Sun Microsystems SunLink SNA 9.1 PU2.1, Руководство по настройке

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D-4 SunLink SNA 9.1 PU2.1 Server Configuration Guide—August 1997
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Frame Control (FC), which is used to identify the type of underlying
information.
•
Destination Address (DA), which is used to identify the intended recipients
of the frame.
•
Source Address (SA), which is used to identify the sender.
•
Routing Information (RI), which is used to optionally include source route
paths.
•
Information (INFO), which is used to include the actual data that is being
transmitted over the token ring network.
•
Frame Check Sequence (FCS), which is used to include a Cyclic Redundancy
Check (CRC) for detecting transmission errors.
•
Ending delimiter (ED) byte.
•
Frame Status (FS), which is used to designate the actions performed on the
frame by the remote stations to which it was addressed.
The types of frame data information identified by the Frame Control are
described as follows:
•
Medium Access Control - MAC is a sublayer to the Data Link Control
(DLC). It is used for lower layer communications activities in various data
communications and network architecture models, such as the Open
Systems Interconnect (OSI) reference model from the International
Standards Organization (ISO), SNA from IBM, and TCP/IP.
•
Logical Link Control - LLC is a sublayer of the DLC. It defines frame
formats and protocols for the transmission of connectionless (Type 1) or
connection-oriented (Type 2) services. Information is transmitted within
LLC Protocol Data Unit (PDU) frames. LLC is described in IEEE Standard
802.2/ISO 8802-2.
LLC frame information is of more value to users of Sun's IBM Token Ring
network connectivity products because LLC frames carry SNA data. The
LLC frame format is shown in the following figure.
Figure D-2 LLC Frame Format
LLC frames consist of the following:
• Destination Service Access Point (DSAP).