The peer$-$to$-$peer $($P$2$P$)$ paradigm. Which of the characteristics below are associated with a P$2$P approach to structuring network applications $($as opposed to a client$-$server approach$)?$ a$.$ A process requests service from those it contacts and will provide service to processes that contact it$.$ b$.$ There is a server that is always on$.$ c$.$ There is not a server that is always on$.$ d$.$ HTTP uses this application structure. e$.$ There is a server with a well$-$known server IP address.