Bob Hinden wrote: >> ID/locator split, which I've been >> a proponent of for very many years, works a lot better with more bits, >> because it allows topological addressing both within and outside an >> organization. > To confirm what your are saying about an ID/locator split in > IPv6, that the other reason why we went with 128-bit address > with a 64/64 split as the common case and defining IIDs > that indicate if they have global uniqueness. This creates > a framework that an ID/locator split could be implemented. I actually implemented such a system about 10 years ago and it worked fine. It was an experiment for hosts to use multiple IPv4 and IPv6 addresses, some of which may have ID/loc separation. DNS was used for ID->loc mapping. Mobility was also supported with multiple home locators and multiple foreign locators. We did something related to end to end multihoming and happy eyeball. ID locator separation was good, because it requires about half amount of space to store multiple addresses sharing an ID. Moreover, rewriting destination locators enables elegant forwarding from home agents to mobile nodes without tunneling (and associated MTU tax), if transport check sums do not involve locators. But, that's all. It was not very interesting that I abandoned further work on it after government funding period expired. > Opinions vary if ID/locator split is useful, but we have a > framework that would allow it without having to roll > out another version of IP. A win IMHO. Assuming address must be 16B long, it may be good to have ID/loc separation. However, if we have choice, having 8B long addresses is much better, because it is more compact than 16B address with ID/loc separation. Even with 8B addresses, we can rewrite destination addresses, if there is a destination header option (or a mandatory field) "original destination address" to be used to confirm transport identity and checksum. So, along with the failure with a lot of confusion to have SLAAC, we can conclude that IPv6 addresses should have been 8B long. Maybe, even with the current IPv6 packet format, routers can look only at first 8B of addresses and ignore the latter 8B (used as "original source/destination address" for source/destination address rewriting). Masataka Ohta _______________________________________________ Ietf mailing list Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf