Abstract:
Provided is a computer implemented method, system, and program for discovering a topology of a switch from an initiator device. The switch includes a plurality of switch ports. A plurality of Input/Output (I/O) devices are connected to the switch ports, wherein each I/O device and the initiator device connect to the switch through one of the switch ports. The initiator and I/O devices communicate on a first network configured by the switch and the initiator device communicates with the switch over a second network. The initiator device performs submitting a first query over the first network to the switch requesting a unique address of a plurality of I/O devices that are accessible to the initiator device over the first network. In response to the first query to the switch on the first network, the unique address of each I/O device is received from the switch. A second query is submitted over the second network to the switch for information on switch ports on the switch. In response to the second query to the switch over the second network, the information on the switch ports is received. Information on a topology of the switch ports and the initiator and I/O devices having the unique address is generated.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method, system, and program for discovering devices communicating through a switch. 
   2. Description of the Related Art 
   A storage area network (SAN) comprises a network linking one or more servers to one or more storage systems. Each storage system could comprise a Redundant Array of Independent Disks (RAID) array, tape backup, tape library, CD-ROM library, or JBOD (Just a Bunch of Disks) components. One common protocol for enabling communication among the various SAN devices is the Fibre Channel protocol, which uses optical fibers or copper wires to connect devices and provide high bandwidth communication between the devices. In Fibre Channel terms the “fabric” comprises one or more interconnected switches, such as cascading switches, that connect the devices. The link is the two unidirectional fibers, which may comprise an optical wire, transmitting to opposite directions with their associated transmitter and receiver. Each fiber is attached to a transmitter of a port at one end and a receiver of another port at the other end. 
   The Fibre Channel protocol defines a fabric topology. A fabric includes one or more interconnected switches, each switch having multiple ports, also referred to as F — Ports. A fiber link may connect an N — Port, or node port, on a device to one F — Port on the switch. An N — Port refers to any port on a non-switch device. An N — Port can communicate with all other N — Ports attached to the fabric to which the N — Port is connected, i.e., N — Ports on the immediate switch or interconnected cascading switches. 
   Another common Fibre Channel topology is the arbitrated loop. The devices in an arbitrated loop are daisy chained together. An L — Port is a port on a device that has arbitrated loop capabilities. An NL — Port is a device port that is part of a loop and capable of communicating with other N — Ports in a fabric. An FL — Port is a switch port connected to a loop. In a private loop In a public loop topology, a switch FL — Port is connected to the arbitrated loop, thereby allowing communication between the fabric devices and the loop devices. However, often legacy private loop devices are unable to communicate on a fabric because the private loop devices utilize an eight bit Arbitrated Loop Physical Address (AL — PA), and do not have the 24 bit address that is used for communication on the fabric. 
   To migrate legacy private loop devices that are only capable of using the eight bit AL — PA to a switched fabric, Q Logic Corporation provides the SANbox-16STD Fibre Channel switch that incorporates multiple private loop devices into a switched fabric. The QLogic switch includes multiple Segmented Loop Ports (SL — Ports), which function as FL — Ports and may have an attached private loop, also referred to as a looplet. Thus, the QLogic switch is comprised of multiple SL — Ports, where each SL port may support a separate arbitrated loop that has attached private loop devices. The SL ports on the switch and any devices attached to looplets attached to the SL — Ports are configured as a single logical Fibre Channel Arbitrated Loop (FC-AL), also referred to as a segmented loop. During initialization, the switch assigns unique eight bit Arbitrated Loop Physical Addresses (AL — PAs) to each SL — Port and to any device attached to a looplet on an SL — Port to form a segmented loop. Within a segmented loop any device within one private looplet attached to one SL — Port may communicate with any device in another private looplet attached to another SL port on the switch. Further details of the SANbox-16STD Fibre Channel switch are described in the QLogic publications “SANbox-16STD Fibre Channel Switch: Installer&#39;s/User&#39;s Manual,” QLogic Publication No. 59012-03 Rev. A (August, 2000) and “Reducing the Complexity of Managing Private Loops”, a White Paper (2000), downloaded from the Internet at “http://www.qlogic.com/products/pdf/private — loops.pdf”, which publications are incorporated herein by reference in their entirety. 
