|FC-4||Application||7||Application||Upper Layer Protocol|
|FC-2||Framing Protocol||4||Transport||Lower Layer Protocol|
FC-2 defines three classes of service
The frame is the basic unit of information interchange and is created using 4 byte words (MSB in byte 0 and LSB in byte 3).
- R_CTL = routing control flags (FT = Frame Type)
- FT-0 link control: Ack, link_response, link_command
- FT-1 data: FC-4 Device_Data, FC-4 Vide_Data, and Link_data (link services)
- D_ID = Destination ID - the WWN of the dest N_port
- S_ID = Source ID - the WWN of the source N_port
- TYPE of FC-4 upper layer protocol being used:
- CP IPI-3 peer, master, or slave
- IPI-3 peer, master, or slave
- SCSI FCP
- Fibre Channel Services
- SBCCS channel or control unit
- F_CTRL - Frame control flags:
- Abort sequence condition
- Invalidate X_ID
- Exchange context
- Pause/continue sequence
- Fill bytes
- Sequence context
- First sequence
- Chained sequence
- Last sequence
- End sequence
- New X_ID assigned
- Sequence initiative
- SEQ_ID - the sequence ID contains an unsigned binary number identifying the sequence of which the frame is a part. the SEQ_ID is assigned by the sequence initiator and is unique for a specific D_ID and S_ID pair, while the sequence is open.
- DF_CTL - the data field control flags identify optional headers (network, association, or device) in the data field and frame header extension.
- Network header consists of two 8-byte fields that are used for communication between and FC port and a non-FC network port, e.g. ethernet port
- Association header consists of a 32-byte field that contains a process associator and an operation associator.
- Device header is a 16-, 32-, or 64-byte field that is entirely defined by the desired FC-4 protocol mapping documents, SCSI, TCP/IP, or HiPPI, for example.
- SEQ_CNT - the sequence count contains an unsigned binary number identifying the order of frame transmission within a single sequence or multiple consecutive sequences for the same exchange. For example, 0 is the first frame, 9 is the tenth frame, and so on. The sequence count of each subsequent data frame is incremented by one.
- OX_ID - the originator exchange ID field identifies the exchange ID assigned by the originator of the exchange. This field is also used by the originator exchange status block to track the progress of a series of sequences that comprise an exchange.
- RX_ID - the responder exchange ID field is assigned by the responder to provide a unique, locally meaningful identifier at the responder for an exchange established by an originator and identified by an OX_ID.
- PARAMETER - this field is a relative offset for data or link control information.
There are two types of frames: data and Link control frames.
Data frames include
Link control frames include
Class 1 service is circuit switched and creates a dedicated circuit and bandwidth between two nodes on the fabric. When the connection is no longer needed, the circuit is torn down.
The upper layer protocols allow for connectionless communication to occur when resources are available. Mixed mode traffic is handled by sub-fabric processing.
When only a fraction of the bandwidth is requested, a virtual circuit is established. The remaining resources are available and managed by the QoS facilitator as a class 4 service.
Class 6 is multicast and reliable.
Fibre Channel Level 4 Protocol Mapping - SCSI
required Fibre Channel protocol (FCP) frames required for SCSI mapping:
FC-AL : Fibre Channel - Arbitrated Loop