Loop network hub using loop initialization insertion

[0001] The present invention relates to an electronic network system, and more specifically, the present invention forces the initial setting (initialization) of a loop when a new node port is inserted into the loop. Related to Loop Network Hubs Designed to Reduce Loop Address Conflict By By [0002] [Conventional Techniques] Electronic data systems are often interconnected using network communication systems. .. Wide area networks and channels are two methods developed for computer network architectures. Traditional networks (eg LANs and WANs) offer great flexibility and relatively long distance communication capabilities. Channels such as The Enterptise System Connection (ESCON) and The Small Computer System Interface (SCSI) have been developed for high performance and reliability. Channels typically use dedicated short-range connections between computers or between computers and peripherals.

[0003] Both channel and network features have been incorporated into a new network standard known as "Fibre Channel". Fiber Channel systems combine channel speed and reliability with network flexibility and connectivity. Fiber Channel products can now operate at very high data rates, such as 266Mbps or 1062Mbps. Such speeds are quite demanding for all demanding applications such as uncompressed, full motion, uncompressed full motion high-quality video. It's fast enough to handle application). Fiber Channel networks are defined in the ANSI specification, for example X3.230-1994. According to this specification, the function of Fiber Channel is divided into five layers. The five functional layers of the Fiber Channel are FC-0 layer: physical medium layer; FC-1 layer: coding and encoding layer; FC-2 layer: real transfer mechanism (framing protocol and flow control between nodes). Includes); FC-3 Layer: Common Services Layer; and FC-4 Layer: Upper Layer Protocol.

[0004] There are generally three methods for deploying Fiber Channel networks. That is, simple point-to-point connections; arbitrated loops, and switched fabrics. The simplest topology is a point-to-point placement configuration, in which the two Fiber Channel systems are simply and directly connected. An arbitrated loop is a Fiber Channel ring connection that provides shared access to bandwidth through arbitration. An exchange Fiber Channel network (called a "fabric") is a form of cross-point switching.

[0005] The conventional Fiber Channel Arbitrated Loop (FC-AL) protocol is a protocol for loop functionality when interconnecting devices or loop segments by node ports. However, the problem of directly interconnecting node ports is that if one node port in one loop fails, generally all loops fail. This difficulty is overcome by the use of hubs in traditional Fiber Channel techniques. The hub has a number of hub ports interconnected in a loop topology. The node port is connected to the hub port and forms a star topology with the central hub. Hub ports that are not connected to a node port or are connected to a failed node port are bypassed. In this way, the loop is maintained regardless of whether the node port is removed or failed.

[0006] More specifically, FIG. 1A shows a normal loop arrangement configuration 100. The four node ports 101, 102, 104, and 106 to which the node ports are connected are shown. Each node port represents a connection to a device or another loop. Node port 101 is connected to node port 102 so that data is transmitted from node port 101 to node port 102. Node port 102 is connected to node port 104 in turn, and node port 104 is connected to node port 106 in turn. Node port 106 is connected to the first node port, ie node port 101. In this way, a loop data path, that is, a loop data path from node port 101 to node port 102, node port 104, node port 106, and then back to node port 101 is established.

FIG. 1B shows loop 107 in which node ports 108, 110, 112, 114 are organized into a physical star topology by a central hub 116. Node port 108 is connected to hub port 118 within hub 116, and similarly node ports 110, 112 and 114 are themselves connected to hub ports 120, 122 and 124, respectively. The inside of the hub 116 is a loop, and the hub ports 118 to 124 of the hub 116 form a data path of the loop similar to the normal loop arrangement configuration shown in FIG. 1A.

Using a hub as a central element of a loop network is such even when one or more hub ports are not connected to a node port, or one or more hub ports are connected to a failed node port. It can be operated by bypassing the hub port. Each hub port generally has a circuit system that provides a bypass mode for the hub port. When a hub port is in bypass mode, data received by that hub port from the hub port before the loop is sent directly to the next hub port in the loop.

[0009] An additional advantage of using a hub is that the node port is hot insertable. The ability to hot insert allows node ports to be inserted into and out of loops without having to power down and then restart the entire loop or hub. However, due to this hot insertion, the address of the node port attached to the loop is not always properly maintained.

