Re: IPv6 prefix lengths - how long?

[Gyan Mishra <[e-mail]>]

6MAN,

I agree with Brian and David on increasing the prefix length past the 64 bit boundary and agree that there are many advantages to alignment on nibble boundaries with the hexadecimal representation of IPv6 addresses. 

The RFC 4291 IPv6 addressing and the original stance on 64bit boundary was based on the EUI64 format for the Mac generated FFFE bit stiff between the 3rd and 4th octet of the station id or random station id.

I agree that a 64bit station id was overkill and was made 20 years ago thinking futuristically that every physical device you can think of would have an IP but now in reality large in my opinion that would never be used and really wasted valuable bits on a station Id that could have been used more wisely to expand the prefix length.

If we make the prefix longer to whatever size makes sense and I am all for it and have wanted to make that change to the standard length for a long time now.

If we all do agree to increasing the prefix length any of the 16 nibble aligned options seem fine with me; /64, /68, /72, /76, /80, /84, /88, /92, /96, /100, /104, /108, /112, /116, /120, /124. 

Of all the nibble values listed above what I am thinking a value that would make sense given how flat we can go with future L2 switching broadcast domain taking into account future IPv6 only but also current dual stack infrastructure of having both IPv4 broadcast and IPv6 constrained multicast what would be the maximum subnet size that is still future looking and future proof.

I can take the onus on creating a new draft that would update RFC 4291 and any other applicable RFCs on the prefix length increase.

6MAN chairs 

Please let me know if you are Ok with be moving forward with creating this draft and I will get started now on 00 revision.

Thank you

Gyan Mishra
Verizon Communications 
Phone: [phone]
email:[e-mail]


> On Jun 7, 2019, at 5:23 PM, David Farmer <[e-mail]> wrote:
> 
> I mostly agree with Brian, other than that are many advantages to alignment on nibble boundaries with the hexadecimal representation of IPv6 addresses. So, any of the 16 nibble aligned options seem fine with me; /64, /68, /72, /76, /80, /84, /88, /92, /96, /100, /104, /108, /112, /116, /120, /124. So, personally, I would argue against /118 on that principle.