   In such segmented loop environments, a systems administrator may want to understand and visualize the topology of all the devices on the segmented loop, such as the relationship of devices in looplets attached to SL — Ports on a switch, including devices in the same zone as well as other zones. Thus, there is a need in the art for improved techniques for ascertaining the topology of an arrangement of private loops attached to a switch. 
   SUMMARY OF THE DESCRIBED IMPLEMENTATIONS 
   Provided is a computer implemented method, system, and program for discovering a topology of a switch from an initiator device. The switch includes a plurality of switch ports. A plurality of Input/Output (I/O) devices are connected to the switch ports, wherein each I/O device and the initiator device connect to the switch through one of the switch ports. The initiator and I/O devices communicate on a first network configured by the switch and the initiator device communicates with the switch over a second network. The initiator device performs submitting a first query over the first network to the switch requesting a unique address of a plurality of I/O devices that are accessible to the initiator device over the first network. In response to the first query to the switch on the first network, the unique address of each I/O device is received from the switch. A second query is submitted over the second network to the switch for information on switch ports on the switch. In response to the second query to the switch over the second network, the information on the switch ports is received. Information on a topology of the switch ports and the initiator and I/O devices having the unique address is generated. 
   In further implementations, at least one I/O device is attached to a loop that is attached to the switch port through which the device connects to the switch. 
   In still further implementations, in response to the first query to the switch over the first network, switch addresses are received. The switch assigns the switch addresses to the I/O devices attached to the switch ports. The topology information is generated to include the received switch addresses for the I/O devices. 
   In yet further implementations, an additional query is submitted on the second network to at least one other initiator device connected to one switch port, wherein the at least one other initiator device generates topology information to determine topology information for I/O devices to which the at least one other initiator device is capable of communicating on the switch. The topology information is updated with topology information received in response to the query on the second network to the at least one other initiator device. 
   Further, the initiator device generates the topology information for I/O device ports and initiator ports, wherein each I/O device and the initiator device are capable of including multiple ports. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
       FIGS. 1 ,  2 , and  3  illustrate network topologies in which the invention is implemented; 
       FIG. 4  illustrates an arrangement of data objects providing information on the topology determined by the logic of  FIGS. 5 and 6  in accordance with implementations of the invention; and 
       FIGS. 5 and 6  illustrate logic to discover the topology illustrated in  FIGS. 1 and 3  in accordance with implementations of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the following description, reference is made to the accompanying drawings which form a part hereof and which illustrate several embodiments of the present invention. It is understood that other embodiments may be utilized and structural and operational changes may be made without departing from the scope of the present invention. 
     FIG. 1  illustrates a switch implementation. A switch  2  includes a plurality of switch ports  4   a ,  4   b ,  4   c ,  4   d  and a switch manager  6  which includes the programs to perform the switch management operations, such as switch  2  initialization, configuration, and management. One or more of the switch ports  4   a ,  4   b ,  4   c ,  4   d  may have an attached private loop  8   a ,  8   b ,  8   c  of private loop (PL) devices  10   a ,  10   b ,  10   c, d ,  10   e ,  10   f ,  10   g , which may comprise any type of device, such as storage devices, hosts, servers, etc., that communicate using an eight bit AL — PA address. For instance, the private loop devices  10   a ,  10   b  . . .  10   g  may comprise legacy devices that are configured to communicate on an arbitrated loop using only an eight bit AL — PA and would not have the full 24 bit Fibre Channel address to communicate on a Fibre Channel fabric. 