[0010] Under the FC-AL protocol, the loop initialization process is used to provide a unique address (Arbitrated Loop Physical Address) (AL_PA) for each node port connected to the loop. (Called ")) is given. Loop initialization is called by generating a sequence of Loop Initialization Primitive (LIP) ordered sets under the FC-AL protocol. Hot insertion. For loops that cannot, after inserting or removing the node port, the entire loop is restarted and initialized again. For hot insertable loops, the loop is not necessarily restarted, so ( Each insertion or removal (of a node port) is not necessarily reinitialized, so that when a new node port is inserted into a loop, a unique address will not necessarily be given if the loop is not reinitialized. Not generated.

[0011] Further, the hub port can be connected to a hub port of another hub. When a hub is linked from one hub to another through a hub port, the hub properly initiates its initialization routine on insertion, especially if it is a dormant hub (ie, if there is no loop traffic on insertion). Often not. At this point, address duplication may occur between the node port of the first hub and the node port of the second hub.

[0012] The problem of such address duplication is illustrated in FIGS. 2A and 2B. As shown in Figure 2A, four node ports A1, B1, C1 and D1 are linked to hub 200. Three node ports A2, B2 and C2 are connected to hub 202. The numbers 1 and 2 are merely illustrations, and in fact the address of each node port is also represented by the letters A, B, C or D. At this point, each node port has a unique address within its own loop. However, when hubs 200 and 202 are concatenated as shown in Figure 2B, the addresses of these node ports are no longer necessarily unique. In the single loop shown in FIG. 2B, two node ports have address A, two node ports have address B, and two node ports have address C. If an address duplicate is detected, an error will occur to start the initialization sequence, resulting in a unique address for each node port. However, before the duplication (inconsistency) is detected, messages received by the improper node port will continue to pass, resulting in data corruption (data). may result in corruption).

[0013] For example, in the state shown in FIG. 2A, when node port B1 sends data to node port A1, node port A1 probably sends data from node port B1 without error because the hub ports are adjacent. Receive. As shown in FIG. 2B, the connection from node port B1 to node port A1 can be initiated without address duplication. This is because the message from B1 successfully reaches node port A1, the intended destination, along the loop unless node port B2 is arbitrated.

However, if node port A1 attempts to send data to node port B1, data corruption may occur. In the state shown in FIG. 2A, the data is sent from node port A1 through node port C1, through node port D1, and then to node port B1, that is, the desired destination. However, in the situation shown in Figure 2B, the data goes from node port A1 through node port C1, through node port D1, through the hub port that connects hub 200 and hub 202, through node port C2, and then through node port B2. Is received by. As mentioned above, the numbers only show the difference between the node port from hub 200 and the node port from hub 202. From the perspective of node port A1, node port B2 is indistinguishable from node port B1. Node port A1 sends the addressed data to node port B. Similarly, node port B2 accepts data addressed to node port B. Therefore, although node port A1 intends to receive the data by node port B1, node port B2 receives the data addressed to node port B. Therefore, "B" is not a unique address. Node port A1 or node port B2 is unaware that node port B2 or node port A1 is present. As a result, data corruption can occur, depending on the nature of the incoming transaction. At some point, a unique error can occur, leading to the initialization sequence. However, it may be too late to prevent or recover from unwanted data corruption.

[0015] The inventors of the present invention provide a unique address when a new node port or new hub is inserted into a loop by forcing the loop to initialize before data corruption occurs. It was decided that it would be desirable to provide a loop network hub that could.

The loop network hub of the preferred embodiment comprises a hub port having a loop initialization insertion mechanism. The loop initialization insertion mechanism causes the hub port that detects a new connection to automatically start generating loop initialization data. The hub port continues to generate loop initialization data until it receives the loop initialization sequence. The loop initialization data propagates to the loop of the hub and stops normal processing. In this way, the entire loop is cleared. Upon receiving the loop initialization sequence, the hub port that generates the loop initialization data stops sending the loop initialization data and inserts a new node port into the loop. At this point, loop initialization begins, and each node port in the loop network gets a unique loop network address.

