on this list and others

"Be conservative in what you send and liberal in what you accept." --Jon
"The future belongs to those who see possibilities before they become
obvious." --unknown
"In essentials, unity; in non-essentials, liberty; in all things, charity"
"Everyone's a hero in their own way, in their own not that heroic way."
--Joss Whedon

More information about the NANOG mailing list