Patent Publication Number: US-8989045-B2

Title: Methods, devices and systems with improved zone merge operation by initiator selection

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This case is related to U.S. Pat. No. 8,700,799, entitled “Methods, Devices and Systems with Improved Zone Merge Operation by Operating on a Switch Basis,” by Eric Warmenhoven, Yi Lin, Sundar Poudyal and James Hu, filed concurrently herewith and U.S. Pat. No. 7,596,100, entitled “Methods, Devices and Systems with Improved Zone Merge Operation by Caching Prior Merge Operation Results,” by Yi Lin, Eric Warmenhoven, James Hu and Sundar Poudyal, filed concurrently herewith, both of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an electronic network and its operation, more specifically to a zone merge operations within such a network. 
     2. Description of the Related Art 
     The Fibre Channel family of standards (developed by the American National Standards Institute (ANSI)) defines a high speed communications interface for the transfer of large amounts of data between a variety of hardware systems such as personal computers, workstations, mainframes, supercomputers, storage devices and servers that have Fibre Channel interfaces. Use of Fibre Channel is proliferating in client/server applications which demand high bandwidth and low latency I/O such as mass storage, medical and scientific imaging, multimedia communication, transaction processing, distributed computing and distributed database processing applications. 
     A Fibre Channel network may consist one or more fabrics. A fabric is an entity that interconnects various ports attached to it and is capable of routing frames using only the D_ID information in an FC-2 frame header. A fabric may have zones to facilitate network management and operation. A zone is a group of zone members, where members of a zone are made aware of each other, but not made aware of other devices outside the zone. A zone can be defined to exist in one or more zone sets. Each zone has a zoning configuration, which includes a zone definition and a zone set state. The zone definition contains parameters that define a zone, including zone name, number of zone members and zone member definitions. The zone member definition contains parameters that define a zone member including the zone member type and zone member information. The zone set state is the state of a switch zone set (activated or deactivated). 
     When two fabrics are joined together, i.e. at least one switch in one fabric is connected to at least another switch in the other fabric, if zoning is present, then the two switches will attempt to merge their zoning information to ensure the zoning information is consistent across the joined fabric. The performance of the merge operation directly affects the processing time needed to allow the whole fabric to return to stable state as well as the overall performance of the switches during the merge operations. 
     The interface on a switch that connects to another device is a port. There are many different ports depending on the network topology and the type of devices that they are connecting. The port on a switch that connects to a port on another switch is an E_port. A port on a switch that connects to an end node is an F_port. The current invention is directed to the merge operation between switches, so only E_ports will be discussed. 
       FIG. 1  shows a small part of a Fibre Channel network  100 , where a switch  102  is connected to another switch  104 . SwitchA  102  has a zone configuration  112  cfgA and switchB  104  has a zone configuration  114  cfgB. Each switch  102 ,  104  has a checksum associated with the zone configuration. A zone configuration may have a size between several kilobytes to many megabytes depending on the switch or fabric configurations. In the examples discussed below, a zone configuration often runs to hundreds of kB. A checksum is typically much smaller, significantly less than 1 kB. A checksum acts as a shorthand or identifier for a particular configuration. In the same examples, a checksum is 32 bytes. 
     A merge computation performs a union of the two configurations in:
 
cfgR=cfgA∪cfgB  (1)
 
A simplified merge exchange is illustrated in  FIG. 2  between switches  102  and  104 . It is simplified in that it does not show all the transactions that may happen when two switches are connected. For example,  FIG. 2  does not show many merge requests sent from switchB  104  to switchA  102 ; it does not show any possible Rejects because of busy conditions; and it does not show any possible retries as well.
 
