Communications Programming Concepts

DLCETHER Device Manager Functions

The Standard Ethernet data link control (DLCETHER) device manager and transport medium use two functional layers, medium access control (MAC) and logical link control (LLC) to maintain reliable link-level connections, guarantee data integrity, and negotiate exchanges of identification. Both connectionless (Type 1) and connection-oriented (Type 2) services are supported.

The Ethernet adapter and the DLCETHER device handler perform the following MAC functions:

• Managing the carrier sense multiple access with collision detection (CSMA/CD) algorithm
• Encoding and decoding the serial bit stream data
• Receiving network address checking
• Routing received frames based on the LLC type field
• Generating cyclic redundancy check (CRC)
• Handling fail-safe time outs.

The DLCETHER device manager also performs the following LLC functions:

• Remote connection services
• Sequencing each link station (LS) on a given port
• Creating network addresses on transmit frames
• Creating service access point (SAP) addresses on transmit frames
• Creating IEEE 802.2 LLC commands and responses on transmit frames
• Recognizing and routing received frames to the proper SAP
• Servicing IEEE 802.2 LLC commands and responses on receive frames
• Sequencing frames and retries
• Handling fail-safe and inactivity time outs
• Handling reliability counters, availability counters, serviceability counters, error logs, and link traces.