   In certain implementations, during initialization, the switch manager  6  assigns each device port  10   a ,  10   b  . . .  10   g  a unique eight bit Arbitrated Loop Physical Address (AL — PA), so that the switch ports  4   a ,  4   b ,  4   c ,  4   d  themselves are addressable using the eight bit AL — PA address. Further, the switch manager  6  would assign each of the private loop devices  10   a ,  10   b  . . .  10   g  a unique eight bit AL — PA address, thereby configuring all the switch ports  4   a ,  4   b ,  4   c ,  4   d  and private loop devices  10   a ,  10   b  . . .  10   g  as a single Fibre Channel Arbitrated Loop that utilizes the eight bit AL — PA addressing scheme. In  FIG. 1 , one of the private loop devices  10   a, b . . . g  comprises a host system  10   a  that includes a discovery tool  12 . Although only one host  10   a  is shown in  FIG. 1 , the topology may include any number of host systems and private loop devices attached to the loops  8   a ,  8   b ,  8   c , limited by the capacity of the switch. 
   The switch manager  6  may assign an address to each device port. Thus, if the device, e.g., host, storage device, etc., includes adaptor cards with multiple ports, each port providing a communication channel to the device would be assigned a unique AL — PA address, as well as have a unique address, such as a worldwide name. Additionally, each device having multiple ports may have a world wide name (WWN) which is the address of the device node aggregating multiple ports. The line shown in  FIGS. 1 and 3  illustrating the connection from the loops  8   a ,  8   b ,  8   c, d  to the private loop devices  10   a ,  10   b  . . .  10   g  should be interpreted to include multiple lines connecting the loop to the device  10   a ,  10   b  . . .  10   g  if the device  10   a ,  10   b  . . .  10   g  has multiple ports connecting to the loop  8   a ,  8   b ,  8   c . . .    
   In the implementation of  FIG. 1 , all the switch ports  4   a ,  4   b ,  4   c ,  4   d  and private loop devices  10   a ,  10   b  . . .  10   g  on separate private loops  8   a ,  8   b ,  8   c  behave as one large private loop. An example of a Fibre Channel technology that configures switch ports  4   a ,  4   b ,  4   c ,  4   d  and private loop devices  10   a ,  10   b  . . .  10   g  as a single arbitrated loop is the segmented loop topology implemented in the QLogic Corporation&#39;s SANbox** 16STD Fibre Channel Switch, described in the QLogic publication “SANbox-16STD Fibre Channel Switch: Installer&#39;s/User&#39;s Manual,” which was incorporated by reference above. The switch manager  6  may include functionality offered by the QLogic SANsurfer switch management application program, described in the QLogic Publication “SANbox-8/16 Switch Management User&#39;s Manual, QLogic Publication No. 59010-06 Rev. A (July, 2001), which publication is incorporated herein by reference in its entirety. The discovery tool  12  is an application program that may be run on any host to determine the physical topology of all the devices attached to the switch  2 , including all the loop segments  8   a ,  8   b ,  8   c  that function as one large arbitrated loop. 
   The switch manager  6  controls switch  2  management. The switch manager  6  is also assigned an Internet Protocol (IP) address to allow communication with the switch manager  6  over an additional network, such as a Local Area Network (LAN) utilizing alternative network technology, such as Ethernet network technology.  FIG. 2  illustrates an additional network  30 , such as an Ethernet LAN, that enables communication between the switch manager  6  and certain private loop devices  10   a ,  10   b  . . .  10   g , such as host  10   a  and any other hosts. The network  30  is out-of-band with respect to the Fibre Channel communication enabled by the switch  2 . In certain implementations, the switch manager  6  implements a web based management tool that allows hosts  10   a  connected to the switch  2  to access and control the switch manager  6  using a web interface, such as a Hypertext Transfer Protocol (HTTP) web browser, over the network  30 . The discovery tool  12  would communicate with the switch manager  6  over the network  30  using switch Application Programming Interfaces (APIs), which allow the discovery tool  12  to query the switch manager  6  for information on the switch  2  and devices attached to the switch  2 . 
