Abstract:
A photonic-based distributed network switch and method where the switch is designed to reduce or filter optical data frames entering a port of the switch so that only data frames that are appropriate for the port are forwarded from the port. This reduces the amount of data that needs to be handled by the port interface, which is especially important where the port may be using legacy interface technology that may be incapable of handling the volume of data entering the port.

Description:
FIELD 
       [0001]    This disclosure relates to a photonic-based distributed network switch useable in a broadcast-based photonic network. 
       BACKGROUND 
       [0002]    Commercial-off-the-shelf switches in conventional networks perform receive channel data processing using a centralized algorithm method based on an application specific integrated circuit (ASIC), field programmable gate array (FPGA), and/or using software. 
       SUMMARY 
       [0003]    A photonic-based distributed network switch and method are described for processing of received multiplexed data-frame streams in a photonic-based distributed switch environment at photonic data rates. The switch is designed to reduce or filter optical data frames entering a port of the switch so that only data frames that are appropriate for the port are forwarded from the port. This reduces the amount of data that needs to be handled by the port interface, which is especially important where the port may be using legacy interface technology that may be incapable of handling the volume of data entering the port. 
         [0004]    In one embodiment, the photonic-based distributed network switch includes a passive optical star, and a plurality of independent ports connected to the optical star. Each port includes a data frame reduction stage that is configured to reduce optical data frames that enter the respective port. For each port, optical data frames that enter the respective port are directed to the data frame reduction stage for reducing the data frames. The optical data frames will typically come from the optical star which routes data frames entering each port to all of the other ports. However, the data frames to be reduced can come from an host external device that is connected to the port. In certain circumstances, depending upon the configuration of the data frame reduction stage, the data frames may not actually be reduced if the data frame reduction parameters of the data frame reduction stage are not met. 
         [0005]    In another embodiment, a photonic-based distributed network switch is provided that includes a passive optical star and a plurality of independent ports connected to the optical star. For each port, a plurality of optical data frames are directed from the passive optical star into the port. The plurality of data frames are directed to a data frame reduction stage in the port, and data frames that exit the data frame reduction stage are directed to an external device that is connected to the port. 
         [0006]    The reduction technique can occur on any flow of data in optical form going to and through the ports. In one example, the data flow takes the form of discrete data packets, each data packet being constructed by combining one or more data frames. Therefore, a data packet constructed from a single data frame could also be considered or referred to as a data frame. As used herein, unless otherwise specified or defined, the terms data packet and data frame are intended to refer generally to any discrete flow of data. The data flow could also be streamed. 
     
    
     
       DRAWINGS 
         [0007]      FIG. 1  illustrates a known photonic-based distributed network switch that can employ the methods described herein. 
           [0008]      FIG. 2  illustrates the operational concept of each of the ports and the passive optical broadcast star of the photonic-based distributed network switch of  FIG. 1 . 
           [0009]      FIG. 3  illustrates the concept of community of interest as applied to the photonic-based distributed network switch. 
           [0010]      FIG. 4  illustrates the concept of data frame reduction in the photonic-based distributed network switch. 
           [0011]      FIG. 5  illustrates an example of data frame reduction using exemplary reduction criteria. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]      FIG. 1  illustrates a known photonic-based distributed network switch  10 . The switch  10  includes a passive photonic or optical broadcast star  12 . A plurality of independent ports  14  are connected to and in communication with the passive broadcast star  12  to route data frames to and receive data frames from the star  12 . The data frames to and from the star  12  are optical data frames suitable for use in a photonic-based system that are multiplexed in a data frame stream.  FIG. 1  shows four ports  14  although a larger or smaller number of ports can be utilized. The ports  14  permit connection of the switch  10  to host external network-enabled devices  16 . The external devices  16  can be any network-enabled devices including, but not limited to, computers, network routers, network switches, storage units, printers, sensor systems, plotters, and wireless access points. 
         [0013]    The terms data packet and data frame are used herein interchangeably and are intended to refer generally to any discrete flow of data. A data packet can be constructed from a plurality of data frames, or from a single data frame in which case the data packet can also be referred to as a data frame. 
         [0014]    Data signals to and from the external devices  16  are in the form of digital signals, while the data signals in the switch  10  are in the form of analog optical signals. The conversion to/from digital signals from/to optical signals can occur in the ports  14  using suitable conversion techniques. The conversion of digital signals to/from optical signals is well known to those of ordinary skill in the art. 
         [0015]    With reference to  FIGS. 1 and 2 , the passive optical broadcast star  12  can be, for example, a passive device that contains only passive optical components and no electronics. The broadcast star  12  replicates all data frames received from a respective port  14  on a one-way incoming channel  18  from a respective port  14  onto multiple one-way outgoing channels  20 . In the illustrated example, there is one channel  18  going to the star  12  from each port  14 , and P channels from the star  12  to each port, with P being the total number of ports. A similar construction to that shown in  FIG. 2  is used for each port. The broadcast star  12  allows each port  14  to see all data frames for all ports  14 . Therefore, any data frame that comes into, for example, port  1  is automatically received by the ports  2 ,  3  and  4  via the star  12 . In addition, each port receives its own information back from the star  12 . 
