If the attached device is a initiator or a target – the port state is changing from G_Port to F_Port (state5).If the attached device is not a loop, the initialization continues into the G_Port stage (state3).If the port receives at least 3 consecutive pritimite sequences, the port is going through the arbitrated loop initialization, becoming a FL_Port (State2).During the Transaction1 port is transmitting at least 12 Primitive Sequences LIP(F7) – as a try for arbitrated loop initialization sequence.If the port can detect that something is connected (something is sending a signal to the port), it goes through the first transaction.
Port Initialization Process becomes from the U_Port (called a State1).(Click on the diagram to see it in better resolution.) It is the connection between two switches. This kind of port is used for inter-switch links (ISL). In other words F_Port means that this port is directly connected to either a initiator or target. It means that the port is connected to a Full Fabric device – so to a N_Port. If a port stayed as a G_Port there is probably some issue during Port Initialization It is a state through-out Port Initialization before a port can become either a F_Port or E_Port. A switch port becomes FL_Port only when it is directly connected to NL_Port on the device side. Normally when nothing is attached to a port it is a U_Port. U_Port means that the Port does not have a topology assigned yet, it is basically waiting to become another port type. But in few words – it need to do that to get 24bit fabric address and be able to exist in Switched Fabric environment. This process I will explain more carefully in futures post. As a consequence, once the device finishes the arbitrated loop initialization it starts sending out FLOGI (fabric logins). The device has an arbitrated loop code, and switched fabric code in its code base. NL_Port – Node Loop Port – a device attached to a loop.In storage world targets are storage arrays, and initiators are hosts/servers. Such device can be either an initiator or a target. N_Port – Node Port – a Fabric device directly attached.If it’s a switch port – it usually becomes either U_Port, F_Port or E_Port. Let me go through port types with short explanation. Depends if the port is a device port – it can become N_Port or NL_Port. During that process every port is categorized under specific type. In SAN environment, every port has to go through initialization process.
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