   The host  10   a  executes the discovery tool  12  to discover the topology of all the private loop devices  10   a ,  10   b  . . .  10   g  and switch ports  4   a, b, c d  on the switch  2 . Certain types of switches  2 , such as the QLogic SANbox switches discussed above, implement a non-standard topology, such as the QLogic segmented loop topology. Such non-standard switch topologies, such as the QLogic segmented loop technology, do not support standardized Fibre Channel methods for obtaining connectivity information, e.g., the standard Fibre Channel discovery techniques described in the publication “Fibre Channel Generic Services-3 (FC-GS-3), Rev. 7.01 ”, proposed draft published by the American Nat&#39;l Standard of Information Technology (Nov. 28, 2000), which publication is incorporated herein by reference in its entirety. 
     FIG. 3  illustrates an implementation of the topology of  FIG. 1  where the switch ports  104   a ,  104   b ,  104   c ,  104   d  on the switch  100  chassis are configured into separate zones A and B, such that any loop device  110   a ,  110   b  . . .  110   i  or other device attached to a switch port  104   a ,  104   b ,  104   c ,  104   d  in one particular zone can only communicate with other devices attached to the same switch port  4   a ,  4   b ,  4   c ,  4   d  or other switch ports in the same zone.  FIG. 3  illustrates two zones, zones A and B, where zone A includes switch ports  104   a  and  104   b , and all the loop devices  110   a ,  110   b ,  110   c ,  110   d  attached thereto, and zone B includes switch ports  104   c  and  104   d  and the loop devices  110   e ,  110   f ,  110   g ,  110   h , and  110   i  attached thereto. In  FIG. 3 , each zone A and B includes one host  110   a  and  110   h , respectively, where each host  110   a  and  110   h  runs an instance of the discovery tool  112   a  and  112   b , respectively. In certain implementations, during initialization, the switch manager  206  would assign eight bit AL — PA addresses to devices within a zone, such that the same eight bit AL — PA may be assigned to devices  110   a ,  110   b  . . .  110   i  that are in different zones on the switch  200 . For this reason, when mapping the topology for the switch  100 , the discovery tool  112   a  and  112   b  must map devices and switch ports to their designated zone as devices and switch ports in different zones may have the same AL — PAs. 
     FIG. 4  illustrates an arrangement of information in a topology database  300  on all the initiator and target devices attached to a switch. In described implementations, an initiator comprises any type of device that initiates an Input/Output (I/O) operation and the target device is the device that receives the I/O operations. The initiator may comprise a host device or a port on an adaptor card in a host system, or any other type of system initiating an I/O request. Additionally, the target device may comprise a storage system or any other device capable of handling an I/O request. The target may comprise the storage device or a port on an adaptor card in the storage device. The database  300  includes a plurality of initiator port objects  302   a  . . .  302   n , one for each initiator port on a host (initiator) device, e.g.,  112   a, b . Each initiator port object  302   a  . . .  302   n  includes the AL — PA  306   a  . . .  306   n  and world wide name (WWN)  310   a  . . .  310   n  of the initiator port as well as the switch port number  308   a  . . .  308   n  to which the initiator port is attached. Each initiator port object is associated with one or more private loop (PL) device port objects  322   a ,  322   b  . . .  322   m  which identify a target device port capable of being accessed by the initiator port through the switch. Each PL device port object  322   a ,  322   b  . . .  322   m  includes the AL — PA  326   a  . . .  326   m  and world wide name (WWN)  330   a  . . .  330   m  of the device port as well as the switch port number  328   a  . . .  328   n  to which the device port is attached. From the information in the topology database  300 , the entire mapping of private loop devices to switch ports can be determined. Those skilled in the art will appreciate that there are numerous database implementations, such as relational and object oriented databases, that may be used to maintain the information shown in  FIG. 7  as well as the association of initiator ports and target devices through the switch. Still further, additional information on the devices to that shown herein may be maintained in the topology database  300 . 
