Back to: FC (Fibre Channel) fundamentals
Fibre Channel (FC) is a high-speed networking technology used primarily for storage area networks (SANs). It is designed to provide high-speed, low-latency, and reliable communication between servers and storage devices. The Fibre Channel protocol is structured into five layers, similar to the OSI model but tailored for storage networking.
Fibre Channel Layers:
1. FC-0 (Physical Layer)
- Defines the physical aspects of Fibre Channel, including:
- Cable types (fiber optic, copper)
- Connector types
- Signal encoding (e.g., 8b/10b, 64b/66b)
- Transmission speeds (e.g., 1G, 2G, 4G, 8G, 16G, 32G, 64G, 128G)
- Determines how data is physically transmitted over the medium.
2. FC-1 (Encoding & Link Control Layer)
- Responsible for:
- Data encoding/decoding (to ensure synchronization and error detection)
- Bit and frame synchronization
- Flow control at the link level
- Uses 8b/10b or 64b/66b encoding to maintain data integrity.
3. FC-2 (Framing & Flow Control Layer)
- Handles Fibre Channel frames, including:
- Frame structure (Header, Payload, CRC, Trailer)
- Flow control mechanisms (Buffer-to-buffer credit)
- Ordered delivery of frames
- Manages classes of service, such as:
- Class 1: Dedicated connection
- Class 2: Connectionless with acknowledgments
- Class 3: Connectionless without acknowledgments (commonly used in SANs)
4. FC-3 (Common Services Layer)
- Provides advanced features and services, such as:
- RAID and encryption services
- Multi-port management
- Striping and spanning across multiple links
- This layer is rarely implemented in most FC implementations.
5. FC-4 (Protocol Mapping Layer)
- Maps upper-layer protocols onto Fibre Channel, such as:
- SCSI (FCP – Fibre Channel Protocol)
- NVMe over Fibre Channel (FC-NVMe)
- IP (FCIP – Fibre Channel over IP)
- FICON (IBM mainframe connectivity)
- Acts as an interface between applications and storage.
Summary
| Layer | Function |
|---|---|
| FC-0 | Physical layer: Defines cables, connectors, and signaling. |
| FC-1 | Encoding & link control: Handles bit-level transmission and error checking. |
| FC-2 | Framing & flow control: Manages frames, flow control, and service classes. |
| FC-3 | Common services: Provides advanced SAN services like encryption and multi-port management. |
| FC-4 | Protocol mapping: Adapts higher-level protocols like SCSI, NVMe, or FICON. |
These layers ensure that Fibre Channel operates efficiently, providing a high-performance, low-latency, and lossless network for enterprise storage environments.