These terms are used when discussing Call manager. Call manager handles call processing in Cisco's implementation of IP Telephony. So it is this particular area of VoIP that we would hear the terms publisher and subscriber. The terms are actually from the Microsoft SQL database that earlier version of call manager utilized. The publisher is the authoritative database for configuration. So when changes are made in configuration, they are made on the publisher and replicated to the subscribers. There is only one publisher and can be multiple subscribers. If the publisher is unavailable, the phones can re-home themselves to a subscriber in order to continue to be functional. This is an illustration as to how they function, but not necessarily best practice.In best practices, the phones should be actually use subscribers as their primary.It's more like the publisher contains the master database in which changes to configuration is made and replicated to the subscribers. For scalability, it is normal to point phones to subscribers, since there is only one publisher and can be many subscribers.