     FIGS. 5 and 6  illustrate logic implemented in the discovery tool  12 ,  112   a ,  112   b  to allow the host  10   a ,  110   a ,  110   h  ( FIGS. 1 and 3 ), respectively, to determine the physical topology using both in-band (Fibre Channel through the switch ports  4   a ,  4   b ,  4   c ,  4   d ) and out-of-band (network  30  in  FIG. 2 ) communication. The topology may be discovered by any host connected to the switch  2  that executes the discovery tool  12 . Upon discovering the topology, the discovery tool  12 ,  112   a ,  112   b  would generate the information for the topology database  300  shown in  FIG. 4 . With respect to  FIG. 5 , control begins at block  400  with the discovery tool  12 ,  112   a ,  112   b  being invoked to generate the topology database  300 . From block  400 , control proceeds to both blocks  402  and  450 , where the discovery tool  12  can invoke separate processes to handle the separate in-band and out-of-band operation flows. The steps from block  402  utilize in-band communication using Fibre Channel protocol through the switch  2 ,  100  and the steps from blocks  450  utilize the out-of-band communication using the network  30  ( FIG. 2 ) and switch Application Programming Interfaces (APIs) to query the switch  2 ,  112  for information. 
   For the in-band communication, a loop is performed at blocks  402  through  410  for each initiator port i on the host  12 ,  112   a ,  112   b  in which the invoked discovery tool  12 ,  112   a ,  112   b  is executing. The discovery tool  12 ,  112   a ,  112   b  sends an inquiry command, such as a Small Computer System Interface (SCSI) inquiry command, using the in-band Fibre Channel network, to obtain the world wide name (WWN) and AL — PA for every target device (e.g.,  10   b ,  10   c  . . .  10   f  in  FIG. 1 and 110   b ,  110   c  . . .  110   c  in  FIG. 3 ) port attached to the switch  12 ,  112 . Note that if the initiator in which the discovery tool  12 ,  112   a ,  112   b  is executing is within a particular zone, then the in-band inquiry command would not discover target devices in other zones. The discovery tool  12 ,  112  then generates (at block  406 ) an initiator i port object  302   a  and device port objects  322   a ,  322   b  . . . ( FIG. 4 ) for each target device port determined from the inquiry command and updates the generated objects with the world wide name (WWN) and AL — PA for the ports determined from the inquiry command. The initiator port i object  302   a  is then associated (at block  408 ) with each of the generated device port objects  322   a ,  322   b  . . . to which the initiator port i can communicate. Control then proceeds (at block  410 ) back to block  402  to generate topology information for the next initiator port in the host  10 ,  110   a , h in which the discovery tool  12 ,  112   a ,  112   b  is executing. 
   The discovery tool  12 ,  112   a ,  112   b  may begin the out-of-band operations from block  450  while the in-band operations at blocks  402  through  412  are executing or after  402  through  410  has completed. At block  450 , the discovery tool  12 ,  112   a ,  112   b  uses switch APIs to query the switch  2 ,  100  to determine the world wide name (WWN) of all initiator ports attached to any of the switch ports  4   a ,  4   b ,  4   c ,  4   d  ( FIG. 1) and 104   a ,  104   b ,  104   c ,  104   d  ( FIG. 3 ). The topology database  300  is updated (at block  452 ) to include an initiator port object  302   b  . . .  302   n  for each determined initiator port and the WWN  310   b . . . n  and switch port number  308   b . . . n  fields in each generated initiator port object  302   b  are updated to include the WWN and switch port number determined when querying the switch at block  450 . Note that because this communication is out-of-band, the determined initiator ports may be in different zones from the initiator ports in the host  10 ,  110   a ,  110   h  in which the discovery tool  12 ,  112   a ,  112   b  is executing. The switch  2 ,  100  is then queried (at block  454 ) to determine the number of switch ports  4   a ,  4   b ,  4   c ,  4   d ,  104   a ,  4   b ,  4   c ,  4   d  ( FIGS. 1 and 3 ). 
