Abstract:
Methods for managing an optical network through out-of-band communication between optical transceiver modules in a heterogeneous network fabric are disclosed. The disclosed methods include methods for performing fabric discovery, communicating error messages, detecting intrusion. Methods are also disclosed for communicating between transceivers of differing protocol versions and memory capacity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of the following applications, which are hereby incorporated by reference: U.S. patent application Ser. No. 11/134,786 filed May 20, 2005; U.S. patent application Ser. No. 11/204,920 filed Aug. 15, 2005; U.S. patent application Ser. No. 11/344,883 filed Feb. 3, 2006; U.S. patent application Ser. No. 11/348,745 filed Feb. 7, 2006; U.S. patent application Ser. No. 11/279,360 filed Apr. 11, 2006; U.S. patent application Ser. No. 11/413,829 filed Apr. 28, 2006; U.S. patent application Ser. No. 11/537,602 filed Sep. 29, 2006; U.S. patent application Ser. No. 11/537,590 filed Sep. 29, 2006; U.S. patent application Ser. No. 11/537,599 filed Sep. 29, 2006; U.S. patent application Ser. No. 11/537,595 filed Sep. 29, 2006; U.S. patent application Ser. No. 11/685,548 filed Mar. 13, 2007; U.S. patent application Ser. No. 11/685,551 filed Mar. 13, 2007; and U.S. patent application Ser. No. 11/744,591 filed May 4, 2007. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. The Field of the Invention 
         [0003]    The present invention relates to systems and methods for out-of-band communication across optical transceiver modules of a network fabric. 
         [0004]    2. The Relevant Technology 
         [0005]    In modern networks, network devices such as switches, routers, host bus adapters (HBA), servers, and the like, are coupled to one another by means of fiber optic transceivers. Many transceivers are “active,” meaning that they have memory and processing capabilities. U.S. patent application Ser. No. 11/070,757, filed Mar. 2, 2005, which is hereby incorporated by reference, discloses systems and methods by which transceiver modules communicate with one another independently of the network device from which they receive data. The &#39;757 application discloses a system wherein an optical transceiver module modulates the peak or average power of a transmitted signal at a low frequency in order to transmit module specific data out of the frequency band carrying the network data transmitted by the module. A receiving module demodulates the out-of-band data by tracking modulation of the peak or average power of the received signal. 
         [0006]    In a typical network, components are not all updated or replaced simultaneously. Both new and old components must therefore be able to communicate with one another even though older components may not be updated. Some transceivers have firmware that may be reprogrammed to facilitate communication with newer modules. However, it is not convenient to update each transceiver in a network each time a newer module is installed. Furthermore, older transceivers have physical limitations, such as a smaller memory, lower processing speed, and less sophisticated optics that cannot be readily updated. 
         [0007]    In view of the foregoing, it would be an advancement in the art to provide systems and methods for enabling out-of-band communication across a heterogeneous fiber optic network including transceiver modules of differing capabilities. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    In one aspect of the invention, communication between transceiver modules having a memory defining a number of tables each having a size and offset address includes determining a table and offset address for requested data according to a table size of an originating module. A system address corresponding to the table and offset address is generated and a read command having a command type indicating a system address size, the system address, a length of the requested data, and a contingency field storing the table size of the originating module is transmitted to a receiving module. The receiving module regenerates the table and offset address from the system address and the table size stored in the contingency field. If the table size stored in the contingency field is the same as a table size of the receiving module, then data having the length of the requested data stored at an address corresponding to the table and offset address is transmitting to the receiving module. If the table size stored in the contingency field is not the same as the table size of the receiving module, data having a length different from the requested length from a table of the receiving module having a table number corresponding to the regenerated table and offset address is transmitted. 
         [0009]    In another aspect of the invention, the receiving module evaluates whether it has sufficient memory to return data having the length of requested data beginning at the regenerated table and offset address, and, if not, evaluating an extended contingency field. If the extended contingency field does not contain an instruction not to truncate, the receiving module transmits to the originating module data beginning at the regenerated table and offset address having a length less than the length of requested data. 
         [0010]    In another aspect of the invention, communication between the originating and receiving modules occurs in an out-of-band optical channel. 
