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In conventional IP networks, the end systems or hosts are the active participants in data communications. The network that links hosts together has one primary goal -- to quickly switch or route host-generated messages from source to destination. Advanced network-based services such as Quality of Service or data encryption may require processing power or "intelligence" in the switch or router, but these services only enhance the transport and are transparent to the end systems. The intelligence to run applications resides at the end systems; the network itself is simply a transport.
SANs, by contrast, have active end systems such as servers, but they also have passive recipients of server requests such as disk arrays and tape subsystems. The active initiator and passive target relationship of storage transactions requires assistance from the network in the form of switch-based intelligence to provide login, device discovery, and zoning services. Storage initiators and targets must each communicate with the network infrastructure independently before they can establish sessions with one another.
In addition, Fibre Channel technology is designed to be largely self-configuring in terms of addressing and fabric building as well as self-monitoring in terms of State Change Notifications. Compared to conventional IP networked devices, storage end systems require additional network-based intelligence for discovery and monitoring, along with traditional switch transport services.