> My main question about ULA-C still stands: how is it > different from PI?
To understand the difference between PI and ULA-C you need to understand the difference between the public Internet and an IP internetwork. Any set of networks that use the Internet Protocols are an IP internetwork. However there is only one public Internet and that is the subset of IP internetworks which have chosen to connect together so that end hosts can communicate without prior arrangements. PI addresses are public Internet addresses which end hosts can use to communicate without prior arrangements. ULA-C addresses can only be used to communicate between end hosts where both ends have made prior arrangements to enable communication between the two ULA-C blocks from which the end-hosts are numbered. Any IP internetwork managed by a single authority can make use of ULA-C addresses because the single authority presumably is in charge of making things work. When two or more authorities who manage internetworks wish to enable inter-authority (inter-AS) communication, they need to make specific arrangements either bilaterally or unilaterally. These arrangements are a lot like Internet peering arrangements although, technically, it is not necessary to use ASes and BGP4 to do this, just hook things up with circuits or tunnels. What is missing in this ULA-C picture is transit. On the public Internet there is the assumption that packets will be carried across as many autonomous networks as necessary to reach their destination. However, when the source address or destination address is ULA-C, the transit assumption breaks down. There is no "assumed" interconnectivity with ULA-C addresses which makes them quite different from PI addresses. There will be some groups of organizations who find the requirement for making prior arrangements to be very useful. They may not want any packets from sources who have not signed a mutual agreement. These Community Of Interest Networks exist today in the IPv4 world and they are thriving. Examples are the auto industry with ANX and ENX, the air transport industry with Aeronet and the global financial services industry with RadianzNet. I am not suggesting that any of these existing networks would use ULA-C but that they represent real-world use-cases for globally unique registered address space that is explicitly *NOT* routed on the public Internet. The big question here is whether ULA-C presents any advantage over simply using PI and selectivly shutting off the characteristics which are not desirable. For instance, if you never announce your PI prefix on the Internet, then you will never receive any packets without prior arrangement. --Michael Dillon P.S. if anyone has other examples besides automotive, air transport and financial services idustries, I would be interested in hearing about them. -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
