Fibre Channel Over TCP/IP (FCIP) describes mechanisms that allow the interconnection of islands of Fibre Channel storage area networks over IP-based networks to form a unified storage area network in a single Fibre Channel fabric. FCIP relies on IP-based network services to provide the connectivity between the storage area network islands over local area networks, metropolitan area networks, or wide area networks.

The primary function of an FCIP Entity is forwarding FC Frames, employing FC Frame Encapsulation. Viewed from the IP Network perspective, FCIP Entities are peers and communicate using TCP/IP. Each FCIP Entity contains one or more TCP endpoints in the IP-based network. Viewed from the FC Fabric perspective, pairs of FCIP Entities, in combination with their associated FC Entities, forward FC Frames between FC Fabric elements. The FC End Nodes are unaware of the existence of the FCIP Link.

FC Primitive Signals, Primitive Sequences, and Class 1 FC Frames are not transmitted across an FCIP Link because they cannot be encoded using FC Frame Encapsulation. The path (route) taken by an encapsulated FC Frame follows the normal routing procedures of the IP Network.

An FCIP Entity MAY contain multiple FCIP Link Endpoints, but each FCIP Link Endpoint (FCIP_LEP) communicates with exactly one other FCIP_LEP. FCIP Entities do not actively participate in FC Frame routing. The FCIP Control & Services module MAY use TCP/IP quality of service features.

It is necessary to statically or dynamically configure each FCIP entity with the IP addresses and TCP port numbers corresponding to FCIP Entities with which it is expected to initiate communication.

If dynamic discovery of participating FCIP Entities is supported, the function SHALL be performed using the Service Location Protocol (SLPv2). Before creating a TCP Connection to a peer FCIP Entity, the FCIP Entity attempting to create the TCP connection SHALL statically or dynamically determine the IP address, TCP port, expected FC Fabric Entity World Wide Name, TCP Connection Parameters, and Quality of Service Information.

FCIP Entities do not actively participate in the discovery of FC source and destination identifiers. Discovery of FC addresses (accessible via the FCIP Entity) is provided by techniques and protocols within the FC architecture.

To support IP Network security, FCIP Entities MUST: 1)implement cryptographically protected authentication and cryptographic data integrity keyed to the authentication process, and 2) implement data confidentiality security features.

On an individual TCP Connection, this specification relies on TCP/IP to deliver a byte stream in the same order that it was sent.

Protocol Structure

Fibre Channel Frame Encapsulation Header Structure C FCIP specific

Common fields:

• Protocol# - IANA-assigned protocol number identifying the protocol using the encapsulation.
• Version - Encapsulation version as specified in [ENCAP]
• -Protocol# - One's complement of the protocol#
• -Version C One's complement of the version
• Flags - Encapsulation flags
• Frame Length - Contains the length of the entire FC Encapsulated frame including the FC Encapsulation Header and the FC frame (including SOF and EOF words) in units of 32-bit words.
• -Flags C One's complement of the Flags field.
• -Frame Length C One's complement of the Frame Length field.
• Time Stamp [integer] - Integer component of the frame time stamp as specified in [ENCAP].
• Time Stamp - Fractional component of the time stamp [fraction] as specified in [ENCAP].
• CRC - Header CRC. MUST be valid for iFCP.

FCIP specific fields:

• Word 1 of the Protocol Specific field SHALL contain an exact copy of word 0 in FC Frame Encapsulation.
• The pFlags (protocol specific flags) field provides information about the protocol specific usage of the FC Encapsulation Header.

The SF (Special Frame) bit indicates whether the FCIP Frame is an encapsulated FC Frame or an FSF (FCIP Special Frame).

The Ch (Changed) bit indicates whether an echoed FSF has been intentionally altered. The Ch bit SHALL be 0 unless the FSF bit is 1.

Related protocols: SCSI, iFCP, FCP, FCIP, TCP, iSNS, iSCSI, SLP

Sponsor: Fibre Channel over TCP/IP iFCIP) is defined by IETF (http://www.ietf.org)

Reference:
http://www.javvin.com/protocol/rfc3643.pdf: Fibre Channel (FC) Frame Encapsulation
http://www.javvin.com/protocol/draft-ietf-ips-fcovertcpip-12.pdf: Fibre Channel Over TCP/IP (FCIP)