         [0011]    In another aspect of the invention a method for discovering a network fabric includes transmitting a first knock knock command from the transmit port of a first transceiver module of a plurality of transceiver modules having receive ports and transmit ports. If a response to the first knock knock command is received at the receive port of the first transceiver module, then the first transceiver records an indicator that it is in a point-to-point network. If a response to the first knock knock command is not received at the receive port of the first transceiver module, then it sends a second knock knock command containing an instruction to forward the second knock knock command N times, where N is greater than 1. If a response to the second knock knock command is received at the receive port of the first transceiver module, then the first transceiver module an indicator that it is in a ring network having N layers. 
         [0012]    if a response to the second knock knock command is not received at the receive port of the first transceiver module, then it sends a plurality of subsequent knock knock commands each containing an instruction to forward, wherein each subsequent knock knock command instructs a receiving transceiver module to forward the subsequent knock knock command M times, where M is the number of times the previous knock knock command of the subsequent knock knock commands instructs the receiving transceiver module to forward the subsequent knock knock command plus an increment value. If a response to one of the subsequent knock knock commands is received, then the first transceiver module records an indicator that the first transceiver module is in a ring network having M layers. If a response to one of the subsequent knock knock commands having a value of M greater than a maximum value is not received, then the first transceiver module records an indicator that the first transceiver module is not in a ring or point-to-point network. 
         [0013]    These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
           [0015]      FIG. 1  illustrates a schematic block diagram of in-band and out-of-band links transceiver modules hosted by network devices in accordance with an embodiment of the present; 
           [0016]      FIG. 2  is a schematic block diagram of a ring network; 
           [0017]      FIG. 3  is a schematic block diagram of a star network; 
           [0018]      FIG. 4  is a schematic block diagram of a network fabric; 
           [0019]      FIG. 5  is a process flow diagram of a method for discovering module connections in accordance with an embodiment of the present invention; 
           [0020]      FIG. 6  is a process flow diagram of a method for reading and writing data between dissimilar transceivers in accordance with an embodiment of the present invention; 
           [0021]      FIG. 7  is a process flow diagram of a method for suppressing error message traffic in accordance with an embodiment of the present invention; 
           [0022]      FIG. 8  is a process flow diagram of a method for discovering a network configuration in accordance with an embodiment of the present invention; and 
           [0023]      FIG. 9  is a process flow diagram of a method for detecting network intrusions in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    Referring to  FIG. 1 , a network  10  includes a number of network devices  12   a ,  12   b . The network devices may be embodied as workstations, servers, switches, routers, host bus adapters, or the like. Transceiver modules  14   a ,  14   b  are coupled to each network device  12   a ,  12   b  and received network data  16  by means of a data channel  18 . In the illustrated embodiment, the transceiver modules  14   a ,  14   b  are optical transceivers including a transmitter optical subassembly (TOSA) and a receiver optical subassembly (ROSA). The transceiver modules  14   a ,  14   b  may conform to any industry standard form factor such as SFP, XFP, X2, XPAK, or XENPAK. 
         [0025]    The transceiver modules  14   a ,  14   b  store module data  20  that includes diagnostic and operational data that is used by the modules  14   a ,  14   b  to control parameters governing the transmission of data over an optical fiber, such as output power, carrier frequency, bit period, duty cycle, rise time, fall time and the like. Module data  20  may include data relating to receiving of data over an optical fiber such as eye profile, eye mask parameters, threshold, sensitivity, and the like. The module data  20  may include diagnostic data regarding itself and another module  14   a ,  14   b  to which it is connected. Such data may include the received power, recovered clock frequency, bit error rate, or the like, of a received signal. The diagnostic data may include self diagnostic data such as the results of self-tests of a module component such as a laser. 
         [0026]    The modules  14   a ,  14   b  are coupled to one another by a data channel  22  and an out-of-band (OOB) channel  24 . In a preferred embodiment, the data channel  22  and OOB channel  24  include the same physical medium, such as an optical fiber. For example, the data channel  22  may include high frequency modulation of an optical signal transmitted over an optical fiber whereas the OOB channel  24  includes low frequency modulation of the power envelope of the same optical signal, such as is disclosed in U.S. patent application Ser. No. 11/070,757, which is incorporated herein by reference. In other embodiments, the data channel  22  includes optical signals transmitted over an optical fiber or wire whereas the OOB channel  24  includes a radio frequency (RF) channel. 
