Re: Extending a /64

What's "impossibly short"?

Again, there are 35 trillion /48s in 2000::/3. How many would you need?

Regards
   Brian

On 16-Nov-20 08:20, Tony Whyman wrote:
> We originally allocated 8 bits for subnetting - hence a /56. That got squeezed down to 4 (and a /60) in order to meet all user requirements while avoiding asking for an impossibly short prefix.
> 
> Tony Whyman, MWA
> 
> -------- Original message --------
> From: S Moonesamy <sm+ietf@elandsys.com>
> Date: 15/11/2020 14:53 (GMT+00:00)
> To: Tony Whyman <tony.whyman@mccallumwhyman.com>, ipv6@ietf.org
> Subject: Re: Extending a /64
> 
> Hi Tony,
> 
> I'll disclose that I am affiliated with a RIR.
> 
> At 05:00 AM 08-11-2020, Tony Whyman wrote:
>>The problem of the /64 limit came up in ICAO working groups earlier
>>this year when developing a global addressing plan for the ATN/IPS
>>and there would be strong support here for allowing subnet prefixes
>>to go beyond the /64 boundary.
>>
>>Our problem is that we wanted to define an addressing plan that uses
>>39 bits to identify each aircraft, allows for a minimum of 4 more
>>bits for subnetting and works within the existing standards. I'll
>>give some background below for those interested in why 39 bits, but
>>the problem is that if you are going to allocate a /64 (deriving
>>from a /60 MNP) to each subnet on an aircraft then you need a /21 as
>>your initial allocation - and this is before you start thinking
>>about other ATN/IPS users such as drones.
>>
>>In order to avoid a potential problem getting a sufficient address
>>allocation, we did look at extending into the "other 64 bits" of an
>>IPv6 address for subnet IDs, which was looking very "unused". After
>>all, you can only cram in a handful of systems into the
> 
> There were proposals to assign a /56 MNP for an aircraft.  That
> "drone" user looks like something different from an aircraft for
> address assignment purposes.
> 
> The procedure for global allocation registration is listed at
> http://r.elandsys.com/r/51238
> 
> Regards,
> S. Moonesamy
> 
> 
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