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PA-4R Half-Duplex Token Ring Port Adapter Installation and Configuration
OL-3589-01
Port Adapter Installation Prerequisites
access unit (MAU). Also, IBM Token Ring specifies twisted-pair cabling, whereas IEEE 802.5 does not
specify media type. Most Token Ring networks use shielded twisted-pair cabling; however, some
networks that operate at 4 Mbps use unshielded twisted-pair cable.
Table 1 shows a comparison of the two types.
Table 1 IBM Token Ring and IEEE 802.5 Comparison
All 4R port adapter interfaces support both 4- and 16-Mbps, half-duplex operation and early token
release. The default for all ports is for 4-Mbps operation and early token release disabled. Both states
are enabled with configuration commands in configuration mode.
To enable 16 Mbps, specify the slot/port address and use the configuration command ring-speed 16; to
return to 4 Mbps operation, use the command ring-speed 4. To enable and disable early token release,
specify the slot/port address and use the configuration command [no] early token release. For complete
descriptions and examples of software commands, refer to the related software configuration
documentation.
In the typical Token Ring network shown in Figure 1, lobe cables connect each Token Ring station (4R
port adapter interface) to the MSAU (or MAU), and patch cables connect adjacent MSAUs (or MAUs)
to form one large ring.
Network Type Data Rates Stations/ Segment Topology Media Signaling Access Method Encoding
IBM Token Ring
network
4, 16 Mbps 260 shielded twisted-pair
72 unshielded twisted-pair
Star Twisted-pair Baseband Token passing Differential
Manchester
IEEE 802.5
network
4, 16 Mbps 250 Not
specified
Not
specified
Baseband Token passing Differential
Manchester