         [0027]    The network data  16  is transmitted over the data channel  22  by the transceiver modules  14   a ,  14   b . Diagnostic and configuration data included in the module data  20  are communicated to other transceiver modules  14   a ,  14   b  in the OOB channel  24 . However, in some embodiments, both diagnostic and configuration and network data are transmitted over the same data channel  22 . For purposes of this disclosure all communication over an OOB channel  24  may also take place over the in-band data channel  22 . OOB channel  24  may also carry instructions from a transceiver  14   a  to a transceiver  14   b . For example, U.S. application Ser. No. 11/966,646 discloses a test transceiver that communicates with a corrective transceiver to generate network errors for diagnostic purposes. Communication between the test transceiver and corrective transceiver in the abovereferenced application may occur in the OOB channel  24 . For example, the test transceiver may instruct the corrective transceiver not to correct for errors that the test transceiver introduces into the data channel  22 . In other applications a transceiver  14   a  may instruct a transceiver  14   b  by means of the OOB channel  24  to encrypt data in the data channel  22 . 
         [0028]    Examples of systems that may use an OOB channel  24  to transmit diagnostic and configuration information include those disclosed in U.S. patent application Ser. No. 11/134,786 filed May 20, 2005; U.S. patent application Ser. No. 11/204,920 filed Aug. 15, 2005; U.S. patent application Ser. No. 11/344,883 filed Feb. 3, 2006; U.S. patent application Ser. No. 11/348,745 filed Feb. 7, 2006; U.S. patent application Ser. No. 11/279,360 filed Apr. 11, 2006; U.S. patent application Ser. No. 11/413,829 filed Apr. 28, 2006; U.S. patent application Ser. No. 11/537,602 filed Sep. 29, 2006; U.S. patent application Ser. No. 11/537,590 filed Sep. 29, 2006; U.S. patent application Ser. No. 11/537,599 filed Sep. 29, 2006; U.S. patent application Ser. No. 11/537,595 filed Sep. 29, 2006; U.S. patent application Ser. No. 11/685,548 filed Mar. 13, 2007; U.S. patent application Ser. No. 11/685,551 filed Mar. 13, 2007; and U.S. patent application Ser. No. 11/744,591 filed May 4, 2007. 
         [0029]    Referring to  FIG. 2 , the network  10  may have a “ring” configuration, in which the transmit port  26  of a transceiver module  14   a , for example, is coupled to the receive port  28  of a transceiver module  14   d  and the receive port  28  of the transceiver module  14   a  is coupled to the transmit port  26  of a transceiver module  14   b . In this manner, data must be circulated through a number of intervening transceiver modules  14   a - 14   d  before reaching a destination module  14   a - 14   d . For example, in order to transmit data from transceiver module  14   a  to transceiver module  14   b , the data must be transmitted through modules  14   d  and  14   c.    
         [0030]    Referring to  FIG. 3 , in some embodiments, the network  10  may have a “star” configuration, in which both the transmit port  26  and receive port  28  of each transceiver  14   a - 14   d  is coupled to a corresponding transmit port  26  and receive port  28  of a hub  30 . The hub  30  routes signals to the receive port  26  of the destination network device  14   a - 14   d . In this manner, data needs to travel through at most one other device before reaching a destination device  14   a - 14   d.    
         [0031]    Referring to  FIG. 4 , in some embodiments, a network  10  is arranged in layers in which a network device  12   a  of layer  0  includes a plurality of modules  14   a - 14   c  each coupled to modules  14   a - 14   c  of network devices  12   b - 12   c  in layer  1 . The network devices  12   b - 12   c  further include modules  14   a - 14   c  that are part of layer  2  coupled to modules  14   a - 14   c  of network devices  12   d - 12   f  defining a layer  3 , and so on. It is readily apparent that some network devices include modules  14   a - 14   c  belonging to two different layers. The network devices  12   a - 12   c  may control routing of data through the network. For example, the network devices  12   a - 12   h  may be embodied as routers or switches for directing network traffic. 
         [0032]    In some embodiments, modules  14   a - 14   c  in a first layer are able to communicate with modules  14   a - 14   c  of a second layer that are coupled to the same network device  12   a - 12   f  by means of a host bridge  32 . The host bridge transfers module data  20  from one module  14   a - 14   c  to another, in the same or a different layer, that are coupled to the same network device  12   a - 12   f . In some embodiments, a module  14   a - 14   c  may set a bit in data output to the network device  12   a - 12   f  to which it is coupled indicating that it has module data  20  to transmit to another module  14   a - 14   c . The network  12   a - 12   f  may then read the module data  20  and transfer it to another module  14   a - 14   c  coupled thereto. The network device  12   a - 12   f  may transfer the data by setting a bit in data provided to the destination module  14   a - 14   c  indicating that module data  24  is available to be input to the destination module  14   a - 14   c . The destination module  14   a - 14   c  may then store data received as module data  20 , rather than transmitting it over the data channel  18 . 
         [0033]    Communications between modules  14   a - 14   c  included in any of the foregoing, and other, network configurations may follow a protocol accommodating different capacities of modules  14   a - 14   c . Communications may include packets of data having fields described in Table 1, below. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Data Packet Field Definitions 
               