   For each determined switch port j, a loop is performed at blocks  456  through  476 . If switch port j does not have an attached initiator, then the discovery tool  12 ,  112   a ,  112   b  queries (at block  460 ) the switch  2 ,  100  to get all of the AL — PAs of target device ports attached to the switch port j. There may be multiple AL — PAs attached to switch port j if switch port j is attached to an arbitrated loop  8   a ,  8   b ,  8   c ,  108   a ,  8   b ,  8   c  ( FIGS. 1 and 3 ). A loop is then performed at blocks  462  through  476  for each determined AL — PA k. At block  464 , the discovery tool  12 ,  112   a ,  112   b  queries the topology database  300  to determine the WWN  320   a, b  . . . of device port objects  322   a, b  . . . having an AL — PA value  326   a, b  . . ., which would have been indicated in the device port object  322   a, b  . . . at step  406 , that matches AL — PA k. In other words, the determined target device port having AL — PA k attached to switch port j is in-band with respect to the host  10   a ,  110   a ,  110   h  including the discovery tool  12 ,  112   a ,  112   b.    
   With respect to  FIG. 6 , a loop is then performed at blocks  466  through  474  for each target device port m having an AL — PA matching AL 13  PA k. At block  468 , the discovery tool  12 ,  112   a ,  112   b  queries the topology database  300  to determine the initiator port object  302   a  of the source host  10   a ,  110   a ,  110   h  associated with the target device port m object  322   a, b  . . . If (at block  470 ) the switch port of  308   a  of the determined initiator port object  302   a  is in the same zone as switch port j, to which the target device port m is attached, then the topology database  300  is updated (at block  472 ) to reflect that the switch port number  328   a ,  328   b  . . . in the device port m object is switch port j. If (at block  470 ), the switch port of the determined initiator port is in a different zone, then such different zone also includes target device port m. From the no branch of block  470  or block  472 , control proceeds (at block  474 ) to block  466  to consider the next determined target device port m. 
   After updating the switch port numbers  328   a ,  328   b  . . . for all of the device port objects  322   a, b . . . n  associated with the initiator port object  302   a , control proceeds (at block  476 ) back to block  462  to process the next AL — PA k. After considering all AL — PAs attached to the switch port j, control proceeds (at block  478 ) back to block  456  to consider the next switch port  4   a ,  4   b ,  4   c ,  4   d ,  104   a ,  4   b ,  4   c ,  4   d  ( FIGS. 1 and 3 ). The result of the in-band and out-of-band processing at blocks  402 – 410  and blocks  450 – 478  is the topology database  300  having information objects for all the initiator ports within the host  10   a ,  112   a, h  from which the discovery tool  12 ,  112   a ,  112   b  is executing and for each target device to which the initiator ports can communication through the switch  2 ,  100 , including the world wide name (WWN), AL — PA, and switch port number for the initiator ports and all the associated target device ports. 
   If (at block  458  in  FIG. 5 ) an initiator port is attached to switch port j, then control proceeds to block  476  to consider the next switch port. After updating, the topology database  300  includes information on the target devices attached to the switch port to which the host  10   a ,  110   a ,  110   h  can communicate, which includes those target devices in the same zone as the host. In such case, control proceeds to  478  to obtain information on target devices, including target devices in zones outside of the zone including the host invoking the discovery tool  12 ,  112   a ,  112   b  operations at block  400  ( FIG. 5 ) At block  478 , the discovery tool  12 ,  112   a ,  112   b  queries (at block  478 ) other host through their initiator port to retrieve the topology database  300  generated by the discovery tool  12 ,  112   a ,  112   b  executing in the queried initiator port. The discovery tool  12 ,  112   a ,  112   b  would include APIs to allow discovery tools executing in hosts to query other hosts for the topology databases  300  generated by the discovery tools  12 ,  112   a ,  112   b , thereby allowing a sharing of topology databases  300  to provide topology information for all initiator and target devices attached to the switch, including information on target devices in other zones. At block  480 , the discovery tool  12 ,  112   a ,  112   b  updates the topology database  300  with information from the retrieved topology database  300  to provide a full view of the devices attached to the switch. Because the queried initiator ports may be in different zones, the discovery tool  12 ,  112   a ,  112   b  is capable of updating its topology database  300  with the topology of devices in other zones that is provided by discovery tools executing in hosts having initiator ports in different zones. 