[0017] In an embodiment of FC-AL, the hub of the preferred embodiment comprises a hub port having a LIP insertion mechanism. The loop initialization insertion mechanism automatically initiates the generation of a LIP (F7, F7) ordered set at the hub port that detects a new connection. The hub port continues to generate a LIP (F7, F7) ordering set until the hub port receives a LIP primitive sequence. That LIP primitive sequence (LIP primitive sequence) contains three consecutive identical LIP ordering sets. The LIP (F7, F7) ordering set propagates to the hub loop, stopping normal processing. In this way the entire loop is cleared. Upon receiving the LIP primitive sequence, the hub port that produces the LIP (F7, F7) ordering set stops inserting the LIP (F7, F7) ordering set and then inserts a new node port into the loop. At this point, loop initialization begins, after which each node port obtains a unique physical address (arbitrated loop physical address AL_PA) according to the known FC-AL protocol.

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment provides a mechanism for forcing a loop initialization when a node port is inserted into a loop network. The present invention will be described below in the context of a Fiber Channel Arbitrated Loop (FC-AL) as an example of a preferred embodiment thereof. However, the present invention can be applied to networks having characteristics similar to FC-AL networks.

[0019] An outline of the loop operation of the loop network will be described below with reference to the arrangement configuration shown in FIG. FIG. 3 shows a hub 300 with six hub ports 302, 304, 306, 308, 310 and 312. Each hub port is connected to another hub port by a unidirectional internal hub link that forms an internal hub loop. In FIG. 3, data flows from hub port 302 to hub port 304, thus counterclockwise. Alternatively, these hub ports can be connected so that the data flows clockwise as long as the loop topology is maintained.

[0020] Three node ports 314, 316, and 318 are attached to the three hub ports 302, 310, and 312. Node port 314 is attached to hub port 302, node port 316 is attached to hub port 312, and node port 318 is attached to hub port 310. Each node port is preferably attached to the hub port by the following two data channels. One data channel sends data from the hub port to the node port, and the other data channel sends data from the node port to the hub port. Thus, the data channel carries data from hub port 302 to node port 314, and another data channel carries data from node port 314 to hub port 302. Data coming out of node port 314 and received by node port 316 goes from node port 314 through the data channel to hub port 302, then from hub port 302 to hub port 304, then to hub port 306, to hub port 308, to hub port. Reach 310. When node port 318 is operating in the loop, its data travels through the data channel to node port 318, then through the data channel back to hub port 310, and then to hub port 312. The data passes through the data channel from hub port 312 and is received at node port 316.

[0021] In a preferred embodiment, data coming into a hub port from a previous hub port in a loop is sent to that node port, if any, to that node port. When the hub port is in bypass mode, the incoming data is sent directly from the hub port to the next hub port in the loop in response to the incoming data, without including data from the node port. A preferred embodiment achieves the bypass using a switching device such as a multiplexer, as described below with reference to FIG. On top of that, the attached node port recognizes whether the data received from the hub port is addressed to that node port and then responds appropriately. The bypass is achieved within the hub port but not within the node port. Therefore, the loop is protected from node port failure. A hub port that does not have a node port attached, such as the hub port 304, 306, or 308 shown in Figure 3, is always in bypass mode and sends data directly to the next hub port. Thus, the signal received by hub port 304 from hub port 302 is sent directly to hub port 306. When a hub port to which a node port is attached, for example hub port 310, 312 or 302 shown in FIG. 3, receives data from the hub port before the loop, the hub port sends the data to the attached node port. The node port responds appropriately and then returns the data to the hub port.

[0022] For example, the data addressed from node port 318 to node port 314 flows from node port 318 to hub port 310 and then to hub port 312. Hub port 312 sends data to node port 316 if node port 316 is not bypassed. Node port 316 recognizes that the data is not addressed to node port 316 and returns the data to hub port 312. Hub port 312 sends that data to hub port 302. Hub port 302 sends the data to node port 314 if node port 314 is not bypassed. Node port 314 recognizes that the data is addressed to node port 314 and responds appropriately.

