Keith, >Fortunately the mistake is easily rectified, so long >as software doesn't get into the habit of expecting the lower 64 bits >of an address to be a unique interface identifier. This is a dangerous prospect. The company I work for makes a networking stack and our IPv6 implementation expects the lower 64 bits to be the unique interface identifier. Other implementations do the same. Now would be the time to change the spec if its going to be done, otherwise it will already have market penetration just like NAT. Dan -----Original Message----- From: owner-ietf@xxxxxxxx [mailto:owner-ietf@xxxxxxxx]On Behalf Of Keith Moore Sent: Tuesday, December 02, 2003 1:03 PM To: Iljitsch van Beijnum Cc: moore@xxxxxxxxxx; anthony@xxxxxxxxxxxxx; ietf@xxxxxxxx Subject: IPv6 addressing limitations (was "national security") > RFC 3513 mandates that all unicast IPv6 addresses except the ones > starting with the bits 000 must have a 64-bit interface identifier in > the lower 64 bits. This was shortsighted, just like having the notion of "class" built into IPv4 addresses was shortsighted. People are going to need to subnet past /64 sooner rather than later, and subnetting past /64 is a LOT better than NAT. Fortunately the mistake is easily rectified, so long as software doesn't get into the habit of expecting the lower 64 bits of an address to be a unique interface identifier. > This has some important advantages, most notably it > allows stateless autoconfiguration. Providing an alternative to stateless autoconfiguration for subnets past /64 might be a acceptable compromise. > Putting a 64-bit crypto-based host identifier in the bottom 64 bits of > > IPv6 addresses shouldn't get in the way of regular IPv6 addressing > mechanisms and/or operation. Putting a crypto-based host identifier in the address is unnecessary, since there's really no need to include a strong host identifier in every packet sent to a host. The locator alone is usually sufficient, and if that's not sufficient, the sender can generally encrypt the traffic with a secret known only to the intended destination. Keith