NetWare Link/X.25 Link Layer

The Link layer (sometimes called the Frame layer) defines the protocol used to ensure reliable data interchange and proper data-link control between the DTE and the network DCE. The NetWare Link/X.25 Link layer performs the following tasks:

• Efficiently transfers data across the link
• Synchronizes the link
• Performs flow control when a local busy condition is detected
• Checks for errors and performs error recovery
• Provides link-up and link-down information to the packet layer

Using the services of the Physical layer, the Link layer is responsible for synchronizing data and for ensuring that the data is error-free.

Data is sent across the access link in transmission units called frames. User data is loaded into the packets at the Packet layer, then passed to the Link layer for transmission. The packets are wrapped with control information and are sent in a continuous segment or frame. The framing is specified by an ITU-T bit-oriented protocol called the High-level Data Link Control (HDLC).

For more information about the NetWare Link/X.25 Link layer, refer to NetWare Link/X.25 Link Layer Characteristics.