     A merge exchange includes several steps. Using  FIG. 2  as a simplified example, the merge exchange may occur as follows. Assuming switchA  102  initiates the merge operation, switchA  102  sends a checksum request to switchB  104  (Req1) and switchB  104  sends a response back, which is its own checksum (Res1:ACC). SwitchA  102  compares the checksum received from switchB  104  with its own. If they are different, switchA  102  sends out an MR request with cfgA (Req2:MERGE). SwitchB  104  responds with cfgB in acknowledgement (Res2:ACC). SwitchB  104  computes ΔB=cfgMerge(cfgB, cfgA) and installs the entries of ΔB. Then switchB  104  has a new configuration cfgR with a new checksum associated with the new configuration cfgR. When switchA  102  gets the response of cfgB, it also does a merge computation ΔA=cfgMerge(cfgA, cfgB) and installs the entries of ΔA. SwitchA  102  now has cfgR. After this, the merge initiated from switchA  102  finishes. SwitchB  104  also attempts or initiates a merge by sending checksum request (Req3:CHECK). SwitchA  102  responds back (Res3:ACC), which is switchA&#39;s  102  new checksum associated with the new cfgR. Since switchB  104  has the same cfgR after the merge operation which was initiated by switchA  102  and the same checksum, the checksums match. So the merge initiated from switchB  104  finishes. 
     As will be discussed below, in the above merge operation, there are many duplicate operations and unnecessary data transmissions in the network. It is desirable to perform the merge operation more efficiently. 
     When a switch  102  is connected to a network of several switches  104 ,  106 ,  108  and  109  as shown in  FIG. 3  or  FIG. 4 , the merge operation may be more complicated and time consuming. In this case, switchA  102  and switchB  104  merge first in the same way as shown in  FIG. 1  and discussed above. SwitchA  102  does cfgMerge (cfgA, cfgB), and switchB  104  does cfgMerge (cfgB, cfgA). Both switches have cfgR as a result. SwitchB  104  broadcasts this to switchC  106 . Since the configuration on switchB  104  changes, there will be a merge operation between switchB  104  and switchC  106 . SwitchB  104  does cfgMerge (cfgC, cfgB) and switchC  106  does cfgMerge (cfgB, cfgC). The same chain of events will propagate further down the path until every pair of connected switches have the same configuration. If one counts the merge exchanges, one can find three merge exchanges, and a total of six merge computations when switchA  102  is connected to the fabric comprising switchB  104 , switchC  106  and deviceDeviceD  108 , in the simple example shown in  FIG. 4 . There are more merge exchanges and merge computations for a more complicated configuration such as shown in  FIG. 3 , because of more connected pairs of switches. However, as will be discussed below, many of the operations are unnecessary. It is desirable to improve the merge operation. 
     Merge operations are typically performed on a connected port basis. If more than one pair of ports on two switches is connected, as shown in  FIG. 5 , each pair of ports will perform merge operations, even though the merges are the same for each pair.  FIG. 5  shows an example where different numbers of pairs of ports are connected between switches within a fabric. In the example shown in  FIG. 5 , switchA  102  and switchB  104  have four (4) pairs of ports connected, i.e. links between ports  121  and  131 , ports  123  and  133 , ports  125  and  135  and ports  127  and  137 . SwitchB  104  and switchC  106  have one pair of ports  136  and  144  linked. SwitchC  106  and deviceD  108  have two pairs of ports linked, ports  156  and  145 , and ports  158  and  147 . In  FIG. 5 , a few details of the network deviceD  108  and switchC  106  are shown. The network deviceD  108  has a network interface  156  containing ports  152  and  154  which are capable to connect to ports on other network devices, such as switchC  106 . Within the deviceD  108 , there is a control module  158  which is coupled to the network interface and controls the operation of the deviceD  108 . The control module  158  is also coupled to a memory module  157  which stores operation data or device information, such as configuration data  159 . DeviceD can be any entity within a network. Similarly, switchC may have several ports  141 - 148 , a control module and a memory module. In the fabric shown in  FIG. 5 , some of the pairs may be trunked, i.e. they act as a single logical link, e.g. links  156 - 145  and  158 - 147  may be trunked as if they were a single link. When port  121  and port  131  are connected, both of them initiate merge operations as discussed above. When the other pairs of ports are connected between switchA  102  and switchB  104 , when the links are not trunked, each of them will perform a merge operation again, even though the merge results are already known from the earlier merge between port  121  and port  131 . Therefore, it is desirable to have a method or devices that can avoid the wasteful operations. 
