Hi David, <snip>
Well, if you NAT the destination identifier into a routing locator when a packet traverses the source edge/core boundary and NAT the locator back into the original destination identifier when you get to the core/destination edge boundary, it might be relevant. The advantages I see of such an approach would be:
- no need to modify existing IPv6 stacks in any way - identifiers do not need to be assigned according to network topology (they could, in fact, be allocated according to national political boundaries, geographic boundaries, or randomly for that matter). They wouldn't even necessarily have to be IPv6 addresses just so long as they could be mapped and unmapped into the appropriate locators (e.g., they could even be, oh say, IPv4 addresses). - locators could change arbitrarily without affecting end-to-end sessions in any way - the core/destination edge NAT could have arbitrarily many locators associated with it - the source edge/core NAT could determine which of the locators associated with a destination it wanted to use
Of course, the locator/identifier mapping is where things might get a bit complicated. What would be needed would be a globally distributed lookup technology that could take in an identifier and return one or more locators. It would have to be very fast since the mapping would be occurring for every packet, implying a need for caching and some mechanism to insure cache coherency, perhaps something as simple as a cache entry time to live if you make the assumption that the mappings either don't change very frequently and/ or stale mappings could be dealt with. You'd also probably want some way to verify that the mappings weren't mucked with by miscreants. This sounds strangely familiar...
Certainly does. Apparently this or a similar idea was suggested back in 1997, and is the root origin of the 64 bits for host address space, according to Christian Huitema, in his IPv6 book - http://www.huitema.net/ipv6.asp. A google search found the draft : "GSE - An Alternate Addressing Architecture for IPv6" M. O'Dell, INTERNET DRAFT, 1997 http://www.caida.org/outreach/bib/networking/entries/odell97GSE.xml
Can two evils make a good? :-)
Not sure, however, two wrongs don't make a right, but three lefts do. Regards, Mark. -- The Internet's nature is peer to peer.