DLC FDDI Device Manager Nodes

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The DLC FDDI device manager operates between two nodes on a fiber distributed data interface (FDDI) local area network (LAN), using IEEE 802.2 logical link control (LLC) procedures and control information as defined in the Token-Ring Network Architecture Reference and media access control procedures as defined in the ANSI standard publication Fiber Distributed Data Interface-Token Ring Media Access Control.

The DLC FDDI device manager supports:

  • Asynchronous disconnected mode (ADM) and asynchronous balanced mode extended (ABME)
  • Two-way simultaneous (full-duplex) data flow
  • Multiple point-to-point logical attachments on the LAN using network and service access point (SAP) addresses
  • Peer-to-peer relationship with remote station
  • Full six-byte addressing
  • Both name-discovery and address-resolve services
  • Source-routing generation for up to 14 bridge hops
  • Asynchronous transmission with eight possible priority levels.

The DLC FDDI provides full-duplex, peer-data transfer capabilities over a FDDI LAN. The FDDI LAN must use the ANSI X3.139 medium access control (MAC) procedure and a superset of the IEEE 802.2 LLC protocol as described in the Token-Ring Network Architecture Reference.

Multiple FDDI adapters are supported, with a maximum of 126 SAP users per adapter. A total of 255 link stations per adapter are supported, which are distributed among the active SAP users.

The term logical link control (LLC) is used to describe the collection of manager, access channel, and link station subcomponents of a generic data link control GDLC component such as DLC FDDI device manager, as illustrated in the DLC[TOKEN, 8032, ETHER, or FDDI] Component Structure figure (Figure 1).

Each link station (LS) controls the transfer of data on a single logical link. The access channel performs multiplexing and demultiplexing for message units flowing from the link stations and manager to MAC. The DLC manager:

  • Establishes and terminates connections
  • Creates and deletes an LS
  • Routes commands to the proper link station.