FIG. 4 shows the internal elements of the hub port according to a preferred embodiment. The hub port 400 shown in FIG. 4 is a hub port equivalent to the hub ports 302, 304, 306, 308, 310 and 312 shown in FIG. An incoming internal hub link 402 enters hub port 400 through a previous hub port (not shown) in the loop. The incoming internal hub link 402 is connected to the hub port transmission circuit 404. Therefore, the data from the previous hub port enters the hub port 400 along the internal hub link 402 and then into the hub port transmission circuit 404. The hub port transmission circuit 404 converts the received data into a form available by the node port 408 and then sends the received data to the node port 408 via the data channel 406. Alternatively, data channel 406 can be connected to a hub port within a different hub to connect hubs to each other.

[0024] Node port 408 outputs data to hub port 400 via data channel 410. Data channel 410 is connected to hub port receiving circuit 412. The hub port receiving circuit 412 converts the data received from the node port 408 into a form that can be used in the hub. In one embodiment, the hub port receiving circuit 412 converts the data from serial to parallel and then decodes the data. The hub port receiving circuit 412 also includes a loop initialization data detection circuit 414 and a hub port output control circuit 416. In the FC-AL embodiment, the loop initialization data detection circuit 414 is a LIP detection circuit. The hub port receiving circuit 412 outputs data via the hub port output line 418. The hub port output control circuit 416 outputs a control signal via the hub port output control line 420. The hub port output line 418 is connected to a switching device 422, for example, the first input A of the multiplexer. The incoming internal hub link 402 is connected to the second input B of the switching device 422. The loop initialization data generator 424 generates loop initialization data and outputs an ordering set of these data to the loop initialization data line 426. In the FC-AL embodiment, the loop initialization data generator 424 is a LIP generator and is a LIP (F7, F7) Generate an ordering set. The loop initialization data line 426 is connected to the third input C of the switching device 422. The hub port output control line 420 is connected to the control input of the switching device 422. In this way, the switching device 422 selects a single input A, B or C to be output according to the control signal generated by the hub port output control circuit 416. The output of switching device 422 is sent to the outgoing internal hub link 428. The outgoing internal hub link 428 sends data to the next hub port in the hub in the same way that the internal hub link 402 enters the hub port 400 and creates a loop as shown in FIG.

When the device is not attached to the hub 400, the hub port output control circuit 416 keeps the hub port 400 in bypass mode. By selecting input B of switching device 422, the data on the incoming internal hub link 402 received from the previous hub port is output to the outgoing internal hub link 428. In bypass mode, data on the incoming internal hub link 402 enters input B of switching device 422 and is output unchanged to the outgoing internal hub link 428 to the next hub port in the loop ( (Not shown).

However, when an operating device, such as the FC-AL NL_ port or loop segment, represented by node port 408, is attached to hub port 400, the signal from node port 408 received by hub port receiving circuit 412 will be It is sent to the next hub port via the outgoing internal hub link 428. To send data to the internal hub link 428 exiting the hub port receiving circuit 412, the hub port output control circuit 416 selects input A of the switching device 422 through the hub port output control line 420.

[0027] In the case of a conventional FC-AL hub port, generally, when the operating device is first attached to the node port 408, the hub port receiving circuit 412 detects the reception of data from the node port 408 and bypass mode ( Input B of the switching device 422 is selected). The data received from node port 408 is inserted into the loop by selecting input A of switching device 422. The data received by the hub port receiving circuit 412 from the node port 408 is immediately sent to the next hub port through the outgoing internal hub link 428. However, as discussed earlier, such immediate insertion into the loop of a new device or hub can lead to address duplication and undesired data corruption.

