Abstract:
An electronic network filter for classified partitioning in an ATM network. The filter has a classified network buffer for identifying whether data is classified or unclassified to define invalid and valid data packets. Invalid data packets are dropped from the classified network buffer and valid data packets are sent to an unclassified network for testing without interrupting the operation of the classified network. In one embodiment, the classified network buffer is programmable to adapt to the continually changing requirements of classified networks.

Description:
GOVERNMENT INTEREST  
       [0001] This invention was developed under a United States government contract, number F29601-91-C-001 and the government may have certain rights to this invention. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates generally to an electronic network filter and more particularly to an electronic network filter for classified partitioning.  
         BACKGROUND OF THE INVENTION  
         [0003]    The Broadband Integrated Services Digital Network (BISDN) is serviced by Asynchronous Transfer mode (ATM) switching networks and is used in a variety of applications, which apply to both classified and unclassified ATM networks. Some applications, such as testing of software developments, require the connection of networks having different classification levels. Current requirements for connecting networks having differing classifications, dictated by the National Industrial Security Program Operating Manual (formerly the Department of Defense Industrial Security Manual for Safeguarding Classified Information), include the need to re-certify security on the network for any software changes. However, the extensive testing required for a developmental test would interrupt the network service. Additionally, the testing procedure may compromise the security of a classified network. These are unacceptable consequences of testing software updates for classified networks.  
           [0004]    There is a need for a secure method of changing and/or testing software changes on an electronic network, and particularly on a classified network that does not interfere with the operation of the network.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention is an electronic network filter for classified partitioning that does not require multiple re-certification leads and tests that are typically required for program software changes in a classified network. The present invention places all controlled software at a single node of a high-speed ATM network in a firmware format. The single node is not externally addressable and therefore, it is impossible to modify without access to the internal components of the network, thereby maintaining tight security. In addition, the filter allows the ATM network to function at full speed with negligible group delay.  
           [0006]    According to the present invention, a re-programmable filter, also called a Classified Network Buffer (CNB), is implemented on the ATM connection to an unclassified sub-network using a firmware filter on the ATM stream. A single node is established by the CNB. At this node, streaming data on the incoming ATM is examined for unclassified traffic and is passed to the output buffer and the remainder of the network. All other traffic is blocked. Incoming traffic, or unclassified network to classified network, is not modified unless desired.  
           [0007]    It is an object of the present invention to allow all controlled software to be placed at a single node of a high-speed ATM. It is a further object of the present invention to maintain tight security without unnecessarily delaying the high-speed ATM network. It is still a further object of the present invention to allow the network to function at full speed with negligible group delay.  
           [0008]    Other objects and advantages of the present invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    For a more complete understanding of this invention, reference should now be had to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention. In the drawings:  
         [0010]    [0010]FIG. 1 is a block diagram of a prior art high-speed ATM network;  
         [0011]    [0011]FIG. 2 is a block diagram of an ATM network having the filter of the present invention; and  
         [0012]    [0012]FIG. 3 is a flow chart of the method of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0013]    [0013]FIG. 1 is a block diagram of a prior art high-speed ATM network  10  having a classified network  20  and an unclassified network  30 . The classified network  20  has a network monitor  12  and a plurality of exchanges  14  each connected to a central ATM switch  16  in the ATM network  10 . The unclassified network  30  has a plurality of test systems  18  and a test data generation unit  22 . The unclassified network  30  can have any number of test systems,  1  through N test systems are shown in FIG. 1.  
         [0014]    When it becomes necessary to analyze data captured from the classified network  20  to the unclassified network  30 , a data filter  24  removes classified data and isolates a desired data file  26 . The file  26  is manually processed to move the data file from the classified network  20  to the unclassified network  30 . Data  28  is read from the file  26  and transferred to the test generation unit  22 .  