             
          
           
               
                 Field 
                 Bits 
                 Description 
               
               
                   
               
               
                 Preamble 
                 8 
                 To inform other device that something will be sent 
               
               
                 Lock 
                 3 
                 To allow other device to lock on start of sequence 
               
               
                 Communication Type 
                 8 
                 0x01 = Knock Knock 
               
               
                 (CT) 
                   
                 0x02 = Acknowledge 
               
               
                   
                   
                 0x03 = Command/system address = 16 bits 
               
               
                   
                   
                 0x04 = Response 16 bits 
               
               
                   
                   
                 0x05 = Communication Corrupted 
               
               
                   
                   
                 0x06 = Communications stopped 
               
               
                   
                   
                 0x07 = Command/system address = 32 bits 
               
               
                   
                   
                 [0x08-0x0F = cross fabric communications for ring 
               
               
                   
                   
                 or star networks] 
               
               
                   
                   
                 0x051 = Mass Error Alert (See FIG. 7) 
               
               
                 Communication 
                 8 
                 Originator creates this starting as a random number. 
               
               
                 ID (C-ID 
                   
                 Respondent returns this same number. Originator 
               
               
                   
                   
                 increments number for each next communication it 
               
               
                   
                   
                 originates 
               
               
                 Sync 
                 8 
                 Alternate bits (01010101) to verify that no bits have 
               
               
                   
                   
                 been dropped such that data is now in the wrong 
               
               
                   
                   
                 place 
               
               
                 Command ID 
                 8 
                 See Table 2 
               
               
                 (CMD) 
               
               
                 System Address 
                 Depends 
                 CT = 0x03 -- 16bits 
               
               
                   
                 on CT 
                 CT = 0x07 -- 32 bites 
               
               
                 Length 
                 Depends 
                 CT = 0x00 -- 0x10 
               
               
                   
                 on CT 
                 CT = 0x0A through 0x FF -- Not yet defined 
               
               
                 Data Bytes 
                 Depends 
               
               
                   
                 on 
               
               
                   
                 Length 
               
               
                 Sync 
                 8 
                 Alternate bits to verify that no bits have been 
               
               
                   
                   
                 dropped such that data is now in the wrong place 
               
               
                   
                   
                 (01010101) 
               
               
                 Status/ 
                 16  
                 Status of response 0x0000 - OK 
               
               
                 Contingency 
                   
                 Other Values - error type 
               
               
                 Extended Status/ 
                 16  
                 Extended status of response. 
               
               
                 Contingency 
                   
                 Meaning of value depends on Status (error 
               
               
                   
                   
                 messages, version information, contingency 
               
               
                   
                   
                 instructions,) 
               
               
                 Wrapper Count 
                 16  
                 Wrapper = Number of Communication IDs 
               
               
                 (WC)/Layer 
                   
                 included in wrapper when communicating across a 
               
               
                   
                   
                 network fabric 
               
               
                   
                   
                 Layers = a layer count incremented for each layer 
               
               
                   
                   
                 across which the data packet is transmitted. May be 
               
               
                   
                   
                 negative depending on the location of module 
               
               
                   
                   
                 originating a data packet in relation to the module 
               
               
                   
                   
                 that initiated communication. 
               
               
                 Wrappers/Layers 
                 (depends 
                 Wrappers = Communication IDs are placed in this 
               
               
                   
                 on WC) 
                 field as a data packet is passed along the fabric, 
               
               
                   
                   
                 creating a trail describing the network. 
               
               
                   
                   
                 Layer = depends on layer of originating module. 
               
               
                   
                   
                 The layer field does not change as the data packet is 
               
               
                   
                   
                 forward along the fabric. Layer may be negative 
               
               
                   
                   
                 where the module originating the message has a 
               
               
                   
                   
                 lower layer number than the module that initiated 
               
               
                   
                   
                 communication. 
               
               
                 Communication 
                 3 
                 Signals communication is over 
               
               
                 Complete 
               
               
                   
               
             
          
         
       
     
         [0034]    The Preamble field contains a sequence of bits that communicate to a receiving transceiver that a data packet is being sent. The Preamble field may be any sequence of bits that serves this function. The Lock field includes a sequence of bits enabling a receiving transceiver to lock onto the start of the sequence. The Lock field may enable the receiving transceiver to recognize the starting bit of the data packet. The Lock field may also enable a clock data recovery (CDR) circuit to generate a clock signal synchronous with bit transitions within data packet. 
         [0035]    Sync Fields are provided at one, two, or more positions within the packet. The Sync Fields may include alternating bits, i.e., 10101010, to enable the receiving transceiver to evaluate whether received bits are properly positioned. For example, if the receiver had shifted one bit position out of synchronization, then evaluation of the Sync Fields would enable detection and correction of the error. The final field of the data packet may be a Communication Complete Field, which contains a data code indicating to the transceiver that the complete data packet has been received. 
         [0036]    The Communication Type field defines how subsequent fields of the data packet will be interpreted. In particular, the number of fields in the packet may be different depending on the Communication Type field. 
         [0037]    In a first example, the Communication Type field defines the number of bits that are used to define the address field in a read or write command. As noted in Table 1, where the Communication Type field is equal to 0x03, a following Command/System Address field has a length of 16 bits. When the Communication Type field is equal to 0x07, a following Command/System Address field has a length of 32 bits. Other values for the Communication Type field may define other lengths for the Command/System Address field. 
         [0038]    In some embodiments, the Communication Type field also communicates information to set up and provide feedback regarding a connection between transceivers. For example, a value of 0x01 may indicate that a data packet is a Knock Knock command instructing the receiving transceiver to respond with a packet having a Communication Type field equal to 0x02, which corresponds to an Acknowledge message. 
         [0039]    In some embodiments a value of 0x05 indicates that communication between the transceivers has become corrupted and a value of 0x06 indicates that communication has stopped. The definitions for values of the Communication Type field are exemplary and may be assigned arbitrarily. 
         [0040]    The Communication ID field identifies the data packet. Upon generating a data packet, the sending transceiver will insert a random string of bits in the Communication ID field. The receiving transceiver will use the same Communication ID in its response. The sending transceiver may then increment the Communication ID and use the incremented value in the next communication. In some embodiments, the value for the initial Communication ID is taken from the transceivers “live data” which refers to measured parameters regarding optical data transmitted from and received by the transceiver, such as output power, received power, temperature, and the like. 
         [0041]    The communication identifier used by the requestor can also be used as an encryption seed for a command or response to a communication in addition to public and private keys known to the transmitting and receiving module. For a subsequent command or response the encryption seed may be based on the next random Communication identifier. The random number may be seeded by a byte of the live data, which tends to be random. 
         [0042]    Exemplary values for the Command Identifier field are summarized in Table 2. As is apparent in Table 2, the function associated with values of the Command Identifier field is dependent on the value of the Command Type field. The function and number of subsequent fields in the data packet may be dependent on the Command Type and Command Identifier fields. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Command Descriptions 
               
