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Communications Programming Concepts
The IEEE 802.3 Ethernet
data link control (DLC8023) 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 DLC8023
device handler can perform the following MAC functions:
- Managing the carrier-sense
multiple access with collision detection (CSMA/CD) LLC algorithm
- Encoding and decoding the
serial-bit stream data
- Receiving network-address
checking
- Routing received frames
based on the LLC Link Protocol Data Unit (LPDU) destination service access
point (SAP) field
- Generating preamble
- Generating cyclic redundancy
checks (CRC)
- Handling fail-safe time outs
The DLC8023 device manager can
also perform the following LLC functions:
- Remote connection services
- Sequencing each link station
on a given port
- Creating the network
addresses on transmit frames
- Creating service access
points 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
- Handling frame sequencing
and retries
- Handling fail-safe and
inactivity time outs
- Handling reliability
counters, availability counters, serviceability counters, error logs, and link
traces
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