[address-policy-wg] IPv6 allocations for 6RD

Hi Remi,

could you help me in understanding why an ISP with, say, a /14 and 2 /16s of address space would need a /28 of space to do 6rd? In my understanding, even using a /56 per customer would give you a requirement for just 19 bits of ipv6 space (18 bits for the /14, 1 extra to also make the /16s fit) on top of the /56s, if you just use 3 instances of 6rd and prefix compression. This gives a requirement of a /37 for deploying 6rd, not a /28. Even if you add a whole bunch of /15s and /24s to the mix, it will only add a few bits to the requirement, not 11.

Not that I don't want to give out the space if needed, but I'm trying to understand the reasoning behind it. I find 'too complicated' a tough argument to swallow given that the current and working IPv4 setup in an environment like this is already way more complicated.

Best,

Remco

-----Original Message-----
From: address-policy-wg-admin at ripe.net [mailto:address-policy-wg-admin at ripe.net] On Behalf Of Rémi Després
Sent: zaterdag 28 november 2009 9:50
To: Mikael Abrahamsson
Cc: address-policy-wg at ripe.net
Subject: Re: [address-policy-wg] IPv6 allocations for 6RD


Le 27 nov. 2009 à 19:36, Mikael Abrahamsson a écrit :

> On Fri, 27 Nov 2009, Rémi Després wrote:
> 
>> No hard feelings, but I felt this needed to be said.
> 
> There is nothing wrong with 6RD in principle, it's when people map the entire IPv4 space into IPv6 blindly and then use a small fraction of it that it becomes wasteful.

Right (that's the use of 6rd which can create problems, not it's design or its implementation in gateways and home gateways).

> I don't have a problem with ISPs will millions of subscribers getting a /24, I have a problem when "every" mom and pop ISP with an AS number is getting a /24 because they want to run 6RD.
> 
> As long as the policy incurs that you need to have a certain amount of customers to warrant running 6RD using all of IPv4 space and thus needing /24 or /28, otherwise you'd better map a smaller part of it and then you'll be able to fit it just fine into your /32 most likely.

/28 for any ISP having several IPv4 prefixes and  committed to deploy 6rd would be IMHO a good choice.
In practice, /60s to customer sites is quite sufficient, at least in the short term.
(Note that mom and pop ISPs, presumably having each only one IPv4 prefix, would remain with /32s.)

Then, going up to /24 for ISPs that deploy 6rd with at least 4 IPv4 prefixes, as you propose in another mail, would not be necessary, but could be a useful option.

Regards,
RD




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