     When two switches are connected, both switches will initiate a merge operation. They are likely to initiate at approximately the same time. The result is that both merge requests will be rejected with a reason of LOGICAL_BUSY. If not treated specially, both switches would wait for the other side to initiate a merge, thus missing the initial MERGE. The default waiting time is different for different switches. So after some waiting time, one switch will try again to initiate a merge request and not getting a rejection. It is desirable to avoid the waiting time. 
     As discussed above, the current merge operation may have redundant merge computations, redundant merge exchanges, unnecessary merge retries across the fabric and extra waiting time. These inefficiencies make the merge operation prolonged and the fabric wait a longer time to be stable. It is desirable to have a method, a device and a system that make merge operations more efficient. 
     BRIEF SUMMARY OF THE INVENTION 
     According the embodiments of the present invention, the zone merge operation is improved. 
     In one embodiment, a port-based merge is changed to a switch-based merge. Only one merge is performed per connected-switch pair, which can reduce the redundant merges among ports connected to the same remote switch. 
     In another embodiment, two switches to be merged are distinguished as a merge initiator and a merge receiver by a switch specific identifier, for example by WWN arbitration. Only a merge initiator can initiate a merge operation and directs the merge calculation. This reduces the number of merge operations. This also avoids the waiting time caused by the conflicts between the two connected switches both trying to perform a merge operation. 
     In another embodiment, one switch transmits its whole configuration to the other switch. The other switch only transmits a configuration difference, or partial configuration, such that the overhead traffic of transmitting zoning configurations is reduced. 
     In a further embodiment, the checksums involved in past merge operations are cached in each switch. When a new merge operation is requested, the switch can check all the prior checksums. If the requesting checksum was used before, then the existing config will be the resulting config after the requested merge operation. Therefore, config will be used directly without the unnecessary merge calculation. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       A better understanding of the invention can be had when the following detailed description of the preferred embodiments is considered in conjunction with the following drawings, in which: 
         FIG. 1  depicts a two switch merge scenario in a network. 
         FIG. 2  depicts merge exchanges in the two switch scenario as shown in  FIG. 1 . 
         FIG. 3  depicts a new switch merging into a group of connected switches. 
         FIG. 4  depicts a special topology of connected switches or other network devices, i.e. chained connection. 
         FIG. 5  depicts more details regarding port connections in a multiple-port connection network as shown in  FIG. 4 . 
         FIGS. 6A ,  6 B,  6 C and  6 D depict merge exchanges in the scenario as shown in  FIG. 1  according to one embodiment of the current invention. 
         FIG. 7  is a high level state diagram of an embodiment of the current invention. 
         FIG. 8  is a state diagram of a principle initiator. 
         FIG. 9  is a state diagram of a non-principle initiator. 
         FIG. 10  is a state diagram of a receiver port. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to the embodiments of the current invention, many current and potential deficiencies in the merge operation are discovered, their sources identified and improvements made to eliminate such deficiencies. 
     According to one embodiment of the current invention, an enhanced zoning merge is implemented using an event driven state machine. A merge event dispatcher may be used. The merge event dispatcher listens to merge related events. On receiving a merge related event, a corresponding operation is initiated. The dispatcher first performs pre-dispatch checking to determine if the event needs to be handled asynchronously. If not, event is handled in context of the caller. Asynchronous events are scheduled for later dispatch. As long as there is a pending event on any E_port, the dispatcher feeds it to the port state-machine to advance it to a next state. When one port is DONE, it moves to the next one with pending events. If all ports are in DONE state merge is finished. 
     During a merge, communication between two switches is based on a “new merge exchanges” format. The new merge exchange is done by using port state-machine transition logic. Each port will be either an initiator or a receiver based on initiator/receiver arbitration. If a new zoning configuration is generated during the merge, the event dispatcher generates an event on the other ports (BROADCAST). The port state-machine may be expanded to include logic to handle a backward compatible mode or an interop mode, if desired. 
     The merger event dispatcher is responsible for: pre-dispatch checking and synchronous event handling; event dispatching; and driving port state-machine transitions. 
     Pre-dispatch checking: Zoning only handles one merge on one port at any time. Some merge requests can be rejected immediately in context of the source of the event. Pre-dispatch checking identifies events that could be handled synchronously. For example, if the dispatcher receives a merge request, pre-dispatch checks to determine if merge is already in progress. If so and the current “in process” port is same as the port associated with the incoming event, the dispatcher handles this event directly by rejecting the request with LOGICAL_BUSY. 
