On Tue, Oct 13, 2009 at 6:34 PM, Cord MacLeod <cordmacleod@gmail.com> wrote:
IPv4? What's the point of a /64 on a point to point link? I'm not clear
IP Addressing uniformity and simplicity. Use of /127s for Point-to-Point links introduces addressing complexity that may be avoided in V6: the scarcity of IPs necessitated it in V4 . At least /112 lies on an even 16-bit boundary, and that makes it the longest prefix that is a very good choice, if you do need a non-standard mask. Unless you have only a /32 of V6 space and 1 billion P2Pt links you need (or similar scenario), there is no utility in practicing rampant prefix length expansion, for the purpose of conservation (there may be other reasons such as preventing autoconfig).
For all intensive purposes a /126 translates to a /30 in IPv4. Do people assign /24's to their point to point links today with
Not really; there's a massive difference of scale. Say there's a big vat that contains all gold in the universe, you get to bring home one bucket of gold flakes to allocate to your customers. In the V4 universe, well you got a /19.. You got a 60 kilogram bucket, and a /30 represents a 1 troy ounce scoop taken out of that bucket.. In the V6 universe, even if you got a measly /48: one /64 from that is a 1 troy ounce gold flake out of your 2000 kilogram bucket. Should you really be worried about cutting up that flake? In reality... if you're an ISP the worst you have is a /32, you can think of a /48 that way, you do have 65536 of those /48s, also known as a 133,588,416kg bucket, since your /32 has a maximum of 4 billion /64s. Normally when you have a P2P link, it will mean you connect an end site also: that end site gets a /48 (Per the justification that allows you as an ISP to get a /32, such a large allocation). After assigning 65536 /64s, or 256 /64s (if you give out /56s to end sites) which you already do for each _end site_ as standard address allocation practice in V6, what's another single /64, seriously? -- -J