Abstract:
An advanced SONET add/drop multiplexer capable of supporting packet over SONET and multiprotocol label switching. The add/drop multiplexer is capable of adding and/or dropping both STM and packet traffic, such as Internet Protocol traffic. This SONET add/drop multiplexer allows Internet Protocol streams which are added or dropped at different nodes to be carried over the same SONET path in a network, thereby greatly saving bandwidth.

Description:
The present invention relates generally to a SONET add/drop multiplexer enhanced so as to support Packet over SONET (POS) and Multiprotocol Label Switching (MPLS). Such a device will allow packet traffic, such as Internet Protocol traffic, which is added to and/or dropped from various points in a SONET network to be carried over the same SONET path on the network. 
     BACKGROUND ART 
     Traditionally telephony networks have been synchronous in nature. They were initially constructed for the purpose of carrying narrowband voice signals, as wideband and broadband traffic, such as data and video, did not exist. Today, both network operators and equipment vendors face the challenge of handling wideband and broadband traffic with an infrastructure that is essentially inadequate because it was not designed for this purpose. 
     With the proliferation of the Internet and the integration of Internet traffic onto telephony networks, the networks are now dealing with large volumes of data traffic. As the Internet grows and more Internet service providers arise, telephony service providers and Internet service providers are investing more money in capital equipment in order to provide more bandwidth and paths for the Internet service traffic to flow. 
     One way Internet Protocol data could be routed in through a telephony network is over an ATM network. However, such a method of transmission of Internet Protocol data is inefficient due to cell header, packet-to-cell adaptation and encapsulation overhead. 
     Another method of routing Internet Protocol data is over a SONET network. Traditionally, if an Internet service provider point of presence would be connected into a SONET network, it would be through a device such as an add/drop multiplexer. If that Internet service provider point of presence was to be connected to another Internet service provider point of presence, a dedicated STS link within the SONET network would need to be established between the two points of presence. As more and more Internet service providers are added to such a network, the number of dedicated STS links dramatically increases, causing allocation of network bandwidth to become very inefficient. 
     Recently, the Internet Engineering Task Force approved a draft of a new standard known as Multiprotocol Label Switching (MPLS). MPLS attempts to merge layer  2  and layer  3  data switching. Under MPLS, an edge node converts regular packets into an MPLS format. The edge node also handles priority. Core nodes, however, do not need to look deeper then the assigned label to perform a switching function. This speeds up the switching process because the core nodes no longer need to look at a packet&#39;s source and destination address and priority. The draft MPLS standards are available to the public for download from the Internet at www.ietf.cnri.reston.va.us/ID.html Currently available drafts include 1) draft-ietf-mpls-arch-04.txt; 2) draft-ietf-mpls-framework-02.txt; 3) draft-ietf-mpls-label-emcaps-03.txt; 4) draft-ietf-mpls-fr-03.txt; 5) draft-ietf-mpls-ldp-03.txt; 6) draft-ietf-mpls-ldp-03.txt; 7) draft-ietf-mpls-rsvp-ldp-tunnel-01.txt; and 8) draft-ietf-mpls-bgp 4 -mpls-02.txt. Each of these draft MPLS standards is hereby incorporated by reference. 
     MPLS offers the Internet service provider community the ability to offer different grades of service. It also provides the ability to create virtual private networks through the stacking of labels. For instance, one label can designate a particular company, while a sub-label can indicate a specific group of users within that company. MPLS also makes it easier for Internet service providers to perform traffic engineering by permitting Internet service providers to explicitly route certain labels to alleviate congestion. 
     However, the MPLS standards do not address integration of MPLS switching into a SONET network. 
     SUMMARY OF THE INVENTION 
     The present invention provides an apparatus and method for efficiently utilizing bandwidth within a SONET network carrying data packets such as Internet Protocol packets. The invention does so by providing packet switching capability within SONET add/drop multiplexers. 
