Patent Abstract:
An Ethernet Metropolitan Area Network ( 10 ) provides connectivity to one or more customer premises ( 16   1   , 16   2   , 16   3 ) to packet-bases services, such as ATM, Frame Relay, or IP while advantageously providing a mechanism for assuring security and regulation of customer traffic. Upon receipt of each customer-generated information frame ( 20 ), an ingress Multi-Service Platform (MSP) ( 12   2 ) “tags” the frame with a customer descriptor ( 22 ′) that specifically identifies the recipient customer. In practice, the MSP tags each frame by overwriting the Virtual Local Area Network (VLAN) identifier ( 22 ) with the routing descriptor. Using the customer descriptor in each frame, a recipient Provider Edge Router (PER) ( 18 ) or ATM switch can map the information as appropriate to direct the information to the specific customer. In addition, the customer descriptor ( 22 ′) may also include Quality of Service (QoS) allowing the recipient Provider Edge Router (PER) ( 18 ) or ATM switch to vary the QoS level accordingly.

Full Description:
TECHNICAL FIELD  
         [0001]    This invention relates to a technique enabling access to packet-based services, such as IP, Frame Relay, and ATM, through an Ethernet Protocol network.  
         BACKGROUND ART  
         [0002]    Presently, communication service providers, such as AT&amp;T, offer high-speed data communications service to customers through a variety of access mechanisms. For example, a customer may gain network access through a private line connection, i.e., a direct link to the communications service provider&#39;s network. Private line access provides a dedicated port not shared by anyone else with facility bandwidth available exclusively to the particular customer. Unfortunately, private line access is expensive, and is practical only for customers that have very high traffic capacity requirements.  
           [0003]    As an alternative to private line access, communications service providers such as AT&amp;T also offer virtual circuit access allowing several customers to logically share a single circuit, thus reducing costs. Such shared circuits, typically referred to as Permanent Virtual Circuits, allow communication service providers to guarantee customer traffic flows that are distinguishable from each, secure, and allow customers to enjoy different service features. An example of such a technique for offering such shared service in a Multi-Protocol Label Switching Network is disclosed in U.S. Pat. No. 6,081,524, assigned to AT&amp;T.  
           [0004]    Presently, there is a trend towards using Ethernet networks in place of Frame Relay and ATM networks especially for transporting traffic among two or more premises belonging to the same customer. Ethernet-based Metropolitan Area Networks (MANs) currently exist in many areas and offer significant cost advantages on a per port basis, as compared to Frame Relay and ATM service. Transmission speeds as high as 100, 1000 or even 10,000 MB/second are possible with such Ethernet MANs. Moreover, optical Ethernet MANs typically offer a rich set of features, flexible topology and simple-end-to end provisioning.  
           [0005]    Present-day Ethernet-based MANs lack the ability to logically separate traffic received from different customers, giving rise to issues of data security. Moreover, such present day Ethernet-based MANs lack the ability to manage bandwidth among customers, thus preventing the network from regulating customer traffic to assure equitable access. Thus, there is a need for a technique for routing data in an Ethernet protocol network that overcomes the aforementioned disadvantages.  
         BRIEF SUMMARY OF THE INVENTION  
         [0006]    Briefly, in accordance with a preferred embodiment, a method is provided for routing data in an Ethernet protocol network having a plurality of platforms, each serving one or more customers. A first platform receives at least one frame from a sending site (e.g., a first customer&#39;s premises) that is destined for a receiving site (e.g., another premises belonging to the same or a different customer.) After receiving the frame, the first platform overwrites a portion of the frame with a customer descriptor that specifically identifies the sending customer. In practice, the first platform will overwrite a Virtual Local Area Network (VLAN) field that is typically employed by the sending customer for the purposes of routing data among various VLANs at the sending premises premises. Rather than overwrite the VLAN field in the frame, the first platform could overwrite another field, such as the source address field, or could even employ a “shim” header containing the customer descriptor. All further use of the term customer descriptor implies that any of the above or similar techniques could be used.  
           [0007]    After overwriting the frame with the customer descriptor, the sending platform routes the frame onto the MAN network for routing among the other platforms, thereby sharing trunk bandwidth and other resources, but logically distinct from other customer&#39;s traffic with different customer descriptors. A destination address in the frame directs the frame to its corresponding receiving platform. Upon receipt of the frame, the receiving platform uses the customer descriptor to segregate the frame for delivery to the proper destination, especially in the event where different customers served by the same platform use overlapping addressing plans. Thus, the customer descriptor in each frame advantageously enables the receiving platform to distinguish between different customers served by that platform.  
