Installation guide

Appendix B. Fibre Operation
187
Point-to-point
A point-to-point topology consists of two and only two devices connected by
N_ports of which are connected directly. In this topology, the transmit Fibre of
one device connects to the receiver Fibre of the other device and vice versa.
The connection is not shared with any other devices. Simplicity and use of the
full data transfer rate make this Point-to-point topology an ideal extension to the
standard SCSI bus interface. The point-to-point topology extends SCSI
connectivity from a server to a peripheral device over longer distances
Arbitrated Loop
The arbitrated loop (FC_AL) topology provides a relatively simple method of
connecting and sharing resources. This topology allows up to 126 devices or
nodes in a single, continuous loop or ring. The loop is constructed by
daisy-chaining the transmission and receive cables from one device to the next
or by using a hub or switch to create a virtual loop. The loop can be
self-contained or incorporated as an element in a larger network. Increasing the
number of devices on the loop can reduce the overall performance of the loop
because the amount of time each device can use the loop is reduced. The ports
in an arbitrated loop are referred as L-Ports.
Switched Fabric
A switched fabric a term is used in a Fibre channel to describe the generic
switching or routing structure that delivers a frame to a destination based on the
destination address in the frame header. It can be used to connect up to 16
million nodes, each of which is identified by a unique, world-wide name.
In a switched fabric, each data frame is transferred over a virtual point-to-point
connection. There can be any number of full-bandwidth transfers occurring
through the switch. Devices do not have to arbitrate for control of the network;
each device can use the full available bandwidth.
A fabric topology contains one or more switches connecting the ports in the FC
network. The benefit of this topology is that many devices (approximately 2-24)
can be connected. A port on a Fabric switch is called an F-Port (Fabric Port).
Fabric switches can function as an alias server, Multicast server, broadcast
server, quality of service facilitator and directory server as well.
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The following elements are the connectivity of storages and Server components
using the Fibre channel technology.