     Event dispatching: The dispatcher may dispatch the event to one port, or a group of ports. During dispatch, events are mapped to unified merge event types. The real dispatch process is simply associating an event with a corresponding port. For any port, only a pending event is possible. Dispatching replaces a current event at the port with a later one. If more than one event is pending, then pending events are put in a queue. 
     Driving the port state machine transition: The dispatcher is also responsible for feeding events into the port state-machine. Whenever there is a pending event on a port, the dispatcher feeds it into the port state-machine by a corresponding transition routine. When a port is done with the merge, and there are no pending events, the dispatcher moves to the next port. After all ports are processed, the dispatcher will be in idle mode until the next event. 
     According to an embodiment of the current invention, when an E_port comes ONLINE after it is connected to another port on another switch, it will be initialized as either the merge initiator or receiver. The role will be determined using a unique identifier or feature of the port. In one implementation, the WWN (World-Wide Name) of the switch is used as the unique identifier because it is unique in the network for each switch and convenient to use. Based on the WWN of a switch, an arbitrator determines a winner of the arbitration, which becomes an initiator and the loser is a receiver. By identifying two different roles for each switch in a connection, and allowing only the initiator to perform the merge operation, the redundant merge operation and conflicts are avoided. 
     According to this embodiment of the current invention, it is immaterial how the arbitrator assigns the two different initiator/receiver roles, or which role performs the whole or parts of the merge operation, as long as only one merge operation is performed between the two switches. One convenient arbitration rule is that the switch with the lower WWN becomes the arbitration winner, i.e. the initiator. 
     Refer back to the fabric shown in  FIG. 1 . Assuming switchA  102  wins the initiator/receiver arbitration, then switchA  102 , which is now the initiator, can initiate the merge operation. SwitchB  104 , which is now a receiver, cannot initiate the merge operation. Therefore, there can be no conflict caused by switchA  102  and switchB  104  initiating merge operation at the same time. The waiting time is thus eliminated. According to this embodiment, half of the merge operations and the defaulting waiting time are eliminated. 
     Refer to  FIG. 6A . As an example, switchA  102  may initiate the merge operation by sending its checksum to switchB  104 . SwitchB  104  compares the checksum from switchA  102  with its own. If they match, then the two switches have the same zone configurations and no merge operation is necessary. SwitchB  104  may respond with an ACCDONE to indicate the end of the merge. 
     Referring to  FIG. 6D , if the checksums do not match, then switchB  104  responds with its configuration cfgB and the checksum. SwitchA  102  performs the merge calculation to get the resulting configuration cfgR and a new checksum for cfgR, and transmits the result to switchB  104 . Both SwitchA  102  and SwitchB  104  can then install the new configuration. SwitchB  104  now has the new configuration cfgR and the new checksum. 
     In another embodiment as shown in  FIG. 6C , if the checksums do not match, then switchB  104  responds with ACCMERGE, which informs switchA  102  that a merge calculation is necessary. SwitchA  102  sends its configuration cfgA and the checksum to switchB with request MERGE. SwitchB  104  performs the merge calculation to get the resulting configuration cfgR and a new checksum for cfgR. SwitchB  104  now has a new configuration cfgR. SwitchB  104  transmits the result to switchA  102  in ACCRESULT. SwitchA  102  can then install the new configuration. The merger operation ends with both switchA  102  and switchB  104  having the new configuration cfgR and the new checksum. 
     Referring to  FIGS. 3 and 4 , similar savings can be achieved according to the embodiment of the current invention. As discussed earlier, for the fabric shown in  FIG. 4 , there are three merge exchanges between switchA  102  and switchB  104 , switchB  104  and switchC  106 , switchC  106  and deviceD  108 , and a total of six merge calculations using the prior art procedure. According to the embodiment, only three merge calculations are performed, a reduction of 50%. As will be discussed below, according to another embodiment, the number of calculations may be further reduced. 
     Referring back to the situation shown in  FIGS. 1 and 2 , the merge computation performs union of the two configurations resulting in cfgR. To achieve a faster merged database installation, each switch usually calculates only ΔA=cfgMerge(cfgA,cfgB), i.e. elements in cfgB not in cfgA. Similarly, the neighbor, or the other switch, calculates ΔB=cfgMerge(cfgB, cfgA).
 
