HP StorageWorks 2/24 FW 07.00.00/HAFM SW 08.06.00 McDATA Products in a SAN Env - Page 183
SAN Extension Transport Technologies, Internet protocol IP.
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Implementing SAN Internetworking Solutions 4 SAN Extension Transport Technologies Dark Fiber There are several extension transport technologies available to connect geographically-dispersed SAN islands, all of which differ in performance, latency, and implementation cost. The primary technologies include: • Dark fiber (repeated or unrepeated). • Wavelength division multiplexing (WDM). • Synchronous optical network (SONET) and synchronous digital hierarchy (SDH). • Internet protocol (IP). Dark fiber refers to an installed fiber-optic infrastructure (including cabling and possibly including repeaters) that is not in use. Dark fiber strands (usually deployed in transmit and receive pairs) provide point-to-point, unprotected connectivity between two locations. Many corporations install excess fiber-optic cabling with the expectation of leasing the infrastructure at a future date. When a telecommunication company installs cable, they often lay additional (unused) cables to avoid retrenching costs. Utility companies often install unused cables coincident with pipelines or electrical power lines. The dark fiber is then leased to companies (dark fiber service) that require dedicated optical connectivity between separate locations. Cable operation and connectivity are not controlled by the service provider. The service lessee is responsible for laser transceivers and other equipment that make the cabling functional. Figure 4-8 illustrates extended-distance connectivity through a dark fiber (dedicated FCP or FICON) interface. The technology: • Is well suited as an extension technology for SDR applications over metropolitan distances up to 22 miles (35 km) without repeaters and up to 75 miles (120 km) with repeaters. The supported bandwidth is dependent on fiber-optic quality and the choice of multiplexing scheme. • Requires sufficient buffer-to-buffer credits (BB_Credits) assigned to the link (such as credits available through the Intrepid 10000 Director buffer pool). Refer to Distance Extension Through BB_Credit for information about requirements. Implementing SAN Internetworking Solutions 4-39