iFCP: Internet Fibre Channel Protocol

Internet Fibre Channel Protocol (iFCP) is a gateway-to-gateway protocol, which provides fibre channel fabric services to fibre channel devices over a TCP/IP network. iFCP uses TCP to provide congestion control, error detection and recovery. iFCP's primary objective is to allow interconnection and networking of existing fibre channel devices at wire speeds over an IP network. The protocol and method of frame address translation defined permit the attachment of fibre channel storage devices to an IP-based fabric by means of transparent gateways.

The fundamental entity in fibre channel is the fibre channel network. Unlike a layered network architecture, a fibre channel network is largely specified by functional elements and the interfaces between them. These consist, in part, of the following:

1. N_PORTs -- The end points for fibre channel traffic.
2. FC Devices -- The fibre channel devices to which the N_PORTs provide access.
3. Fabric Ports -- The interfaces within a fibre channel network that provide attachment for an N_PORT. 
4. The network infrastructure for carrying frame traffic between N_PORTs.
5. Within a switched or mixed fabric, a set of auxiliary servers, including a name server for device discovery and network address resolution.

The iFCP protocol enables the implementation of fibre channel fabric functionality on an IP network in which IP components and technology replace the fibre channel switching and routing infrastructure.

The main function of the iFCP protocol layer is to transport fibre channel frame images between locally and remotely attached N_PORTs. When transporting frames to a remote N_PORT, the iFCP layer encapsulates and routes the fibre channel frames comprising each fibre channel Information Unit via a predetermined TCP connection for transport across the IP network.

When receiving fibre channel frame images from the IP network, the iFCP layer de-encapsulates and delivers each frame to the appropriate N_PORT. The iFCP layer processes the following types of traffic:

1. FC-4 frame images associated with a fibre channel application protocol.
2.  FC-2 frames comprising fibre channel link service requests and responses
3. Fibre channel broadcast frames
4. iFCP control messages required to setup, manage or terminate an iFCP session.

Protocol Structure - iFCP: Internet Fibre Channel Protocol

Common fields:

• Protocol# - IANA-assigned protocol number identifying the protocol using the encapsulation. For iFCP, the value assigned by [ENCAP] is 2.
• Version - Encapsulation version as specified in [ENCAP]
• -Protocol# - One's complement of the protocol#
• -Version - 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 - One's complement of the Flags field.
• -Frame Length - 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.

iFCP specific fields:

• LS_COMMAND_ACC - For a special link service ACC response to be processed by iFCP, the LS_COMMAND_ACC field SHALL contain a copy of bits 0 through 7 of the LS_COMMAND to which the ACC applies. Otherwise the LS_COMMAND_ACC field SHALL be set to zero.
• iFCP Flags - iFCP-specific flags:

SES: Session control frame

TRP: Transparent mode Flag

SPC: Special processing flag

• SOF - Copy of the SOF delimiter encoding
• EOF - Copy of the EOF delimiter encoding

Internet Fibre Channel Protocol (iFCP) is defined by IETF (www.ietf.org )

http://www.javvin.com/protocol/rfc3643.pdf : Fibre Channel (FC) Frame Encapsulation
http://www.javvin.com/protocol/draft-ietf-ips-ifcp-14.pdf : iFCP - A Protocol for Internet Fibre Channel Storage Networking