Serial Communication Tapping and Transmission to Routable Networks

Abstract

Apparatuses and methods for tapping serial communications and transforming the serial data into a format appropriate for routable networks are significant for purposes of security and troubleshooting, especially in critical infrastructure networks. Communication taps should be completely passive such that any failure would not interrupt the serial communications. Furthermore, automatic determination of unspecified serial protocol frames allow general implementation across various networks, or across devices within a single network, without the need to customize for each implementation.

We claim: 
     
         1 . An apparatus to passively tap serial communications having serial protocol frames that are unspecified to the apparatus, the apparatus characterized by:
 Passive, serial-communications, interception circuitry comprising at least one serial communications pass-through and a processor, each serial communications pass-through connected to the processor and interfaced to a serial communication cable through which the serial communications are transmitted;   The processor executing programming to determine serial protocol frames according to characteristics of the serial communications, to wrap the serial protocol frames in a routable protocol, thereby forming a routable packet, and to transmit the routable packets to one or more routable addresses through an interface connecting the processor to a routable network.   
     
     
         2 . The apparatus of  claim 1 , wherein the pass-through comprises a pair of serial ports directly connected to the serial communication cable and wherein the passive, serial-communications, interception circuitry has an impedance greater than that of the serial communication cable. 
     
     
         3 . The apparatus of  claim 1 , wherein the pass-through comprises an inductive coupling. 
     
     
         4 . The apparatus of  claim 1 , wherein the pass-through comprises a capacitive coupling 
     
     
         5 . The apparatus of  claim 1 , wherein the characteristics of serial communications comprise timing-based signals, and the processing device executes further programming to associate timing gaps between the timing-based signals with frame edges that define the serial protocol frames. 
     
     
         6 . The apparatus of  claim 1 , wherein the characteristics of serial communications comprise frame synchronization delimiters and length fields and the processing device executes further programming to define the beginning and the length of serial protocol frames according to the frame synchronization delimiters and length fields, respectively. 
     
     
         7 . The apparatus of  claim 1 , wherein the characteristics of serial communications comprise frame synchronization delimiters and frame end delimiters and the processing device executes further programming to define the beginning and the end of serial protocol frames according to the frame synchronization delimiters and frame end delimiters, respectively. 
     
     
         8 . The apparatus of  claim 1 , wherein the characteristics of serial communications comprise time variance between signals and the processing device executes further programming to identify a baseline time gap in the signals and to define statistically significant deviations from the baseline time gap as the beginnings and the ends of serial protocol frames. 
     
     
         9 . The apparatus of  claim 1 , wherein the characteristics of serial communications comprise byte frequency and the processing device executes further programming to identify statistically significant occurrences of byte frequency patterns and to define the statistically significant occurrences with the beginnings and the ends of serial protocol frames. 
     
     
         10 . The apparatus of  claim 1 , wherein the characteristics of serial communications comprise byte frequency as well as time variance between signals and the processing device executes further programming to identify statistically significant occurrences of byte frequency patterns, to identify a baseline time gap in the signals, and to define statistically significant deviations from the baseline time gap combined with statistically significant occurrences of byte patterns as the beginnings and the ends of the serial protocol frames. 
     
     
         11 . The apparatus of  claim 1 , wherein the unspecified serial protocol frames are based on a process control serial protocol. 
     
     
         12 . The apparatus of  claim 1 , further comprising storage circuitry storing the programming, wherein the pass-through, the processor, the storage circuitry, and the interface are assembled as an embedded system. 
     
     
         13 . A method to passively tap serial communications, which have serial protocol frames that are unspecified, transmitted through a serial communication cable between a source and a receiver, the method executed by a processor and characterized by the steps of:
 Passively intercepting the serial communications through a serial communications pass-through connected to the processor and to the serial communication cable;   Determining serial protocol frames according to characteristics of the serial communications;   Forming routable packets by wrapping the serial protocol frames in a routable protocol; and   Transmitting the routable packets to one or more routable addresses through an interface connecting the processor to a routable network.   
     
     
         14 . The method of  claim 13 , wherein the characteristics of serial communications comprise timing-based signals, and said determining comprises associating timing gaps between the timing-based signals with frame edges that define the serial protocol frames. 
     
     
         15 . The method of  claim 13 , wherein the characteristics of serial communications comprise frame synchronization delimiters and length fields and said determining comprises defining the beginning and the length of serial protocol frames according to the frame synchronization delimiters and length fields, respectively. 
     
     
         16 . The method of  claim 13 , wherein the characteristics of serial communications comprise frame synchronization delimiters and frame end delimiters and said determining comprises defining the beginning and the end of serial protocol frames according to the frame synchronization delimiters and frame end delimiters, respectively. 
     
     
         17 . The method of  claim 13 , wherein the characteristics of serial communications comprise time variance between signals and said determining comprises to identifying a baseline time gap in the signals and defining statistically significant deviations from the baseline time gap as the beginnings and the ends of serial protocol frames. 
     
     
         18 . The method of  claim 13 , wherein the characteristics of serial communications comprise byte frequency and said determining comprises identifying statistically significant occurrences of byte frequency patterns and defining the occurrences of byte frequency patterns with the beginnings and the ends of serial protocol frames. 
     
     
         19 . The method of  claim 13 , wherein the characteristics of serial communications comprise byte frequency as well as time variance between signals and said determining comprises identifying statistically significant occurrences of byte frequency patterns, identifying a baseline time gap in the signals, and defining statistically significant deviations from the baseline time gap combined with statistically significant occurrences of byte patterns as the beginnings and the ends of the serial protocol frames. 
     
     
         20 . The method of  claim 13 , wherein the unspecified serial protocol frames are based on a process control serial protocol.