     An embodiment of the present invention provides for the inclusion of MPLS switching capability within a SONET add/drop multiplexer. 
     Another embodiment of the present invention provides for the inclusion of packet switching capability within a SONET add/drop multiplexer along with ATM switching capability. 
     Another embodiment of the present invention provides for the inclusion of edge node service adaptation functionality within a SONET add/drop multiplexer. 
     Thus, it is an object of the present invention to optimize allocation of SONET transport bandwidth carrying packet traffic. 
     It is a further object of the present invention to provide the ability to offer different grades of packet traffic service in a SONET network. 
     It is another object of an embodiment of the present invention to provide the ability to create virtual private networks over a SONET network. 
     It is a further object of embodiment of the present invention to provide the ability to perform traffic engineering in a SONET network carrying packet traffic. 
     It is another object of the present invention to reduce capital costs for Internet service providers connecting to SONET networks. 
     It is a further object of the present invention to reduce the amount of state information that must be maintained in a SONET network. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages of this 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: 
     FIG. 1 (Prior Art) is a block diagram of a SONET network carrying packet traffic of the prior art; 
     FIG. 2 is a block diagram according to an embodiment of the present invention of a SONET network; 
     FIG. 3 is a block diagram of a SONET network according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention will be better understood by reference to the accompanying drawings. 
     FIG. 1 (prior art) depicts a SONET network consisting of SONET add/drop multiplexers  71  through  78 , regional Internet service provider points of presence  81  through  83 , and national Internet service provider points of presence  84  and  85  of the prior art. Under the prior art, if each local Internet service provider point of presence was to be connected to both of the national Internet service provider points of presence, and the two national Internet service provider points of presence were to be interconnected, then 7 separate STS links within the SONET network would have to be dedicated to carrying the packet traffic between the various Internet service providers. 
     For example, to connect regional Internet service provider point of presence  81  to national Internet service provider point of presence  85 , add/drop multiplexer  71  would have to connect input  51  from regional Internet service provider  81  to add/drop multiplexer  78  through dedicated STS link  91 . Add/drop multiplexer  78  would then have to connect dedicated STS link  91  to line  61  to connect it to the national Internet service provider  85 . To connect regional Internet service provider  81  to national Internet service provider  84 , add/drop multiplexer  71  would have to connect input  52  to add/drop multiplexer  77  through dedicated STS link  92 . Add/drop multiplexer  77  would then have to connect STS link  92  to national Internet service provider  84  through line  60 . 
     To connect regional Internet service provider  82  to national Internet service provider  85 , add/drop multiplexer  74  would have to connect input line  53  to add/drop multiplexer  78  through dedicated STS link  97 . Add/drop multiplexer  78  would then have to connect dedicated STS link  97  to line  62 . To connect regional Internet service provider  82  to national Internet service provider  84 , add/drop multiplexer  74  would have to connect input line  54  to add/drop multiplexer  77  through dedicated STS link  96 . Add/drop multiplexer  77  would then have to connect dedicated STS link  96  to input line  59 . 
     To connect regional Internet service provider  83  to national Internet service provider  85 , add/drop multiplexer  76  would have to connect input line  55  to add/drop multiplexer  78  through dedicated STS link  95 . Add/drop multiplexer  78  would then have to connect dedicated STS link  95  to input line  63 . To connect regional Internet service provider  83  to national Internet service provider  84 , add/drop multiplexer  76  would have to connect input line  56  to add/drop multiplexer  77  via dedicated STS link  94 . Add/drop multiplexer  77  would then have to connect dedicated STS link  94  to line  58 . 
     To connect the two national Internet service providers  84  and  85  to each other, add/drop multiplexer  78  would have to connect input line  64  to add/drop multiplexer  77  via dedicated STS link  93 . Add/drop multiplexer  77  would then have to connect dedicated STS link  93  to input line  57 . 
