why use IPv6, was: Lazy network operators

Patrick W.Gilmore patrick at ianai.net
Sun Apr 18 10:16:58 UTC 2004


On Apr 18, 2004, at 4:32 AM, Iljitsch van Beijnum wrote:

> On 18-apr-04, at 4:48, Paul Jakma wrote:

>> Well, let's be honest, name one good reason why you'd want IPv6
>> (given you have 4)?
>
> Let me count the ways... At home it's great because of the extra 
> address space. I have a /29 at home, which is pretty luxurious 
> compared to what most people have, but not nearly enough to give all 
> my boxes a real address if I turn them all on at the same time. Worse, 
> I still haven't figured out a way to give some machines always the 
> same address (if available) but also use that address for something 
> else if the "owner" is turned off. In IPv6 all of this is a breeze: a 
> single /64 gives you all the addresses you'll ever need and boxes 
> configure themselves with the same address each time they boot, even 
> when using different routers and no need for DHCP.

Dunno what your problem is, I have no problem getting as much address 
space as I need as long as I can justify it.  Perhaps you need to speak 
to your provider?


> Another thing I really like about IPv6 is the much smarter "on-link" 
> behavior. In IPv4, it's not uncommon to have two hosts on the same 
> physicial subnet, but with addresses from different prefixes. These 
> hosts will then have to communicate through a router, which in this 
> time of cheap 10/100/1000 cards usually isn't the fastest option. In 
> IPv6 each subnet prefix has enough addresses to hold all hosts that 
> you can possibly connect to a layer 2 network in the first place. But 
> it also handles this situation much better, if it comes up: routers 
> can advertise additional prefixes as "on-link" so hosts know they can 
> reach destinations in those prefixes directly over layer 2. Redirects 
> also work across prefixes. (Similarly, routing protocols use link 
> local addresses which make it possible to run RIP or OSPF between two 
> routers that don't share any prefixes.)

Those are semi-nice features.  Not sure I would use it as an excuse to 
migrate, though, since the need for them can easily be avoided in v4.


> Since there is no need for NAT, every IPv6 host can run a server for 
> any protocol without trouble.

Have you been reading this thread?  There is a need for NAT in v6.  In 
fact, the lack of multi-homing support in v6 alone outweighs all its 
nice features, IMHO.


> Because of the large address space, scanning address blocks is no 
> longer an option.

You have a /64, scanning that would be an issue.  Is scanning a /96 
really "no longer an option"?  How about in a year?  Two years?


> If you have multiple routers, you pretty much have HSRP/VRRP 
> functionality automatically.

Again, nice, but since I have that in v4....


> Renumbering is much easier.

I like this one.


> It's also very handy to be able to log in to a box, completely screw 
> up its IPv4 configuration and rebuild it from scratch without having 
> to worry that the host becomes unreachable and needs a powercycle.

s/v4/v6

I would not say this is an argument for v6 in particular, but maybe an 
argument to run two protocols simultaneously.


>> And, to be more on-topic, name one good reason
>> why a network operator would want it? Especially given that, apart
>> from the traditional bleeding edges (academic networks), no customers
>> are asking for it.
>
> I think "no customers" is rounding it down slightly. Yes, demand is 
> low, but so is supply, hard to tell which causes which. And customers 
> who do ask, are routinely turned down.

Certainly no customers on "The Web".  Maybe some niche applications.


>> As Paul Vixie points out, without a multihoming solution beyond that
>> offered by 4, v6 networks will look just v4 - most of it will be on
>> non-global address space and NAT. Not really interesting..
>
> Multihoming can be done the same way many people do it for IPv4: take 
> addresses from one ISP and announce them to both. Obviously your /48 
> will be filtered, but as long as you make sure it isn't filtered 
> between your two ISPs, you're still reachable when the link to either 
> fails. However, this means renumbering when switching to another 
> primary ISP. Not much fun, despite the fact that renumbering is much 
> easier in IPv6.

This does not address the issue.  If my /48 is filtered, I am still at 
the mercy of the provider with the super-CIDR.  If that network is 
down, so am I.  (And don't even think about saying backbones never go 
down.)  The point of multi-homing is to _not_ be dependent on a 
provider.

Statements like "Obviously your /48 will be filtered" show why v6 is 
going to take much longer to catch on than people in the v6 camp 
probably would like.


>> I know, what's worse is that I know it need not be so. (how's your
>> MHAP doing?  How's Iljitsch's geo-assigned addressing proposal?)
>
> Michel is no longer in the IPv6 business, and I've failed miserably at 
> convincing people that geographic aggregation is helpful here. So 
> currently, multi6 is looking at approaches that allow transport 
> protocols to jump addresses in the middle of a session.

I should pay more attention to the multi6 list, but to be honest, it 
just does not seem to be worth the effort.  IPv4 is doing fine, v6 is 
struggling to find a market.

IPv6 was designed with some very kewl features (thanx, AppleTalk :), 
but it obviously was influenced by "big providers" who thought the 
world should be run by the top 10 networks and everyone else should 
just shut up and do as they are told.  Since that is not how the world 
does work, surprise, there was resistance.  And the resistance is not 
going away until we stop trying to apply bandaids and give the *USERS* 
what they want and need.

One of the biggest things the users want is a way for their corporate 
networks to have good connectivity to the Internet even if a backbone 
provider falls down.  We have this in v4, we should have it in v6.  
Filtering (/19s, /48s), and other impediments to _real_ multi-homing 
have been a complete and miserable failure in the past.  Any proposal 
which values the end-user's network (read: "THE PEOPLE WHO PAY FOR IT") 
less than the "backbone" networks will fail.

All, IMHO, of course. :)

-- 
TTFN,
patrick




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