Hence, cfgR=cfgA∪ΔA=cfgB∪ΔB  (2)
 
     Thus, with the prior art implementation, redundant computation exists across the fabric. Take the two switches with a single ISL scenario as an example, as illustrated in  FIG. 1 . Assume the cfgA on SwitchA  102  and cfgB on switchB  104  are compatible. Assume they are mid-sized configurations: cfgA is 40 k, cfgB is 50 k, and the merge result cfgR is 60 k. 
     As observed by the inventors in the current invention, calculations of cfgMerge(cfgA,cfgB) and cfgMerge(cfgB,cfgA) are identical procedurally. Both calculations need to traverse the two configurations and find the difference. According to an embodiment of the current invention, deltaA and deltaB are calculated in one shot. In this embodiment, switchA  102  initiates merge operation. SwitchB  104  responds with a NoMatch signal indicating a merge is necessary. SwitchA  102  sends its configuration cfgA to switchB  104 . SwitchB  104  performs the merge calculation. After merge happens on switchB  104 , switchB  104  responds with deltaA directly, rather than the whole resulting configuration cfgR. After receiving and installing deltaA, switchA  102  has the resulting configuration cfgR. Here, the computation is performed only on switchB  104 . Also less Fibre Channel frame traffic is sent, because only the difference is sent back. 
     In this particular example, using the prior art procedure, the generated traffic is roughly 90 k, i.e. 40 k (cfgA from switchA to switchB)+50 k (cfgB from switchB to switchA) with cfgMerge. According to the embodiment of the current invention, with cfgMergeNew, the traffic will be only 60 k, i.e. 40 k (cfgA from switchA to switchB)+(60 k−40 k) (deltaA from switchB to switchA). So in this example, the amount of network traffic is reduced by 30 k. The more the overlap between the two configurations, the more the savings. 
     As will be discussed below, in another embodiment, both deltaA and deltaB are transmitted to the other switch. In that case, the traffic will be only 70 k, i.e. 40 k (cfgA from switchA to switchB)+(60 k−40 k) (deltaA from switchB to switchA)+(60 k−50 k) (deltaB from switchB to switchA). So in this example, the amount of network traffic is reduced by 20 k. But more savings will be realized in multiple switch networks as will be explained. 
     According to one embodiment of the current invention, when two switches are linked with multiple Inter-Switch Links (ISLs), only one link needs to be involved in the merge. This way, the merge is done on per-switch basis, rather than per-port basis and the number of merge operations is reduced, sometimes dramatically depending on the number of ISLs. All E_ports are associated with corresponding neighbor switches. Switches may be identified by their World Wide Numbers (WWN). For every neighbor, a principle E_port is selected. In one implementation, the selection may be done during E_port ONLINE. A list of all E_ports may be maintained, such that each E_port has a sequence or priority to become a principle E_port. If an E_port is the first one associated a particular WWN, it is selected as the principle E_port. Only the principle E_port participates in a merge operation. At the end of the merge operation of the principle E_port on the initiator, the status is updated accordingly for all non-principle E_ports. Any requests received by non-principal ports will be rejected with LOGICAL_BUSY. If the principle E_port goes down, the next one in the priority list may be designated as the new principle. 
     With switch-based merge operations, only one merge operation is performed even if there are multiple ISLs between two switches. In the example shown in  FIG. 5 , according to this embodiment of the current invention, there will be only one merge operation among the four ISLs between the switchA  102  and switchB  104 , rather than eight merge operations as in the prior art. 
     Still referring to the example shown in  FIG. 4 , it is observed that: 
     from cfgR=cfgA∪cfgB, 
     we also have cfgR=cfgR∪cfgB or cfgR=cfgR∪cfgA 
     which means, we could predict the merge result of cfgB (or cfgA) and cfgR if cfgR comes from the merge of cfgA and cfgB. Caching last or prior merge results may prevent unnecessary merge exchanges. When switchA  102  joins the fabric, switchB  104  performs the initial merge; caches the merge operation results, and responds to switchA  102 . SwitchA  102  may cache or store cfgR (this is always stored in switchA  102 , because it is the current configuration of switchA  102  after the merge), deltaA, deltaB, and the checksums associated with cfgA, cfgB and cfgR. SwitchB  104  may cache the same information. Once the merge operation is complete, the prior configurations of switchA  102  and switchB  104 , i.e. cfgA and cfgB are no longer needed. If they are ever needed, they can be reconstructed from deltaA, deltaB and cfgR. To save storage space, they are stored separately as individual configurations. 
     Then switchB  104  sends a cache enhanced checksum request to switchC. From that, switchC  106  knows its configuration, i.e. cfgB, was involved in a previous merge, and switchB  104  has the results for it. So switchC  106  directly asks switchB  104  to send the merge results, i.e. deltaA, deltaB. Hence merge exchanges between switchB  104  and switchC  106  are avoided and switchC gets the results directly. The same thing happens between switchC  106  and deviceD  108 . During the whole merge process, only one full merge exchange (between switchA and switchB) is performed. At same time, the merge computation is performed only once in entire fabric. 
     If a new switch with cfgC joins the fabric, by comparing the checksum associated with cfgC with the checksums associated with cfgA, cfgB and cfgR, one could know if a fresh merge is needed. If the checksum is the same as that associated with cfgA or cfgB, it means that cfgC was involved in a previous merge computation. The merge results of cfgC and cfgR will still be the same as cfgR. In this case, the new switch needs to get the corresponding delta (either deltaA or deltaB) to get the fabric&#39;s zoning configuration. If the checksum of cfgC matches that of cfgR, then no merge and zoning installation are needed. If cfgC does not match the cached configurations, then a new merge will be performed and the result will update the current cached contents. 
     Matching checksums of configurations may provide further optimization. In this case, we may cache only: deltaA, deltaB, checksumA, checksumB, checksumR in order to know if a new merge is needed when a switch joins the fabric. 
     This embodiment may be further illustrated using a numeric example. If we assume-cfgA, cfgB and cfgR are mid-sized zoning configurations e.g.: 40 k, 50 k and 60 k, the network traffic without caching would be: 40 k (switchA send to switchB cfgA)+50 k (switchB send to switchA)+60 k (switchB send cfgR to switchC)+50 k (switchC send to switchB cfgB)+60 k (switchC send cfgR to deviceD)+50 k (deviceD send cfgB back to switchC)=310 k; 
     The network traffic with caching according to an embodiment of the current invention would be: 40 k (switchA sends to switchB cfgA)+(20 k+10 k) (two deltas in the results)+2×(20 k+10 k) (same results passed from switchB to switchC and from switchC to deviceD)=130 k. This is more than a 50% of reduction in network traffic. Since in most network scenarios, the differences in zone configurations between switches are relatively small, the savings in network traffic are typically much greater than shown in the numeric examples. 
     To further improve the embodiments described above, a new merge exchange involving cache sensitive requests and responses may be employed. One merge exchange could include multiple requests and responses. 
     In new merge exchanges, the initiator sends merge requests. Requests can be of type: CHECKSUM, TAKECACHEDRESULT or MERGE. The following table describes these requests in detail. Not all components of the listed request content are always included in a particular request. The components included in a request depend on the embodiment implemented. For example, the LocalCachedA and LocalCachedB components are only included if the configuration caching as described above is implemented. DeltaA and DeltaB in the TAKECACHEDRESULT may be included if the partial data transmission is implemented. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Merge2 Request List 
               