[0028] To overcome this difficulty, a preferred embodiment provides a loop initialization insertion mechanism. When the operating device or hub is attached to hub port 400, the hub port receiving circuit 412 detects the new device or hub by detecting the reception of stylized data through data channel 410, which previously had no data. The data from the node port 408 is not immediately sent to the outgoing internal hub link 428 through the hub port output line 418, and the hub port output control circuit 416 selects input C of the switching device 422. The loop initialization data generator 424 generates a constant flow of loop initialization data that indicates that a new device or hub has been installed to other hub ports in the loop. When the other hub port in the loop receives the loop initialization sequence, it sends out that sequence. The loop initialization sequence is a specified combination of loop initialization data. In an FC-AL embodiment, the LIP primitive sequence consists of three consecutive identical LIP ordering sets of the same type. In this way, the processing of the loop transaction is stopped, and then each hub port starts sending or generating loop initialization data. The loop initialization data generator 424 repeatedly generates loop initialization data, preferably in cooperation with an appropriate frame sequence for the loop network.

The hub port output control circuit 416 continues to select input C of the hub port switching device 422 until the loop initialization data detection circuit 414 detects the loop initialization sequence received from the node port 408. As described above, the node port 408 receives the signal from the incoming internal hub link 402 through the hub port transmission circuit 404. The input selection of switching device 422 does not affect the reception of data by node port 408. This is because the switching device 422 controls the output of the hub port 400 to the loop and not the input from the loop.

[0030] In the FC-AL embodiment, the loop initialization data is a LIP (F7, F7) ordering set. These LIP (F7, F7) ordering sets are preferably in FC-AL protocol compliant form (K28.5 D21.0 D23.7 D23.7).

Thus, the loop initialization sequence generated from the port before the loop (which may be the same port) goes into hub port 400 on the incoming internal hub link 402, and then into the hub port transmission circuit. It is sent to node port 408 through 404. Node port 408 sends the loop initialization sequence to hub port receiving circuit 412. The loop initialization data detection circuit 414 detects the loop initialization sequence. When such a loop initialization sequence is detected, the hub port output control circuit 416 switches from the selection of the input C of the switching device 422 to the selection of the input A of the switching device 422. At this point, the loop initialization procedure begins according to the appropriate network protocol.

[0032] When the LIP detection circuit 414 detects a LIP primitive sequence (not necessarily the same LIP (F7, F7) primitive sequence), it generates an affirmative detection signal. The LIP primitive sequence found does not have to be a sequence from the same hub port that discovered the new device or hub and started generating the LIP (F7, F7) ordering set first.

For hub ports other than the hub port that generates loop initialization data, when the node port receives the loop initialization data from the hub port, the node port returns some of the loop initialization data to the hub port. In a preferred embodiment, the hub port sends out data from the node port (by selecting input A of the switching device shown in FIG. 4).

[0034] Therefore, when a new operating device or a new hub is attached to an existing hub, loop initialization is enforced. In a preferred embodiment, when the loop initialization sequence is generated and propagated, normal loop operation is stopped and loop initialization begins. As mentioned above, it is desirable that the initial setting of the loop is performed when connecting a new device or when connecting the second loop to the first loop. This is because the loop initialization process is a reliable way to assign a unique physical address to each device on a newly established loop under a network protocol such as the FC-AL protocol.

[0035] FIGS. 5A and 5B show an embodiment in which the operating device is inserted into the loop according to a preferred embodiment. Figure 5A shows the loops and elements before inserting the new device. The hub 500 has four hub ports 502, 504, 506, 508. As shown in FIG. 5A, the hub 500 has only four hub ports, but the hub may have more than four or less than four hub ports. The number of hub ports shown in FIG. 5A is for illustrative purposes only. Hub ports 502, 504, 506, 508 are connected to each other by internal hub links to form a loop. Two node ports 510 and 512 are attached to hub ports 502 and 508, respectively. Data from node port 510 to node port 512 flows into hub port 502 through the data channel. Hub port 502 outputs the above data to hub port 504 along the internal hub link. Since no operating device is attached to the hub port 504, it is in bypass mode. Therefore, hub port 504 sends data from hub port 502 to hub port 506 along the internal hub ring. Hub port 506 is also in bypass mode, so send the above data to hub port 508 through the internal hub link. Hub port 508 is not in bypass mode because the operating device is attached to node port 512. Similarly, data sent from node port 512 to node port 510 reaches hub port 508 through the data channel and then along the internal hub link to hub port 502. Hub port 502 sends the data to node port 510 along the data channel. In this way, hub ports 502 to 508 and hub 500 operate to maintain the loop topology.

