Fibre Channel Primer

52 Fibre Channel: Connection to the Future
of the group. The fabric assigns the first available N_Port within this
hunt group as the destination for the service class. In Class 1, hunt
groups facilitate selection of an available N_Port for a dedicated
connection. In Class 2 or 3, hunt groups can be deployed to increase
bandwidth, reduce latency, or both.
Quality of Service Server
The quality of service server is used to enter the desired QoS
established for Class 4 service on virtual channels. The QoS server is
an entity within the fabric, required for Class 4, for establishing and
maintaining the QoS parameters for all dormant and active Virtual
Circuits (VCs). The QoS parameters are guaranteed minimum
bandwidth and guaranteed maximum end-to-end delay on each VC.
The QoS server is also responsible for the management of Class 4
circuit connection set up and tear down. It makes sure that the
requested QoS is provided, based on the available resources, before
granting connections. All QoS parameters are negotiable for each
virtual circuit.
Class 6 Multicast Server
The Class 6 multicast server is an optional fabric entity that
manages the responses coming from all destination N_Ports belonging
to a Class 6 multicast group. The server returns a single response to
the source N_Port. Class 6 multicast provides a reliable multicast
service based on dedicated connections. The frame to be multicast is
sent to the Class 6 multicast server for replication and transmission
to the destination N_Ports on separate dedicated connections through
the fabric. The fabric is responsible for the delivery of these frames
to the destination N_Ports. The frame header contains all the N_Port
IDs of the multicast group used by the Class 6 multicast server. An
N_Port becomes a member of the multicast group when a connection
is established. When the multicast connection is removed, the N_Port
ceases to be a member of that multicast group.