Cisco Systems PA-4R manual IBM Token Ring and Ieee 802.5 Comparison

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
Network Type		Data Rates	Stations/ Segment	Topology	Media	Signaling	Access Method	Encoding
IBM Token Ring		4, 16 Mbps	260 shielded twisted-pair	Star	Twisted-pair	Baseband	Token passing	Differential
network			72 unshielded twisted-pair					Manchester
IEEE 802.5		4, 16 Mbps	250	Not	Not	Baseband	Token passing	Differential
network				specified	specified			Manchester

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.

PA-4R Half-Duplex Token Ring Port Adapter Installation and Configuration

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