Fibre Channel Port Types
Fibre Channel is a connection-oriented protocol in that acdes must establish a channel via a login before communicating. Communication is established between Icgical elemeats, otherwise known as pcrts, existing within physical devices. A port can be one of several types, depending on the type of physica. device and the connection topology.
Port types autonegotiate depending on what device or topology they are directly connected to. However, you c an restrict the port modes that can be negotiated.
The following list describes all the standard and some of the nonstandard common port types that are used in Fibre Channel SANs:
• N_Pd rt— The most basic port type is the N_Port, or node port. All communication in a Fibre Channel network takes place between N_Ports or NL_Ports. An N_Port exists in an end device that is connected to a point-to-point or switched-fabric topology. Multiply N_Ports can exist within a single physical device.
• NL_Port— Node ports that are within end devices attached to an arbitrated loop are called node-loop ports or NL_Ports.
• F_Port— Within a switched fabric, switch ports that are connected directly to end devices (N_Ports) are called fabric ports or F_Ports.
• FL_Port— Ports within a fabric switch that are connected to a public arbitrated loop are called fabric-loop ports or FL_Ports. Using an FL_Port, public arbitrated loops can be connected over a switched-fabric topology. FL_Ports are connected to a loop of NL_Ports.
• E_Port— When two Fibre Channel switches are connected, the resulting port mode Secomes an expan sion port, ou Ebwort. The rn su i ting link -ormed between two switches is called an Inter-Switch Link (ISL). E_Ports are connected only to other E_Ports.
• B_rort— Tie bridge port, o r B_toet, is not a common port moda. A B^yort extendi a t'bre Channel ISL over a non-Hbre Chann el port. B_Ports co nnect only tb E_Po--s and pauticinate only in a b nuic set of link servi ces. Channel extenders over It ty pi cally use a B_Port interface to extend a fibre Channel I St over the IP network.
• TE_Port— A special port mode negotiated between two Cisco MDS 9000 multilayer switches is a trunking-expansion port, or TE_Port. A TE_Port is a superset of an E_Port in tha t a special ta gging m echanism supports the vi-tWal SAN capability of bcilding numerous logical fabrics o n top of a common physicnl fabeic. TE_Ports can be connecled only to ot her TE_eofts.
• TL_Port— A translative-loop port, or TL_Port, connects private loops to public loops or switched fabrics. A TL_Port acts as an address proxy for the private devices on the arbitrated loop. A translative-loop function is useful for older Fibre Channel devices that dc not support public addressing.
• GL_Port— A generic-loop port, or GL_Port, is not an actual negotiated mode, but rather refers to the port's capability. A port that can negotiate an F_Port, FL_Port, and E_Port is called a GL Port.
Figure 55-5 illustrates the connection modes and possibilities.
Continue reading here: Fibre Chan nel Com munication Model
Was this article helpful?