            
           
           
               
               
               
            
               
                 Name 
                 Description 
                 Contents 
               
               
                   
               
               
                 Req1: CHECKSUM 
                 Merge checksum requests with cache information it 
                 Version Number 
               
               
                   
                 has. It is compatible with CHECK command for 
                 Capability 
               
               
                   
                 legacy switches. Sender sends cached checksums 
                 LocalCurrentChecksum: 
               
               
                   
                 of all elements involved in the last logical merge. 
                 Checksum of merge 
               
               
                   
                 Receiver will match its checksum with the cached 
                 computation result or 
               
               
                   
                 checksum and respond to indicate the next step 
                 checksum of current 
               
               
                   
                 in merge. 
                 result if no cache. 
               
               
                   
                   
                 LocalCachedA: 
               
               
                   
                   
                 checksum of cached 
               
               
                   
                   
                 cfgA in last merge. 
               
               
                   
                   
                 LocalCachedB: 
               
               
                   
                   
                 checksum of cached 
               
               
                   
                   
                 cfgB in last merge. 
               
               
                 TAKECACHEDRESULT 
                 Request to let receiver take cached merge results 
                 Version 
               
               
                   
                 directly. 
                 ChecksumA 
               
               
                   
                   
                 ChecksumB 
               
               
                   
                   
                 DeltaA 
               
               
                   
                   
                 DeltaB 
               
               
                 MERGE 
                 Merge request, sender sends its current config 
                 Version 
               
               
                   
                   
                 Local Config 
               
               
                   
               
            
           
         
       
     
     The response in MERGE2 is multifunctional. Besides normal acknowledgement, the merger response contains control data instructing how further merge steps are to occur. The Responder performs real the merge computation. Response codes are illustrated in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 MERGE2 Response List 
               
            
           
           
               
               
            
               
                 Name 
                 Description 
               
               
                   
               
               
                 REJBUSY 
                 Reject with reason busy. 
               
               
                 REJCANTPERFORM 
                 Reject with reason “can&#39;t perform requested 
               
               
                   
                 operation” 
               
               
                 ACCDONE 
                 Acknowledgement indicating end of merge 
               
               
                   
                 session. 
               
               
                 ACCMERGE 
                 Acknowledgement indicating of need continue 
               
               
                   
                 merge with (by sending embedded checksum). 
               
               
                 ACCCACHED 
                 Acknowledgement indicating checksum match. 
               
               
                 ACCRESULT 
                 Acknowledgement containing resulting 
               
               
                   
                 configuration. 
               
               
                 ACCSEGMENT 
                 Acknowledgement requesting segmenting 
               
               
                   
                 port (conflict). 
               
               
                   
               
            
           
         
       
     
     Referring to  FIGS. 6A ,  6 B and  6 C, the merge operation according the various embodiments of the current invention may be described in the following basic steps: 
     First Checksum Exchange: 
     A merge exchange is initiated by one of the two connecting E_ports (i.e. the merge initiator) sending the CHECK request. The receiver matches the checksum with its own checksum and sends acknowledgement to the initiator. If the receiver matches the remote current checksum, it sends ACCDONE indicating no further merge is needed, as shown in  FIG. 6A . If cached checksum matches, it sends back ACCCACHED, see  FIG. 6B . If no match is found, ACCMERGE is sent, see  FIG. 6C . Receiver then waits for initiator to send its config, as in  FIG. 6C . 
     TAKECACHED Exchange: 
     If the initiator gets an ACCCACHED response, it sends TAKECACHED. The receiver takes the cached merge result, installs the new configuration and finishes the merge by sending ACCDONE response, as shown in  FIG. 6B . 
     Logical Merge: 
     On getting an ACCMERGE response the initiator sends MERGE request. The receiver begins the logical merge of the two configs. If they are not compatible, it segments the linked E_ports and sends ACCSEGMENT. Otherwise it updates its own cache and sends ACCRESULT as shown in  FIG. 6C . The initiator will take the merge results and the merge session is over. It also updates its cache. Both switches will post BROADCAST events on their other principal E_ports. 
     When all E_ports reach the merge-done state, the merge is considered to be over. 
     As illustrated by  FIGS. 6A ,  6 B and  6 C, in the merge operation according to embodiments of the current invention, many redundant steps or operations are eliminated from the prior art merge process. Only the initiator of the two connected switch pair initiates the merge operation. The receiver does not initiate the merge operation. When there is a cached-configuration available on the receiver/initiator, then only the cached configuration is transmitted, not the whole configuration. 
     The various embodiments and their operations may be explained using state diagrams of the event driven state machines. A high level state machine is shown in  FIG. 7 . The associated states and events that that can cause transitions between various states are shown in Tables 3 and 4. Referring to  FIG. 7 , an E_port is in a M0 state when it goes online, and it changes to M5 when it goes offline. While doing a merge, if the port is arbitration winner, it will switch to initiator (principal or non-principal), otherwise it will be a receiver (composite state M3). If a port is the first one of the joining neighbor switch and its role is initiator, the composite state is M1. Otherwise the port becomes a non-principal initiator (M2). When the E_port finishes the merge, it will transit to M4 waiting for further events. On receiving a further event, it will transition through appropriate states once again. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 High Level States 
               
            
           
           
               
               
               
            
               
                 Label 
                 State Name 
                 Description 
               
               
                   
               
               
                 M0 
                 INITIALIZED 
                 Before E_port online. 
               
               
                 M1 
                 IPRINCIPAL 
                 Composite state: E_port as principal 
               
               
                   
                   
                 initiator 
               
               
                 M2 
                 INONPRINCIPLE 
                 Composite state: E_port as non-principal 
               
               
                   
                   
                 initiator 
               
               
                 M3 
                 RECEIVER 
                 Composite state: E_port as receiver 
               
               
                 M4 
                 FINISHED 
                 Merge finished on this port. 
               
               
                 M5 
                 UNINITIALIZED 
                 After E_port offline or before E_port 
               
               
                   
                   
                 online. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 High Level State Transitions 
               
            
           
           
               
               
            
               
                 Transition 
                   
               
               
                 (Start:End) 
                 Events (including conditions) 
               
               
                   
               
               
                 M0:M1 
                 EvtMStart - start merge, port is an arbitration 
               
               
                   
                 winner, and it is the only one connected with 
               
               
                   
                 that neighbor switch. 
               
