IBM 8270, Инструкция по установке и обслуживанию

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Length Recommendations for Dedicated-Media LAN Segments
The IBM Token-Ring Network dedicated-media connections support only one
attached entity (workstation or 8270) per connection.
For all supported cable types except optical fiber, the recommended maximum
cable lobe length is 190 m (624 ft) plus a 10-m (33-ft) total allowance for the patch
cords in the office and telecommunications closets.
In the IBM Token-Ring Network, the section of cable that attaches a device to an
access unit is called a
lobe.
Lobe Wiring Rules for Dedicated-Media LAN Segments
Table A-4, Table A-5, and Table A-6 specify the maximum supported lobe lengths
for the indicated types of cables. An additional 10 m (33 ft) per lobe length is
allowed to accommodate patch cables, unless otherwise specified.
The maximum lengths reflect the longest lengths supported by the transmission
characteristics of IEEE 802.5-compliant adapters. The recommended distances for
the various cable types are set by North American and international commercial
building wiring standards. These standards state that standards-compliant
horizontal copper cabling shall not exceed 90 m (295 ft), leaving 10 m (33 ft) total
for required patch cabling in both the office and telecommunications closet. For
optical fiber, the recommended maximum cable lobe length is 2000 m (1.2 miles).
It is good practice to follow the cabling standards guidelines when installing building
cabling to help ensure a longer useful life for your cabling infrastructure, migration
to new technologies, and maximum flexibility for your network configuration.
Table A-4. Lobe Lengths for 150-Ohm, Shielded Media
Ring
Speed Types 1 and 1A
Types 2 and 2A
Type 8 Type 9
4 Mbps 750 m (2460 ft) 376 m (1234 ft) 500 m (1640 ft)
16 Mbps 290 m (951 ft) 146 m (479 ft) 200 m (656 ft)
Note: Subtract 10 m (33 ft) from the allowed Type 1 or 2 distance each time a 2.4-m (8-ft) patch cable
is replaced by a Type 6, 9-m (30-ft) patch cable on that lobe.
Table A-5. Lobe Lengths for 100-/120-Ohm, Shielded or
Unshielded Cable
Ring
Speed
Type 3
Category 3
4 Mbps 100 m (328 ft) 250 m (820 ft)
16 Mbps Not Supported 100 m (328 ft)
Note: Unshielded media requires appropriate filtering.
Table A-6. Lobe Lengths for 100-/120-Ohm, Shielded or
Unshielded Cable
Ring
Speed
Category 4
Category 5
4 Mbps 350 m (1148 ft) 350 m (1148 ft)
16 Mbps 200 m (656 ft) 200 m (656 ft)
Note: Unshielded media requires appropriate filtering.
Appendix A. Cable and Pin Information
A-5