Abstract:
A communications device and method for effectively managing bandwidth within a telecommunications network carrying both time division multiplexed signals as well as data signals. The communications device having dialable TDM/cell and/or packet-based bandwidth management capability so that a network operator can select to manage bandwidth for any particular signal on in STS, VT, or cell or packet basis.

Description:
[0001]    The present invention relates generally to a network element for use in a telecommunications network in which the bandwidth utilized by various signals is dialably managed so as to improve efficiency. This management is selectively performed on an STS, VT, or data cell or packet basis.  
         BACKGROUND ART  
         [0002]    Network elements that manage bandwidth to improve efficiency exist, such as SONET add/drop multiplexers and SONET cross connects. However, such devices traditionally manage bandwidth at a STS or a virtual tributary (VT) level. In recent years, more and more data services are being added to telecommunications networks. As data services are added to telecommunications networks, the need for more efficient use of bandwidth by data services will grow. However, the need for efficient use of bandwidth by synchronous time division multiplexed (TDM) signals will remain. Thus, there is a need for products that address the changing the telecommunications environment by permitting network operators to efficiently and dialably manage bandwidth utilized by both traditional TDM signals and data signals, such as ATM traffic.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention provides an apparatus and method for efficiently managing bandwidth in a telecommunications network carrying both TDM services and data services. By efficiently managing bandwidth, network operators are able to save money on capital expenditures for equipment and thereby keep operating costs down. In the highly competitive telecommunications services arena, this provides network operators with a competitive advantage.  
           [0004]    An embodiment of the present invention provides a network element that is outfitted to accept signals from a telecommunications network. The signals are then routed to an STS selector that routes the signals to a bandwidth management device. The bandwidth management device for each signal being dialably selectable by a network operator. The bandwidth management devices include a device for managing signals on an STS level, on a VT level, and on a data packet or cell level. For simplicity purposes, the word cell, as used hereinafter, shall be understood to mean cell or packet, as the principles of the present invention are as easily applicable to packet-based signals as they are to cell-based signals.  
           [0005]    An embodiment of the present invention provides a network element for managing bandwidth capable of circuit-based multiplexing at and STS-n and a VT-n level and capable of cell-based multiplexing.  
           [0006]    An embodiment of the present invention provides that the device for managing signals at a cell level, manages both the virtual channel and virtual path of ATM cells.  
           [0007]    It is thus an object of present invention to selectively and effectively manage bandwidth utilized within telecommunications networks having both circuit-based and cell-based traffic.  
           [0008]    It is a further object of an embodiment of the present invention to selectively and effectively manage bandwidth utilized within a telecommunications network having both TDM and ATM signals.  
           [0009]    It is a further object of an embodiment of the present invention to selectively and effectively manage bandwidth at an STS level, at a VT level, or at a virtual channel and virtual path level. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    These and other objects and advantages of the present invention will become more apparent and more readily appreciated by reference to the description of the preferred embodiments, taken in conjunction with the accompanying drawings, of which:  
         [0011]    [0011]FIG. 1 is a block diagram of a network element according to an embodiment of the present invention.  
         [0012]    [0012]FIG. 2 is a more detailed block diagram of a network element according to an embodiment of the present invention.  
         [0013]    [0013]FIG. 3 is an example of traffic flow through the network element depicted in FIG. 2.  
         [0014]    [0014]FIG. 4 is a block diagram of a network element according to another embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0015]    The present invention will be better understood by reference to the accompanying drawings.  
         [0016]    [0016]FIG. 1 depicts a network element  11  according to an embodiment of the present invention, equipped to accept various types of signals. For instance, a DS 1 signal from the telecommunications network (not shown) can be accepted into network element  11  through input interface  12 , a DS 3 signal from the telecommunications network can be accepted into network element  11  through input interface  13 , an OC-n signal from the telecommunications network can be accepted into network element  11  through input interface  14 , and a data signal, from a LAN for instance, can be accepted into network element  11  through input interface  15 . Preferably, each of the interface cards  12  through  15  is be outfitted so as to be capable of receiving different types of signals. The signals accepted from the telecommunications network on input interfaces  12  through  15  are then built up into STS-n signals, such as STS-1s, and passed from the input interfaces  12  through  15  to STS selector  23 . STS selector  23  then the routes each of the STS-n signals it receives from input interfaces  12  through  15  to STS time slot interchanger  20 , VT time slot interchanger  21  or data switch  22  respectively. It should be noted that STS selector  23  may also multiplex and/or demultiplex STS-n signals to other STS rates prior to routing them for ease of transport within the network element  11 .  
