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Re: why use IPv6, was: Lazy network operators

  • From: Iljitsch van Beijnum
  • Date: Mon Apr 19 05:20:35 2004 
On 18-apr-04, at 23:25, Paul Jakma wrote:


Sure. But I do find myself saying "if we were doing IPv6 right now
we wouldn't have this problem" more and more.



Which problem is that? ;)





(and if it involves NAT... sorry, no.)




There are actually problems in networking that don't involve NAT... :-)



Here's a good one: a customer of mine is a fast growing web hosting
outfit. Many of their customers start out with one or two boxes and a
handful addresses, and then grow. They put a bunch of these customers
in a /24, but after a while the /24 is full and/or the customer gets a
subnet of their own. So far so good. They use a layer 2 setup with
significant redundancy, which inevitably leads to traffic being flooded
by the switches some of the time. This means a customer receives a LOT
of traffic they have no interest in. The solution here would be giving
each customer their own VLAN, but this is hard to do at this juncture
as the IP subnets are tightly interwoven between customers. (Doing it
from the start would take too much configuration and burn address space
a lot faster.) And since invariably one of the first IP addresses such
a customer gets is used as an authoritative DNS, they're in no hurry to
renumber.



With IPv6, every customer would get their own /48, whether they need a
single address or thousands. This makes moving a customer from one VLAN
to another very simple, allowing the flooding problem to be controlled
much better.




See http://countipv6.bgpexpert.com/. The different numbers under
"site" represent different web pages. 8 is a fairly standard one,
and it gets around 0.15% visits from people who are v6-capable.





And are these sites in any way related to IPv6 or networking? (news
at 11, Web sites about IPv6 get less than 1% v6 traffic ;) )



Number 8 isn't. The other ones are to different degrees.

Haesu wrote:




Renumbering is much easier.





I like this one.





Now this is a funny one about IPv6.
How is renumbering *any* easier than IPv4? Yes you have autoconf
based on route advertisements/solicits on the client end from the
routers, but how is that any different than IPv4+DHCP?





Is it perhaps b/c IPv6 uses "classful" styled numbering scheme?
(i.e. you have /64 to end sites, where you simply
 s/old:old:old:old/new:new:new:new/ )




This helps in editing the config files of course. However, the main
difference is that with IPv6 you can change router advertisements, and
within minutes all the boxes start using the new addresses, *without*
breaking running sessions toward the old addresses. With DHCP you're at
the mercy of the lease time timeouts and the way operating systems
handle those. (For instance, under certain circumstances Windows stores
its DHCP address on disk and doesn't bother to refresh it even after a
reboot. Nice.)



Michel's bottom line:




- Today, what to do with IPv6 is simple: nothing. Whether you are an

end-user/small business, large enterprise or provider everyone is in
the

same situation: is costs money to upgrade, causes trouble,


Actually it's cheaper and easier than expected:
http://nwfusion.com/news/2003/1215ipv6.html




not the only thing we have to do anyway, there is no demand and
therefore no ROI. It is urgent to wait.



The nice (but sometimes frustrating) thing about IPv6 is that we can
take (in internet time) forever to upgrade. At this point, the most
important thing is to avoid building new stuff that will get in the way
of IPv6 when the time comes that deploying v6 starts making sense.
Unfortunately, few people understand the idea of taking 5 or 10 years
to upgrade, they think this means doing nothing for 4,5 or 9,5 years
and then frantically start throwing money at the problem. Oh well.