             
          
           
               
                 Communication 
                   
                   
                   
               
               
                 Type 
                 Command 
                 Description 
                 Fields 
               
               
                   
               
               
                 0x01 
                 0x00 
                 Knock knock 
                 C-ID/Sync/CMD/status/extended 
               
               
                   
                   
                   
                 status/checksum/communication 
               
               
                   
                   
                   
                 complete 
               
               
                 0x01 
                 0x01 
                 Knock knock 
                 C-ID/Sync/CMD/status/extended 
               
               
                   
                   
                   
                 status/layer 
               
               
                   
                   
                   
                 count/layer/checksum/communication 
               
               
                   
                   
                   
                 complete 
               
               
                 0x02 
                 0x00 
                 Acknowledge 
                 C-ID/Sync/CMD/status/extended 
               
               
                   
                   
                   
                 status/checksum/communication 
               
               
                   
                   
                   
                 complete 
               
               
                 0x02 
                 0x01 
                 Acknowledge 
                 C-ID/Sync/CMD/status/extended 
               
               
                   
                   
                   
                 status/layer count/layer/ 
               
               
                   
                   
                   
                 checksum/communication complete 
               
               
                 0x03 
                 0x01 
                 Read request 
                 C-ID/sync/CMD/system address 16 
               
               
                   
                   
                   
                 bits/length/sync/ 
               
               
                   
                   
                   
                 contingency/extended 
               
               
                   
                   
                   
                 contingency/checksum/ 
               
               
                   
                   
                   
                 communication complete 
               
               
                 0x03 
                 0x02 
                 Write request 
                 C-ID/synclCMD/system address 16 
               
               
                   
                   
                   
                 bits/length/data 
               
               
                   
                   
                   
                 bytes/sync/contingency/extended 
               
               
                   
                   
                   
                 contingency/checksum/ 
               
               
                   
                   
                   
                 communication complete 
               
               
                 0x04 
                 0x01 
                 Read response 
                 C-ID/sync/CMD/system address 16 
               
               
                   
                   
                   
                 bits/length/data bytes/sync/status/ 
               
               
                   
                   
                   
                 extended status/checksum/ 
               
               
                   
                   
                   
                 communication complete 
               
               
                 0x04 
                 0x02 
                 Write response 
                 C-ID/sync/CMD/system address 16 
               
               
                   
                   
                   
                 bits/length/sync/status/extended 
               
               
                   
                   
                   
                 status/checksum/communication 
               
               
                   
                   
                   
                 complete 
               
               
                 0x05 
                 0x00 
                 Sync byte out of 
                 C-ID/sync/CMD/status/extended 
               
               
                   
                   
                 place 
                 status/checksum/communication 
               
               
                   
                   
                   
                 complete 
               
               
                 0x05 
                 0x01 
                 Checksum 
                 C-ID/sync/CMD/status/extended 
               
               
                   
                   
                 problem 
                 status/checksum/communication 
               
               
                   
                   
                   
                 complete 
               
               
                 0x06 
                 0x00 
                 Not receiving 
                 C-ID/sync/CMD/status/extended 
               
               
                   
                   
                 out-of-band 
                 status/checksum/communication 
               
               
                   
                   
                   
                 complete 
               
               
                 0x06 
                 0x01 
                 Not receiving 
                 C-ID/sync/CMD/status/extended 
               
               
                   
                   
                 data 
                 status/checksum/communication 
               
               
                   
                   
                   
                 complete 
               
               
                 0x07 
                 0x01 
                 Read request 
                 C-ID/sync/CMD/system address 32 
               
               
                   
                   
                   
                 bits/length/sync 
               
               
                   
                   
                   
                 contingency/extended 
               
               
                   
                   
                   
                 contingency/checksum/communication 
               
               
                   
                   
                   
                 complete 
               
               
                 0x07 
                 0x02 
                 Write request 
                 C-ID/sync/CMD/system address 32 
               
               
                   
                   
                   
                 bits/length/sync/contingency/extended 
               
               
                   
                   
                   
                 contingency/checksum/communication 
               
               
                   
                   
                   
                 complete 
               
               
                 0x08 
                 0x01 
                 Read Response 
                 C-ID/sync/CMD/system address 32 
               
               
                   
                   
                   
                 bits/length/data 
               
               
                   
                   
                   
                 bytes/sync/status/extended 
               
               
                   
                   
                   
                 status/checksum/communication 
               
               
                   
                   
                   
                 complete 
               
               
                 0x08 
                 0x02 
                 Write Response 
                 C-ID/sync/CMD/system address 32 
               
               
                   
                   
                   
                 bits/length/sync/status/extended 
               
               
                   
