Fibre Channel Protocol Architecture Fibre Channel Layered Model
FC-2: Framing & Flow Control
FC-2 defines the structure, organization, and delivery of the data:
Link initialization and recovery Initiates login Class of Service support Constructs and manages frames Manages information flow Manages flow control Frame error detection (CRC32)
ULPs
FC-3 Common Services FC-4
FC-2 Framing & flow control
FC-0 Physical Interface FC-1 Encoding
FC-2 defines framing and flow control:
The datalink layer is where Ethernet carries out framing, in Fibre Channel FC-2 does the framing. The network layer – equivalent of an IP address – is the FC_ID, the 24 bit logically assigned address. At the transport layer in Fibre Channel, we use Class of Service. Class 2 and Class 3 are analogous to TCP and UDP. Transport, network and datalink layers combined define the FC-2 layer.
FC-2 always operates at the 8 bit level. Once FC-2 has done the framing, 8 bit bytes are passed through the FC-1 layer. FC-2 is responsible for link initialization. It initiates login. Here we do a LIP or Fabric Login to get an address Constructs and manages frames. Looks after flow control, frame error detection. Every frame contains a 32 bit cyclic redundancy check. This is used for frame error detection. Between every frame, fibre channel sends a minimum of 6 idles to create an inter frame gap.