         [0017]    By use of a user interface  25 , a network operator is able to select or dial, preferably for each individual STS-1 contained within the STS-n signals entering the STS selector  23 , how the STS-n signals from the input interfaces  12  through  15  are routed by STS selector  23 . The selection process is preferably implemented through software, although it may be performed through hardware, such as switches or relays, or through firmware. It should be noted that the selection process could be done in a manner that is automated, rather than a having a network operator make the selection. Further, in the case where a network operator is making the selection, it need not be on a real-time basis.  
         [0018]    For STS signals that are routed to STS time slot interchanger  20  by STS selector  23 , STS time slot interchanger  20  manages their bandwidth on an STS level, preferably on an STS-1 level. For implementations where the incoming signals are STS-n rates of higher than STS-1s, the management may be at any STS-n rate up to the lowest rate of an incoming signal into STS time slot interchanger  20 .  
         [0019]    For STS-n signals that are routed to VT time slot interchanger  21  by STS selector  23 , VT time slot interchanger  21  manages their bandwidth on a VT-n level, preferably a VT-1 level.  
         [0020]    For STS-n signals that are routed to data switch  22  by STS selector  23 , data switch  22  manages bandwidth on a cell level. Should data switch  22  be an ATM switch, it should preferably manage both the virtual channel and virtual path of each cell.  
         [0021]    STS time slot interchanger  20 , VT time slot interchanger  21  and data switch  22  then send managed signals built back up into STS-n signals, to STS distributor  24 . STS distributor  24  then distributes the signals to the appropriate output interfaces  16  through  19 . Output interfaces  16  through  19  then pass the outgoing signals back out to the network. The outgoing signals from the output interfaces  16  through  19  can be of any type, but preferably of an OC-n type.  
         [0022]    [0022]FIG. 2 depicts a more detailed view of STS selector  23 , STS distributor  24  and their interworkings with STS time slot interchanger  20 , VT time slot interchanger  21  and data switch  22  according to an embodiment of the present invention. For sake of simplicity, redundant components are not shown.  
         [0023]    As can be seen in FIG. 2, signals coming into STS selector  23  enter APS (Automatic Protection Switching) selector  26 . In an arrangement where redundant components are being used, APS selector  26  selects the signals received from those interfaces that are active. APS selector  26  may also demultiplex any higher rate STS-n signals it receives so that all STS-n signals it passes on will be of the same rate. Preferably, this is an STS-1 rate. APS selector  26  then provides the signals to a 1:2 bridge  27 . The 1:2 bridge  27  provides selective connectivity between the signals received from APS selector  26  and STS time slot interchanger  20  or time slot interchanger  28 . For instance, if the network operator has dialed a certain STS-1 signal to be managed on an STS basis, 1:2 bridge  27  will provide connectivity between APS selector  26  and STS time slot interchanger  20 . If the network operator has dialed the certain STS-1 signal to be managed on a VT or a cell basis, 1:2 bridge  27  will provide connectivity between APS selector  26  and time slot interchanger  28 .  
         [0024]    For the signals provided to time slot interchanger  28 , time slot interchanger  28  outputs two sets of signals (preferably STS-1 signals) to Vx director  29 . The first set of signals being those for which the network operator has dialed to be managed on a VT basis and the second set being those for which the network operator has dialed to be managed on a cell basis. Vx director  29  preferably multiplexes the incoming STS-1 signals to be managed on a VT basis into higher rate STS-n signals, such as STS-12 signals, and provides them to VT time slot interchanger  21 . Vx director  29  preferably multiplexes the incoming STS-1 signals to be managed on a cell basis into higher rate STS-n signals and provides them to data switch  22 . It should be noted that Vx director may pass the signals on without multiplexing them into higher rate signals or the signals may be passed directly from time slot interchanger  28  on to VT time slot interchanger  21  and/or data switch  22 .  
         [0025]    Vx distributor may also make copies of the incoming signals and provide them to a spare VT time slot interchanger and data switch (not shown).  
         [0026]    As described above, VT time slot interchanger  21  manages the bandwidth of signals entering it on a VT basis and data switch  22  manages the bandwidth of signals entering it on a cell basis.  
         [0027]    Both data switch  22  and VT time slot interchanger  21  pass managed signals at STS-n rates such as STS-12s on to Vx selector  30 . If an active/spare arrangement is utilized, Vx selector  30  will select the signals from the active data switch  22  and VT time slot interchanger  21  to pass on to time slot interchanger  31 . Additionally, if Vx distributor  29  multiplexed the signals it accepted, Vx selector  30  will demultiplex them back into the STS-n rates equivalent to those that entered the Vx distributor  29 , such as STS-1s.  