                   
                   
                 status/checksum/communication 
               
               
                   
                   
                   
                 complete 
               
               
                   
               
             
          
         
       
     
         [0043]    Referring to  FIG. 5 , a method  40  may be used for initiating communication between a transmitting module and a receiving module. The method  40  may include evaluating whether a Knock Knock message has been received recently at step  42 . If so, in order to prevent a storm of Knock Knock messages, the transmitting module may suppress sending of a Knock Knock command for a waiting period at step  44 . Step  42  may then be repeated. If at step  42  no Knock Knock message has been received, step  46  may be executed by transmitting a Knock Knock message to the receiving module. Step  46  may include transmitting a Knock Knock message directly to the receiving module without any instruction to pass it on to another module. For the example commands of Table 2, this may be accomplished by transmitting a data packet having CT=0x01 and CMD=0x00. 
         [0044]    At step  48 , the method  40  includes evaluating at the transmitting module whether a response has been received at the receiving module. A response may include an Acknowledge message including data packet having CT=0x02 and CMD=0x00 as illustrated in Table 2. If a response is received at step  48 , then the network type is point-to-point wherein the transmitter and receiver of the transmitting module are coupled to the receiver and transmitter, respectively of the receiving module. Step  50  may therefore include recording this fact within the transmitting module, such as by setting a Network Type variable or setting to a value corresponding to a point-to-point network, such as a value for a layer count of the network equal to 1 or 0 indicating a point to point connection. 
         [0045]    If no response is received at step  48 , then step  52  is performed, which includes sending a Knock Knock message that instructs the receiving module to retransmit the message. The Knock Knock message may further instruct N subsequent receiving modules to retransmit the message. For example, the transmitting module may transmit a message having CT=0x01 and CMD=0x01. As noted in Table 2, this command includes Layer Count and Layer fields. The Layer field may indicate the number of times that the message is to be re-transmitted. The Layer count may indicate to a receiving module how many times the message has already been retransmitted. The receiving module, and any subsequent receiving module, may then compare the Layer Count to the Layer field, if the layer count is less than the layer field, then the module will increment the layer count and retransmit the message. Step  52  may include setting the Layer field to an initial value N, such as 10, or some other value. 
         [0046]    In some embodiments, the Layer Count and Layer field relate to Wrappers, rather than layers. For some communications, a receiving module will generate a data packet, or wrapper, having a received data packet embedded therein, such as in the Data field. In such embodiments, the Layer Count field indicates the number of wrappers in the data packet. In such instances the Layer field indicates the number of wrappers at which the original data packet has reached its destination. In some embodiments, the wrappers may be used to conduct fabric discovery as each intervening module that receives a discovery request adds a wrapper that may include a unique Communication ID, and perhaps other data such as the live data of the intervening module. The final wrapper will therefore contain data from each of the intervening modules. Alternatively, wrappers may consist only in addition of a module identifier or communication ID into the wrapper field. A module forwarding a data packet with a wrapper may also increment the wrapper count field. 
         [0047]    Step  54  may include evaluating at the original transmitting module whether a response has been received. The response may include one of the Acknowledge messages outlined in Table 2. A response may be received from a transceiver having its transmit port coupled to the receiver port of the original transmitting module. 
         [0048]    If a response is received at step  54 , then the network is a ring network wherein the transmitter and receiver of the transmitting module are coupled to the receiver and transmitter of different modules, such as is illustrated in  FIG. 2 . Step  56  may therefore include recording this fact within the transmitting module, such as by setting a Network Type variable or setting to a value corresponding to a ring network. Step  56  may also include noting that the number of layers in the ring network is equal to the value of the Layer field in the Knock Knock message sent in the last iteration of step  52 . 
         [0049]    If no response has been received at step  54 , then step  58  may be performed which includes comparing the value of the layer field from step  52  (or previous iteration of step  64  described below) to determine whether it exceeds an L MAX  value. If it does, then step  60  includes recording within the original transmitting module that the network is a star type. 
         [0050]    If the value of the layer field from step  52  (or a previous iteration of step  64  described below) does not equal or exceed the L MAX  value, then the layer field is incremented by an increment amount D, such as 1, 5, 10, or some other value at step  62 . Inasmuch as a ring networks typically do not have more than twenty layers, L MAX  may be equal to 20 in some embodiments. At step  64 , another Knock Knock message is transmitted having the Layer field equal to the incremented value calculated at step  62 . Step  54  may then be repeated. 
         [0051]    In many networks, transceiver modules are replaced one at a time as they begin to fail. Accordingly, newer transceivers will often be required to communicate with older transceivers with less functionality. Accordingly, the method  70  of  FIG. 6  may be used to accommodate such differences. 
         [0052]    In typical transceiver modules, data is accessed with reference to a table number and a position or “offset” within the table corresponding to the table number. The size of each table may vary depending on the amount of memory in the module and the standard or “multi-source agreement” (MSA) with which it complies. As standards develop, the type of data stored in each table may be augmented, but previously defined table locations are maintained the same. Accordingly, as table sizes increase, the initial storage locations in each table may conform to previous standards, whereas subsequent table locations contain other types of data defined by newer standards. Methods in accordance with embodiments of the present invention accommodate such table/offset standards, but are capable of use in the absence of such standards. 
