v4 exhaustion and v6 impact [Re: cost of dual-stack vs v6-only]

Pekka Savola pekkas at netcore.fi
Thu Mar 13 17:39:33 UTC 2008


On Thu, 13 Mar 2008, Owen DeLong wrote:
>> While the goal may be good, a reality check might be in order. AFAICS, the 
>> impact will be that residential and similar usage will be more heavily 
>> NATted.  Enterprises need to pay higher cost per public v4 address.  IPv4 
>> multihoming practises will evolve (e.g., instead of multihoming with PI, 
>> you multihome with one provider's PA space; you use multiconnecting to one 
>> ISP instead of multihoming).  Newcomers to market (whether ISPs or those 
>> sites which wish to start multihoming) are facing higher costs (the latter 
>> of which is also a good thing). Obviously DFZ deaggregation will increase 
>> but we still don't end up routing /32's globally.
>
> I am confused by your statement.  It appears you are saying that it 
> is a good thing for sites that wish to multihome to face higher 
> costs.  If that is truly what you are saying, then, I must 
> strenuously disagree.  I think that increased cost for resilient 
> networking is a very bad thing.

I understand your reasoning (we've been through this before so we'll 
just have to agree to disagree).  If a site is unwilling to pay, e.g., 
10000$/yr for its multihoming, maybe it should stop polluting the 
global routing table and instead use other redundancy mechanisms. 
Today, it's too cheap to pollute global DFZ; increasing the cost 
motivates finding other mechanisms to obtain redundancy.

>> While price for a /20 or /16 of address space might go up pretty high, a 
>> /24 can still be obtained with a reasonable cost.  Those ISPs with lots of 
>> spare or freeable v4 space will be best placed to profit from new customers 
>> and as a result v6 will remain an unattractive choice for end-users.
>> 
> Only for some limited period of time.  Even those "freeable" /24s will get
> used up fairly quickly.

Even a single /8 will allow 64K allocations for multihoming 
perspective; that's more than we have today, and there is a lot more 
spare or freeable space to use.

[...]
> However, once we reach somewhat minimal critical mass in IPv6 
> content, and, NAT-PT solutions are more readily available and better 
> understood, I think you'll see most new enterprise deployments being 
> done with IPv6.

I agree with most of what you're saying but given that most enterprise 
admins are familiar with v4 and not with v6, if the enterprise is 
going to be completely behind a NAT or NAT-PT anyway, it may be 
difficult to find the benefit to deploy the enterprise network with v6 
rather than with v4 private addresses.  Easier company mergers is 
probably one of the highest on the list, "futureproofing the network" 
is probably not considered worth the expense.

>> So v6 capabilities in the ISP backbones will improve but the end-users and 
>> sites still don't get v6 ubiquituously.  This is a significant improvement 
>> from v6 perspective but is still not enough to get to 90% global v6 
>> deployment.
>> 
> I'm not sure why 90% is necessary or even desirable in the short
> term.  What's magic about 90%?

Don't ask me for the magic number -- I just took what Leo offered. :-)

>  What I think is more interesting is arriving at the point where you 
> can deploy a new site entirely with IPv6 without concerns about 
> being disconnected from some (significant) portion of the internet 
> (intarweb?).

I agree that's an interesting (earlier) scenario. To me what you 
require represents a situation where basically every ISP is offering 
v6 and it's widely considered to have similar SLAs as v4 today has, 
and it's used sufficiently widely and is reliable.

To get there in practice, ISPs will need users which require this kind 
of SLAs and reliability.  So, while 90% user and content penetration 
is is not needed to reach this goal, it will need to be significantly 
higher than, say, 5%.  Who are going to be the first v6 end-sites and 
content provides?  It's a thankless job to be on the bleeding edge and 
it may be difficult to define a business case for it.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings



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