Each IRC network consists of one or more IRC servers that form a virtual chat network together. The communication on these virtual chat networks is based on the IRC protocol. According to this you talk about IRC networks. Users that are connected via directly or crabwise connected servers are able to chat together. – Here you see the 100 largest and most popular IRC networks that take part in netsplit.de's comparison, but please consider that there are still some big non-competitive IRC networks!