         [0053]    In one embodiment, the method  70  includes determining at  72  by a transmitting module the table/offset address of data that the transmitting module intends to write to or request from a receiving module as defined by a standard with which the transmitting programmed has been programmed to comply. 
         [0054]    At step  74 , the transmitting module translates the table/offset address into a system address. The division of transceiver memory into tables is typically logical and the data is actually stored in random access memory embodied as an undifferentiated array of memory locations 0-N. Accordingly, the table/offset address may be mapped to a specific memory location referred to as a system address. For example, where a transceiver has tables of 256 bytes, table 0/offset  124 , may be mapped to system address  124 , whereas table 1/offset  124  may be mapped to system address  380 . 
         [0055]    At step  76 , a Read or Write request is transmitted to a receiving module. The request may include data packet having CT=0x03 and CMD=0x01 (16 bit read request), CT=0x03 and CMD=0x02 (16 bit write request), CT=0x07 and CMD=0x01 (32 bit read request), CT=0x07 and CMD=0x02 (32 bit write request) as defined by Table 2. The request may also include some other Read or Write request that define layer and layer count fields in order to address a transceiver other than to which the transmitting receiver is immediately coupled. 
         [0056]    A read request preferably includes a Command Type (CT) field that defines the system address length (e.g. 16 or 32 bits). The read request may also indicate the system address calculated at step  74  in the System Address field and the length of requested data in the Length field. In some embodiments of the invention, the read request also stores the table size of the transmitting module in the Status/Contingency field. A write request may additionally include data stored in the Data field to be written in the memory of the receiving module. In a write request, the Length field may refer to the number of bytes included in the Data field, or the number of address locations occupied by the data included in the Data field 
         [0057]    At step  78 , the read or write request is received. At step  80 , the receiving module evaluates whether it recognizes the Command Type field. Where the receiving module is older than the transmitting module, the Command Type field may not be recognized. If the command type is not recognized, then step  82  may be executed, which include sending an error message, which may be embodied as a data packet having the Extended Status field storing an identifier of the protocol version of the receiving module. On receiving the error message the original transmitting module may transmit subsequent Read and Write requests that conform to the protocol indicated in the error message. 
         [0058]    If the command type is recognized, then step  84  may be executed, which includes determining whether the table size stored in the Status/Contingency field of the read or write request is the same as that of the receiving module. If they are the same, then the method  70  may include sending the data stored at the system address of the receiving module indicated in a read request or writing data to the system address indicated in a write request at step  86 . 
         [0059]    If the table sizes are not the same, then at step  88  the system address of the read or write request may be translated into a table and offset of the transmitting module using the table size stored in the Contingency field of the read or write request. At step  90 , the receiving module evaluates whether it has sufficient memory to read or write the amount of data specified in the Length field beginning at the table/offset determined at step  88 . If it does, then the requested data may be transmitted to the transmitting module or written to the memory of the receiving module at step  86 . 
         [0060]    If the receiving module is found not to have sufficient memory, then the Extended Contingency field of the read or write request may be examined at step  92 . If the Extended Contingency field contains a value instructing the receiving module not to truncate its response, then an error message is sent at step  94  with an Extended Status field storing the table size of the receiving module. If the Extended Contingency field does not instruct the receiving module not to truncate its response, then the value of the Length field of the read or write request is truncated at step  96  and the truncated amount of data is either transmitted to the original transmitting module or written to the receiving module at step  98  according to the table/offset calculated at step  88 . Step  98  may include transmitting a Write Response or Read Response (see Table 2) having an Extended Status field storing the table size of the receiving module. In some embodiments, where the receiving module has a larger memory or at least a larger table size, the receiving module will analyze the table size in a received read or write request and transmit only data in tables up to the table size of the transmitting module to the receiving module. For example, if the transmitting module has a table size of 128 and the receiving module has a table size of 256, then the receiving module may respond to a request for data in table 1, for example, by sending only 128 bytes of data therefrom. 
         [0061]    Referring to  FIG. 7 , in some embodiments a network device  12   a - 12   b  may cooperate with a plurality of transceiver modules  14   a - 14   b  coupled thereto to control the amount of out-of-band data transmitted across the network fabric according to a method  100 . At step  102  a first transceiver module receives an error message from another transceiver module in the fabric. At step  104 , the first transceiver module examines the Command Type field of the error message. If the Command Type is a value corresponding to a high priority error, designated here as RED ALERT, then the first transceiver module suppresses any error messages for a wait period at step  106 . 
         [0062]    If the error message is found not to be a RED ALERT, then the first transceiver module notifies the host network device to which it is immediately coupled that it has an error message to transmit at step  108 . At step  110 , the host network device evaluates whether other transceiver modules to which it is immediately coupled have provided notice of pending error messages. If so, then the host network device instructs the first transceiver module to suppress the error message at step  112  for a wait period. If not, then the host network device instructs the first transceiver module to transmit the error message at step  114 . The first transceiver module then transmits the error message at step  116 . 