               
                 M0:M2 
                 EvtMStart - port is anarbitration winner but not 
               
               
                   
                 the first one connected with that neighbor switch. 
               
               
                 M0:M3 
                 EvtMStart - port is an arbitration loser. 
               
               
                 M1:M3 
                 EvtRejBusyReceived - port changes to receiver role. 
               
               
                 M2:M1 
                 EvtPrincipal - current principal merge initiator 
               
               
                   
                 went OFFLINE, next one associated with neighbor 
               
               
                   
                 becomes principal initiator. 
               
               
                 M3:M1 (1) 
                 EvtRejBusySent - dispatcher responds to merge 
               
               
                   
                 request and toggles port role to principal initiator. 
               
               
                 M3:M1 (2) 
                 EvtTO - after merge on other ports is done and idle 
               
               
                   
                 time exceeds in receiver role. Port takes over 
               
               
                   
                 initiator role [This transition is done for 
               
               
                   
                 principal port only]. 
               
               
                 M3:M2 
                 EvtTO - same as M3:M1 (2) except port is not principal. 
               
               
                 M0:M5 
                 E_port goes OFFLINE 
               
               
                 M1:M4 
                 If none of the above events happens 
               
               
                 M2:M4 
                 If none of the above events happens 
               
               
                 M3:M4 
                 If none of the above events happens 
               
               
                 M4:M5 
                 EvtOffline, E_port went offline. 
               
               
                   
               
            
           
         
       
     
       FIG. 8  shows the state machine of the principle port of a merge Initiator. The associated Tables 5 and 6 show the states and events that cause transitions between the states. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Principle Initiator States 
               
            
           
           
               
               
               
            
               
                 Label 
                 State Name 
                 Description 
               
               
                   
               
               
                 IP0 
                 IPINITIALIZED 
                 Initiated as Principle Initiator E_port 
               
               
                 IP1 
                 CHKSUMSENT 
                 Sent Checksum request. 
               
               
                 IP2 
                 CACHEDSEND 
                 Send cached merge info. 
               
               
                 IP3 
                 RRESULTRECEIVED 
                 Remote merge result received. 
               
               
                 IP4 
                 MERGE2SENT 
                 MERGE request sent. 
               
               
                 M6 
                 SEGMENT 
                 Need to SEGMENT port. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Principle Initiator State Transitions 
               
            
           
           
               
               
            
               
                 Transition 
                   
               
               
                 (Start:End) 
                 Events (including conditions) 
               
               
                   
               
               
                 IP0:IP1 
                 Always 
               
               
                 IP1:M4 
                 Received ACCDONE response for checksum request 
               
               
                 IP1:IP2 
                 Received ACCCached response. 
               
               
                 IP1:IP3 
                 Received ACCResult response (refer R0:R1 in Table) 
               
               
                 IP1:IP4 
                 Received ACCMerge response 
               
               
                 IP2:M4 
                 Received ACCDone 
               
               
                 IP3:M4 
                 Always 
               
               
                 IP4:IP3 
                 Received ACCResult response. 
               
               
                 IP4:M6 
                 Received ACCSegment 
               
               
                 IP4:M3 
                 Received Reject Busy 
               
               
                   
               
            
           
         
       
     
       FIG. 9  shows the state machine of a non-principle port on an initiator. The associated Tables 7 and 8 lists the relevant states and events. 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 Non-Principle Initiator States 
               
            
           
           
               
               
               
            
               
                 Label 
                 State Name 
                 Description 
               
               
                   
               
               
                 INP0 
                 INPINITIALIZED 
                 Initiated as Non-Principle Initiator E_port 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Non-Principle Initiator State Transitions 
               
            
           
           
               
               
            
               
                 Transition 
                   
               
               
                 (Start:End) 
                 Events (including conditions) 
               
               
                   
               
               
                 INP0:M1 
                 EvtPRINCIPAL - this event is generated when the current 
               
               
                   
                 principle port goes OFFLINE and the dispatcher selects 
               
               
                   
                 current one as the new principal. 
               
               
                 INP1:M4 
                 EvtPORTDONE - this event is generated when the principal 
               
               
                   
                 port finishes the merge successfully. 
               
               
                 INP1:M6 
                 EvtSEGMENT- this event is generated when the principal 
               
               
                   
                 port finishes the merge with conflicts. 
               
               
                   
               
            
           
         
       
     
       FIG. 10  shows a merge receiver&#39;s state machine. The following Tables 9 and 10 list the states and events. 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 Receiver States 
               
            
           
           
               
               
               
            
               
                 Label 
                 State Name 
                 Description 
               
               
                   
               
               
                 R0 
                 RINITIATED 
                 Initialized as receiver. 
               
               
                 R1 
                 ACCRESULTSEND 
                 ACCResult response is sent to checksum 
               
               
                   
                   
                 request (to indicate merge result is 
               
               
                   
                   
                 cached and the initiator gets merge 
               
               
                   
                   
                 result directly). 
               
               
                 R2 
                 ACCMERGESEND 
                 ACCMerge response to checksum request 
               
               
                   
                   
                 indicates that a merge is necessary. 
               
