System and method for selecting fibre channel switched fabric frame paths

Abstract

A system and method for measuring data transmission activity through a port of a switch device interconnecting nodes of a storage area network, the port transmitting data as words of predetermined length, one data word indicating idle port activity. The method includes steps of counting a number of transmitted words received from the port in a first counter device; and, for each word counted, comparing that word with a predetermined word indicating no (idle) port transmission activity. In response to the comparing, a number of matches are counted in a second counter device. In this manner, a ratio of a number of counted matches with a total amount of words counted indicates available bandwidth for transmitting additional data over that link. Preferably, this available bandwidth information is included in a link state record that the switch communicates to other switch devices interconnecting that link. Processing devices at the switches determine a link cost factor, based on the available bandwidth of that link and, in addition, the link speed, the cost factor being used to optimize path selection over links in the network according to a path routing algorithm.

1 . A system for optimizing data transmission activity through ports of a switch device interconnecting nodes of a network, the port transmitting data as words of predetermined length, one data word indicating idle port activity, said system comprising: 
 first counter means for counting a fixed amounts of transmitted words received from said port;    means for comparing each received word of said fixed amount with a predetermined word indicating said idle port transmission activity; and,    means for counting a number of matches in a second counter means,    a processing device for computing a ratio of a number of counted matches with said fixed amount of words counted, said ratio indicating available bandwidth for transmitting additional data through said port,    said processing device communicating said available bandwidth information to other switch devices to thereby optimize transmission of data through ports interconnecting said switch devices.    
   
   
       2 . The system as claimed in  claim 1 , wherein said network is a fiber channel network comprising switch devices interconnecting nodes by communication links, said links carrying data in serial form between switch devices in a switch fabric of said fiber channel network, said processing device further computing a cost of transmission over a link interconnecting said port in the network as a basis for determining transmission of data over a path including said interconnected link, 
 wherein said link cost considers a speed of said link and said available bandwidth information.    
   
   
       3 . The system as claimed in  claim 2 , wherein said data words are communicated over said link in serial form and received as a serial stream, said system further comprising: 
 a means for synchronizing receipt of said data words from said serial stream and generating a clock signal indicating receipt of a transmitted word in said serial stream; and,    a means for de-serializing said data stream and converting each received word to a parallel format.    
   
   
       4 . The system as claimed in  claim 2 , wherein said link cost forming a basis for routing data in said network is calculated according to: 
       Link Cost= S* ( n/ Baud Rate)  
     with S and n being pre-defined values, and Baud Rate indicating said link speed.  
   
   
       5 . The system as claimed in  claim 4 , wherein said ratio indicating available bandwidth for transmitting additional data through said port is defined as a variable w′ of byte length, said processing device further computing a used bandwidth, w, of a link according to: 
         w= 1− w′ /255.  
   
   
       6 . The system as claimed in  claim 5 , wherein said link cost forming a basis for routing data in said network is calculated according to: 
       Link Cost =S*w* ( n/ baud rate)  
     with S and n being pre-defined values, and Baud Rate indicating said link speed.  
   
   
       7 . The system as claimed in  claim 5 , wherein said processing device generates a Link State Record (LSR) for communicating said available bandwidth information to other switch devices in said network, said available bandwidth information inserted in said LSR as said byte W′.  
   
   
       8 . The system as claimed in  claim 7 , wherein said network implements a Fabric Shortest Path First algorithm for determining frame routing through said network based on link speed and said available bandwidth information provided in said LSR.  
   
   
       9 . A switch device for routing data over links interconnecting nodes of a network, each switch including a port interfaced to a link for communicating data along paths including one or more links in the network, each port transmitting data as words of predetermined length, one data word indicating idle port activity, the switch device comprising: 
 first counter means for counting a fixed amounts of transmitted words received from said port;    means for comparing each received word of said fixed amount with a predetermined word indicating said idle port transmission activity; and,    means for counting a number of matches in a second counter means,    a processing device for computing a ratio of a number of counted matches with said fixed amount of words counted, said ratio indicating available bandwidth for transmitting additional data through said port,    said processing device communicating said available bandwidth information to other switch devices to thereby optimize transmission of data through ports interconnecting said switch devices.    
   
   
       10 . The switch device as claimed in  claim 9 , wherein said network is a fiber channel network comprising switch devices interconnecting nodes by said links, said links carrying data in serial form between switch devices in a switch fabric of said fiber channel network, said processing device further computing a cost of transmission over a link interconnecting said port in the network as a basis for determining transmission of data over a path including said interconnected link, 
 wherein said link cost considers a speed of said link and said available bandwidth information.    
   
   
       11 . The switch device as claimed in  claim 10 , wherein said processing device calculates said link cost as: 
       Link Cost =S* ( n/ Baud Rate)  
     with S and n being pre-defined values, and Baud Rate indicating said link speed.  
   
   
       12 . The switch device as claimed in  claim 11 , wherein said ratio indicating available bandwidth for transmitting additional data through said port is defined as a variable w′ of byte length, said processing device farther computing a used bandwidth, w, of a link according to: 
         w= 1− w′/ 255.  
   
   
       13 . The switch device as claimed in  claim 12 , wherein said link cost forming a basis for routing data in said network is calculated according to: 
       Link Cost= S*w* ( n/ baud rate)  
     with S and n being pre-defined values, and Baud Rate indicating said link speed.  
   
   
       14 . The switch device as claimed in  claim 12 , wherein said processing device generates a Link State Record (LSR) for communicating said available bandwidth information to other switch devices in said network, said available bandwidth information inserted in said LSR as said byte w′.  
   
   
       15 . A storage area network comprising: 
 a plurality of network nodes each capable of receiving and transmitting data;    one or more switch devices for routing data over links interconnecting said nodes, each switch including a port interfaced to a link for communicating data along paths including one or more links in the network, each port transmitting data as words of predetermined length, one data word indicating idle port activity, wherein the switch device comprises: 
 first counter means for counting a fixed amounts of transmitted words received from said port;  
 means for comparing each received word of said fixed amount with a predetermined word indicating said idle port transmission activity; and,  
 means for counting a number of matches in a second counter means,  
 a processing device for computing a ratio of a number of counted matches with said fixed amount of words counted, said ratio indicating available bandwidth for transmitting additional data through said port, and said processing device communicating said available bandwidth information to other switch devices to thereby optimize path selection over links in the network according to a path routing algorithm.