DLCTOKEN Device Manager Functions

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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.