         [0063]    Referring to  FIG. 8 , while referring again to  FIG. 4 , the host network devices  12   a - 12   f  may facilitate discovery of the fabric layout according to a method  118  in order to facilitate out-of-band communication between transceiver modules  14   a - 14   c  of different layers. In some embodiments, one of the network devices, such as network device  12   a  may be designated a listening portal to which fabric layout information will be transmitted. 
         [0064]    The method  118  may include evaluating at step  120  at an individual transceiver module whether a discovery request has been received from another transceiver module. If so, then the individual transceiver module may suppress discovery requests indefinitely, or for a wait period, at step  122  in order to avoid generating undue chatter. If a discovery request has not been received, then at step  124 , the individual transceiver module will discover modules to which it is connected. Step  124  may include sending Knock Knock messages according to the method of  FIG. 5 . The individual transceiver module may then evaluate responses to determine which transceiver modules it is connected to. Step  124  may include sending a message instructing other modules to add a wrapper and/or other data to the message and retransmit, such that when a response circulates back to the individual transceiver module over a ring network, for example, it will contain data regarding all intervening modules. Step  124  may include discovery conducted without involvement of any network devices hosting the modules. 
         [0065]    At step  126 , the individual transceiver module transmits a discovery request to the network device to which it is immediately coupled. At step  128 , the individual transceiver module also transmits connection information determined at step  124  to its host network device. At step  130 , the host network device transmits a fabric discovery request to other network devices. The request may be transmitted in-band rather than out-of-band. Upon receiving the discovery requests, the other network devices may transmit discovery requests to transceiver modules that they host at step  132 . In response to step  132 , the transceiver modules will discover out-of-band module connections at step  134 , such as by sending Knock Knock messages according to the method of  FIG. 5  or as described with respect to step  124  and evaluating responses to determine which transceiver modules it is connected to. 
         [0066]    At step  136 , the transceiver modules of steps  132  and  134  will transmit the connection information from step  134  to the host network device to which they are immediately coupled. At step  138 , the network devices transmit the connection information collected at step  136  to the listening portal. At step  140 , the listening portal assembles the information transmitted from the network devices during step  138  into a description of the network fabric. At step  142 , the listening portal broadcasts the fabric description to the network devices. Step  142  may include transmitting the data in-band rather than out-of-band. At step  144 , each network device may transfer all or part of the fabric description to transceiver modules that it hosts. 
         [0067]    Referring to  FIG. 9 , while also referring to  FIG. 4 , in some embodiments, communication in an OOB channel  24  may be used to detect unauthorized intrusion in a network. For example, a tap may be placed on an optical link  150  between transceiver module  14   c  of layer  2  hosted by network device  12   c  and the transceiver module  14   b  of layer  3  hosted by network device  12   g . Alternatively, one of the modules  14   c  and  14   b  coupled to link  150  may be replaced by an unauthorized transceiver. 
         [0068]    Accordingly, the method  152  of  FIG. 9  may be used to detect the intrusion and reroute data, such as over link  154  between module  14   a  of layer  2  hosted by network device  12   c  and module  14   b  of layer  3  hosted by network device  12   e.    
         [0069]    At step  156 , the method  152  includes evaluating whether a break in communication in the OOB channel has occurred. If so, then one or both of the modules  14   c  and  14   b  coupled to link  150  will notify the listening portal  12   a  of the breach at step  158 . Notification may include providing notice to one or both of the network devices  12   c  and  12   g  of the breach, which may then provide notice to the listening portal  12   a  either through the data channel  22  or the OOB channel through one of the other modules hosted by the network devices  12   c  and  12   g.    
         [0070]    At step  160 , the method includes evaluating whether a transient interruption in the optical connection between a transmitting module and a receiving module has occurred. If not, communication of data continues at step  162 . If so, then step  164  includes evaluating whether an input to the transmitting module was interrupted. If so, then transmission continues at step  166 . If not, then step  168  includes evaluating whether a drop in received optical power followed the transient interruption. If not, then transmission continues at step  166 . If so, then step  170  includes evaluating whether the transmitting module has reduced its transmit power, such as by inquiring over the OOB channel  24  whether a drop has occurred. If so, then transmission of data continues at step  162 . If not, then step  172  includes the transmitting module raising its output power by X decibels. At step  174 , the receiving module evaluates whether more than Y % of the X decibel increase has been detected. The transmitting module may communicate the value of X to the receiving module by means of the OOB channel  24 . The value of Y may be 90, 80, or some other value. If more than Y % of the X decibel increase is detected, than at step  162 , data transmission continues. If not, then at step  176 , the receiving module notifies its host network device that a security breach has occurred. At step  178 , the network device hosting the receiving module takes steps necessary to route data through an alternate link. For example, if link  150  is found to be compromised, data may be routed through link  154  instead. At step  180 , the transmitting and receiving module may begin to either encrypt data communicated therebetween or send random data. At step  182  a listening portal may be notified of the security breach by one or both of the network devices hosting the transmitting and receiving modules. 
         [0071]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.