     It doesn&#39;t take too many Internet service providers to make this SONET network of the prior art very inefficient. Moreover, an expensive IP switch port would be necessary for each of the connections. Thus, two IP switch ports would be necessary at each of the regional Internet service provider points of presence  81  through  83  and four IP switch ports would be necessary at each of the national Internet service provider points of presence  84  and  85 . 
     In FIG. 2, a SONET network according to an embodiment of present invention is shown. In this figure, at least SONET add/drop multiplexers  101 ,  104 ,  106 ,  107  and  108  are equipped with POS/MPLS capability. This enables the add/drop multiplexers to process labels and concentrate label switch paths into a single STS path between the add/drop multiplexer nodes. Add/drop multiplexers  102 ,  103 , and  105  may be of the traditional type or may include the MPLS capability. Preferably, each of the add/drop multiplexers would include this capability to enable Internet service providers to connect directly to add/drop multiplexers  102 ,  103  and  105  in the future. By including POS/MPLS capability in SONET add/drop multiplexers  101 ,  104 ,  106 ,  107  and  108 , a single STS link between each of the nodes can be devoted to carrying packet data. This STS link would flow along the path of  111 ,  112 ,  113  and  114 . The MPLS labels with PPP or frame relay encapsulation would define virtual circuits over the SONET network. SONET add/drop multiplexers  101 ,  104 ,  106 ,  107  and  108  can then concentrate/groom the MPLS label delineated virtual circuits onto a common SONET transport path. Additionally, communications between the Internet service provider points of presence and their respective add/drop multiplexers can now be combined into one respective pipe. This reduces the number of IP switch ports required at each Internet service provider point presence down to one. 
     Traditional engineering methods can be utilized by one skilled in the art to design POS/MPLS capability into a SONET add/drop multiplexer. 
     Although it is preferable to provide POS/MPLS capability within the SONET add/drop multiplexer, similar savings can be realized in bandwidth and switch port costs without utilizing MPLS. For instance, if layer  2  encapsulation is frame relay, then the SONET add/drop multiplexer can utilize the frame relay address (DLCI) field to delineate virtual circuits for concentration into the common STS path  111 ,  112 ,  113  and  114 . 
     An additional benefit of providing POS/MPLS capability within the SONET add/drop multiplexer is that MPLS label switched paths can be merged to form multipoint-to-point trees. This reduces the amount of state information that must be maintained by the network. 
     Preferably, the SONET add/drop multiplexers of the present invention would each contain a route processor that would run standard IP routing protocols such as OSPF, BGP, and multicast (e.g. PIM) as well as label distribution protocols, such as LDP. Additionally, the SONET add/drop multiplexers would contain interfaces for Ethernet, DS 3, OC-3, OC-12, and others. The SONET add/drop multiplexers of the present invention may also contain an ATM switching fabric in order to switch ATM traffic that may be present on the SONET network. Again, traditional engineering methods can be used by those skilled in the art to build such devices. 
     FIG. 3 depicts a SONET network according to an embodiment of present invention. In this figure, edge node service adaptation function has been incorporated into the POS/MPLS add/drop multiplexer. As can be seen in FIG. 3, SONET add/drop multiplexers  121 ,  123 , and  124  have MPLS router functions built into them,  131 ,  133  and  134  respectively. SONET add/drop multiplexers  122 ,  125  and  126  have MPLS functionality as discussed previously. This functionality enables them to label switch. By providing MPLS edge router functionality in SONET add/drop multiplexers  121 ,  123  and  124 , computer network  141  and computer network  142  can be connected in a virtual private network. Additionally, computer networks  141  and  142  can access the Internet through line  150  to an Internet service provider (not shown). Such devices can be built by those skilled in the art using traditional engineering methods. 
     Although each of the preferred embodiments discussed above was discussed with reference to a SONET network, the same may be applicable to an SDH network or any other synchronous optical network. 
     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.