October 30, 2012

Fibre Channel Ports

 

Fibre Channel standards use the term node to describe any device connected to one or more other devices over Fibre Channel. Each node has at least one port that connects (directly or through a switch or fabric) to other ports on other nodes.  These ports are called end ports. 

In general, the ports of a switch are called switch ports, but further distinction is made depending on what the ports are connected to. The types of Fibre Channel ports used in discussions of zoning in are as follows:

N_Port (Node Port): All node ports are called N_Ports. This could be an HBA in a server or a target port on a storage array. 

N_Ports can only attach to other N_Ports or to F_Ports in a point-to-point protocol. 

N-port to N-port is uncommon, so when two nodes are direct-attached it is through an arbitrated loop (NL_Port to NL_Port). 

An N_Port handles creation, detection, and flow of message units to and from the connected system.

F_Port (Fabric Port): An F_Port is a port on a Fibre Channel switch that is connected to an N_Port.  That means the port into which a server’s HBA or a storage array’s target port is connected is called as an F_Port. 

F_Ports can only be attached to N_Ports. 

F_Port provides access to Fabric Services (eg. Fabric Name server & Fabric Login Server etc).

E_Port (Expansion Port): An E_Port is a port on a Fibre Channel switch that is connected to another E_Port on the same or on a different Fibre Channel switch. Or simply, it is the connection between two Fibre channel switches to build a larger switched fabric.

The connection between two E_Ports forms an Inter-Switch Link (ISL).

E_Ports can only attach to other E_Ports.

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