Independent of all this discussion we are witnessing regarding to the IPv6 deployment I'd like to write down some high-level requirements for transport layer protocols in Internetworks (such as the global Internet). Lets have a look at required attributes of such an ideal transport layer protocol for Internetworks without regard to any existing protocols: 1) It should have sufficient address space to allow every human and corporation on this planet to have all his/her electronic devices online with a unique address at the same time. [Large address space.] 2) It should have indivdually routeable fixed- or variable sized netblocks. [No individual number allocation. Aggregation of individual addresses into routable blocks.] 3) It should function in a global dynamic and automatic routing system based on netblocks. [BGP or better.] 4) It should have routing of any netblock independent of political or national hierarchies or assignments. [Aggregation follows the network structure, not political/geographical borders.] 5) It should have globally unique netblocks which are allocated to connectivity providers who then redistribute/assign parts to end user connectivity. [The delta between address/netblock per individual user vs. routable netblock should be larger than 2^12. Provider aggregation.] 6) It should have globally unique netblocks which are independent of connectivity providers and assigned directly to end users with sufficient requirements. [Provider independent address space. This address space may or may not be directly routable.] 7) It should have minimum requirements for netblocks in size and aggregation to participate in the global routing system. [Minimum allocation.] 8) It should restrict itself entirely to the transport layer (OSI layer 3). [No source routing, flow labels and such. That's the job of layer 2.5.] 9) It should only be used for transport layer purposes. [Only for packet forwarding. No additional meaning as in phone numbers, etc.] 10) KISS. Keep it simple, stupid. [If it takes $10k worth of courses to understand it's unsuitable.] When going through this list we see a couple of points in which IPv4 and IPv6 fail miserably. Food for thought. Get the discussion started. -- Andre