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Implementing SAN Internetworking Solutions
4
SONET and SDH
McDATA Products in a SAN Environment - Planning Manual
4-42
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Requires sufficient BB_Credits assigned to the link (such as
credits available through the Intrepid 10000 Director buffer pool).
Because WDM is a method to transmit multiple signals over the
same fiber-optic cable, there is no BB_Credit limitation difference
between WDM and dark fiber. Refer to
BB_Credit
for information about requirements.
•
Creates one logical Fibre Channel fabric through a stretched
E_Port connection. The connection is vulnerable to disruptions
caused by events at each site or to disruptions caused by
problems with the extended-distance WDM link.
Several network service providers provide metropolitan and long-
distance (intercity) WDM transport services. WDM service can be
purchased on a monthly basis in accordance with a negotiated service
level agreement (SLA). A typical SLA specifies the availability,
minimum dedicated bandwidth (usually scalable), latency, security
level, monitoring level, packet loss, and mean time to repair (MTTR).
Like dark fiber, WDM is not practical for long-distance ADR
applications. In addition, WDM technology is still evolving and
equipment is relatively expensive.
The telecommunications industry developed SONET and SDH
standards for transport of time division multiplexed (TDM) data over
fiber-optic cable. SONET is used in North America (United States and
Canada) and Japan. SDH is used elsewhere, primarily in Europe.
SONET and SDH are closely related standards that specify interface
parameters, rates, framing formats, multiplexing methods, and
management for synchronous TDM data transport.
The physical-layer protocol multiplexes n incoming bit streams,
optically modulates the result, and transmits the signal at a rate equal
to the incoming bit rate times n. As an example, four data streams
arriving at a SONET multiplexer at 2.5 Gbps are transmitted as one
stream at 10 Gbps (four times 2.5 Gbps). Low bit-rate streams of
information are multiplexed into higher bit-rate streams and
transmitted at the rate of the SONET or SDH network. TDM ensures
a constant stream of data through a network and takes advantage of
the available bandwidth.
Distance Extension Through
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