Inserting a new device attached to node port 514 proceeds with the process described earlier for FIG. Node port 514 is attached to hub port 504. Hub port 504 detects a new node port 514 because there is data coming into hub port 504 with a particular data configuration. When hub port 504 detects node port 514, it does not immediately send data from node port 514. Hub port 504 synchronizes timing and frames with data from node port 514 to ensure proper operation of node port 514. As described above, the hub port 504 receives the loop initialization data (eg, LIP (F7, F7) ordering set) by selecting the input of the switching device in the hub port 504 corresponding to the loop initialization data generator. Start sending along the internal hub link. The loop initialization data reaches hub port 506 along the internal hub link.

Hub port 506 is in bypass mode because the node port is not attached to hub port 506. Therefore, the loop initialization data reaches hub port 508 along the internal hub link.

Hub port 508 sends loop initialization data to node port 512 if node port 512 has not already been bypassed. The operating device attached to the node port 512 preferably responds to the loop initialization data, and then the node port 512 returns the loop initialization data to the hub port 508. In a preferred embodiment, hub port 508 selects the signal received from node port 512 and hubs because the operating device attached to node port 512 produces a proper response to the loop initialization data. Send along 500 internal hub links. A hub port, such as the hub port 508, is attached to the operating device through a node port, but by selecting input A of the hub port switching device as shown in Figure 4, it sends the loop initialization data received from that node port. .. Therefore, the loop initialization data is preferably sent to the next hub port along the internal hub link.

As shown in FIG. 5B, hub port 508 sends loop initialization data to hub port 502. Since the hub port 502 is also equipped with the operating device represented by the node port 510, the hub port 502 follows a process similar to that of the hub port 508. Therefore, the loop initialization data goes from hub port 502 to hub port 504.

[0040] The hub port 504 receives the loop initialization data, and if the node port 514 has not been bypassed yet, transmits the loop initialization data to the node port 514. The node port 514 returns the loop initialization data to the hub port 504 in the same manner as the node ports 512 and 510. The loop initialization data detection circuit (414 shown in FIG. 4) in the hub port reception circuit of the hub port 504 detects the loop initialization data. Hub port 504 stops outputting loop initialization data when a loop initialization sequence is received. In this case, hub port 504 may have received the loop initialization sequence generated by hub port 504. However, as described above, the hub port 504 stops outputting loop initialization data when it detects a loop initialization sequence from any source (origin). In an FC-AL embodiment, the hub port stops outputting the LIP (F7, F7) ordering set when it detects any type of LIP primitive sequence. In another embodiment, a hub port transmit logic circuit (hub port transmit). logic) detects the loop initialization sequence received along the internal hub link and does not necessarily wait for a response from the connected node port. In either case, hub port 504 outputs loop initialization data (by selecting input C of the switching device as shown in FIG. 4), and thus loop initialization defined (defined) by an appropriate network protocol. Switch to the setting procedure.

[0041] Figures 6A and 6B show the connection of one hub loop to a second hub loop. In general, this process is similar to the process shown in Figures 5A and 5B, where a new operating device is inserted into a single hub loop.

FIG. 6A shows a first hub 600 having six hub ports 602, 604, 606, 608, 610, 612. Three node ports 614, 616 and 618 are connected to hub ports 602, 604 and 606, respectively. The second hub 620 also has six hub ports 622, 624, 626, 628, 630 and 632. The three node ports 634, 636 and 638 are connected to the three hub ports 622, 624 and 626, respectively. The hub ports of each hub are connected in one loop.

FIG. 6B shows the connection of hub 600 to hub 620. A pair of data channels connect hub port 608 to hub port 632. One data channel carries data from hub port 608 to hub port 632. Another data channel carries data from hub port 632 to hub port 608. In this way, two loops contained in two separate hubs are connected to form a single loop. The new circular data path between hub ports has the following pattern: That is, the pattern of returning to hub port 608 610 612 602 604 606 608, then returning to hub port 632 622 624 626 628 630 632, and then returning to hub port 608 to complete the circle. Is. When data enters hub port 606 from hub port 606, the data passes through the transmission circuit of hub port 608 (see Figure 4) and then through the data channel to hub port 632. The data has not yet entered the receiving circuit of hub port 608 and will not enter the receiving circuit of hub port 608 until the data returns from hub port 632. In this way, the data flows through the two hubs in a circular pattern, and the two previously physically separate loops act as effectively one loop.

