shim6 @ NANOG

Stephen Sprunk stephen at
Fri Mar 3 20:24:04 UTC 2006

Thus spake "Iljitsch van Beijnum" <iljitsch at>
> Man, I hope I never become as cynical as you.

A pessimist is never disappointed.

> On 2-mrt-2006, at 11:09, Stephen Sprunk wrote:
>> Why is it even remotely rational that a corporate admin trust 100k+ 
>> hosts infested with worms, virii, spam, malware, etc. to handle 
>> multihoming decisions?
> They trust those hosts to do congestion control too, which is even  more 
> important.

No, they don't.  That's why nearly every enterprise has deployed intradomain 
QoS of some sort.

Nearly everyone doing VoIP has to use QoS to prevent hosts (with "congestion 
control") from messing with their voice traffic.  Others have had to deploy 
it to prevent non-mission-critical (or even prohibited) apps from 
interfering with mission-critical stuff.  I had one customer that had to 
implement QoS on their entire WAN just to keep Outlook and web access from 
starving out their serial-over-X.25-over-IP business application.

The people who pay for the network want to have control over it.

>> Especially when we don't even have a sample of working code today?
> The IAB goes out of its way to solicit input on ongoing work, and now  you 
> whine about lack of working code?

I'm not whining (at least I don't think so), but I think it's very premature 
to talk about shim6 as the solution to IPv6 multihoming when it's not a 
deployable solution or even a fully specified one.

>> Now, some may take that as a sign the IETF needs to figure out how  to 
>> handle 10^6 BGP prefixes...  I'm not sure we'll be there for a  few years 
>> with IPv6, but sooner or later we will, and someone needs  to figure out 
>> what the Internet is going to look like at that point.
> It won't look good. ISPs will have to buy much more expensive  routers. At 
> some point, people will start to filter out routes that  they feel they 
> can live without and universal reachability will be a  thing of the past.

That's one possible end case.  The other is that all of this is a tempest in 
a teapot and the growth of IPv6 PI routes will continue to be non-dominant 
just as PI is with IPv4.  As others have noted, one prefix per ASN (which is 
the goal of IPv6 PI policy) is nowhere near enough to create a problem 
unless there's a serious explosion in ASN assignment.  The policies for IPv4 
are pretty darn lax, so if we don't have a problem today, why do people 
think we'll have a problem with stricter policies on the IPv6 side?

And I'm the cynic...

> It will be just like NAT: every individual problem will be solvable,  but 
> as an industry, or even a society, we'll be wasting enormous  amounts of 
> time, energy and money just because we didn't want to bite  the bullet 
> earlier on.

People pay what they perceive to be the lowest cost to themselves; so far, 
NAT has that honor.  I'm more confident that we'll find an answer to the IDR 
problem sooner than we'll convince people to act in the good of the 
community at their own expense.


Stephen Sprunk        "Stupid people surround themselves with smart
CCIE #3723           people.  Smart people surround themselves with
K5SSS         smart people who disagree with them."  --Aaron Sorkin 

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