Fibre Channel Primer

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Chapter 5
UPPER LAYERS
Fibre Channel is a transport service, moving data reliably and fast,
with the scalability to meet virtually any application requirements.
The Common Services layer, FC-3, and the Upper Layer Protocol
(ULP) mapping, FC-4, enhance the functionality and provide common
implementations for interoperability.
COMMON SERVICES: FC-3
FC-3 defines functions that are available to all N_Ports. Functions
that are currently defined include Name Server and Alias Server.
Additional services are described in Chapter 7.
l Name Server – The Name Server provides a directory of N_Ports
within a fabric. The Name Server maintains a database of such
items as ID, worldwide name, and supported FC-4s for each N_Port.
An N_Port may query the Name Server at any time to discover
other N_Ports attached to the fabric.
l Alias Server – The Alias Server is used to assign alias IDs to
multicast groups and hunt groups. A multicast frame is delivered
to all N_Ports assigned to the alias ID for the multicast group. A
hunt group is a set of associated N_Ports attached to a single node.
The Alias Server assigns an alias identifier that allows any frames
containing this alias ID to be routed to any available (non-busy)
N_Port within the set. This improves efficiency by decreasing the
chance of reaching a busy N_Port.