However, connecting one hub to another can result in address duplication and unwanted data corruption, as previously mentioned for Figures 2A and 2B. The loop initialization insertion mechanism provided by the preferred embodiment overcomes this problem and enforces loop initialization. Hub port 608 detects a connection of hub 620 to hub port 632 by receiving new properly formatted data. When the hub port 632 is detected, the hub port 608 follows the procedure defined above for detecting a new device. The hub port 608 selects the loop initialization data generator inside the hub port 608, and then outputs the loop initialization data along the hub loop. Therefore, the loop initialization data goes from hub port 608 to hub port 610. Since the hub port 610 does not have a node port attached, it is in bypass mode. Hub port 610 sends loop initialization data to the next hub port, and the process continues as described earlier for Figure 5B. Similarly, hub port 632 detects a connection of hub 600 to hub port 608. Therefore, the hub port 632 selects the loop initialization data generator inside the hub port 632 and outputs the loop initialization data to the hub loop of the hub 620.

[0045] Therefore, hub ports 608 and 632 each generate loop initialization data sent along the loop. The loop initialization data from hub port 608 is from hub port 608 610 612 602 node port 614 (if node port 614 is not bypassed) hub port 602 604 node port 616 (node port 616 is bypassed). (If not) Hub port 604 606 Node port 618 (if node port 618 is not bypassed) Hub port 606 Then return to 608. However, in a preferred embodiment, at this point, hub port 608 does not detect loop initialization data. This is because the loop initialization data detection circuit of hub port 608 is located in the hub port receiving circuit of hub port 608. The loop initialization data received from hub port 606 along the internal hub link is in the hub port transmission circuit of hub port 608. Therefore, the loop initialization data reaches hub port 632. The hub port 632 receives the loop initialization data at the hub port receiving circuit, and then detects the loop initialization data using the loop initialization data detection circuit. When the hub port 632 detects the loop initialization sequence from the loop initialization data generated by the hub port 608 in this case, the hub port 632 receives the input of the switching device inside the hub port 632 so that the loop initialization proceeds. Change your selection. By selecting the loop initialization data generator, the bypass achieved inside hub port 632 ends and the loop initialization begins.

Similarly, hub port 608 receives the loop initialization data generated by hub port 632. This data eventually goes from hub port 632 to hub port 608 along the hub 620 internal hub link. The loop initialization data detection circuit in the hub port receiving circuit of hub port 608 detects the loop initialization sequence, terminates the bypass, and then begins the loop initialization process according to the standard FC-AL protocol. Therefore, both hub ports 608 and 632 start the loop initialization process. The loop initialization process is understood and defined as before, according to network protocols such as the FC-AL protocol. Moreover, this technique is still valid as long as at least one hub in the loop operates according to the present invention, even if one of the interconnected hubs is a regular hub.

Although various embodiments of the present invention have been described with reference to the drawings, the scope of the invention should not be limited by the description provided herein, but only by the claims of the present application. Also, another embodiment that falls within the scope of the claims will be apparent to the technician in the art.

BRIEF DESCRIPTION OF THE DRAWINGS [Fig. 1A] A loop of the prior art connecting from a node port to a node port is shown.

FIG. 1B shows a prior art loop involving a hub.

FIG. 2A shows two separate prior art loops.

FIG. 2B shows two prior art loops connected to generate a single loop.

FIG. 3 shows a loop containing a hub.

FIG. 4 is a block diagram of a hub port according to a preferred embodiment.

FIG. 5A shows a hub with two node ports.

FIG. 5B shows a hub with three node ports.

FIG. 6A shows two separate loops containing a hub.

FIG. 6B shows two loops containing hubs connected by hub ports.