1731 uses this as
a basis and also added Performance Management (ratifi ed in 2007)
In Progress 802.1ah Provider Backbone Bridges (PBB)
In Progress 802.1Qay Provider Backbone Bridges ??“ Traffi c Engineering (PBB-TE). Also
referred to as Provider Backbone Trunking (PBT)
In Progress 802.1aj 2 port Relay and Demarcation
Source: IEEE, Wikepedia
Ethernet: From LAN to the WAN 15
The primary ring was used for data transmission during normal operation, while the
secondary ring remained idle; if the primary ring failed, the secondary ring took over. The
primary purpose of the dual rings was to provide superior reliability and robustness.
FDDI was used mainly because it supported higher bandwidth at greater distances
than usually possible over copper.26 It also supported hundreds of users, and its dual
ring architecture afforded reliability and fault-tolerance at distances greater than
100 miles. These capabilities made FDDI an attractive technology to build backbones
for networks that extended beyond traditional enterprise LANs.
Table 1.2 offers a brief comparison of these standardized LAN technologies as of the
mid-1980s and early 1990s, when they had been standardized with similar feature sets.
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