Fabric Login Process - Storage Basics-9

Below are the three login processes which are responsible for the creation and maintenance of communication link between initiator and target.

  1. Fabric Login:- It is known as FLOGI. It establishes the session between N-port and F-port. It is mandatory process for point-to-point and Fabric topology, without it N_port will not able to send or receive data. It is optional for Arbitrated loop. It performs below function so that N_port can register to the fabric.

• As soon as N_port is connected to F_port, it will register itself in the fabric by sending the fabric login request. In return F_port will assign a 24-bit FCID to the N-port.
• N_port also negotiate the link flow control parameter i.e. Buffer-to-Buffer credit with F_port.
• If N_port and F_port supports authentication then they are negotiate the authentication parameters during FLOGI.

   N_port sends the Flogi frame (containing WWNN, WWPN and B2B credit) to a well-known address of 0xFFFFFE. In return switch will send the accept frame (ACC).

  2. N-Port Login:- It is also known as PLOGI. It creates a FC4 session between the end devices.  It is responsible to create and maintain the session between two N-Port. During PLOGI, N_port will negotiate the end-to-end credit. PLOGI also enables N_port to learn other characteristics like WWNN, WWPN etc. of other end N_port.

N_port sends the PLOGI on a well-known address of 0xFFFFFC.

  3. Process Login:- Also known as PRLI. It creates and maintains a session between two FC4 processes that are connected via two different N_port between initiator and target.