Abstract:
A network gateway for time-critical and mission-critical networks is provided. The network gateway comprises a decision unit for determining, based on at least one network event; a processing unit for processing frames determined to be associated with the at least one service; a queue for buffering frames; and a traffic shaper for performing bandwidth management on frames stored in the queue.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of International Patent Application No. PCT/US2009/043887 filed on May 14, 2009, now pending; the International Patent Application claims the benefit of U.S. provisional application No. 61/060,270 filed on Jun. 10, 2008, the contents of which are herein incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates generally to data networks, and more particularly to network devices for allowing communications between ground and aerial data networks. 
       BACKGROUND OF THE INVENTION 
       [0003]    A transport control protocol (TCP) is used extensively by many of the network communication applications including, for example, the World Wide Web (WWW), e-mail, file transfer protocol (FTP), streaming media applications, and the like. The TCP is a reliable stream delivery service that guarantees to deliver a stream of data sent from one host to another without duplication or losing data. The TCP implements a positive acknowledgment technique that includes retransmission of packets to guarantee reliability of packet transfers. This technique requires the receiver to respond with an acknowledgment message as it receives the packet, when such message is not received within a predefine time window, the sender retransmits the packet. As the TCP is optimized for accurate delivery, the protocol sometimes incurs relatively long delays and extensive bandwidth usage. Therefore, the TCP is not particularly suitable for applications where real-time delivery is needed. 
         [0004]    A user datagram protocol (UDP) is usually utilized in applications require timely delivery. The UDP does not guarantee reliability or ordering of packets, thus packets (or datagrams) may arrive out of order, appear duplicated, or go missing without notice. The UDP is faster and less bandwidth consuming than the TCP as the overhead of checking when every packet actually arrives is eliminated. 
         [0005]    In the related art network devices (e.g., gateways, switches, routers, etc.) implementing network communication using either a UDP or a TCP, cannot provide efficient mechanisms to support communication over special-purpose time-critical and mission-critical networks where both timely and guaranteed delivery are essential. Typically, such networks are utilized in military applications, communication between ground and aerial devices, and so on. 
         [0006]    An example for a time-critical and mission-critical network is an IP military network that requires more complex architecture than a civilian IP network. At least the following factors contribute to this complexity: unstable end-to-end connectivity between a source device and a destination device in such a network: a limited bandwidth allowance per source and/or destination, a strict prioritization requirements, real-time requirements, and traffic and protocols restrictions because of special military network devices (e.g., gateways, encoders, firewalls, etc.). 
         [0007]    Furthermore, such networks demand to support non-compromised requirements, such as bandwidth management over limited bandwidth, quality of service per every packet, no latency, transparency, and so on. 
         [0008]    It would be therefore advantageous to provide a network device that can support the requirements of special-purpose data networks while being fully compliant standard network protocols and devices and fully transparent to other network entities. 
       SUMMARY OF THE INVENTION 
       [0009]    Certain embodiments of the invention include network gateway. The network gateway includes a decision unit for determining based on at least one network event if each frame of incoming frames is associated with at least one service; a processing unit for processing frames determined to be associated with the at least one service; a queue for buffering frames; and a traffic shaper for performing bandwidth management on frames stored in the queue. The network gateway is fully transparent to other network entities. 
         [0010]    Certain embodiments of the invention also include a method for enabling efficient data communication between a ground network and an aerial network. The method comprises transparently intercepting a frame flowing between the ground network and the aerial network; determining if at least one service is associated with an intercepted frame; processing the intercepted frame according to the at least one service being associated with the frame; and relaying the processed frame to a data link between the ground network and the aerial network. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings. 
           [0012]      FIG. 1  is a diagram of a data network used to describe the principles of the invention; 
           [0013]      FIG. 2  is a block diagram of the network gateway realized in accordance with an embodiment of the invention; 
           [0014]      FIG. 3  is an example for a service table constructed in accordance with an embodiment of the invention; and 
           [0015]      FIG. 4  is a flowchart describing the operation of the network gateway implemented in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    It is important to note that the embodiments disclosed by the invention are only examples of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of the present application do not necessarily limit any of the various claimed inventions. Moreover, some statements may apply to some inventive features but not to others. In general, unless otherwise indicated, singular elements may be in plural and vice versa with no loss of generality. In the drawings, like numerals refer to like parts through several views. 
         [0017]      FIG. 1  is an exemplary diagram of a data network  100  used to describe the principles of the invention. The network  100  includes sub-networks  110 - 1  and  110 - 2  connected through a data link  130 . Each of the sub-networks  110  include a network device  140  (e.g., a router, a switch, an airborne Ethernet switch, etc.) and a network gateway  150  constructed in accordance with certain embodiments of the invention. Each of the sub-networks  110  may be, for example, a local area network (LAN) and the data link  130  may be either a wireless link or a wired link adapted to carry UDP traffic. In a preferred embodiment the data link  130  is a wireless link connecting a ground sub-network  110 - 1  to an aerial sub-network  110 - 2 . An example for such configuration may be controlling of systems installed in unmanned aerial vehicles (UAV), air plans, etc. from a ground station. 
         [0018]    To enable reliable communication between the sub-networks  110 - 1  and  110 - 2 , the gateway  150  supports all the requirements of special purpose data networks which include, but are not limited to, bandwidth management, quality of service per every message, no latency, transparency, and so on. With this aim, the network gateway  150  is a transparent device that monitors traffic flows between the sub-networks  110 . Specifically, the network gateway  150  inspects the data frames flow between the sub-networks  110  and processes the frames based on predefined networks events. Acting as a transparent device, the network gateway  150  has no IP address that other network entities should address their frames to (an IP address may be used only for maintenance and configuration purposes). Network entities merely send frames to each other while the gateway  150  intercepts these frames at the data link layer. In certain embodiments of the invention the network gateway  150  may include the network device  140 . 
