Alien noise is removed from one or more receptor DSL lines after self-FEXT has been eliminated or reduced. After end-to-end connectivity is established, preferably the hosts communicate with each other by relaying data packets via the overlay network relay servers. If the requested content does not exist in memory or on disk, it generates a request to an origin site to obtain the content. A ceramic catalytic substrate is wrapped in a ceramic-fiber mounting mat and inserted into the shell.