         [0016]    The ports  14  include the interfaces and logic that actively process and forward data frames in and from the switch  10  and connect the switch to the external devices  16 . A two-way external channel  22  connects each port  14  to the external devices. The ports  14  operate independent of one another, with each port including the switching and protocol processing logic needed to perform network address resolution and data frame processing and forwarding. 
         [0017]    The external devices  16  can be connected to the ports  14  via conventional interface and protocol technology, including wireless and wired technologies. Examples of wired connection technologies include for example, but not limited to, Ethernet, RS-232, RS-422, and USB. Examples of wireless connection technologies include for example, but not limited to, radio frequency, infrared light, laser light, visible light, and other technologies that can transfer data frames without the use of wires. 
         [0018]    Any number of external devices can be connected to each port. In  FIG. 1 , three external devices (for example computers A, B, C) are shown connected to port  1 , two external devices (for example computers D and E) are connected to port  2 , two external devices (for example computers F and G) are connected to port  3 , and three external devices (for example computers H, I and J) are connected to port  4 . 
         [0019]    The general construction of the switch illustrated in  FIGS. 1 and 2  is known. However, because each port receives all data frames from other ports (and receives its own data frames) via the optical star  12 , each port may receive data frames that are not required by the port or do not need to be forwarded by the port to any external devices connected to that port. Therefore, each port  14  differs from conventional ports in that each port is provided with means to reduce or filter data frames entering the port by dropping certain data frames based on desired selection criteria, so that only data frames that are appropriate for the port are forwarded from the port. Although the description and drawings refer to reduction of data frames coming from the optical star, it is contemplated that reduction or filtering of data frames may also occur on data frames that enter each port from the external devices before the data frames are forwarded from the ports to the optical star for distribution to the other ports. 
         [0020]    The reduction means in each port includes one or more data frame reduction stages  30  ( FIG. 4 ) in each port that include decision logic that determines which data frames to drop and action logic that determine what to do with remaining data frames (i.e. data frames that are not dropped). 
         [0021]    Any criteria for determining which data frames to drop and which data frames to let through, and what to do with the remaining data frames, can be used. The selection criteria can be static or dynamically changing.  FIG. 3  illustrates one example of suitable selection criteria. In this example, the external devices are segregated into communities of interest (COI)  32 ,  34 . A COI is a segregation of network assets, in this case the external devices  16 , into discrete groups for some established purpose. 
         [0022]    An example of a reason for creating the COI&#39;s  32 ,  34  includes, but is not limited to, separating the external devices into different security classification levels. In this example, COI  32  and any data frames coming therefrom could have a security level of “classified” while COI  34  and any data frames coming therefrom have a security level of “unclassified”. The COI&#39;s  32 ,  34  need to be kept separated so that data frames from COI  32  are not provided to COI  34 , thereby preventing COI  34  from accessing classified data. For purposes of this example, it is assumed that one also wants to prevent data frames from COI  34  from being provided to COI  32 , even though data frames from COI  34  are unclassified. 
         [0023]    In the photonic-based distributed network switch  10 , segregation of the COI&#39;s  32 ,  34  is enforced by the ports  14 . The data frame reduction means in each port is designed to determine whether a data frame coming into the port from the optical star  12  is suitable for transmission to one or more of the external devices  16  connected to that port. In one exemplary implementation, using the data frame reduction means in each port, the ports  14  prevent data frames from the COI&#39;s  32  from being transmitted to the COI&#39;s  34 , and likewise prevent data frames from the COI&#39;s  34  from being transmitted to the COI&#39;s  32 . 
         [0024]      FIG. 4  illustrates the data frame reduction concept with respect to port  4  of the switch  10 . The other ports of the switch operate in a similar manner in that they are designed to reduce data frames. However, it is to be understood that the selection criteria used to determine reduction need not be the same in each port. 
         [0025]    As shown in  FIG. 4 , each port  14  includes a plurality of channel demultiplexers  40  that are connected to the optical star  12  via a respective one of the channels  20 . Each channel  20  includes one of the demultiplexers  40 . Each channel  20  carries a multiplexed optical data frame stream from the star  12  to the respective demultiplexer  40 . Each demultiplexer  40  separates the multiplexed data frames into individual data frames  42 . The data frames  42  are then provided to the data frame reduction stage(s)  30 . In the illustrated example, each reduction stage  30  includes data frame scheduling information  44  and a data frame scheduling approach  46  that process the data frames. 
         [0026]    The data frame scheduling information  44  can be thought of as a decision stage which defines the rules for how a data frame will be processed and includes decision logic that determines which data frames to drop. The scheduling information  44  can include any rules or selection criteria for allowing a decision to be made about whether or not a data frame  42  should be dropped. Examples of selection criteria include, but are not limited to, information relating to distribution or addressing of data frames from the respective port, such as COI membership, and/or media access control (MAC) addresses or internet protocol (IP) addresses of external devices connected to the port. 
