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Fabric OS Administrator’s Guide
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Chapter
20
Managing Long Distance Fabrics
In this chapter
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 distance 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 on obtaining and installing licensed features, se
. The Extended Fabrics feature enables the following:
Fabric interconnectivity over Fibre Channel at longer distances 
ISLs can use long distance dark fiber connections to transfer data. Wave division multiplexing, 
such as DWDM (Dense Wave Division Multiplexing), CWDM (Coarse Wave Division 
Multiplexing), and TDM (Time Division Multiplexing), 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 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, an approach that simplifies 
deployment and administration.
Optimized switch buffering 
When Extended Fabrics is installed on gateway switches (E_Port connectivity from one switch 
to another), the ISLs (E_Ports) are configured with a large pool of buffer credits. The enhanced 
switch buffers help ensure that data transfer can occur at near-full bandwidth to efficiently 
utilize the connection over the extended links. This ensures the highest possible performance 
on ISLs.