scalability: unlimited with IPv6, the number of IP address will become huge, almost unlimited 50 years from now, I'm not too sure of course increasing number of devices will get connected to the IPv6 network today: 10 IP addresses per capita coming days: 1000 IP addresses per capita: robots and microcontrollers anything that limits scalability must be avoided state table (NAT, firewall) centralized database (DHCP lease database) centralized servers and relays (SIP gateway) of course there are things that are inherently centralized more peer-to-peer apps: skype, winny, BitTorrent less aggregation of traffic onto servers: clients will communicate with each other directly