         [0027]    The data frame scheduling approach  46  can be thought of as an action stage with action logic which defines how data frames that are not dropped will be forwarded to the external devices connected to the port. The scheduling approach  46  can include any criteria for defining how data frames will be forwarded. Examples of criteria include, but are not limited to: priority based forwarding; round-robin based forwarding (for example, channel  1  is processed first, channel  2  processed next, channel  3  next, etc.); queue based forwarding (i.e. first-come-first-served; for example, the first data frame to arrive gets processed first); and quality of service criteria such as assigning priorities to data based on applications, users, or data flows, or to provide a certain level of performance to a data flow, for example a predetermined bit rate, delay, jitter, packet dropping probability and/or bit error rate. 
         [0028]    If desired, the data frames can be passed to multiple reduction stages  30 .  FIG. 4  illustrates three (3) reduction stages  30  although a larger or smaller number of stages  30  can be used. The stages  30  can operate in series or sequentially, in parallel, or a combination of series and parallel. For example, in a series arrangement, all data frames can pass into a first reduction stage, and any data frames passing through the first reduction stage then pass into a second reduction stage, as shown in  FIG. 5 . Alternatively, all of the data frames  42  can be passed into a first reduction stage as well as passed into a second reduction stage operating in parallel to one another. There could be a reduction stage followed in series by two reduction stages operating in parallel, or two reduction stages operating in parallel followed in series by a one or more additional reduction stages. Any combination of reduction stages can be employed depending in part upon the amount and type of data frame reduction that is desired and the selection criteria being used. 
         [0029]    In addition, all data frames do not need to pass through each reduction stage. For example, some data frames passing through a first reduction stage could bypass a second reduction stage while other data frames passing through the first stage are passed into the second stage. 
         [0030]    Data frames  48  that make it through the data frame reduction stage(s)  30  flow to a port interface  50  and to the appropriate external device  16  over the channel  22 . The interface  50  can be conventional interface technology, for example, Ethernet. The interface  50  can send out the data frames immediately if its transmission rate is high enough, or it can buffer data frames before transmitting the data frames. 
         [0031]    To help better explain the concept of data frame reduction by the ports  14 , a specific example will be described with respect to the port  4  shown in  FIG. 5 . It is to be realized that the data frame reduction concept is not limited to the specific example described in  FIG. 5  and can be implemented in other manners. In addition, the other ports can have a similar construction to that shown in  FIG. 5 . 
         [0032]    In  FIG. 5 , two serial or sequential reduction stages are provided. One reduction stage  60  is a COI reduction stage that determines if the incoming data frame  42  is in a community of interest that the external device  16  connected to the interface  50  is a member of. If it is, the data frame  42  is passed through to a second reduction stage  62 . If not, the data frame  42  is dropped and does not pass through the reduction stage  60 . The reduction stage  62  is a local device stage that determines if the incoming data frame is for an external device  16  that is interfaced to the port. If so, the data frame is forwarded to the external device. If not, the data frame is dropped and does not pass through the stage  62 . 
         [0033]    The COI reduction stage  60  includes COI membership definitions  64  which define COI members that may be connected to the switch  10  and that form the selection criteria for determining whether or not an incoming data frame is in a community of interest that the local external device  16  is a member of. The COI reduction stage  60  also includes a COI scheduling approach  66  that defines how data frames belonging to the COI of interest will be forwarded to the COI. 
         [0034]    The local device stage  62  includes a local device port forwarding table  68  or other information related to the distribution or addressing of data frames from the port to the external devices  16 . The forwarding table can include any information that is used for distributing or addressing the data frames from the port to the external devices. Examples of information in the port forwarding table can include, but are not limited to, media access control (MAC) addresses or internet protocol (IP) addresses of the external devices, and local port identifiers. Further information on a port forwarding table in a photonic-based distributed network switch is disclosed in U.S. patent application Ser. No. ______, filed on ______, titled METHOD FOR UPDATING PORTS IN A PHOTONIC-BASED DISTRIBUTED NETWORK SWITCH (attorney docket 20057.0135US01). 
         [0035]    The local device stage  62  also includes a local device scheduling approach  70  that defines how data frames will be forwarded to the external devices connected to the port. For example, the scheduling approach  60  can define how the data frames are transmitted to each external device based on criteria including, but not limited to, for example how busy an external device is, whether an external device has priority over other external devices in the COI, the data transfer rate preferred by each external device, the current operational state of the external device, etc. 
         [0036]    As indicated above, while the data frames have been described and illustrated as coming from the optical star for transmission to the external devices, it is contemplated that the data frame reduction concepts described herein can be applied to data frames entering the ports from the external devices prior to being forwarded from the ports to the optical star. 
         [0037]    The examples disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.