           [0008]    For traffic with a destination beyond the MAN, this method provides a convenient and efficient way to map the customer-descriptor to similar identifiers in a Wide Area Network (WAN), such as a Permanent Virtual Circuit (PVC), a Virtual Private Network (VPN), or an MPLS Label Switched Circuit.  
           [0009]    Overwriting each frame with the customer-descriptor thus affords the ability to logically segregate traffic on the Ethernet MAN to provide Virtual Private Network (VPN) services of the type offered only on more expensive Frame Relay and ATM networks. Moreover, the customer descriptor used to tag each frame can advantageously include Quality of Service (QoS) information, allowing the sender to specify different QoS levels for different traffic types, based on the Service Level Agreement (SLA) between the customer and the communications service provider. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 depicts an Ethernet Protocol Metropolitan Area Network (MAN) in which each information frame is tagged with a customer descriptor in its VLAN field in accordance with the present principles;  
         [0011]    [0011]FIG. 2 illustrates a sample information frame for transmission over the network of FIG. 1;  
         [0012]    [0012]FIG. 3 illustrates a portion of the MAN showing the various stages in the tagging process;  
         [0013]    [0013]FIG. 4 illustrates a portion of a MAN showing the use of the priority bits within the VLAN field to establish different Quality of Service levels;  
         [0014]    [0014]FIG. 5 illustrates a portion of a MAN showing the manner in which information frames are mapped to different Permanent Virtual Circuits by an ATM switch;  
         [0015]    [0015]FIG. 6 illustrates a portion of a MAN showing the manner in which information frames are mapped into different Multi-Protocol Label Switching (MPLS) tunnels; and  
         [0016]    [0016]FIG. 7 illustrates a portion of a MAN showing the manner in which information frames are mapped into different service networks. 
     
    
     DETAILED DESCRIPTION  
       [0017]    [0017]FIG. 1 depicts an Ethernet Protocol Metropolitan Area Network (MAN)  10  comprised of a plurality of Multi-Service Platforms (MSPs)  12   1 - 12   n  where n is an integer, each MSP taking the form of an Ethernet switch or the like. In the illustrated embodiment n=4 although the network  10  could include a smaller or larger number of MSPs. A fiber ring or SONET ring infrastructure  14  connects the platforms  12   1 - 12   4  in daisy-chain fashion allowing each MSP to statistically multiplex information onto, and to statistically de-multiplexing information off the ring infrastructure  14 .  
         [0018]    Each of MSPs  12   1 - 12   3  serves at least one, and in some instances, a plurality of premises  16  belonging to one or more customers. In the illustrated embodiment of FIG. 1, the MSP  12   1  serves a single customer premises  16   1  belonging to customer  1  whereas, the MSP  12   2  serves premises  16   2 , and  16   3  belonging to customers  2  and  3 , respectively. The MSP  12   3  serves a single premises  16   4  that belongs to customer  3 . The MSPs  12   1 - 13   3  are linked to their corresponding premises via 10, 100 or 1000 MB links  18 . The MSP  12   4  bears the legend “CO MSP” because it serves as a central office to route traffic from the MAN  10  to a Provider Edge Router (PER)  18  for delivery to other networks, such as Frame Relay, ATM, MPLS networks or the Internet as discussed hereinafter. By the same token, the PER  18  can route traffic from such other networks onto the MAN  10  via the CO MSP  12   4    
         [0019]    The traffic routed onto and off of the MAN  10  by each MSP takes the form of one or more information frames  20  depicted in FIG. 2. Heretofore, traffic routed onto the network  10  from a particular customer&#39;s premises was combined with other customer&#39;s traffic with no logical separation, thus raising security concerns. Moreover, since all customers&#39; traffic share the same bandwidth, difficulties existed in prior art Ethernet MANs in regulating the traffic from each customer&#39;s premises, and in affording different customers different Quality of Service (QoS) level in accordance with individual Service Level Agreements.  
