HP Mainframe Connectivity Design Guide

Gb/s, and 1 Gb/s. When planning for SAN extension, BB_credits are an important consideration
in WDM network configurations. Typical WDM implementations for storage replication include a
primary and secondary path. You must have enough BB_credits to cover the distances for both the
primary path and secondary path so that performance is not affected if the primary path fails.
For more information about BB_credits in a FICON SAN environment, see HP StorageWorks XP
Disk Array and Mainframe white paper and the HP StorageWorks P9500 Disk Array and Mainframe
white paper, available at the HP Large Enterprise Business website http://h20195.www2.hp.com/
v2/erl.aspx?reg=uk&lang=en&doctype=white%20paper&docreg=ww|us|usca|amer&
keywords=xp+mainframe&logic=AND&numberitems=all&sortedby=recentdate&sortorder=desc&
query=yes.
Implementation
WDM-based networks provide a lower-cost way to respond quickly to increased bandwidth
demands and protocol changes. The quick response occurs because each wavelength is a new,
full-bandwidth communications link. In many areas of the world, it is less expensive to deploy
WDM devices on existing fiber than it is to install new fiber.
After implementing WDM, service providers can establish a “grow as you go” infrastructure.
Service providers can expand capacity in any portion of their networks. Carriers can address
areas of congestion resulting from high-capacity demands.
WDM enables you to partition and maintain dedicated wavelengths for different customers. For
example, service providers can lease wavelengths (instead of an entire fiber) to their high-use
business customers.
Architecture
The WDM system architectures are as follows:
• Passive (optical transmission protocol)
• Active signal amplification
• Active protocol handling
Most WDM products use one of these architectures or combine attributes of each.
Table 83 (page 133) summarizes the WDM system architectures.
132 FICON and FICON SAN extension