   With the above described implementations, a host that is attached to an arbitrated loop, such as one of the private arbitrated loops  108   a ,  108   b ,  108   c ,  10   d , that is attached to a switch  2  that does not implement standard Fibre Channel discovery protocols may nevertheless ascertain the topology of the devices that are attached to switch ports on the same switch. For instance, in implementations where the switch  2 ,  100  is utilizing the segmented loop technology of QLogic, the described implementations allow hosts to discover the topology of all hosts and devices attached to loops on the segmented loop switch ports of the switch when all the devices are assigned a unique eight bit AL — PA. 
   Additional Implementation Details 
   The above described method, apparatus or article of manufacture for discovering a switch topology may be implemented using standard programming and/or engineering techniques to produce software, firmware, hardware, or any combination thereof. The term “article of manufacture” as used herein refers to code or logic implemented in hardware logic (e.g., an integrated circuit chip, Field Programmable Gate Array (FPGA), Application Specific Integrated Circuit (ASIC), etc.) or a computer readable medium (e.g., magnetic storage medium (e.g., hard disk drives, floppy disks,, tape, etc.), optical storage (CD-ROMs, optical disks, etc.), volatile and non-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs, SRAMs, firmware, programmable logic, etc.). Code in the computer readable medium is accessed and executed by a processor. The code in which preferred embodiments of the configuration discovery tool are implemented may further be accessible through a transmission media or from a file server over a network. In such cases, the article of manufacture in which the code is implemented may comprise a transmission media, such as a network transmission line, wireless transmission media, signals propagating through space, radio waves, infrared signals, etc. Of course, those skilled in the art will recognize that many modifications may be made to this configuration without departing from the scope of the present invention, and that the article of manufacture may comprise any information bearing medium known in the art. 
   Certain implementations concerned a switch that utilized the segmented loop technology developed by QLogic. However, those skilled in the art will recognize that the discovery techniques described herein may apply to any other switch technologies that do not enable all the Fibre Channel discovery tools. In such case, the described discovery implementations may be used to gather device information from both a switch manager program and the devices themselves using a combination of in-band and out-of-band communications. 
   The described implementations provide a discovery technique used in a Fibre Channel architecture to allow discovery of devices attached to a Fibre Channel network that utilize an 8 bit AL — PA addressing scheme. However, those skilled in the art will appreciate that the discovery techniques of the described implementations may be utilized with network transmission protocols other than Fibre Channel when groups of devices in the network use different addressing schemes. Accordingly, the invention is not limited to the Fibre Channel protocol environment, but may also be used to discover the topology of a switched network in non-Fibre Channel environments when information may be gathered by accessing the devices in the topology through different networks. 
   In described implementations, the switch  2 ,  200  configured the switch ports and loop devices to have an eight bit AL — PA address. In alternative implementations, alternative addressing schemes may be used. 
   The topology of  FIGS. 1 ,  2  and  7  are provided for illustration. The described address mapping implementations may apply to any switch topology involving any number of interconnected switches, switch ports, and devices attached to either the switch port directly or through a loop attached to the switch port. 
   The described implementations involved the discovery of devices attached to ports on a single switch. In additional implementations, the discovery techniques of the described implementations may be used to discover devices across switches in the same fabric. 
   In the described implementations, the discovery tool was executed from a host system  10   a ,  110   a ,  110   h  . Additionally, the discovery tool may be executed on loop or non-loop devices other than hosts, such as a network appliance capable of performing logical I/O operations and capable of both in-band communication with the switch on a switch implemented network, e.g., the SAN, and out-of-band communication with other network devices on an additional network, e.g., an Ethernet. 
   In the described implementations, the loop devices and switch ports were queried for information concerning their eight bit AL — PA and world wide name. Additionally, the loop devices and switch ports may be queried for additional information on the device that may be added to the switch port and loop device objects in the mapping. 
   The foregoing description of various implementations of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.