         [0020]    These difficulties are overcome in accordance with the present principles by “tagging” each frame  20  routed onto the network  10  at a particular MSP, say MSP  12   3 , with a customer descriptor  22 ′ (best seen in FIG. 2) that identifies the customer sending that frame. As discussed in greater detail below, each MSP receiving a frame  20  on the fiber ring infrastructure  14  uses the customer descriptor  22 ′ in that frame to maintain distinct routing and addressing tables that are assigned to each customer served by that MSP. This permits each customer to use their own addressing plan without fear of overlap with other customers, as they are all maintained as logically separate.  
         [0021]    [0021]FIG. 2 depicts the structure of an exemplary Ethernet protocol frame  20  specified by Ethernet Standard 802.1Q. Among the blocks of bytes within each frame  20  is a Virtual Local Area Network (VLAN) Identifier  22  comprised of sixteen bits. In practice, the VLAN identifier  22 , in conjunction with a VLAN flag block  23  within the frame, facilitates routing of the frame within a customer&#39;s premises to a particular VLAN. However, the VLAN identifier  22  has no influence on routing of the frame  20  after receipt at a MSP.  
         [0022]    In accordance with the present principles, the prior disadvantages associated with conventional Ethernet networks, namely the lack of security and inability to regulate QoS levels, are overcome by overwriting the VLAN identifier  22  in each frame  20  with the customer descriptor maintained by the service provider. Overwriting the VLAN identifier  22  of FIG. 2 of each frame  20  with the customer descriptor  22 ′ serves to “tag” that frame with identity of its sending customer identity, thus affording each MSP in the network  10  the ability to route those frames only among the premises belonging to that same sending customer. Such tagging affords the operator of the network  10  the ability to provide security in connection with frames transmitted across the network, since frames with customer ID A would not be delivered to any premises of customer with ID B. As an example, two or more customers served by a single MSP may use overlapping IP addressing schemes. In the absence of any other identifier, the MSP receiving such frame lacks the ability to assure accurate delivery.  
         [0023]    In the illustrated embodiment depicted in FIG. 2, each MSP of FIG. 1 tags the frame  20  by overwriting the VLAN identifier  22  with the customer descriptor  22 ′. However, tagging could occur in other ways, rather than overwriting the VLAN identifier  22 . For example, the source address block  25  within the frame  20  could be overwritten with the customer descriptor  22 ′. Alternatively, the data field  25  could include a shim header comprising the customer descriptor  22 ′.  
         [0024]    The tagging of each frame  20  with the customer descriptor  22 ′ affords several distinct advantages in connection with routing of the frames through the MAN. First, as discussed above, the tagging affords each recipient MSP the ability to distinguish traffic destined for customers with overlapping address schemes, and thus allows for segregating traffic on the MAN. Further, tagging each frame  20  with the customer descriptor  22 ′ enables mapping of the frames from a MAN  100  depicted in FIG. 3 to corresponding one of a plurality of customer Virtual Private Networks  26   1 - 26   3  within an MPLS network  28 . As seen in FIG. 3, an MSP  120   2  within the MAN  100  receives traffic from premises  160   1 ,  160   2 , and  160   3  belonging to customer  1 , customer  2  and customer  3 , respectively, which enjoy separate physical links to the MSP. Upon receipt of each from a particular customer, the MSP  120   2  overwrites that frame with the customer descriptor corresponding to the sending customer.  
         [0025]    After tagging each data frame, the MSP  120   2  statistically multiplexes the frames onto the fiber ring infrastructure  14  for transmission to a CO MSP  120   4  for receipt at a destination PER  180  that serves the MPLS network  28  within which are customer Virtual Private Networks  26   1 - 26   3 . Using the customer descriptor in each frame, the PER  180  maps the frame to the corresponding VPN identifier associated with a particular one of customer Virtual Private Networks  26   1 - 26   3  to properly route each frame to its intended destination.  
         [0026]    The tagging scheme of the present invention also affords the ability to route information frames with different QoS levels within a MAN  1000  depicted in FIG. 4. As seen in FIG. 4, an MSP  1200   2  within the MAN  1000  receives traffic from premises  1600   2 , and  1600   3  belonging to customer  2  and customer  3 , respectively, which enjoy separate physical links to the MSP, allowing each to send information frames into the MAN. In the illustrated embodiment of FIG. 4, the frames originating from the premise  1600   2  may contain either voice or data and have corresponding QoS level associated with each type of frame. Upon receiving such frames, the MSP  1200   2  overwrites the frame with the customer descriptor corresponding to the particular customer sending the frame. The customer descriptor will not only contain the identity of the sending customer, but the corresponding QoS level associated with that frame.  