         [0019]      FIG. 2  shows an exemplary and non-limiting block diagram of the network gateway  150  implemented in accordance with an embodiment of the invention. The network gateway  150  includes a decision unit  210 , a processing unit  220 , a queue  230  and a traffic shaper  240 . The network gateway  150  inspects each incoming data frame, detects network events and determines based on the network events what type of services should be associated with the frames. A network event may be, for example, a predefined data pattern, a predefined frame sequence, a virtual channel, any combination of network addresses, and the like. A virtual channel carries traffic that always originates from the same source IP address and port number and directed to the same destination IP address and port number. That is, the virtual channel is defined as a combination of source/destination IP addresses and port numbers. The services that can be associated with a frame may include, but are not limited to, retransmission of the frames (i.e., guaranteed delivery), redirection of frames to one or more destinations, address resolution (e.g., acting as an ARP proxy), protocol conversion, bandwidth management, prioritization, encryption and decryption of data by implementing, for example, an IPSec protocol, signalling, alarming, and so on. The protocol conversion service enables converting an Internet protocol (IP) to legacy protocols, such as MIL-STD-1553, Hotlink; serial protocols, such as RS 485, RS 422, RS 235 and the like. In addition this service enables converting an analog video format to a digital format compliant with, for example, the H.264 and MPEG-4 formats. It is appreciated that the network gateway can be easily adapted to support other type of services and that the services listed above are merely examples. 
         [0020]    The decision unit  210  receives an incoming frame relayed by a network device  140  and determines if further processing is required for that frame. The decision is taken using a service table stored in the decision unit  210 . The table defines for each network event what should be the service(s) to be associated with frames comply with the detected event. An exemplary and non-limiting service table is provided in  FIG. 3 , where the network event is a virtual channel. Entries in the service table designated as “null” indicate that no processing is required on frames received on the respective virtual channels. Such frames are forwarded directly to the queue  230 . The service table is preconfigured and can be dynamically updated by a user (e.g., a system administrator). 
         [0021]    To ensure in order transmission of frames while the decision unit  210  evaluates a frame, no new frames are received. It is appreciated that the evaluation of frames includes a look-up table operation to locate the respective virtual channel entry, thus there is no latency involved with the operation of the decision unit  210 . 
         [0022]    Frames that should be processed are input to the processing unit  220 , which handles each frame according to the service(s) associated with the frames. Each service requires different handling by the processing unit  220 . For example, to guarantee reliable delivery a copy of the frame is retransmitted predefined number of times, redirection of a frame includes modifying the destination IP address and port number to specify the new destination, dropped frames are not transmitted, conversion of unicast frames to multicast frames, and prioritizing of frames by inserting “prioritized” frames into the head of the queue  230 . In fact, processed (non-prioritized) frames are saved in the queue  230  according to the order in which they were received. 
         [0023]    The traffic shaper  240  retrieves frames stored in the queue  230  and performs the task of bandwidth management to meet the available bandwidth on the data link  130 . Typically, traffic shaper  240 , buffers a set of frames, thereby imposing additional delay on those frames such that they conform to a predetermined constraint of the data link&#39;s  130  bandwidth. This ensures elimination of burst transmissions and transmitting data at a transfer rate which is no higher than the permitted rate. 
         [0024]      FIG. 4  shows an exemplary and non-limiting flowchart  400  describing the operation of the network gateway  150  provided in accordance with an embodiment of the invention. At S 410  a frame sent from a network device (e.g., device  140 ) is intercepted. At S 420 , a check is made to determine if one or more predefined services are associated with a frame. As mentioned above, the check is performed by matching a virtual channel of the frame and/or a network event against the service table. If S 420  results with a “yes” answer the execution continues with S 430 ; otherwise, the execution proceeds to S 440 . 
         [0025]    At S 430 , the frame is processed according to service(s) associated with the frame. The processing tasks include, but are not limited to, redirection of the frame, dropping the frame, prioritizing the frame, retransmission of the frame, protocol conversion and address resolution. In a preferred embodiment the processing further includes generating alarms and signalling the users based on detected network events through the processing step. For example, a network event may be a frame that matches a predefined sequence, thus if such a frame is detected an alarm may be generated. As another example, the gateway  150  may signal the user if a frame is sent to or from an unknown address, which is an address that is not configured in the gateway. At S 440 , bandwidth management is performed by shaping “processed” and “non-processed” frames. Thereafter, at S 450  frames are relayed to the data link  130 . 
         [0026]    The principles of the invention are implemented as any combination of hardware, firmware, and software. Moreover, the software is preferably implemented as an application program tangibly embodied on a program storage unit or computer readable medium. The application program may be uploaded to, and executed by, a machine comprising any suitable architecture. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units (“CPUs”), a memory, and input/output interfaces. The computer platform may also include an operating system and microinstruction code. The various processes and functions described herein may be either part of the microinstruction code or part of the application program, or any combination thereof, which may be executed by a CPU, whether or not such computer or processor is explicitly shown. In addition, various other peripheral units may be connected to the computer platform such as an additional data storage unit and a printing unit. Furthermore, a non-transitory computer readable medium is any computer readable medium except for a transitory propagating signal. 
         [0027]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.