|  | 13.1 | The Session Layer
| 13.1.2 | Session layer analogies
The session layer establishes, manages, and terminates sessions between applications. This includes starting, stopping, and re-synchronizing two computers that are having a "rap session". The session layer coordinates applications as they interact on two communicating hosts. Data communications travel on packet-switched networks, not like telephone calls that travel on circuit-switched networks. Communication between two computers involves many mini-conversations, thus ensuring that the two computers can communicate effectively. One requirement of these mini-conversations is that each host plays dual roles: requesting service - like a client; and, replying with service - like a server. Determining which role they are playing at any given moment is called dialogue control.