FW V06.XX/HAFM SW V08.02.00 HP StorageWorks SAN High Availability Planning Guide (AA-RS2DD-TE, July 2004)

Planning Considerations for Fibre Channel Topologies
120 SAN High Availability Planning Guide
■ Data networks introduce variable delay and usually support high latency.
SANs require minimal delay and latency.
■ Data networks rely on a software protocol stack such as Transmission Control
Protocol/Internet Protocol (TCP/IP) to provide communications. Such stacks
impose prohibitive performance penalties in SANs because data traffic
quickly overloads servers.
Because of these differences, SANs are based on Fibre Channel technology
optimized for storage environments and offer high-speed, low-overhead
communication between servers and storage devices. Data networks are often
implemented using Internet Protocol (IP) over gigabit Ethernet. IP is appropriate
for data networking because a high level of protocol processing is provided. The
protocol conversion approaches to integrating Fibre Channel fabric SANs over a
geographically dispersed network (WAN extension) are:
■ Fibre Channel over TCP/IP (FCIP).
■ Internet Fibre Channel Protocol (iFCP)
■ Internet Small Computer Systems Interface Protocol (iSCSI).
FCIP Protocol
The FCIP protocol encapsulates Fibre Channel frames (Fibre Channel or SCSI
protocol) into IP packets and fabric domains to IP addresses. This process of
encapsulating one information packet inside another is called protocol tunneling.
With FCIP, a single SAN fabric is created by connecting multiple SAN islands
through IP network tunnels. Figure 47 illustrates FCIP WAN extension.