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Simultaneous Acquisition of Port Identifiers Disclosure Number: IPCOM000012655D
Original Publication Date: 2003-May-19
Included in the Prior Art Database: 2003-May-19
Document File: 2 page(s) / 44K

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The Fibre Channel standard allows a Fabric to assign multiple port addresses (N_Port IDs) to each attached N_Port. Each N_Port ID is acquired by sending a request to the Fabric, and awaiting a response. Without use of the scheme described below, N_Port IDs must be acquired one at a time. In applications which require the assignment of hundreds of N_Port IDs, this is unacceptable. The scheme described here resolves this problem by allowing all N_Port IDs to be acquired simultaneously.

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Simultaneous Acquisition of Port Identifiers

  Reference - "Fibre Channel-Framing and Signalling (FC-FS)," American National Standards Institute, INCITS Project 1331-D."

FibreChannel allows a fabric to assign multiple port addresses (N_Port IDs) to an N_Port which is attached to the fabric. A typical configuration requiring the fabric to assign more than one N_Port ID to an N_Port is shown in figure 1. In figure 1, N_Port 2 is shared by three system logical partitions, A, B, and C. Each system logical partition requires its own N_Port ID so that it can be recognized when sending frames to other N_Ports. Therefore, N_Port 2 requires three N_Port IDs, where each N_Port ID corresponds to a different logical partition.

  In order to acquire an N_Port ID, a logical partition sends a request for an N_Port ID containing a tag (OX_ID) and other unrelated information. The fabric returns a response which includes the OX_ID and the assigned N_Port ID.

  Fibre Channel standards require that all outstanding requests from a particular partition have unique OX_IDs; however, the standards do not require outstanding requests from different partitions to have unique OX_IDs. Therefore, it is possible for two different partitions to simultaneously send requests containing the same OX_ID. When this occurs, the fabric will return two responses, each containing the same OX_ID and an assigned N_Port ID. In this case, it is impossible to determine which response is associated with each request, and, therefore, which N_Port ID to assign to each partition.

  An inferior solutio...