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Technology Stocks : The New QLogic (ANCR) -- Ignore unavailable to you. Want to Upgrade?

To: KJ. Moy who wrote (14737)	2/26/1998 6:35:00 PM
From: Douglas Nordgren	Read Replies (2) \| Respond to of 29386

K.J., If I've got your question right, I think you may be correct. I been doing a little reading up: "Nodes containing a single N_Port with a fiber pair link can be interconnected in one of three different topologies. Each topology supports bidirectional flow between source and destination N_Ports. The three basic topologies include: Point-to-point: A single link between two N_Ports. Fabric: More than two N_Ports can be interconnected using a 'fabric' which consists of a network of one or more 'switch elements.' A switch element contains two or more facilities for receiving and transmitting data under the protocol, termed 'F_Ports.' "Arbitrated Loop: Multiple N_Ports [point to point] can also be connected together without the benefit of a fabric by attaching the incoming and outgoing fibers to different Ports to make a loop configuration. A Port which incorporates the small amount of extra function required for operation in this topology is termed an 'NL_Port.' This is a blocking topology - a single NL_Port arbitrates for access to the entire loop and prevents access by any other NL_Ports while it is communicating. However, it provides connectivity between multiple Ports while eliminating the expense of incorporating a switch element." "In addition to F_Ports, which attach directly to N_Ports in a switched Fabric topology, several other types of Fabric Ports are defined. In a multi-layer network, switches are connected to other switches through 'E_Ports' (Expansion Ports), which may use standard media, interface, and signaling protocols or may use other implementation-dependent protocols." A Fabric Port that incorporates the extra Port states, operations, and Ordered Set recognition to allow it to connect to an Arbitrated Loop is termed an 'FL_Port'." I wonder if the Arcxel "Stealth" loop mode is actually an NL_Port implementation that can't be called that since the switch claims a nonblocking architecture? They say it does "F_Port, FL_Port, 'Stealth' loop mode, E_Port." The source is Alan F. Benner's "Fibre Channel - Gigabit communications and I/O for Computer Networks," McGraw-Hill (thanks George). I think a little bit of this book's knowledge makes me dangerous now <g>. Hope I haven't got it all wrong. Douglas

To: KJ. Moy who wrote (14737)	3/2/1998 11:46:00 AM
From: Craig Stevenson	Read Replies (1) \| Respond to of 29386

KJ, I found some additional information on Public/Private loops, straight from T11. Here is a link to a document called, "Fibre Channel Private Loop SCSI Direct Attach". It is in PDF format, so you will need Acrobat Reader to view it. ftp://ftp.dpt.com/t11/pub/fc/plda/plda_21.pdf I think the relevant portion to our discussion is this quote: "4 Private versus Public Port behavior When an NL_Port is operating in an Arbitrated Loop topology as defined by FC-AL and successfully completes a Fabric Login (FLOGI) is called a Public NL_Port. An NL_Port that does not attempt a Fabric Login is called a Private NL_Port. Public NL_Ports whose Fabric Login fails revert to Private NL_Port behavior." It appears as if a Private Loop is simply a loop that doesn't log in to the fabric, while a Public Loop is one that does. It doesn't seem terribly complex, at least on the surface. If Arcxel only supports private loops, perhaps that's why they need "Stealth Mode", to allow communication between loops. Craig