         [0027]    After tagging each data frame, the MSP  1200   2  statistically multiplexes the frames onto the fiber ring infrastructure  14  for transmission to a CO MSP  1200   4  for receipt at a destination PER  1800  that serves an MPLS network  280  within which are customer Virtual Private Networks  260   2  and  260   3 . Using the customer descriptor in each frame, the PER  1800  of FIG. 4 maps the frame to the corresponding customer VPN to properly route each frame to its intended customer premises. Further, the PER  1800  of FIG. 4 also maps the QoS level specified in the customer descriptor in the frame to assure that the appropriate quality of service level is applied to the particular frame.  
         [0028]    In the above-described embodiments, the frames of customer traffic have been assumed to comprise IP packets that terminate on a router (i.e., Provider Edge Routers  18 ,  180  and  1800 ) and that the VPNs employ MPLS-BGP protocols. However, some customers may require multi-protocol support, or may otherwise require conventional PVCs so that the traffic streams must be mapped into Frame Relay or ATM PVCs as depicted in FIG. 5, which illustrates a portion of a MAN  10000  having a CO MSP 12000   4  serving an ATM switch  30  that receives traffic from the MAN. As seen in FIG. 5, each of premises  16000   1 ,  16000   2  and  16000   3  belonging to customer  1 , customer  2  and customer  3 , respectively 5 may originate information frames for receipt at MSP  12000   2  in the MAN  10000 . The MSP  12000   2  tags each frame with the corresponding customer descriptor prior to statistically multiplexing the data for transmission on the fiber ring infrastructure  14  to the CO MSP  12000   4  for receipt at the ATM switch  30 . The ATM switch  30  then maps the frame to the appropriate PVC in accordance with the customer descriptor in the frame in a manner similar to the mapping described with respect to FIG. 3. Thus, the ATM switch  30  could map the frame to one of Frame Relay recipients&#39;  32   1 ,  32   2 , or  32   3 , ATM recipients  32   4  or  32   5  or IMA (Inverse Multiplexing over ATM) recipient  32   6 .  
         [0029]    [0029]FIG. 6 depicts a portion of a MAN network  100000  that routes frames onto separate MPLS tunnels  40   1 - 40   3  (each emulating a private line  32  in an MPLS network  2800 ) in accordance with the customer descriptor written into each frame by a MSP  120000   2  in the MAN. Each of customer premises  160000   1 ,  160000   2  and  160000   3  depicted in FIG. 6 originate information frames for receipt at MSP  120000   2 . The MSP  120000   2  tags each frame with the customer descriptor prior to statistically multiplexing the data for transmission on the fiber ring infrastructure  14  for delivery to a CO MSP  120000   4  that serves a PER  18000 . The PER  18000  translates the customer descriptors written onto the frames by the MSP  120000   2  into the MPLS tunnels  40   1 - 40   3  to enable the PER to route the traffic to the intended customer.  
         [0030]    [0030]FIG. 7 depicts a portion of a MAN network  1000000  for routing traffic (i.e., information frames) onto separate networks in accordance with the customer descriptor written into each the frame by a MSP  120000   2  in the MAN. Each of customer premises  1600000   2  and  16000003  depicted in FIG. 7 originates information frames for receipt by the MSP  1200000   2 . The MSP  1200000   2  tags each frame with the customer descriptor prior to statistically multiplexing the data for transmission on the fiber ring infrastructure  14  for delivery to a CO MSP  1200000   4  that serves a PER  180000 . In accordance with the customer descriptor, the PER  1800000  of FIG. 7 routes traffic to a particular one of several different networks, e.g., an Intranet VPN  42   1 , a voice network  42   2  and the Internet  42   3 , in accordance with the customer descriptor written onto the frame by the MSP  12   2 .  
         [0031]    The above-described embodiments merely illustrate the principles of the invention. Those skilled in the art may make various modifications and changes that will embody the principles of the invention and fall within the spirit and scope thereof. descriptor, the PER  1800000  of FIG. 7 routes traffic to a particular one of several different networks, e.g., an Intranet VPN  42   1 , a voice network  42   2  and the Internet  42   3 , in accordance with the customer descriptor  22 ′ written onto the frame by the MSP  1200000   2 .

Technology Classification (CPC): 7