         [0015]    This process is extremely involved and requires a lot of processing time. The process of manually moving a data file from the classified network to the unclassified network is unacceptable for frequent software changes. The process must be capable of re-certification of security on the network every time a software change is tested and implemented, without adversely affecting subscribers on the network. Furthermore, the data must be closely monitored to prevent classified data from inadvertently being passed to the unclassified network.  
         [0016]    The present invention, shown in FIG. 2, has a classified network  20  having an ATM switch  16  connecting a plurality of exchanges  14 . According to the present invention, a re-programmable filter or Classified Network Buffer (CNB)  32  filters ATM packets having unclassified data and places them in the unclassified network  30 . The CNB  32  has hardware interfaces between the classified network  20  and the unclassified network  30  and has programmable firmware to perform the filter operations. This allows the CNB to be adjusted as needed for different applications without having to make significant hardware changes.  
         [0017]    Referring now to FIG. 3, the method  100  of the present invention will be described. The present invention is applicable to a User Datagram Protocol (UDP) system as well as a Transmission Control Protocol (TCP) system. In a UDP system an acknowledgement is not sent to the sender of the data. However, for a TCP system, an acknowledgment is sent to the sender. The flowchart of FIG. 3 is directed to both protocols.  
         [0018]    From the standpoint of sending data from the classified network to the unclassified network, ATM packets are received  102  by the CNB. For a TCP system  104 , an acknowledgement  106  is sent to the sender of the data. For either UDP or TCP, each ATM packet has a message identifier. These are examined  108  by the CNB to determined if the packet contains classified data. For example, the data is filtered for required sets of unclassified information destined for the unclassified sub-network. This aspect of the CNB is programmable firmware, which can be programmed for specific identifiers of classified data.  
         [0019]    When the CNB determines the packet contains classified data, the CNB goes on to either drop the data packet entirely, or make a determination  109  of which values in the data are classified. This is done in any one of several methods known to those of ordinary skill in the art. For example, an algorithm may be used. An alternative to the algorithm method is a look-up table stored in memory in the CNB. The CNB filtering process is done at a high enough speed, i.e. in embedded processing, to pass acceptable packets to the unclassified sub-network, or dropping the entire message if it does not meet the clearance requirements.  
         [0020]    A packet containing classified data, also called an invalid packet, is dropped entirely at this point. In the alternative, a packet having identified classified portions can be modified to disguise, or hide the classified portions before the packet is sent on to the unclassified network. A packet containing unclassified data, also called a valid packet, may be formatted before being sent on to the unclassified network. For example, an unclassified packet may be combined with other unclassified packets before being sent.  
         [0021]    Once the CNB determines the packet&#39;s contents, a validity check  110  is done to ensure the ATM packet being sent is a valid packet. A valid packet contains only unclassified data and/or classified data that has been reformatted by the CNB. Invalid ATM packets are dropped  112  by the CNB. Valid and reformatted, ATM packets are sent to the unclassified network  114  through hardware interface.  
         [0022]    Referring again to FIG. 2, the data sent to the unclassified network is tested by any number, N, of test systems. The advantage to the filter of the present invention is that the results of any tests performed in the unclassified network are sent and received in real time by the classified network.  
         [0023]    Referring back to FIG. 3, once the tests are complete, data that is representative of the test results as well as control signals and system operational protocol information is sent  116  from the unclassified network back to the CNB. Again it should be noted that in the case of TCP  122 , an acknowledgment  124  is sent to the sender of the data from the unclassified network.  
         [0024]    For security purposes, the data sent from the unclassified network to the classified network is formatted  118  by programmable firmware in the CNB before being sent  120  to the classified network in real time. For simple systems, this format change may be merely changing network formats. For example, one solution would be to change from TCP packet format to UDP packet format. More complex systems would require more significant security monitoring. For example, on an airborne laser network, the formats and content ranges are controlled by an error-handling system for a ground segment, which ultimately renders the system non-functional should classified data be placed in an unclassified ATM packet.  
         [0025]    The invention covers all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the appended claims.