North American Network Operators Group

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Re: v6 subnet size for DSL & leased line customers

  • From: Deepak Jain
  • Date: Fri Dec 21 13:54:59 2007

Given that a "subnet" in the current model consists of a network that is
capable of swallowing the entire v4 Internet, and still being virtually
empty, it should be clear that *number of devices* will never be a serious
issue for any network, business or residential.  You'll always be able to
get as many devices as you'd like connected to the Internet with v6.  This
may ignore some /current/ practical issues that devices such as switches
may impose, but that doesn't make it any less true.

This is the part about V6 I haven't really gotten my head around. It really seems like it takes the position (possibly due to WG-delay) that everything we've learned to do with V4 is done and not-needed.

For example... Within one's own network (or subnet if you will) we can absorb all the concepts of V4 today and have lots of space available. For example... for the DMZ of a business... Why not give them 6 bits (/122?) are we anticipating topology differences UPSTREAM from the customers that can take advantage of subnet differences between /64 and /56 ?

Do we really believe that in our "home" topology where everything has a unique address that my refrigerator won't be able to route to my movie player? And if it can, and if I need a firewall between my in-home networks why does it need to be at /64 boundaries... can I subnet my /64 into a huge number of /116s? I know some IPV6 boxen won't support DHCP and other things at such small network sizes, but I haven't figured out a use for as much space as we are providing even joe-home-user.... or why there is some nobility to making boxes that are less flexible that the IPv4 boxen we have today... between the /48 and /128 boundaries (inclusive)... shouldn't IPv6 be just IPv4 with more space?

My previous understanding was the idea that everyone would get an IP4 universe (or several) to theoretically number everything they could ever conceive of, AND have enough left over to handle things like thousands of interfaces with thousands of simultaneous permanent and semi-permanent conversations going on --even separated by large TTLs (> years) without any concern for numbering/renumbering within their assigned block. I am aware of the idea of renumbering the left portion of the IP space in an IPv6 world...

For example... My car manufacturer could give every car in his universe a unique IP within a network. As an owner of that car, I just need to create a tunnel from my IP space provided by my provider to my car's unique IP (the manufacturer's network won't accept packets for my car NOT from my IP space). So now I can create a webpage from my home that shows all the silly things I do with my car... and its unique and permanent to the rest of the world -- even as I change cars. When I'm "on-the-job" as a physical package courier, my car might even gain another IP with another access model tunneled over to it.

So, I can see a place where LOTS of devices have LOTS of addresses all in different contexts/topologies based on your access model. What I don't understand is why an end user connection today that justifies a /30 needs a /64.. or multiple ones. What at the ISP changes between a /30 and a /56 that we are going to do for that user to support his "multiple random networks of convenience?"

Thanks for any help with my understanding,