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AIX Version 4.3 Communications Programming Concepts
DLCTOKEN Device Manager Functions
The token-ring data link control (DLCTOKEN) 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 token-ring adapter and the DLCTOKEN device handler perform the following MAC functions:
- Handling ring-insertion protocol
- Handling token detection and creation
- Encoding and decoding the serial bit-stream data
- Checking received network, group, and functional addresses
- Routing of received frames based on the LLC or MAC indicator and using the destination service access point (SAP) address if an LLC frame was received
- Generating cyclic redundancy checks (CRC)
- Handling frame delimiters, such as start or end delimiters and frame status fields.
- Handling fail-safe time outs.
DLCTOKEN performs additional MAC functions, such as:
- Framing control fields on transmit frames
- Network-addressing on transmit frames
- Routing information on transmit frames.
DLCTOKEN is also responsible for all LLC functions:
- Handling remote connection services and bridge routing, using the address-resolve and name-discovery procedures
- Sequencing of link stations on a given port
- Generating SAP addresses on transmit frames
- Generating IEEE 802.2 LLC commands and responses on transmit frames
- Recognizing and routing of received frames to the proper SAP
- Servicing IEEE 802.2 LLC commands and responses on receive frames
- Handling frame sequencing and retries
- Handling fail-safe and inactivity time outs
- Handling reliability/availability/serviceability (RAS) counters, error logs, and link traces.
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