         [0028]    Time slot interchanger  31  reassembles the signals received from Vx selector  30  back into the appropriate arrangement to match that of the signals received at the inputs to time slot interchanger  28 . Thus, time slot interchanger  31  undoes the arranging of the signals that was performed to route the signals to either VT time slot interchanger  21  or data switch  22 . Time slot interchanger  31  then provides these signals to 2:1 selector  32 .  
         [0029]    As discussed above, STS time slot interchanger  20  manages the signals it receives (from 1:2 bridge  27 ) on an STS level. It provides managed signals to 2:1 selector  32 .  
         [0030]    2:1 selector  32  then selects the appropriate input line to be passed on to the APS distributor  33  based upon whether the bandwidth was to be managed at a STS level, a VT level or a data cell level. The 2:1 selector then provides connectivity between the appropriate input line and APS distributor  33 .  
         [0031]    In an active/spare arrangement, APS distributor  33  will provide the output signals to the active output interfaces. If any output interfaces are of a higher data rate than that of the signals received by APS distributor  33 , APS distributor  33  may multiplex them up to the requisite rates.  
         [0032]    An example of traffic flow through a network element according to an embodiment of the present invention as depicted in FIG. 2 is shown in FIG. 3. In this example, input signals  41  and  43  are to be managed on a data cell level input signals  42  and  45  are to be managed on a STS level and input signals  44  in  46  are to be managed on a VT level.  
         [0033]    Input signals  41  and  43  are both routed to APS selector  26 . As these are active signals, APS selector routes them on to 1:2 bridge  27 . Because a network operator has dialed these signals to be managed on a data cell level, incoming signals  41  and  43  are connected to time slot interchanger  28  by 1:2 bridge  27 . Time slot interchanger  28  then switches incoming signals  41  and  43  so as to route them to data switch  22  and provides incoming signals  41  and  43  to Vx distributor  29 . Vx distributor  29  copies incoming signals  41  and  43  and provides the signals to both data switch  22  and a spare data switch (not shown). Data switch  22  then manages the bandwidth within the incoming signals  41  and  43  and passes managed signals out to Vx selector  30 . Vx selector selects the managed signals  41 ′ and  43 ′ from active data switch  22  and provides them to time slot interchanger  31 . Time slot interchanger  31  then routes the managed signals  41 ′ and  43 ′ to 2:1 selector  32 . Because input signals  41  and  43  were to be managed on a data cell basis, 2:1 selector passes managed signals  41 ′ and  43 ′ on to APS distributor  33 . APS distributor passes managed signals  41 ′ and  43 ′ out to the appropriate active output interfaces (not shown).  
         [0034]    The data flow for input signals  42  and  45  is somewhat different. Because they are to be managed on an STS level, input signals  42  and  45  are input to the APS selector  26 . As input signals  42  and  45  are on active input interfaces, APS selector  26  passes them onto 1:2 bridge  27 . 1:2 bridge  27  then provides connectivity for input signals  42  and  45  to time slot interchanger  20 . Time slot interchanger  20  then manages the bandwidth on an STS level and passes the managed signals  42 ′ and  45 ′ onto 2:1 selector  32 . 2:1 selector  32  provides connectivity between STS time slot interchanger  20  and APS distributor  33  for managed signals  42 ′ and  45 ′ because they were to be managed at an STS level. APS distributor  33  outputs managed signals  42 ′ and  45 ′ to the appropriate active output interfaces.  
         [0035]    The data flow for input signals  44  and  46  is also different. Input signals  44  and  46  are passed to APS selector  26 . As these are active signals, APS selector routes them on to 1:2 bridge  27 . Because they are to be managed on a VT level, 1:2 bridge  27  provides connectivity for incoming signals  44  and  46  to time slot interchanger  28 . Time slot interchanger  28  then switches incoming signals  44  and  46  so as to route them to VT time slot interchanger  21  and provides input signals  44  and  46  to Vx distributor  29 . Vx distributor  29  copies input signals  44  and  46  and provides the signals to both VT time slot interfchanger  21  and a spare time slot interchanger (not shown). VT time slot interchanger  21  manages the bandwidth of incoming signals  44  and  46  on a VT level and outputs managed signals  44 ′ and  46 ′ to Vx selector  30 . Vx selector selects the managed signals  44 ′ and  46 ′ from active VT time slot intetchanger  21  and provides them to time slot interchanger  31 . Time slot interchanger  31  connects managed signals  44 ′ and  46 ′ to 2:1 selector  32 . Because input signals  44  and  46  were to be managed on a VT basis, 2:1 selector  32  provides managed signals  44 ′ and  46 ′ to APS distributor  33 . APS distributor  33  then provides managed signals  44 ′ and  46 ′ to the appropriate active output interfaces.  
