Inter-Fabric Routing

Abstract

A method and apparatus is shown for communicating Fibre Channel frames between distinct fabrics. A proxy zone is established in each fabric with a physically present local device and a remote fabric device. A router creates a proxy device in each fabric for every device not physically connected to the fabric. The proxy devices appear to be directly attached to the router. The router handles all address translations between proxy and physical addresses. When multiple routers are encountered, the ingress router does all address translation. No routing or encapsulation headers are used except when routing between two routers. The source ID and the originator exchange identifier are stored at the egress router for all link requests that require special handling. When replies pass through that router, the destination ID and originator exchange identifier are compared with the stored information. On a match, the reply is specially handled.

Description

PRIORITY[0001]This application claims the benefit of U.S. Provisional Patent Application No. 60 / 589,099, filed Jul. 19, 2004.FIELD OF THE INVENTION[0002]The invention presented in this application pertains generally to the routing of information between remote devices. More particularly, the present invention relates to the routing of Fibre Channel frames between separate Fibre Channel fabrics.BACKGROUND OF THE INVENTION[0003]Fibre Channel is a switched communications protocol that allows concurrent communication among servers, workstations, storage devices, peripherals, and other computing devices. Fibre Channel can be considered a channel-network hybrid, containing enough network features to provide the needed connectivity, distance, and protocol multiplexing, and enough channel features to retain simplicity, repeatable performance, and reliable delivery. Fibre Channel is capable of full-duplex transmission of frames at rates extending from 1 Gbps (gigabits per second) to 10 Gbps....

AI Technical Summary

Benefits of technology

[0024]To allow more complicated routing, the present invention proposes an inter-fabric routing header. This routing header is not needed when a single router connects multiple fabrics, or where a link between two routers does not require routing. However, the routing header does provide mechanisms to detect stale frames, prioritize frames, and to detect routing loops. To ensure that frames having a router header can pass through legacy fabrics, the present invention proposes the use of an encapsulation header.

[0025]Certain link service messages require special handling in the contest of inter-fabric Fibre Channel communications. These original link service frames can be detected by examining the R_CTRL value and the command value for a link service frame. However, many replies to link, service messages use the same command value. Hence, it is not practical to determine which replies require special handling simply by examining R_CTRL and command values. The present invention solves this problem by storing at the egress router a source ID and an originator exchange identifier for each link service request sent to a device that required special handling. When replies pass through the same router, the destination ID and the originator exchange identifier are compared with the stored information. If a match is found, the ingress (formerly egress) router can identify the context of the reply and perform the required special handling.

Problems solved by technology

Unfortunately, this type of zoning is meaningless if the devices are ever physically moved from one port on a switch to another.

Although this is a large number of switches for most circumstances, this limit requires the physical separation of one fabric from another.

It would not be possible to create a world-wide storage area network similar to the Internet given a limitation of 237 switches.

Unfortunately, the requirement for unique port identifiers 80 has made it impossible to transmit frames between fabrics without considerable concern over the port identifiers involved in the communication.

Unfortunately, neither of the above approaches provides a flexible enough technique so as to allow inter-fabric data communication between Fibre Channel fabrics.

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