HP StorageWorks 2/24 FW 07.00.00/HAFM SW 08.06.00 McDATA Products in a SAN Env - Page 167

Implementing SAN Internetworking Solutions 4 From the standpoint of fabric build events, the only difference between a local and stretched E_Port connection is the latency introduced by the TCP/IP link and associated WDM or FCIP hardware. A disruptive build fabric event at one local site propagates to the connected site. Likewise, a disruption in the TCP/IP link may cause the extended SAN to segment into separate SAN islands. For mission-critical storage over distance (such as disaster recovery applications) an extended SAN may inadvertently create instabilities that defeat the intent of highly-reliable data access. iFCP operates at a higher level and addresses problems that direct connectivity and FCIP do not. iFCP is similar to FCP but uses IP for OSI Layer 3 (network layer) and TCP for OSI Layer 4 (transport layer). In contrast, mFCP uses IP for OSI Layer 3 and UDP for OSI Layer 4. Connectivity is provided through an iSNS database with a WWN-to-IP address look-up table in each fabric. When a Fibre Channel frame is transmitted to a device in a different fabric, the frame is encapsulated and sent over the TCP/IP link to the destination fabric. The encapsulating wrapper is stripped off by iFCP and the Fibre Channel frame delivered to the destination device. iFCP can accommodate up to 64 TCP sessions per port. A TCP session opens for each pair of port WWNs that initiate a process login. SAN routers have both FCP and IP interfaces. The Eclipse 1620 SAN router has two ports that provide IP network connectivity at up to full-duplex 100 Base-T Fast Ethernet (100 Mbps) transmission speed. The Eclipse 2640 SAN router has four ports that provide IP network connectivity at up to full-duplex GbE (1,000 Mbps) transmission speed. Figure 4-6 shows the physical connectivity of two mSANs (to form an iSAN) through Eclipse 2640 SAN Routers and an IP wide area network (WAN). Implementing SAN Internetworking Solutions 4-23