always on
- Always-on is the name given to services via which the user is constantly online with a carrier. The advantage of always-on operation is that the user does not have to dial in and log out all the time. For economic reasons, however, the service requires connections with data packet switching; however, the term always-on operation is also used for fixed connections.
- Always-on operation exists in ISDN as Always On/Dynamic ISDN (AO/ DI) using the D channel. Other services such as Asymmetric Digital Subscriber Line( ADSL) also offer Always-On, although the connection is regularly disconnected by the provider.
- Always-on service is also interesting in the mobile communications sector for implementing instant messaging( IM) or e-mail at low cost. However, for the mobile subscriber to be constantly connected to the carrier at reasonable cost, this requires packet-switched networks such as General Packet Radio Service( GPRS) or UMTS. In always-on mode, the subscriber can dial into the Internet, mailbox or other services once and automatically receive the latest data or messages as needed. In the case of packet-switched connections, costs are billed exclusively according to the volume of data transferred and not according to the connection time.
- With Fibre Channel, Enterprise System Connection( ESCON) or Gigabit Ethernet, "always-on" describes the operating state of an effective connection. Frames, idles or filler words are transmitted continuously over this connection. The network management of Firbre Channel can detect errors in the transmission level on every single transmitted word in this "always-on operation".