On Mon, Jan 25, 2010 at 1:01 PM, TJ <trej...@gmail.com> wrote: >> -----Original Message----- >> From: Richard A Steenbergen [mailto:r...@e-gerbil.net] >> Sent: Monday, January 25, 2010 12:08 >> To: TJ >> Cc: nanog@nanog.org >> Subject: Re: Using /126 for IPv6 router links >> >> On Mon, Jan 25, 2010 at 09:10:11AM -0500, TJ wrote: >> > While I agree with parts of what you are saying - that using the "simple >> > 2^128" math can be misleading, let's be clear on a few things: >> > *) 2^61 is still very, very big. That is the number of IPv6 network >> > segments available within 2000::/3. >> > *) An end-user should get something between a /48 and a /56, _maybe_ as > low >> > as a /60 ... hopefully never a /64. Really. >> > **) Let's call the /48s enterprise assignments, and the /56s home >> > assignments ... ? >> > **) And your /56 to /64 is NOT 1-256 IPs, it is 1-256 segments. >> >> It is if we are to follow the "always use a /64 as a single IP" >> guidelines. Not that I'm encouraging this, I'm just saying this is what >> we're told to do with the space. I for one have this little protocol >> called DHCP that does IP assignments along with a bunch of other things >> that I need anyways, so I'm more than happy to take a single /64 for >> house as a single lan segment (well, never minding the fact that my >> house has a /48). > > Interesting. I have never seen anyone say "always use a /64 as a single IP" > ... perhaps you mean as an IP segment or link? > You are assigned a /64 if it is "known" that you only need one segment, > which yields as many IPs as you want (18BillionBillion or so) - and the > reality is that a home user should get a /56 and an enterprise should get a > /48, at the very least - some would say a /48 per site. > > >> > **) And, using the expected /48-/56, the numbers are really 256-64k > subnets. >> ... >> > Note: "All we've really done is buy ourselves an 8 to 16 bit improvement > at >> > every level of allocation space" >> > *) And you don't think 8-16 bits _AT EVERY LEVEL_ is a bit deal?? >> >> I'm not saying that 8-16 bits isn't an improvement, but it's a far cry >> from the bazillions of numbers everyone makes IPv6 out to be. By the >> time you figure in the overhead of autoconfiguration, restrictive >> initial deployments, and the "now that the space is much bigger, we >> should be reallocating bigger blocks" logic at every layer of >> redistribution, that is what you're left with. So far all we've really >> done with v6 is created a flashback to the days when every end user >> could get a /24 just by asking, every enterprise could get a /16 just by >> asking, and every big network could get a /8 just by asking, just bit >> shifted a little bit. That's all well and good, but it isn't a >> bazillion. :) > > There are some similarities between IPv6 and old classful addressing, but > the bit-boundaries chosen were intentionally made big and specifically > factoring in the then-ongoing scarcity (Ye olde Class B exhaustion). The > scale of the difference *is* the difference. I am not quite sure what a > bazillion is, but when we get into the Billion Billion range I think that is > close enough! :) > > > /TJ > > >
2^128 is a "very big number." However, from a network engineering perspective, IPv6 is really only 64bits of network address space. 2^64 is still a "very big number." An end-user assignment /48 is really only 2^16 networks. That's not very big once you start planning a human-friendly repeatable number plan. An ISP allocation is /32, which is only 2^16 /48s. Again, not that big. Once you start planning a practical address plan, IPv6 isn't as big as everybody keeps saying... -- Tim:> Sent from Brooklyn, NY, United States