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

Dear Colleagues,

During the discussion on the APWG list about 6rd, several people have  
inquired about the exact way Registration Services evaluates requests  
for 6rd deployment. This email will try to answer these inquiries.

The RIPE NCC considers current policy to be completely agnostic to  
6rd, it neither specifically supports nor disallows 6rd deployment.  
This means that Registration Services will evaluate IPv6 allocation  
requests that include 6rd deployments according to the established  
policies and procedures of justified need.

During the evaluation of an IPv6 allocation request the IPRA will look  
at the assignment size and the expected number of assignments to  
arrive at the size of the allocation that is justified.

When an LIR wants to deploy 6rd by encoding the full 32 bits of the  
IPv4 addresses in the IPv6 end-user prefix, the allocation that would  
be needed is often much larger than would otherwise be justified using  
this principle as almost all of the reserved end-user prefixes would  
remain unused.

Two examples with some numbers:

An average size ISP has 1 million residential customers, intends to  
deploy 6rd and assign each end-user a /48.

1 million /48 end-site assignments would justify a /28, ignoring for  
the moment other requirements such as LIR infrastructure that might  
require more space. Deploying 6rd by encoding the full 32 bits of the  
IPv4 address would inflate the need to a /16.

Currently, in this case, the IPRA would not consider allocating a /16  
to be justified.

Another LIR, who has 3 million customers, intends to deploy 6rd with / 
60 assignments. Currently, the IPRA would consider 3 million /60  
assignments to fit into a /38, thus the default /32, while the 6rd  
deployment would require a /28.

Note that neither of these LIRs would qualify easily for an additional  
allocation under the HD-ratio rules.

Best regards,

Alex Le Heux
RIPE NCC