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Fabric OS Administrator’s Guide 551
53-1002745-02
Chapter
23
Managing Long-Distance Fabrics
In this chapter
•Long-distance fabrics overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551
•Extended Fabrics device limitations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552
•Long -distance link modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552
•Configuring an extended ISL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553
•Buffer credit management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555
•Buffer credit recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566
•Forward error correction on long-distance links . . . . . . . . . . . . . . . . . . . . . 568
Long-distance fabrics overview
The most effective configuration for implementing long-distance SAN fabrics is to deploy Fibre
Channel switches at each location in the SAN. Each switch handles local interconnectivity and
multiplexes traffic across long-distance dark fiber or wave division multiplexing (WDM) links, while
the Brocade Extended Fabrics software enables SAN management over long distances.
Brocade Extended Fabrics is an optional licensed feature for Brocade SAN deployment over
distances beyond 10 km. A Brocade Extended Fabrics license is required before you can implement
long-distance dynamic (LD) and long-distance static (LS) distance levels. The LD and LS settings
are necessary to achieve maximum performance results over inter-switch links (ISLs) that are
greater than 10 km.
For details about obtaining and installing licensed features, refer to Chapter 18, “Administering
Licensing”.
The Extended Fabrics feature enables the following functionality:
• Fabric interconnectivity over Fibre Channel at longer distances
ISLs can use long-distance dark fiber connections to transfer data. Wavelength division
multiplexing, such as dense wavelength division multiplexing (DWDM), coarse wavelength
division multiplexing (CWDM), and time division multiplexing (TDM), can be used to increase
the capacity of the links. As Fibre Channel speeds increase, the maximum distance decreases
for each switch.
The Extended Fabrics feature extends the distance the ISLs can reach over an extended fiber.
This extension is accomplished by providing enough buffer credits on each side of the link to
compensate for latency introduced by the extended distance.
• Simplified management over distance
Each device attached to the SAN appears as a local device, which simplifies deployment and
administration.