The INCITS/Fibre Channel (T11) Technical Committee adopted the following standards between 2019 – 2021:
- FC-FS-6: Congestion Signals (r0.3) – Defines new alarms and warning signals.
- FC-LS-5: Notifications (r5.01) – Defines notifications using Extended Link Services (ELS).
- FC-SW-8: Fabric detection and generation (r1.01) – Defines error detection, signaling, notification and registration to receive switch error messages.
These standards focused on:
- The creation of a new “Fabric Performance Impact Notification (FPIN)” Extended Link Service (ELS). These ELS messages are sent at the FC-2 layer to end-devices (example: storage and HBAs) that have registered to receive them. The messages are designed for best-effort delivery with no acknowledgement from the receiver and just like normal FC I/O traffic, they can be impacted by network congestion. FPINs are delivered only to the end-devices that are zoned to have access to an impacted port (device).
- The creation of a new Congestion Signal Primitives (CSPs) that can be used to communicate congestion on a hop-by-hop (link-based) basis. These primitives are not impacted by network congestion. These primitives are exchanged between devices at the FC-1 layer.
Please note, for the remainder of this white paper the term Fabric Notifications is used to refer to both FPINs and CSPs.