               
                 R3 
                 ACCCACHEDSEND 
                 ACCCached response indicates that the 
               
               
                   
                   
                 initiator should send cached results. 
               
               
                 R4 
                 ACCDONESENT 
                 ACCDone response indicates that the 
               
               
                   
                   
                 merge is finished. 
               
               
                 R5 
                 ACCSEGMENTSEND 
                 ACCSegment response indicates that 
               
               
                   
                   
                 the merge resulted in a conflict. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                 Receiver State Transition 
               
            
           
           
               
               
            
               
                 Transition 
                   
               
               
                 (Start:End) 
                 Events (including conditions) 
               
               
                   
               
               
                 R0:R1 
                 Received CHECKSUM request, found remote config 
               
               
                   
                 matches local cached config. Send ACCRESULT 
               
               
                   
                 with merge results to initiator. 
               
               
                 R0:R2 
                 Received CHECKSUM request, found no checksum 
               
               
                   
                 match, a merge is needed. Sent ACCMERGESEND 
               
               
                   
                 response to initiator. 
               
               
                 R0:R3 
                 Received CHECKSUM request, found local config 
               
               
                   
                 matches initiator&#39;s cached config. Send 
               
               
                   
                 ACCCACHED to initiator, which sends cached 
               
               
                   
                 merge result. 
               
               
                 R0:R4 
                 Received CHECKSUM request, found 
               
               
                   
                 configurations are consistent. No merge needed. 
               
               
                 R2:R5 
                 Received MERGE request, the merge result is in 
               
               
                   
                 conflict. Need to segment. Send ACCSEGMENT 
               
               
                   
                 response to ask initiator to segment the port. 
               
               
                 R2:R1 
                 Received MERGE request, merge result is success. 
               
               
                   
                 Send result over to let initiator take result 
               
               
                   
                 and install it. 
               
               
                 R3:R4 
                 Received TAKECACHED and sent ACCDONE to 
               
               
                   
                 indicate merge is over. 
               
               
                 R4:M4 
                 Always 
               
               
                 R5:M4 
                 Always 
               
               
                 R1:M4 
                 Always 
               
               
                 R0:M2 
                 Same as M3:M2 
               
               
                 R0:M1 
                 Same as M3:M1 
               
               
                   
               
            
           
         
       
     
     Table 11 below further illustrates the benefits of implementing embodiments of the current invention. The benefits include the reduction of merge computation times, the traffic generated by the merge, the merge exchange times and the number of merge retries. 
                     TABLE 11                  Performance comparison                             Number of times merge   Number of merge exchanges           computing is performed   initiated                                     According   According to   According to   According to           to prior art   embodiments of   prior art   embodiments of       Scenario   operation   current invention   operation   current invention               Two Switches Join Together   2   1   2   1       New switch joins N chained switches   2 × N   1   2 × N   1       Core switch joins back to N   N + 1   1   2 × N   1       switch fabric with new config       New switch joins N switches in   Up to   1   Up to   1       a full mesh fabric   N(N + 1)       N(N + 1)                    
In the above Table 11, for the embodiments according to the current invention column, it is assumed that all of the optimizations described above are active. It is also noted that the values in the last row are for full payload merge exchanges.
 
     When the Fibre Channel network contains only a few switches (i.e. N in the above table is small), the delay and redundant operations due to the merge operation may not be significant, but once the number of switches increases, the deficiency will become significant quickly. As shown in the last row of Table 11, the number of merger operations could be proportional to the second order of the number of switches in the fabric. By employing the embodiments according to the current invention, the overhead operation and delay due to the merge operation are limited and do not increase at all when the number of switches in the network increases. The embodiments according to the current invention make the merge operation much more scalable. The deficiencies discovered by the current invention may not be appreciable when the number of network switches is small or static, as in many current networks. But when the number increases and/or the topology of the network changes frequently, the network overhead and delay caused by such deficiencies can increase dramatically. Such increase in overhead may overwhelm the entire network. By implementing the embodiments of the current invention, those deficiencies can be preempted. Therefore, the current invention greatly improves zone merge operation in a network. The current invention makes a network more robust for changes and/or expansions. 
     The above description of the embodiments of the current invention is focused on switches and ports within such switches, but the invention is applicable to any other network devices, as long as they are capable to communicate with other devices within the network. The device only needs to have a network interface to connect to another network device or a fabric. The deviceD  108  in  FIG. 5  shows the minimum necessary components in a network device to take advantage of the current invention. The device has a control module  158  to control, manage the network communication. The control module has access to a memory module  157  to store the device related information, such as zoning configuration  159 , past zone merge operations etc. When the device D  108  is connected to a fabric and needs to update its zone configuration with the rest of the fabric, it can go through the procedure as described above. The device D  108  may be an independent network device, or a component of a larger entity, such as a port on a switch. 
     The above description and examples are discussed using Fibre Channel networks. But the current invention is not limited to such networks. The current invention may be applied in any networks that incorporate zoning concepts and need to update the zoning configurations when the network topology changes. The current invention makes zoning configuration updates very efficient and very scalable. 
     While illustrative embodiments of the invention have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.