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By Kimberly
Caisse
Network World,
12/24/01
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Back to Can Ethernet be your MAN? ]
How big Ethernet wins in the metropolitan-area network
depends largely on the work of at least two standards bodies.
The 50-member Metro Ethernet Forum is addressing Optical
Ethernet's shortcomings "such as lack of resiliency and the inability
to carry [time division multiplexing] traffic," says Nan Chen, the forum's
president.
New Optical Ethernet equipment is being developed with
wave division multiplexing (WDM) integration, Chen says. This equipment will
add recovery rates and TDM support "comparable to that achieved in SONET
networks," he says.
Currently, Ethernet's Spanning Tree Protocol provides
a failure-and-recovery time - commonly known as failover - that ranges between
3 and 30 seconds, according to Kamran Sistanizadeah, CTO at Yipes Communications.
This failover rate is usually adequate for most data communications
customers, he says. However, it can be improved by the standard being proposed
by the IEEE's Resilient Packet Ring Working Group, Sistanizadeah says.
The proposed standard seeks to create an additional media
access control (MAC) layer for use in Layer 2 fiber ring topologies, says
Mike Takefman, the working group's chairman and manager of engineering at
Cisco. "Rings are a well-known and widely deployed technology in the
metropolitan space for building networks with redundancy," he says.
If approved, the new MAC layer could be used in LANs,
MANs and WANs at speeds ranging from 100M bit/sec to more than 10G bit/sec.
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