         [0036]    [0036]FIG. 4 depicts another embodiment of present invention. In that figure, input signals are accepted into network element  51  through input interfaces  52 ,  53  and  54 . Network element  51  accepts different signal types and formats from the telecommunications network. For example, input interface  52  may accept a DS 3 signal, input interface  53  may accept a DS 1 signal, and input interface  54  may accept data traffic on an OC-3 line. The signals from input interfaces  52 ,  53  and  54  are then routed to the appropriate bandwidth management device through connectors  66   a - 66   c,    67   a - 67   c  and  68   a - 68   c,  respectively. Preferably, input interfaces  52 ,  53  and  54  reside on cards which slide into a card cage. Connectors  66   a - 66   c,    67   a - 67   c  and  68   a - 68   c  would reside on the backplane of the card cage and make contact with input interfaces  52 ,  53  and  54 , respectively, when the cards have been inserted into the cage. Each of the connectors a-c may reside on a single connector or multiple connectors. Connectors  66   a,    67   a  and  68   a  would provide connectivity to STS time slot interchanger  55 . Connectors  66   b,    67   b  and  68   b  would provide connectivity to VT time slot interchanger  56 . Connectors  66   c,    67   c  and  68   c  would provide connectivity to data switch  57 .  
         [0037]    There may also be a Layer  3  switch  64  connected to data switch  57 , to input interface card  63 , and to STS distributor  58 . Additionally, Layer  3  switch  64  can communicate with data switch  57  to provide Layer  3  switching functionality.  
         [0038]    STS time slot interchanger  55 , VT time slot interchanger  56 , data switch  57  and Layer  3  switch  64  are connected to STS distributor  58 . STS distributor  58  than distributes signals it receives from STS time slot interchanger  55 , VT time slot interchanger  56 , data switch  57  and Layer  3  switch  64  to the appropriate output interfaces  60  through  62 . The signals output from interface cards  60  through  62  can be of an OC-n type.  
         [0039]    Alternatively, the STS selector  58  may be replaced by the use of connectors similar to  66   a - 66   d,    67   a - 67   d,    68   a - 68   d  and  69   a - 69   d  attached to output interfaces  60  through  62  providing connectivity to STS time slot interchanger  55 , VT time slot interchanger  56 , data switch  57  and Layer  3  switch  64 .  
         [0040]    In the embodiment of FIG. 4, the selectability of which input interfaces  52  through  54  and  63  are mapped to which elements  55  through  57  and  64  is managed by a network operator through user interface  70 . Alternatively, this can be done automatically by detecting the presence of a certain type of input interface card in a slot in the device upon power up, or by detecting the type of traffic being carried by the input interface cards  52  through  54  and  63 . As another alternative, this could be done on the input interface card itself through the use of a switch or similar device.  
         [0041]    Preferably, the selectability function would be implemented through the use of software, but may be implemented through hardware, such as switches or relays, or through firmware.  
         [0042]    A sample of traffic flow through the embodiment depicted in FIG. 4 is shown in FIG. 5. The DS 3 signal received by input interface  52  is built into an STS-n signal and routed by connector  66   a  to STS time slot interchanger  55 . STS time slot interchanger  55  manages the bandwidth of this signal on an STS level and outputs an STS-n signal to STS distributor  58 . This signal is then routed to output interface  62  and output to the network.  
         [0043]    The DS 1 signal received by input interface  53  is built into an STS-n signal and passed to VT time slot interchanger  56  through connector  67   b.  VT time slot interchanger  56  manages the bandwidth of this signal on a VT level and outputs and STS-n signal to STS distributor  58 . This signal is then routed to output interface  60  and output to the network.  
         [0044]    The data traffic received by input interface  54  is built into an STS-n signal and passed to data switch  57  through connector  68   c.  Data switch  57  manages the bandwidth of data signals sent into it on a cell level and outputs an STS-n signal. This signal is passed to Layer  3  switch, if Layer  3  switching is desired.  
         [0045]    A data connection from a LAN, for instance, may be input into input interface  63  and that data may be passed on to Layer  3  switch  64  through connector  69   d.  Layer  3  switch  64  then manages the Layer  3  data and outputs managed data to STS distributor  58 . This data is then routed to output interface  61  and output to the network.  
         [0046]    Although the preferred embodiments of the present invention have been described and illustrated in detail, it will be evident to those skilled in the art that various modifications and changes may be made thereto without departing from the spirit and scope of the invention as set forth in the appended claims and equivalents thereof: