On Dec 31, 2007 3:26 PM, Church, Charles <cchurc05@harris.com> wrote:
like a natural choice, leaving 80 bits for network addressing. This waste of space seems vaguely familiar to handing out Class A netblocks 20+ years ago. "We'll never run out"... Maybe it's just me though.
The comparison is mistaken. Not without a major fundamental change in the way ip addresses are used (ridiculous waste of addresses by end-sites causing them to require numerous subnets and request additional /48s) IPv6 provides ample room for growth at end sites, and giving out /32s or so to ISPs and telling them to hand out /48s and /56s seems reasonably conservative. 64-bits maximum length network address. It's not much a waste for every end-user to get a /56 Think of it as IPv4, but instead of everyone having gotten a Class A, every end site got on average 0.00000006 of an IPv4 /32 (host address), no matter how large their site. 1 IPv4 Class A is approximately 0.39% of available IPv4 space 1.67*10^7/(4.29*10^9) 1 IPv6 /48 is approximately 0.00000000000000000000827% of available IPv6 space. You need a calculator for that second one :) But assignable space in V6 could be exhausted without end-site IPs running out. The place where major problems could be run into is deciding how big a block your ISPs and LIRs get, or if the registries are entertaining the concept of PI space for v6.. how large those blocks are. Does a small ISP ever get such a small block that they may run out of /48s to assign? Does a large ISP ever get such a large block, the RIRs may run out of ISP blocks to assign? Both situations would be extremely undesirable. In the former case, they need multiple blocks, but RIR policy for v6 might not provide a way for them to get that.... the utilization of additional allocations also add undesirable complexity to networks, which is very bad: design of IPv6 is supposed to avoid such things. In the latter case... IPv6 IP addresses have not been 'exhausted', but now, there can now be no new ISPs or PI allocations; everything having been assigned to some major provider who has not given out very many of their /48s yet, or who is giving out /56s and hording the rest of the address space, never to be assigned..... -- -J